• Home
  • Textbooks
  • Thermodynamics: An Engineering Approach
  • Mass and Energy Analysis of Control Volumes

Thermodynamics: An Engineering Approach

Yunus A. Cengel, Michael A. Boles

Chapter 5

Mass and Energy Analysis of Control Volumes - all with Video Answers

Educators

+ 6 more educators

Chapter Questions

View

Problem 1

Name four physical quantities that are conserved and two quantities that are not conserved during a process.

Lien Le
Lien Le
Numerade Educator
01:03

Problem 2

Define mass and volume flow rates. How are they related to each other?

Dading Chen
Dading Chen
Numerade Educator
00:27

Problem 3

Does the amount of mass entering a control volume have to be equal to the amount of mass leaving during an unsteady-flow process?

Dading Chen
Dading Chen
Numerade Educator
00:25

Problem 4

Consider a device with one inlet and one outlet. If the
volume flow rates at the inlet and at the outlet are the same, is the flow through this device necessarily steady? Why?

Dading Chen
Dading Chen
Numerade Educator
01:39

Problem 5

The ventilating fan of the bathroom of a building has a volume flow rate of $30 \mathrm{~L} / \mathrm{s}$ and runs continuously. If the density of air inside is $1.20 \mathrm{~kg} / \mathrm{m}^{3},$ determine the mass of air vented out in one day.

Dading Chen
Dading Chen
Numerade Educator
02:33

Problem 6

Air enters a 16-cm-diameter pipe steadily at $200 \mathrm{kPa}$ and $20^{\circ} \mathrm{C}$ with a velocity of $5 \mathrm{~m} / \mathrm{s}$. Air is heated as it flows, and it leaves the pipe at $180 \mathrm{kPa}$ and $40^{\circ} \mathrm{C}$. Determine $(a)$ the volume flow rate of air at the inlet, $(b)$ the mass flow rate of air, and
(c) the velocity and volume flow rate at the exit.

Naman Kumar
Naman Kumar
Numerade Educator
02:31

Problem 7

A steam pipe is to transport $200 \mathrm{lbm} / \mathrm{s}$ of steam at 200 psia and $600^{\circ} \mathrm{F}$. Calculate the minimum diameter this pipe can have so that the steam velocity does not exceed $59 \mathrm{ft} / \mathrm{s}$.

Naman Kumar
Naman Kumar
Numerade Educator
01:10

Problem 8

A garden hose attached with a nozzle is used to fill a 20-gal bucket. The inner diameter of the hose is 1 in and it reduces to 0.5 in at the nozzle exit. If the average velocity in the hose is $8 \mathrm{ft} / \mathrm{s},$ determine $(a)$ the volume and mass flow rates of water through the hose, $(b)$ how long it will take to fill the bucket with water, and $(c)$ the average velocity of water at the nozzle exit.

Naman Kumar
Naman Kumar
Numerade Educator
05:09

Problem 9

A steady-flow compressor is used to compress helium from 15 psia and $70^{\circ} \mathrm{F}$ at the inlet to 200 psia and $600^{\circ} \mathrm{F}$ at the outlet. The outlet area and velocity are $0.01 \mathrm{ft}^{2}$ and $100 \mathrm{ft} / \mathrm{s},$ respectively, and the inlet velocity is $50 \mathrm{ft} / \mathrm{s} .$ Determine the mass flow rate and the inlet area.

Dading Chen
Dading Chen
Numerade Educator
01:58

Problem 10

Air enters the $1-\mathrm{m}^{2}$ inlet of an aircraft engine at $100 \mathrm{kPa}$ and $20^{\circ} \mathrm{C}$ with a velocity of $180 \mathrm{~m} / \mathrm{s}$. Determine the volume flow rate, in $\mathrm{m}^{3} / \mathrm{s}$, at the engine's inlet and the mass flow rate, in $\mathrm{kg} / \mathrm{s}$, at the engine's exit.

Naman Kumar
Naman Kumar
Numerade Educator
01:13

Problem 11

A $2-m^{3}$ rigid tank initially contains air whose density is $1.18 \mathrm{~kg} / \mathrm{m}^{3}$. The tank is connected to a high-pressure supply line through a valve. The valve is opened, and air is allowed to enter the tank until the density in the tank rises to $5.30 \mathrm{~kg} / \mathrm{m}^{3}$. Determine the mass of air that has entered the tank.

Dading Chen
Dading Chen
Numerade Educator
01:30

Problem 12

Air enters a nozzle steadily at $2.21 \mathrm{~kg} / \mathrm{m}^{3}$ and $40 \mathrm{~m} / \mathrm{s}$ and leaves at $0.762 \mathrm{~kg} / \mathrm{m}^{3}$ and $180 \mathrm{~m} / \mathrm{s}$. If the inlet area of the nozzle is $90 \mathrm{~cm}^{2}$, determine $(a)$ the mass flow rate through the nozzle, and $(b)$ the exit area of the nozzle.

Naman Kumar
Naman Kumar
Numerade Educator
01:46

Problem 13

A spherical hot-air balloon is initially filled with air at $120 \mathrm{kPa}$ and $20^{\circ} \mathrm{C}$ with an initial diameter of $5 \mathrm{~m}$. Air enters this balloon at $120 \mathrm{kPa}$ and $20^{\circ} \mathrm{C}$ with a velocity of $3 \mathrm{~m} / \mathrm{s}$ through a 1 -m-diameter opening. How many minutes will it take to inflate this balloon to a 17 -m diameter when the pressure and temperature of the air in the balloon remain the same as the air entering the balloon?

Naman Kumar
Naman Kumar
Numerade Educator
01:21

Problem 14

Water enters the constant 130 -mm inside-diameter tubes of a boiler at $7 \mathrm{MPa}$ and $65^{\circ} \mathrm{C}$ and leaves the tubes at $6 \mathrm{MPa}$ and $450^{\circ} \mathrm{C}$ with a velocity of $80 \mathrm{~m} / \mathrm{s}$. Calculate the velocity of the water at the tube inlet and the inlet volume flow rate.

Naman Kumar
Naman Kumar
Numerade Educator
01:39

Problem 15

A desktop computer is to be cooled by a fan whose flow rate is $0.34 \mathrm{~m}^{3} / \mathrm{min}$. Determine the mass flow rate of air through the fan at an elevation of $3400 \mathrm{~m}$ where the air density is $0.7 \mathrm{~kg} / \mathrm{m}^{3}$. Also, if the average velocity of air is not to exceed $110 \mathrm{~m} / \mathrm{min}$, determine the diameter of the casing of the fan.

Dading Chen
Dading Chen
Numerade Educator
02:12

Problem 16

A hair dryer is basically a duct of constant diameter in which a few layers of electric resistors are placed. A small fan pulls the air in and forces it through the resistors where it is heated. If the density of air is $1.20 \mathrm{~kg} / \mathrm{m}^{3}$ at the inlet and $0.95 \mathrm{~kg} / \mathrm{m}^{3}$ at the exit, determine the percent increase in the velocity of air as it flows through the dryer.

Naman Kumar
Naman Kumar
Numerade Educator
04:38

Problem 17

Refrigerant-134a enters a 28-cm-diameter pipe steadily at $200 \mathrm{kPa}$ and $20^{\circ} \mathrm{C}$ with a velocity of $5 \mathrm{~m} / \mathrm{s}$. The refrigerant gains heat as it flows and leaves the pipe at $180 \mathrm{kPa}$ and $40^{\circ} \mathrm{C} .$ Determine $(a)$ the volume flow rate of the refrigerant at the inlet, $(b)$ the mass flow rate of the refrigerant, and $(c)$ the velocity and volume flow rate at the exit.

Dading Chen
Dading Chen
Numerade Educator
00:25

Problem 18

What are the different mechanisms for transferring energy to or from a control volume?

Mayukh Banik
Mayukh Banik
Numerade Educator
01:04

Problem 19

How do the energies of a flowing fluid and a fluid at rest compare? Name the specific forms of energy associated with each case.

Dading Chen
Dading Chen
Numerade Educator
02:54

Problem 20

An air compressor compresses $6 \mathrm{~L}$ of air at $120 \mathrm{kPa}$ and $20^{\circ} \mathrm{C}$ to $1000 \mathrm{kPa}$ and $400^{\circ} \mathrm{C}$. Determine the flow work, in $\mathrm{kJ} / \mathrm{kg}$, required by the compressor.

Naman Kumar
Naman Kumar
Numerade Educator
01:23

Problem 21

A house is maintained at 1 atm and $24^{\circ} \mathrm{C}$, and warm air inside a house is forced to leave the house at a rate of $90 \mathrm{~m}^{3} / \mathrm{h}$ as a result of outdoor air at $5^{\circ} \mathrm{C}$ infiltrating into the house through the cracks. Determine the rate of net energy loss of the house due to mass transfer.

Naman Kumar
Naman Kumar
Numerade Educator
03:22

Problem 22

Refrigerant-134a enters the compressor of a refrigeration system as saturated vapor at 0.14 MPa and leaves as superheated vapor at $0.8 \mathrm{MPa}$ and $60^{\circ} \mathrm{C}$ at a rate of $0.06 \mathrm{~kg} / \mathrm{s}$. Determine the rates of energy transfers by mass into and out of the compressor. Assume the kinetic and potential energies to be negligible.

Mukesh Devi
Mukesh Devi
Numerade Educator
04:39

Problem 23

Steam is leaving a pressure cooker whose operating pressure is 20 psia. It is observed that the amount of liquid in the cooker has decreased by 0.6 gal in 45 minutes after the steady operating conditions are established, and the cross-sectional area of the exit opening is $0.15 \mathrm{in}^{2}$. Determine $(a)$ the mass flow rate of the steam and the exit velocity, (b) the total and flow energies of the steam per unit mass, and $(c)$ the rate at which energy is leaving the cooker by steam.

Dading Chen
Dading Chen
Numerade Educator
01:17

Problem 24

How is a steady-flow system characterized?

Naman Kumar
Naman Kumar
Numerade Educator
01:43

Problem 25

Can a steady-flow system involve boundary work?

Naman Kumar
Naman Kumar
Numerade Educator
00:12

Problem 26

A diffuser is an adiabatic device that decreases the kinetic energy of the fluid by slowing it down. What happens to this lost kinetic energy?

Dading Chen
Dading Chen
Numerade Educator
00:34

Problem 27

The kinetic energy of a fluid increases as it is accelerated in an adiabatic nozzle. Where does this energy come from?

Dading Chen
Dading Chen
Numerade Educator
04:20

Problem 28

The stators in a gas turbine are designed to increase the kinetic energy of the gas passing through them adiabatically. Air enters a set of these nozzles at 300 psia and $700^{\circ} \mathrm{F}$ with a velocity of $80 \mathrm{ft} / \mathrm{s}$ and exits at 250 psia and $645^{\circ} \mathrm{F}$. Calculate the velocity at the exit of the nozzles.

Dading Chen
Dading Chen
Numerade Educator
03:26

Problem 29

The diffuser in a jet engine is designed to decrease the kinetic energy of the air entering the engine compressor without any work or heat interactions. Calculate the velocity at the exit of a diffuser when air at $100 \mathrm{kPa}$ and $30^{\circ} \mathrm{C}$ enters it with a velocity of $350 \mathrm{~m} / \mathrm{s}$ and the exit state is $200 \mathrm{kPa}$ and $90^{\circ} \mathrm{C}$

Dading Chen
Dading Chen
Numerade Educator
09:29

Problem 30

Air enters a nozzle steadily at 50 psia, $140^{\circ} \mathrm{F},$ and $150 \mathrm{ft} / \mathrm{s}$ and leaves at 14.7 psia and $900 \mathrm{ft} / \mathrm{s} .$ The heat loss from the nozzle is estimated to be 6.5 Btu/lbm of air flowing. The inlet area of the nozzle is $0.1 \mathrm{ft}^{2} .$ Determine $(a)$ the exit temperature of air and $(b)$ the exit area of the nozzle.

Dading Chen
Dading Chen
Numerade Educator
06:48

Problem 31

Air at $600 \mathrm{kPa}$ and $500 \mathrm{~K}$ enters an adiabatic nozzle that has an inlet-to-exit area ratio of 2: 1 with a velocity of $120 \mathrm{~m} / \mathrm{s}$ and leaves with a velocity of $380 \mathrm{~m} / \mathrm{s}$. Determine
(a) the exit temperature and $(b)$ the exit pressure of the air.

Dading Chen
Dading Chen
Numerade Educator
06:03

Problem 32

Carbon dioxide enters an adiabatic nozzle steadily at $1 \mathrm{MPa}$ and $500^{\circ} \mathrm{C}$ with a mass flow rate of $6000 \mathrm{~kg} / \mathrm{h}$ and leaves at $100 \mathrm{kPa}$ and $450 \mathrm{~m} / \mathrm{s}$. The inlet area of the nozzle is $40 \mathrm{~cm}^{2}$. Determine $(a)$ the inlet velocity and $(b)$ the exit temperature.

Dading Chen
Dading Chen
Numerade Educator
02:04

Problem 33

Steam enters a nozzle at $400^{\circ} \mathrm{C}$ and $800 \mathrm{kPa}$ with a velocity of $10 \mathrm{~m} / \mathrm{s},$ and leaves at $375^{\circ} \mathrm{C}$ and $400 \mathrm{kPa}$ while losing heat at a rate of $25 \mathrm{~kW}$. For an inlet area of $800 \mathrm{~cm}^{2}$, determine the velocity and the volume flow rate of the steam at the nozzle exit.

Naman Kumar
Naman Kumar
Numerade Educator
01:21

Problem 34

Air at $80 \mathrm{kPa}$ and $127^{\circ} \mathrm{C}$ enters an adiabatic diffuser steadily at a rate of $6000 \mathrm{~kg} / \mathrm{h}$ and leaves at $100 \mathrm{kPa}$. The velocity of the airstream is decreased from 230 to $30 \mathrm{~m} / \mathrm{s}$ as it passes through the diffuser. Find $(a)$ the exit temperature of the air and $(b)$ the exit area of the diffuser.

Naman Kumar
Naman Kumar
Numerade Educator
05:59

Problem 35

Air at 13 psia and $65^{\circ} \mathrm{F}$ enters an adiabatic diffuser steadily with a velocity of $750 \mathrm{ft} / \mathrm{s}$ and leaves with a low velocity at a pressure of 14.5 psia. The exit area of the diffuser is 3 times the inlet area. Determine $(a)$ the exit temperature and $(b)$ the exit velocity of the air.

Dading Chen
Dading Chen
Numerade Educator
01:57

Problem 36

Refrigerant-134a at $700 \mathrm{kPa}$ and $120^{\circ} \mathrm{C}$ enters an adiabatic nozzle steadily with a velocity of $20 \mathrm{~m} / \mathrm{s}$ and leaves at $400 \mathrm{kPa}$ and $30^{\circ} \mathrm{C}$. Determine $(a)$ the exit velocity and $(b)$ the ratio of the inlet to exit area $A_{1} / A_{2}$.

Kratika Bhadauria
Kratika Bhadauria
Numerade Educator
View

Problem 37

Refrigerant-134a enters a diffuser steadily as saturated vapor at $600 \mathrm{kPa}$ with a velocity of $160 \mathrm{~m} / \mathrm{s},$ and it leaves at $700 \mathrm{kPa}$ and $40^{\circ} \mathrm{C}$. The refrigerant is gaining heat at a rate of $2 \mathrm{~kJ} / \mathrm{s}$ as it passes through the diffuser. If the exit area is 80 percent greater than the inlet area, determine $(a)$ the exit velocity and
(b) the mass flow rate of the refrigerant.

Victor Salazar
Victor Salazar
Numerade Educator
06:06

Problem 38

Air at $80 \mathrm{kPa}, 27^{\circ} \mathrm{C},$ and $220 \mathrm{~m} / \mathrm{s}$ enters a diffuser at a rate of $2.5 \mathrm{~kg} / \mathrm{s}$ and leaves at $42^{\circ} \mathrm{C} .$ The exit area of the diffuser is $400 \mathrm{~cm}^{2}$. The air is estimated to lose heat at a rate of $18 \mathrm{~kJ} / \mathrm{s}$
during this process. Determine $(a)$ the exit velocity and $(b)$ the exit pressure of the air.

Dading Chen
Dading Chen
Numerade Educator
01:25

Problem 39

Air enters an adiabatic nozzle steadily at $300 \mathrm{kPa}$ $200^{\circ} \mathrm{C},$ and $45 \mathrm{~m} / \mathrm{s}$ and leaves at $100 \mathrm{kPa}$ and $180 \mathrm{~m} / \mathrm{s} .$ The
inlet area of the nozzle is $110 \mathrm{~cm}^{2}$. Determine $(a)$ the mass flow rate through the nozzle, $(b)$ the exit temperature of the air, and $(c)$ the exit area of the nozzle.

Naman Kumar
Naman Kumar
Numerade Educator
02:02

Problem 40

Reconsider Prob. 5-39. Using appropriate software, investigate the effect of the inlet area on the mass flow rate, exit temperature, and the exit area. Let the inlet area vary from $50 \mathrm{~cm}^{2}$ to $150 \mathrm{~cm}^{2}$. Plot the final results against the inlet area, and discuss the results.

Naman Kumar
Naman Kumar
Numerade Educator
02:25

Problem 41

Consider an adiabatic turbine operating steadily. Does the work output of the turbine have to be equal to the decrease in the energy of the steam flowing through it?

Naman Kumar
Naman Kumar
Numerade Educator
00:28

Problem 42

Will the temperature of air rise as it is compressed by an adiabatic compressor? Why?

Dading Chen
Dading Chen
Numerade Educator
00:15

Problem 43

Somebody proposes the following system to cool a house in the summer: Compress the regular outdoor air, let it cool back to the outdoor temperature, pass it through a turbine, and discharge the cold air leaving the turbine into the house. From a thermodynamic point of view, is the proposed system sound?

Dading Chen
Dading Chen
Numerade Educator
01:58

Problem 44

Air is expanded from $1000 \mathrm{kPa}$ and $600^{\circ} \mathrm{C}$ at the inlet of a steady-flow turbine to $100 \mathrm{kPa}$ and $200^{\circ} \mathrm{C}$ at the outlet. The inlet area and velocity are $0.1 \mathrm{~m}^{2}$ and $30 \mathrm{~m} / \mathrm{s}$, respectively, and the outlet velocity is $10 \mathrm{~m} / \mathrm{s}$. Determine the mass flow rate and outlet area.

Naman Kumar
Naman Kumar
Numerade Educator
02:12

Problem 45

Air enters a gas turbine at 150 psia and $700^{\circ} \mathrm{F}$ and leaves at 15 psia and $100^{\circ} \mathrm{F}$. Determine the inlet and outlet volume flow rates when the mass flow rate through this turbine is $5 \mathrm{lbm} / \mathrm{s}$.

Naman Kumar
Naman Kumar
Numerade Educator
01:58

Problem 46

Refrigerant-134a enters a compressor at $100 \mathrm{kPa}$ and $-24^{\circ} \mathrm{C}$ with a flow rate of $1.35 \mathrm{~m}^{3} / \mathrm{min}$ and leaves at $800 \mathrm{kPa}$ and $60^{\circ} \mathrm{C}$. Determine the mass flow rate of $\mathrm{R}-134 \mathrm{a}$ and the power input to the compressor.

Naman Kumar
Naman Kumar
Numerade Educator
01:48

Problem 47

Refrigerant-134a enters a compressor at $180 \mathrm{kPa}$ as a saturated vapor with a flow rate of $0.35 \mathrm{~m}^{3} / \mathrm{min}$ and leaves at $900 \mathrm{kPa}$. The power supplied to the refrigerant during the compression process is $2.35 \mathrm{~kW}$. What is the temperature of R-134a at the exit of the compressor?

Naman Kumar
Naman Kumar
Numerade Educator
07:15

Problem 48

Steam flows steadily through an adiabatic turbine. The inlet conditions of the steam are $4 \mathrm{MPa}, 500^{\circ} \mathrm{C},$ and $80 \mathrm{~m} / \mathrm{s},$ and the exit conditions are $30 \mathrm{kPa}, 92$ percent quality, and $50 \mathrm{~m} / \mathrm{s}$. The mass flow rate of the steam is $12 \mathrm{~kg} / \mathrm{s}$. Determine $(a)$ the change in kinetic energy, $(b)$ the power output, and $(c)$ the turbine inlet area.

Dading Chen
Dading Chen
Numerade Educator
01:29

Problem 49

Reconsider Prob. 5-48. Using appropriate software, investigate the effect of the turbine exit pressure on the power output of the turbine. Let the exit pressure vary from 10 to $200 \mathrm{kPa}$. Plot the power output against the exit pressure, and discuss the results.

Naman Kumar
Naman Kumar
Numerade Educator
03:31

Problem 50

Steam flows steadily through a turbine at a rate of $45,000 \mathrm{lbm} / \mathrm{h}$, entering at 1000 psia and $900^{\circ} \mathrm{F}$ and leaving at 5 psia as saturated vapor. If the power generated by the turbine is $4 \mathrm{MW}$, determine the rate of heat loss from the steam.

Dading Chen
Dading Chen
Numerade Educator
01:52

Problem 51

Steam enters an adiabatic turbine at $8 \mathrm{MPa}$ and $500^{\circ} \mathrm{C}$ at a rate of $3 \mathrm{~kg} / \mathrm{s}$ and leaves at $20 \mathrm{kPa}$. If the power output of the turbine is $2.5 \mathrm{MW}$, determine the temperature of the steam at the turbine exit. Neglect kinetic energy changes.

Naman Kumar
Naman Kumar
Numerade Educator
01:57

Problem 52

An adiabatic air compressor compresses $10 \mathrm{~L} / \mathrm{s}$ of air at $120 \mathrm{kPa}$ and $20^{\circ} \mathrm{C}$ to $1000 \mathrm{kPa}$ and $300^{\circ} \mathrm{C}$. Determine $(a)$ the work required by the compressor, in $\mathrm{kJ} / \mathrm{kg},$ and $(b)$ the power required to drive the air compressor, in $\mathrm{kW}$.

Naman Kumar
Naman Kumar
Numerade Educator
04:47

Problem 53

Carbon dioxide enters an adiabatic compressor at $100 \mathrm{kPa}$ and $300 \mathrm{~K}$ at a rate of $0.5 \mathrm{~kg} / \mathrm{s}$ and leaves at $600 \mathrm{kPa}$ and $450 \mathrm{~K}$. Neglecting kinetic energy changes, determine ( $a$ ) the volume flow rate of the carbon dioxide at the compressor inlet and $(b)$ the power input to the compressor.

Dading Chen
Dading Chen
Numerade Educator
01:27

Problem 54

Steam flows steadily into a turbine with a mass flow rate of $26 \mathrm{~kg} / \mathrm{s}$ and a negligible velocity at $6 \mathrm{MPa}$ and $600^{\circ} \mathrm{C}$. The steam leaves the turbine at $0.5 \mathrm{MPa}$ and $200^{\circ} \mathrm{C}$ with a velocity of $180 \mathrm{~m} / \mathrm{s}$. The rate of work done by the steam in the turbine is measured to be $20,350 \mathrm{~kW}$. If the elevation change between the turbine inlet and exit is negligible, determine the rate of heat transfer associated with this process.

Naman Kumar
Naman Kumar
Numerade Educator
01:02

Problem 55

Air is compressed by an adiabatic compressor from $100 \mathrm{kPa}$ and $20^{\circ} \mathrm{C}$ to $1.8 \mathrm{MPa}$ and $400^{\circ} \mathrm{C}$. Air enters the $\mathrm{com}-$ pressor through a $0.15-\mathrm{m}^{2}$ opening with a velocity of $30 \mathrm{~m} / \mathrm{s}$. It exits through a $0.08-\mathrm{m}^{2}$ opening. Calculate the mass flow rate of air and the required power input.

Naman Kumar
Naman Kumar
Numerade Educator
04:03

Problem 56

Air enters the compressor of a gas-turbine plant at ambient conditions of $100 \mathrm{kPa}$ and $25^{\circ} \mathrm{C}$ with a low velocity and exits at $1 \mathrm{MPa}$ and $347^{\circ} \mathrm{C}$ with a velocity of $90 \mathrm{~m} / \mathrm{s}$. The compressor is cooled at a rate of $1500 \mathrm{~kJ} / \mathrm{min}$, and the power input to the compressor is $250 \mathrm{~kW}$. Determine the mass flow rate of air through the compressor.

Dading Chen
Dading Chen
Numerade Educator
01:11

Problem 57

A portion of the steam passing through a steam turbine is sometimes removed for the purposes of feedwater heating as shown in Fig. $\mathrm{P} 5-57 .$ Consider an adiabatic steam turbine with $12.5 \mathrm{MPa}$ and $550^{\circ} \mathrm{C}$ steam entering at a rate of $20 \mathrm{~kg} / \mathrm{s} .$ Steam is bled from this turbine at $1000 \mathrm{kPa}$ and $200^{\circ} \mathrm{C}$ with a mass
flow rate of $1 \mathrm{~kg} / \mathrm{s}$. The remaining steam leaves the turbine at $100 \mathrm{kPa}$ and $100^{\circ} \mathrm{C}$. Determine the power produced by this turbine.

Naman Kumar
Naman Kumar
Numerade Educator
00:18

Problem 58

Why are throttling devices commonly used in refrigeration and air-conditioning applications?

Dading Chen
Dading Chen
Numerade Educator
00:24

Problem 59

Would you expect the temperature of air to drop as it undergoes a steady-flow throttling process? Explain.

Dading Chen
Dading Chen
Numerade Educator
00:48

Problem 60

During a throttling process, the temperature of a fluid drops from 30 to $-20^{\circ} \mathrm{C}$. Can this process occur adiabatically?

Dading Chen
Dading Chen
Numerade Educator
01:22

Problem 61

Someone claims, based on temperature measurements, that the temperature of a fluid rises during a throttling process in a well-insulated valve with negligible friction. How do you evaluate this claim? Does this process violate any thermodynamic laws?

Naman Kumar
Naman Kumar
Numerade Educator
03:30

Problem 62

Refrigerant-134a is throttled from the saturated liquid state at $700 \mathrm{kPa}$ to a pressure of $160 \mathrm{kPa}$. Determine the temperature drop during this process and the final specific volume of the refrigerant.

Dading Chen
Dading Chen
Numerade Educator
02:22

Problem 63

A saturated liquid-vapor mixture of water, called wet steam, in a steam line at $1500 \mathrm{kPa}$ is throttled to $50 \mathrm{kPa}$ and $100^{\circ} \mathrm{C}$. What is the quality in the steam line?

Dading Chen
Dading Chen
Numerade Educator
02:28

Problem 64

An adiabatic capillary tube is used in some refrigeration systems to drop the pressure of the refrigerant from the condenser level to the evaporator level. The $\mathrm{R}-134 \mathrm{a}$ enters the capillary tube as a saturated liquid at $50^{\circ} \mathrm{C}$ and leaves at $-20^{\circ} \mathrm{C}$. Determine the quality of the refrigerant at the inlet of the evaporator.

Naman Kumar
Naman Kumar
Numerade Educator
01:43

Problem 65

A well-insulated valve is used to throttle steam from $8 \mathrm{MPa}$ and $350^{\circ} \mathrm{C}$ to $2 \mathrm{MPa}$. Determine the final temperature of the steam. Answer: $285^{\circ} \mathrm{C}$

Naman Kumar
Naman Kumar
Numerade Educator
01:47

Problem 66

Reconsider Prob. 5-65. Using appropriate software, investigate the effect of the exit pressure of steam on the exit temperature after throttling. Let the exit pressure vary from 6 to 1 MPa. Plot the exit temperature of steam against the exit pressure, and discuss the results.

Naman Kumar
Naman Kumar
Numerade Educator
03:22

Problem 67

Refrigerant-134a enters the expansion valve of a refrigeration system at 120 psia as a saturated liquid and leaves at 20 psia. Determine the temperature and internal energy changes across the valve.

Dading Chen
Dading Chen
Numerade Educator
02:34

Problem 68

Air at 200 psia and $90^{\circ} \mathrm{F}$ is throttled to the atmospheric pressure of 14.7 psia. Determine the final temperature of the air.

Naman Kumar
Naman Kumar
Numerade Educator
00:24

Problem 69

Consider a steady-flow mixing process. Under what conditions will the energy transported into the control volume by the incoming streams be equal to the energy transported out of it by the outgoing stream?

Dading Chen
Dading Chen
Numerade Educator
00:54

Problem 70

Consider a steady-flow heat exchanger involving two different fluid streams. Under what conditions will the amount of heat lost by one fluid be equal to the amount of heat gained by the other?

Dading Chen
Dading Chen
Numerade Educator
00:17

Problem 71

When two fluid streams are mixed in a mixing chamber, can the mixture temperature be lower than the temperature of both streams? Explain.

Dading Chen
Dading Chen
Numerade Educator
01:36

Problem 72

Refrigerant-134a at $700 \mathrm{kPa}, 70^{\circ} \mathrm{C},$ and $8 \mathrm{~kg} / \mathrm{min}$ is cooled by water in a condenser until it exists as a saturated liquid at the same pressure. The cooling water enters the condenser at $300 \mathrm{kPa}$ and $15^{\circ} \mathrm{C}$ and leaves at $25^{\circ} \mathrm{C}$ at the same pressure. Determine the mass flow rate of the cooling water required to cool the refrigerant.

Naman Kumar
Naman Kumar
Numerade Educator
00:58

Problem 73

Hot and cold streams of a fluid are mixed in a rigid mixing chamber. The hot fluid flows into the chamber at a mass flow rate of $5 \mathrm{~kg} / \mathrm{s}$ with an energy in the amount of $150 \mathrm{~kJ} / \mathrm{kg} .$ The cold fluid flows into the chamber with a mass flow rate of $15 \mathrm{~kg} / \mathrm{s}$ and carries energy in the amount of $50 \mathrm{~kJ} / \mathrm{kg} .$ There is heat transfer to the surroundings from the mixing chamber in the amount of $5.5 \mathrm{~kW}$. The mixing chamber operates in a steady-flow manner and does not gain or lose energy or mass with time. Determine the energy carried from the mixing chamber by the fluid mixture per unit mass of fluid, in $\mathrm{kJ} / \mathrm{kg}$.

Naman Kumar
Naman Kumar
Numerade Educator
03:41

Problem 74

A hot-water stream at $80^{\circ} \mathrm{C}$ enters a mixing chamber with a mass flow rate of $0.5 \mathrm{~kg} / \mathrm{s}$ where it is mixed with a stream of cold water at $20^{\circ} \mathrm{C}$. If it is desired that the mixture leave the chamber at $42^{\circ} \mathrm{C}$, determine the mass flow rate of the cold-water stream. Assume all the streams are at a pressure of 250 kPa.

Prashant Bana
Prashant Bana
Numerade Educator
03:26

Problem 75

Water at $80^{\circ} \mathrm{F}$ and 20 psia is heated in a chamber by mixing it with saturated water vapor at 20 psia. If both streams enter the mixing chamber at the same mass flow rate, determine the temperature and the quality of the exiting stream.

Naman Kumar
Naman Kumar
Numerade Educator
03:19

Problem 76

An adiabatic open feedwater heater in an electric power plant mixes $0.2 \mathrm{~kg} / \mathrm{s}$ of steam at $100 \mathrm{kPa}$ and $160^{\circ} \mathrm{C}$ with $10 \mathrm{~kg} / \mathrm{s}$ of feedwater at $100 \mathrm{kPa}$ and $50^{\circ} \mathrm{C}$ to produce feedwater at $100 \mathrm{kPa}$ and $60^{\circ} \mathrm{C}$ at the outlet. Determine the outlet mass flow rate and the outlet velocity when the outlet pipe diameter is $0.03 \mathrm{~m}$.

Naman Kumar
Naman Kumar
Numerade Educator
02:07

Problem 77

Cold water $\left(c_{p}=4.18 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\right)$ leading to a shower enters a thin-walled double-pipe counterflow heat exchanger at $15^{\circ} \mathrm{C}$ at a rate of $0.60 \mathrm{~kg} / \mathrm{s}$ and is heated to $45^{\circ} \mathrm{C}$ by hot water $\left(c_{p}=4.19 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\right)$ that enters at $100^{\circ} \mathrm{C}$ at a rate of $3 \mathrm{~kg} / \mathrm{s}$ Determine the rate of heat transfer in the heat exchanger and the exit temperature of the hot water.

Naman Kumar
Naman Kumar
Numerade Educator
01:35

Problem 78

$5-78 \mathrm{E}$ exchanger at $75^{\circ} \mathrm{F}$. Cooling water enters the tubes at $50^{\circ} \mathrm{F}$ at a rate of $45 \mathrm{lbm} / \mathrm{s}$ and leaves at $65^{\circ} \mathrm{F}$. Assuming the heat exchanger to be well-insulated, determine the rate of heat transfer in the heat exchanger and the rate of condensation of the steam.

Naman Kumar
Naman Kumar
Numerade Educator
07:14

Problem 79

Air $\left(c_{p}=1.005 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\right)$ is to be preheated by hot exhaust gases in a cross-flow heat exchanger before it enters the furnace. Air enters the heat exchanger at $95 \mathrm{kPa}$ and $20^{\circ} \mathrm{C}$ at a rate of $0.6 \mathrm{~m}^{3} / \mathrm{s} .$ The combustion gases $\left(c_{p}=1.10 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\right)$ enter at $160^{\circ} \mathrm{C}$ at a rate of $0.95 \mathrm{~kg} / \mathrm{s}$ and leave at $95^{\circ} \mathrm{C}$. Determine the rate of heat transfer to the air and its outlet temperature.

Dading Chen
Dading Chen
Numerade Educator
02:26

Problem 80

An open feedwater heater heats the feedwater by mixing it with hot steam. Consider an electric power plant with an open feedwater heater that mixes $0.1 \mathrm{lbm} / \mathrm{s}$ of steam at 10 psia and $200^{\circ} \mathrm{F}$ with $2.0 \mathrm{lbm} / \mathrm{s}$ of feedwater at 10 psia and $100^{\circ} \mathrm{F}$ to produce 10 psia and $120^{\circ} \mathrm{F}$ feedwater at the outlet. The diameter of the outlet pipe is $0.5 \mathrm{ft}$. Determine the mass flow rate and feedwater velocity at the outlet. Would the outlet flow rate and velocity be significantly different if the temperature at the outlet were $180^{\circ} \mathrm{F}$ ?

Naman Kumar
Naman Kumar
Numerade Educator
05:22

Problem 81

Refrigerant-134a at 1 MPa and $90^{\circ} \mathrm{C}$ is to be cooled to $1 \mathrm{MPa}$ and $30^{\circ} \mathrm{C}$ in a condenser by air. The air enters at $100 \mathrm{kPa}$ and $27^{\circ} \mathrm{C}$ with a volume flow rate of $600 \mathrm{~m}^{3} / \mathrm{min}$ and leaves at $95 \mathrm{kPa}$ and $60^{\circ} \mathrm{C}$. Determine the mass flow rate of the refrigerant.

Dading Chen
Dading Chen
Numerade Educator
04:14

Problem 82

The evaporator of a refrigeration cycle is basically a heat exchanger in which a refrigerant is evaporated by absorbing heat from a fluid. Refrigerant-22 enters an evaporator at $200 \mathrm{kPa}$ with a quality of 22 percent and a flow rate of $2.65 \mathrm{~L} / \mathrm{h}$ R-22 leaves the evaporator at the same pressure superheated by $5^{\circ} \mathrm{C} .$ The refrigerant is evaporated by absorbing heat from air whose flow rate is $0.75 \mathrm{~kg} / \mathrm{s} .$ Determine $(a)$ the rate of heat absorbed from the air and $(b)$ the temperature change of air. The properties of $\mathrm{R}-22$ at the inlet and exit of the condenser are $h_{1}=220.2 \mathrm{~kJ} / \mathrm{kg}, \mathrm{v}_{1}=0.0253 \mathrm{~m}^{3} / \mathrm{kg},$ and $h_{2}=398.0 \mathrm{~kJ} / \mathrm{kg}$.

Dading Chen
Dading Chen
Numerade Educator
03:10

Problem 83

An air-conditioning system involves the mixing of cold air and warm outdoor air before the mixture is routed to the conditioned room in steady operation. Cold air enters the mixing chamber at $7^{\circ} \mathrm{C}$ and $105 \mathrm{kPa}$ at a rate of $0.55 \mathrm{~m}^{3} / \mathrm{s}$ while warm air enters at $34^{\circ} \mathrm{C}$ and $105 \mathrm{kPa}$. The air leaves the room at $24^{\circ} \mathrm{C}$. The ratio of the mass flow rates of the hot to cold airstreams is 1.6 . Using variable specific heats, determine ( $a$ ) the mixture temperature at the inlet of the room and $(b)$ the rate of heat gain of the room.

Naman Kumar
Naman Kumar
Numerade Educator
01:51

Problem 84

Hot exhaust gases of an internal combustion engine are to be used to produce saturated water vapor at 2 MPa pressure. The exhaust gases enter the heat exchanger at $400^{\circ} \mathrm{C}$ at a rate of $32 \mathrm{~kg} / \mathrm{min}$ while water enters at $15^{\circ} \mathrm{C}$. The heat exchanger is not well insulated, and it is estimated that 10 percent of heat given up by the exhaust gases is lost to the surroundings. If the mass flow rate of the exhaust gases is 15 times that of the water, determine the temperature of the exhaust gases at the heat exchanger exit and the rate of heat transfer to the water. Use the constant specific heat properties of air for the exhaust gases.

Naman Kumar
Naman Kumar
Numerade Educator
01:31

Problem 85

$\begin{array}{llll} \text { A well-insulated shell-and-tube heat exchanger is }\end{array}$ used to heat water $\left(c_{p}=4.18 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\right)$ in the tubes from 20 to $70^{\circ} \mathrm{C}$ at a rate of $4.5 \mathrm{~kg} / \mathrm{s}$. Heat is supplied by hot oil $\left(c_{p}=2.30 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\right)$ that enters the shell side at $170^{\circ} \mathrm{C}$ at a rate of $10 \mathrm{~kg} / \mathrm{s} .$ Determine the rate of heat transfer in the heat exchanger and the exit temperature of oil.

Naman Kumar
Naman Kumar
Numerade Educator
03:58

Problem 86

Steam is to be condensed in the condenser of a steam power plant at a temperature of $50^{\circ} \mathrm{C}$ with cooling water from a nearby lake, which enters the tubes of the condenser at $18^{\circ} \mathrm{C}$ at a rate of $101 \mathrm{~kg} / \mathrm{s}$ and leaves at $27^{\circ} \mathrm{C} .$ Determine the rate of condensation of the steam in the condenser.

Dading Chen
Dading Chen
Numerade Educator
01:34

Problem 87

Reconsider Prob. 5-86. Using appropriate software, investigate the effect of the inlet temperature of cooling water on the rate of condensation of steam. Let the inlet temperature vary from 10 to $20^{\circ} \mathrm{C},$ and assume the exit temperature to remain constant. Plot the rate of condensation of steam against the inlet temperature of the cooling water and discuss the results.

Naman Kumar
Naman Kumar
Numerade Educator
01:27

Problem 88

Two streams of water are mixed in an insulated container to form a third stream leaving the container. The first stream has a flow rate of $30 \mathrm{~kg} / \mathrm{s}$ and a temperature of $90^{\circ} \mathrm{C} .$ The flow rate of the second stream is $200 \mathrm{~kg} / \mathrm{s},$ and its temperature is $50^{\circ} \mathrm{C}$. What is the temperature of the third stream?

Naman Kumar
Naman Kumar
Numerade Educator
01:34

Problem 89

Two mass streams of the same ideal gas are mixed in a steady-flow chamber while receiving energy by heat transfer from the surroundings. The mixing process takes place at constant pressure with no work and negligible changes in kinetic and potential energies. Assume the gas has constant specific heats.
(a) Determine the expression for the final temperature of the mixture in terms of the rate of heat transfer to the mixing chamber and the inlet and exit mass flow rates.
(b) Obtain an expression for the volume flow rate at the exit of the mixing chamber in terms of the volume flow rates of the two inlet streams and the rate of heat transfer to the mixing chamber.
(c) For the special case of adiabatic mixing, show that the exit volume flow rate is the sum of the two inlet volume flow rates.

Naman Kumar
Naman Kumar
Numerade Educator
02:02

Problem 90

Water is heated in an insulated, constant-diameter tube by a $7-\mathrm{kW}$ electric resistance heater. If the water enters the heater steadily at $20^{\circ} \mathrm{C}$ and leaves at $75^{\circ} \mathrm{C},$ determine the mass flow rate of water.

Dading Chen
Dading Chen
Numerade Educator
03:55

Problem 91

A 110 -volt electrical heater is used to warm $0.3 \mathrm{~m}^{3} / \mathrm{s}$ of air at $100 \mathrm{kPa}$ and $15^{\circ} \mathrm{C}$ to $100 \mathrm{kPa}$ and $30^{\circ} \mathrm{C}$. How much current in amperes must be supplied to this heater?

Dading Chen
Dading Chen
Numerade Educator
01:25

Problem 92

The ducts of an air heating system pass through an unheated area. As a result of heat losses, the temperature of the air in the duct drops by $4^{\circ} \mathrm{C}$. If the mass flow rate of air is $120 \mathrm{~kg} / \mathrm{min},$ determine the rate of heat loss from the air to the cold environment.

Naman Kumar
Naman Kumar
Numerade Educator
01:13

Problem 93

The fan on a personal computer draws $0.3 \mathrm{ft}^{3} / \mathrm{s}$ of air at 14.7 psia and $70^{\circ} \mathrm{F}$ through the box containing the $\mathrm{CPU}$ and other components. Air leaves at 14.7 psia and $83^{\circ} \mathrm{F}$. Calculate the electrical power, in $\mathrm{kW}$, dissipated by the $\mathrm{PC}$ components.

Dominador Tan
Dominador Tan
Numerade Educator
02:02

Problem 94

Saturated liquid water is heated in a steady-flow steam boiler at a constant pressure of $2 \mathrm{MPa}$ at a rate of $4 \mathrm{~kg} / \mathrm{s}$ to an outlet temperature of $250^{\circ} \mathrm{C}$. Determine the rate of heat transfer in the boiler.

Naman Kumar
Naman Kumar
Numerade Educator
04:36

Problem 95

Water enters the tubes of a cold plate at $70^{\circ} \mathrm{F}$ with an average velocity of $40 \mathrm{ft} / \mathrm{min}$ and leaves at $105^{\circ} \mathrm{F}$. The diameter of the tubes is 0.25 in. Assuming 15 percent of the heat generated is dissipated from the components to the surroundings by convection and radiation, and the remaining 85 percent is removed by the cooling water, determine the amount of heat generated by the electronic devices mounted on the cold plate.

Dading Chen
Dading Chen
Numerade Educator
04:22

Problem 96

Consider a hollow-core printed circuit board $9 \mathrm{~cm}$ high and $18 \mathrm{~cm}$ long, dissipating a total of $15 \mathrm{~W}$. The width of the air gap in the middle of the $\mathrm{PCB}$ is $0.25 \mathrm{~cm}$. If the cooling air enters the $12-\mathrm{cm}$ -wide core at $25^{\circ} \mathrm{C}$ and $1 \mathrm{~atm}$ at a rate of $0.8 \mathrm{~L} / \mathrm{s},$ determine the average temperature at which the air leaves the hollow core.

Dading Chen
Dading Chen
Numerade Educator
04:57

Problem 97

A computer cooled by a fan contains eight $\mathrm{PCBs}$, each dissipating $10 \mathrm{~W}$ power. The height of the $\mathrm{PCBs}$ is $12 \mathrm{~cm}$ and the length is $18 \mathrm{~cm}$. The cooling air is supplied by a $25-\mathrm{W}$ fan mounted at the inlet. If the temperature rise of air as it flows through the case of the computer is not to exceed $10^{\circ} \mathrm{C},$ determine (a) the flow rate of the air that the fan needs to deliver and $(b)$ the fraction of the temperature rise of air that is due to the heat generated by the fan and its motor.

Dading Chen
Dading Chen
Numerade Educator
02:26

Problem 98

A desktop computer is to be cooled by a fan. The electronic components of the computer consume $60 \mathrm{~W}$ of power under full-load conditions. The computer is to operate in environments at temperatures up to $45^{\circ} \mathrm{C}$ and at elevations up to $3400 \mathrm{~m}$ where the average atmospheric pressure is $66.63 \mathrm{kPa}$ The exit temperature of air is not to exceed $60^{\circ} \mathrm{C}$ to meet the reliability requirements. Also, the average velocity of air is not to exceed $110 \mathrm{~m} / \mathrm{min}$ at the exit of the computer case where the fan is installed to keep the noise level down. Determine the flow rate of the fan that needs to be installed and the diameter of the casing of the fan.

Naman Kumar
Naman Kumar
Numerade Educator
01:08

Problem 99

Repeat Prob. $5-98$ for a computer that consumes $100 \mathrm{~W}$ of power.

Naman Kumar
Naman Kumar
Numerade Educator
02:31

Problem 100

A $4-m \times 5-m \times 6-m$ room is to be heated by an electric resistance heater placed in a short duct in the room. Initially, the room is at $15^{\circ} \mathrm{C},$ and the local atmospheric pressure is $98 \mathrm{kPa}$. The room is losing heat steadily to the outside at a rate of $150 \mathrm{~kJ} / \mathrm{min}$. A 200 -W fan circulates the air steadily through the duct and the electric heater at an average mass flow rate of $40 \mathrm{~kg} / \mathrm{min}$. The duct can be assumed to be adiabatic, and there is no air leaking in or out of the room. If it takes 25 min for the room air to reach an average temperature of $25^{\circ} \mathrm{C},$ find $(a)$ the power rating of the electric heater and $(b)$ the temperature rise that the air experiences each time it passes through the heater.

Naman Kumar
Naman Kumar
Numerade Educator
02:39

Problem 101

A house has an electric heating system that consists of a $300-\mathrm{W}$ fan and an electric resistance heating element placed in a duct. Air flows steadily through the duct at a rate of $0.6 \mathrm{~kg} / \mathrm{s}$ and experiences a temperature rise of $7^{\circ} \mathrm{C}$. The rate of heat loss from the air in the duct is estimated to be $300 \mathrm{~W}$. Determine the power rating of the electric resistance heating element.

Dading Chen
Dading Chen
Numerade Educator
01:35

Problem 102

A long roll of 2 -m-wide and 0.5 -cm-thick 1 -Mn manganese steel plate $\left(\rho=7854 \mathrm{~kg} / \mathrm{m}^{3}\right.$ and $\left.c_{p}=0.434 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\right)$ coming off a furnace at $820^{\circ} \mathrm{C}$ is to be quenched in an oil bath at $45^{\circ} \mathrm{C}$ to a temperature of $51.1^{\circ} \mathrm{C}$. If the metal sheet is moving at a steady velocity of $10 \mathrm{~m} / \mathrm{min}$, determine the required rate of heat removal from the oil to keep its temperature constant at $45^{\circ} \mathrm{C}$. Answer: $4368 \mathrm{~kW}$

Naman Kumar
Naman Kumar
Numerade Educator
02:07

Problem 103

Reconsider Prob. 5-102. Using appropriate software, investigate the effect of the moving velocity of the steel plate on the rate of heat transfer from the oil bath. Let the velocity vary from 5 to $50 \mathrm{~m} / \mathrm{min}$. Plot the rate of heat transfer against the plate velocity, and discuss the results.

Naman Kumar
Naman Kumar
Numerade Educator
01:40

Problem 104

The hot-water needs of a household are to be met by heating water at $55^{\circ} \mathrm{F}$ to $180^{\circ} \mathrm{F}$ with a parabolic solar collector at a rate of $4 \mathrm{lbm} / \mathrm{s}$. Water flows through a 1.25 -in-diameter thin aluminum tube whose outer surface is black-anodized in order to maximize its solar absorption ability. The centerline of the tube coincides with the focal line of the collector, and a glass sleeve is placed outside the tube to minimize the heat losses. If solar energy is transferred to water at a net rate of $400 \mathrm{Btu} / \mathrm{h}$ per ft length of the tube, determine the required length of the parabolic collector to meet the hot-water requirements of this house.

Naman Kumar
Naman Kumar
Numerade Educator
01:23

Problem 105

Argon steadily flows into a constant-pressure heater at $300 \mathrm{~K}$ and $100 \mathrm{kPa}$ with a mass flow rate of $6.24 \mathrm{~kg} / \mathrm{s} .$ Heat transfer in the rate of $150 \mathrm{~kW}$ is supplied to the argon as it flows through the heater. ( $a$ ) Determine the argon temperature at the heater exit, in ${ }^{\circ} \mathrm{C}$. $(b)$ Determine the argon volume flow rate at the heater exit, in $\mathrm{m}^{3} / \mathrm{s}$.

Naman Kumar
Naman Kumar
Numerade Educator
03:27

Problem 106

Steam enters a long, horizontal pipe with an inlet diameter of $D_{1}=16 \mathrm{~cm}$ at $2 \mathrm{MPa}$ and $300^{\circ} \mathrm{C}$ with a velocity of $2.5 \mathrm{~m} / \mathrm{s} .$ Farther downstream, the conditions are $1.8 \mathrm{MPa}$ and $250^{\circ} \mathrm{C},$ and the diameter is $D_{2}=14 \mathrm{~cm} .$ Determine $(a)$ the mass flow rate of the steam and $(b)$ the rate of heat transfer.

Dading Chen
Dading Chen
Numerade Educator
02:16

Problem 107

Refrigerant-134a enters the condenser of a refrigerator at $900 \mathrm{kPa}$ and $60^{\circ} \mathrm{C}$ and leaves as a saturated liquid at the same pressure. Determine the heat transfer from the refrigerant per unit mass.

Dading Chen
Dading Chen
Numerade Educator
01:42

Problem 108

A hair dryer is basically a duct in which a few layers of electric resistors are placed. A small fan pulls the air in and forces it through the resistors where it is heated. Air enters a 1200-W hair dryer at $100 \mathrm{kPa}$ and $22^{\circ} \mathrm{C}$ and leaves at $47^{\circ} \mathrm{C}$. The cross-sectional area of the hair dryer at the exit is $60 \mathrm{~cm}^{2}$. Neglecting the power consumed by the fan and the heat losses through the walls of the hair dryer, determine $(a)$ the volume flow rate of air at the inlet and $(b)$ the velocity of the air at the exit.

Naman Kumar
Naman Kumar
Numerade Educator
02:41

Problem 109

Reconsider Prob. 5-108. Using appropriate software, investigate the effect of the exit cross-sectional area of the hair dryer on the exit velocity. Let the exit area vary from 25 to $75 \mathrm{~cm}^{2}$. Plot the exit velocity against the exit cross-sectional area, and discuss the results. Include the effect of the flow kinetic energy in the analysis.

Naman Kumar
Naman Kumar
Numerade Educator
05:15

Problem 110

Air enters the duct of an air-conditioning system at 15 psia and $50^{\circ} \mathrm{F}$ at a volume flow rate of $450 \mathrm{ft}^{3} / \mathrm{min}$. The diameter of the duct is 10 in, and heat is transferred to the air in the duct from the surroundings at a rate of $2 \mathrm{Btu} / \mathrm{s} .$ Determine (a) the velocity of the air at the duct inlet and $(b)$ the temperature of the air at the exit.

Dading Chen
Dading Chen
Numerade Educator
02:21

Problem 111

Steam enters an insulated pipe at $200 \mathrm{kPa}$ and $200^{\circ} \mathrm{C}$ and leaves at $150 \mathrm{kPa}$ and $150^{\circ} \mathrm{C}$. The inlet-to-outlet diameter ratio for the pipe is $D_{1} / D_{2}=1.80 .$ Determine the inlet and exit velocities of the steam.

Naman Kumar
Naman Kumar
Numerade Educator
01:38

Problem 112

An insulated rigid tank is initially evacuated. A valve is opened, and atmospheric air at $95 \mathrm{kPa}$ and $17^{\circ} \mathrm{C}$ enters the tank until the pressure in the tank reaches $95 \mathrm{kPa}$, at which point the valve is closed. Determine the final temperature of the air in the tank. Assume constant specific heats.

Naman Kumar
Naman Kumar
Numerade Educator
04:02

Problem 113

A rigid, insulated tank that is initially evacuated is connected through a valve to a supply line that carries steam at 4 MPa. Now the valve is opened, and steam is allowed to flow into the tank until the pressure reaches $4 \mathrm{MPa},$ at which point the valve is closed. If the final temperature of the steam in the tank is $550^{\circ} \mathrm{C}$, determine the temperature of the steam in the supply line and the flow work per unit mass of the steam.

Dading Chen
Dading Chen
Numerade Educator
05:40

Problem 114

A $2-\mathrm{m}^{3}$ rigid insulated tank initially containing saturated water vapor at 1 MPa is connected through a valve to a supply line that carries steam at $400^{\circ} \mathrm{C}$. Now the valve is opened, and steam is allowed to flow slowly into the tank until the pressure in the tank rises to 2 MPa. At this instant the tank temperature is measured to be $300^{\circ} \mathrm{C}$. Determine the mass of the steam that has entered and the pressure of the steam in the supply line.

Dading Chen
Dading Chen
Numerade Educator
03:35

Problem 115

Consider a 35-L evacuated rigid bottle that is surrounded by the atmosphere at $100 \mathrm{kPa}$ and $22^{\circ} \mathrm{C}$. A valve at the neck of the bottle is now opened and the atmospheric air is allowed to flow into the bottle. The air trapped in the bottle eventually reaches thermal equilibrium with the atmosphere as a result of heat transfer through the wall of the bottle. The valve remains open during the process so that the trapped air also reaches mechanical equilibrium with the atmosphere. Determine the net heat transfer through the wall of the bottle during this filling process.

Dading Chen
Dading Chen
Numerade Educator
01:50

Problem 116

A $2-\mathrm{m}^{3}$ rigid tank initially contains air at $100 \mathrm{kPa}$ and $22^{\circ} \mathrm{C} .$ The tank is connected to a supply line through a valve. Air is flowing in the supply line at $600 \mathrm{kPa}$ and $22^{\circ} \mathrm{C}$. The valve is opened, and air is allowed to enter the tank until the pressure in the tank reaches the line pressure, at which point the valve is closed. A thermometer placed in the tank indicates that the air temperature at the final state is $77^{\circ} \mathrm{C}$. Determine (a) the mass of air that has entered the tank and $(b)$ the amount of heat transfer.

Naman Kumar
Naman Kumar
Numerade Educator
02:43

Problem 117

A $0.2-\mathrm{m}^{3}$ rigid tank equipped with a pressure regulator contains steam at $2 \mathrm{MPa}$ and $300^{\circ} \mathrm{C} .$ The steam in the tank is now heated. The regulator keeps the steam pressure constant by letting out some steam, but the temperature inside rises. Determine the amount of heat transferred when the steam temperature reaches $500^{\circ} \mathrm{C}$.

Dading Chen
Dading Chen
Numerade Educator
02:00

Problem 118

A $3-f t^{3}$ rigid tank initially contains saturated water vapor at $300^{\circ} \mathrm{F}$. The tank is connected by a valve to a supply line that carries steam at 200 psia and $400^{\circ} \mathrm{F}$. Now the valve is opened, and steam is allowed to enter the tank. Heat transfer takes place with the surroundings such that the temperature in the tank remains constant at $300^{\circ} \mathrm{F}$ at all times. The valve is closed when it is observed that one-half of the volume of the tank is occupied by liquid water. Find $(a)$ the final pressure in the tank, $(b)$ the amount of steam that has entered the tank, and $(c)$ the amount of heat transfer.

Naman Kumar
Naman Kumar
Numerade Educator
01:42

Problem 119

An insulated $40-\mathrm{ft}^{3}$ rigid tank contains air at 50 psia and $120^{\circ} \mathrm{F}$. A valve connected to the tank is now opened, and air is allowed to escape until the pressure inside drops to 25 psia. The air temperature during this process is kept constant by an electric resistance heater placed in the tank. Determine the electrical work done during this process.

Naman Kumar
Naman Kumar
Numerade Educator
01:22

Problem 120

A 4 -L pressure cooker has an operating pressure of $175 \mathrm{kPa}$. Initially, one-half of the volume is filled with liquid and the other half with vapor. If it is desired that the pressure cooker not run out of liquid water for 75 min, determine the highest rate of heat transfer allowed.

Naman Kumar
Naman Kumar
Numerade Educator
06:49

Problem 121

An air-conditioning system is to be filled from a rigid container that initially contains $5 \mathrm{~kg}$ of liquid $\mathrm{R}-134 \mathrm{a}$ at $24^{\circ} \mathrm{C}$. The valve connecting this container to the air-conditioning system is now opened until the mass in the container is $0.25 \mathrm{~kg}$, at which time the valve is closed. During this time, only liquid R-134a flows from the container. Presuming that the process is isothermal while the valve is open, determine the final quality of the $\mathrm{R}-134 \mathrm{a}$ in the container and the total heat transfer.

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
01:57

Problem 122

Oxygen is supplied to a medical facility from ten $1.5-\mathrm{ft}^{3}$ compressed oxygen tanks. Initially, these tanks are at 1500 psia and $80^{\circ} \mathrm{F}$. The oxygen is removed from these tanks slowly enough that the temperature in the tanks remains at $80^{\circ} \mathrm{F}$. After two weeks, the pressure in the tanks is 300 psia. Determine the mass of oxygen used and the total heat transfer to the tanks.

Naman Kumar
Naman Kumar
Numerade Educator
02:19

Problem 123

A $0.05-\mathrm{m}^{3}$ rigid tank initially contains refrigerant$134 \mathrm{a}$ at $0.8 \mathrm{MPa}$ and 100 percent quality. The tank is connected by a valve to a supply line that carries refrigerant- $134 \mathrm{a}$ at $1.2 \mathrm{MPa}$ and $40^{\circ} \mathrm{C} .$ Now the valve is opened, and the refrigerant is allowed to enter the tank. The valve is closed when it is observed that the tank contains saturated liquid at $1.2 \mathrm{MPa}$. Determine $(a)$ the mass of the refrigerant that has entered the tank and $(b)$ the amount of heat transfer.

Naman Kumar
Naman Kumar
Numerade Educator
01:57

Problem 124

A $0.12-\mathrm{m}^{3}$ rigid tank contains saturated refrigerant$134 \mathrm{a}$ at $800 \mathrm{kPa}$. Initially, 25 percent of the volume is occupied by liquid and the rest by vapor. A valve at the bottom of the tank is now opened, and liquid is withdrawn from the tank. Heat is transferred to the refrigerant such that the pressure inside the tank remains constant. The valve is closed when no liquid is left in the tank and vapor starts to come out. Determine the total heat transfer for this process.

Naman Kumar
Naman Kumar
Numerade Educator
05:01

Problem 125

A $0.3-\mathrm{m}^{3}$ rigid tank is filled with saturated liquid water at $200^{\circ} \mathrm{C}$. A valve at the bottom of the tank is opened, and liquid is withdrawn from the tank. Heat is transferred to the water such that the temperature in the tank remains constant. Determine the amount of heat that must be transferred by the time one-half of the total mass has been withdrawn.

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
01:51

Problem 126

The air-release flap on a hot-air balloon is used to release hot air from the balloon when appropriate. On one hot-air balloon, the air release opening has an area of $0.5 \mathrm{~m}^{2}$ and the filling opening has an area of $1 \mathrm{~m}^{2}$. During a twominute adiabatic flight maneuver, hot air enters the balloon at $100 \mathrm{kPa}$ and $35^{\circ} \mathrm{C}$ with a velocity of $2 \mathrm{~m} / \mathrm{s}$; the air in the balloon remains at $100 \mathrm{kPa}$ and $35^{\circ} \mathrm{C}$; and air leaves the balloon through the air-release flap at velocity $1 \mathrm{~m} / \mathrm{s}$. At the start of this maneuver, the volume of the balloon is $75 \mathrm{~m}^{3}$. Determine the final volume of the balloon and the work produced by the air inside the balloon as it expands the balloon skin.

Naman Kumar
Naman Kumar
Numerade Educator
02:09

Problem 127

A balloon initially contains $40 \mathrm{~m}^{3}$ of helium gas at atmospheric conditions of $100 \mathrm{kPa}$ and $17^{\circ} \mathrm{C} .$ The balloon is connected by a valve to a large reservoir that supplies helium gas at $125 \mathrm{kPa}$ and $25^{\circ} \mathrm{C}$. Now the valve is opened, and helium is allowed to enter the balloon until pressure equilibrium with the helium at the supply line is reached. The material of the balloon is such that its volume increases linearly with pressure. If no heat transfer takes place during this process, determine the final temperature in the balloon.

Naman Kumar
Naman Kumar
Numerade Educator
01:45

Problem 128

An insulated $0.15-\mathrm{m}^{3}$ tank contains helium at $3 \mathrm{MPa}$ and $130^{\circ} \mathrm{C}$. A valve is now opened, allowing some helium to escape. The valve is closed when one-half of the initial mass has escaped. Determine the final temperature and pressure in the tank.

Naman Kumar
Naman Kumar
Numerade Educator
05:10

Problem 129

A vertical piston-cylinder device initially contains $0.2 \mathrm{~m}^{3}$ of air at $20^{\circ} \mathrm{C}$. The mass of the piston is such that it maintains a constant pressure of 300 kPa inside. Now a valve connected to the cylinder is opened, and air is allowed to escape until the volume inside the cylinder is decreased by one-half. Heat transfer takes place during the process so that the temperature of the air in the cylinder remains constant. Determine $(a)$ the amount of air that has left the cylinder and (b) the amount of heat transfer.

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
01:47

Problem 130

A vertical piston-cylinder device initially contains $0.25 \mathrm{~m}^{3}$ of air at $600 \mathrm{kPa}$ and $300^{\circ} \mathrm{C}$. A valve connected to the cylinder is now opened, and air is allowed to escape until three-quarters of the mass leaves the cylinder, at which point the volume is $0.05 \mathrm{~m}^{3} .$ Determine the final temperature in the cylinder and the boundary work during this process.

Naman Kumar
Naman Kumar
Numerade Educator
07:13

Problem 131

A vertical piston-cylinder device initially contains $0.01 \mathrm{~m}^{3}$ of steam at $200^{\circ} \mathrm{C}$. The mass of the frictionless piston is such that it maintains a constant pressure of $500 \mathrm{kPa}$ inside. Now steam at $1 \mathrm{MPa}$ and $350^{\circ} \mathrm{C}$ is allowed to enter the cylinder from a supply line until the volume inside doubles. Neglecting any heat transfer that may have taken place during the process, determine $(a)$ the final temperature of the steam in the cylinder and $(b)$ the amount of mass that has entered.

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
00:55

Problem 132

A piston-cylinder device initially contains $0.6 \mathrm{~kg}$ of steam with a volume of $0.1 \mathrm{~m}^{3} .$ The mass of the piston is such that it maintains a constant pressure of $800 \mathrm{kPa}$. The cylinder is connected through a valve to a supply line that carries steam at 5 $\mathrm{MPa}$ and $500^{\circ} \mathrm{C}$. Now the valve is opened and steam is allowed to flow slowly into the cylinder until the volume of the cylinder doubles and the temperature in the cylinder reaches $250^{\circ} \mathrm{C},$ at which point the valve is closed. Determine $(a)$ the mass of steam that has entered and $(b)$ the amount of heat transfer.

Naman Kumar
Naman Kumar
Numerade Educator
01:09

Problem 133

The air in an insulated, rigid compressed-air tank whose volume is $0.5 \mathrm{~m}^{3}$ is initially at $2400 \mathrm{kPa}$ and $20^{\circ} \mathrm{C}$. Enough air is now released from the tank to reduce the pressure to $2000 \mathrm{kPa}$. Following this release, what is the temperature of the remaining air in the tank?

Naman Kumar
Naman Kumar
Numerade Educator
04:17

Problem 134

The weighted piston of the device shown in Fig. P5-134E maintains the pressure of the piston-cylinder contents at 200 psia. Initially, this system contains no mass. The valve is now opened, and steam from the line flows into the cylinder until the volume is $10 \mathrm{ft}^{3}$. This process is adiabatic, and the steam in the line remains at 300 psia and $450^{\circ} \mathrm{F}$. Determine the final temperature (and quality if appropriate) of the steam in the cylinder and the total work produced as the device is filled.

Naman Kumar
Naman Kumar
Numerade Educator
02:18

Problem 135

Repeat Prob. 5-134E when the supply line carries oxygen at 300 psia and $450^{\circ} \mathrm{F}$.

Naman Kumar
Naman Kumar
Numerade Educator
01:23

Problem 136

Underground water is being pumped into a pool whose cross section is $6 \mathrm{~m} \times 9 \mathrm{~m}$ while water is discharged through a 7 -cm-diameter orifice at a constant average velocity of $4 \mathrm{~m} / \mathrm{s}$. If the water level in the pool rises at a rate of $2.5 \mathrm{~cm} /$ min, determine the rate at which water is supplied to the pool, in $m^{3} / s$.

Naman Kumar
Naman Kumar
Numerade Educator
01:41

Problem 137

A long roll of 1 -m-wide and 0.5 -cm-thick 1 -Mn manganese steel plate $\left(\rho=7854 \mathrm{~kg} / \mathrm{m}^{3}\right)$ coming off a furnace is to be quenched in an oil bath to a specified temperature. If the metal sheet is moving at a steady velocity of $10 \mathrm{~m} / \mathrm{min}$, determine the mass flow rate of the steel plate through the oil bath.

Dading Chen
Dading Chen
Numerade Educator
00:54

Problem 138

Helium steadily enters a pipe with a mass flow rate of $8 \mathrm{~kg} / \mathrm{s}$ at $427^{\circ} \mathrm{C}$ and $100 \mathrm{kPa}$ and leaves the pipe at $27^{\circ} \mathrm{C} .$ The pressure during the process is constant at $100 \mathrm{kPa}$. ( $a$ ) Determine the heat transfer for the process, in $\mathrm{kW}$. $(b)$ Determine the volume flow rate of the helium at the pipe exit, in $\mathrm{m}^{3} / \mathrm{s}$.

Naman Kumar
Naman Kumar
Numerade Educator
02:03

Problem 139

Air at $4.18 \mathrm{~kg} / \mathrm{m}^{3}$ enters a nozzle that has an inlet-toexit area ratio of 2: 1 with a velocity of $120 \mathrm{~m} / \mathrm{s}$ and leaves with a velocity of $380 \mathrm{~m} / \mathrm{s}$. Determine the density of air at the exit.

Naman Kumar
Naman Kumar
Numerade Educator
02:04

Problem 140

Water is boiled at $100^{\circ} \mathrm{C}$ electrically by a $3-\mathrm{kW}$ resistance wire. Determine the rate of evaporation of water.

Naman Kumar
Naman Kumar
Numerade Educator
04:12

Problem 141

An air compressor compresses $15 \mathrm{~L} / \mathrm{s}$ of air at $120 \mathrm{kPa}$ and $20^{\circ} \mathrm{C}$ to $800 \mathrm{kPa}$ and $300^{\circ} \mathrm{C}$ while consuming $6.2 \mathrm{~kW}$ of power. How much of this power is being used to increase the pressure of the air versus the power needed to move the fluid through the compressor?

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
03:04

Problem 142

A steam turbine operates with $1.6 \mathrm{MPa}$ and $350^{\circ} \mathrm{C}$ steam at its inlet and saturated vapor at $30^{\circ} \mathrm{C}$ at its exit. The mass flow rate of the steam is $22 \mathrm{~kg} / \mathrm{s},$ and the turbine produces $12,350 \mathrm{~kW}$ of power. Determine the rate at which heat is lost through the casing of this turbine.

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
01:35

Problem 143

Refrigerant-134a enters an adiabatic compressor at 15 psia and $20^{\circ} \mathrm{F}$ with a volume flow rate of $10 \mathrm{ft}^{3} / \mathrm{s}$ and leaves at a pressure of 100 psia. The power input to the compressor is 45 hp. Find $(a)$ the mass flow rate of the refrigerant and $(b)$ the exit temperature.

Naman Kumar
Naman Kumar
Numerade Educator
01:22

Problem 144

Nitrogen gas flows through a long, constantdiameter adiabatic pipe. It enters at 100 psia and $120^{\circ} \mathrm{F}$ and leaves at 50 psia and $70^{\circ} \mathrm{F}$. Calculate the velocity of the nitrogen at the pipe's inlet and outlet.

Naman Kumar
Naman Kumar
Numerade Educator
02:27

Problem 145

A 110-V electric water heater warms $0.1 \mathrm{~L} / \mathrm{s}$ of water from 18 to $30^{\circ} \mathrm{C}$. Calculate the current in amperes that must be supplied to this heater.

Naman Kumar
Naman Kumar
Numerade Educator
01:48

Problem 146

A fan is powered by a 0.5 -hp motor and delivers air at a rate of $85 \mathrm{~m}^{3} / \mathrm{min}$. Determine the highest value for the average velocity of air mobilized by the fan. Take the density of air to be $1.18 \mathrm{~kg} / \mathrm{m}^{3}$

Naman Kumar
Naman Kumar
Numerade Educator
01:13

Problem 147

Steam enters a long, insulated pipe at $1200 \mathrm{kPa},$ $250^{\circ} \mathrm{C},$ and $4 \mathrm{~m} / \mathrm{s},$ and exits at $1000 \mathrm{kPa}$. The diameter of the pipe is $0.15 \mathrm{~m}$ at the inlet, and $0.1 \mathrm{~m}$ at the exit. Calculate the mass flow rate of the steam and its speed at the pipe outlet.

Naman Kumar
Naman Kumar
Numerade Educator
04:22

Problem 148

Steam enters a nozzle with a low velocity at $150^{\circ} \mathrm{C}$ and $200 \mathrm{kPa}$, and leaves as a saturated vapor at $75 \mathrm{kPa}$. There is a heat transfer from the nozzle to the surroundings in the amount of $26 \mathrm{~kJ}$ for every kilogram of steam flowing through the nozzle. Determine $(a)$ the exit velocity of the steam and ( $b$ ) the mass flow rate of the steam at the nozzle entrance if the nozzle exit area is $0.001 \mathrm{~m}^{2}$.

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
05:19

Problem 149

Consider a heat exchanger that uses hot air to heat cold water. Air enters this heat exchanger at 20 psia and $200^{\circ} \mathrm{F}$ at a rate of $100 \mathrm{ft}^{3} / \mathrm{min}$ and leaves at 17 psia and $100^{\circ} \mathrm{F}$. Water enters this unit at 20 psia and $50^{\circ} \mathrm{F}$ at a rate of $0.5 \mathrm{lbm} / \mathrm{s}$ and exits at 17 psia and $90^{\circ} \mathrm{F}$. Determine the total flow power, in hp, required for this unit and the flow work, in Btu/lbm, for both the air and water streams.

Nicholas Mogoi
Nicholas Mogoi
Numerade Educator
01:21

Problem 150

Saturated steam at 1 atm condenses on a vertical plate that is maintained at $90^{\circ} \mathrm{C}$ by circulating cooling water through the other side. If the rate of heat transfer by condensation to the plate is $180 \mathrm{~kJ} / \mathrm{s},$ determine the rate at which the condensate drips off the plate at the bottom.

Dading Chen
Dading Chen
Numerade Educator
01:14

Problem 151

Steam at $40^{\circ} \mathrm{C}$ condenses on the outside of a 5 -m-long, 3-cm-diameter thin horizontal copper tube by cooling water that enters the tube at $25^{\circ} \mathrm{C}$ at an average velocity of $2 \mathrm{~m} / \mathrm{s}$ and leaves at $35^{\circ} \mathrm{C}$. Determine the rate of condensation of steam.

Naman Kumar
Naman Kumar
Numerade Educator
07:00

Problem 152

In large steam power plants, the feedwater is frequently heated in a closed feedwater heater by using steam extracted from the turbine at some stage. Steam enters the feedwater heater at $1 \mathrm{MPa}$ and $200^{\circ} \mathrm{C}$ and leaves as saturated liquid at the same pressure. Feedwater enters the heater at $2.5 \mathrm{MPa}$ and $50^{\circ} \mathrm{C}$ and leaves at $10^{\circ} \mathrm{C}$ below the exit temperature of the steam. Determine the ratio of the mass flow rates of the extracted steam and the feedwater.

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
02:01

Problem 153

In large gas-turbine power plants, air is preheated by the exhaust gases in a heat exchanger called the regenerator before it enters the combustion chamber. Air enters the regenerator at $1 \mathrm{MPa}$ and $550 \mathrm{~K}$ at a mass flow rate of $800 \mathrm{~kg} / \mathrm{min}$. Heat is transferred to the air at a rate of $2700 \mathrm{~kJ} / \mathrm{s}$. Exhaust gases enter the regenerator at $140 \mathrm{kPa}$ and $800 \mathrm{~K}$ and leave at $130 \mathrm{kPa}$ and $600 \mathrm{~K}$. Treating the exhaust gases as air, determine $(a)$ the exit temperature of the air and $(b)$ the mass flow rate of exhaust gases.

Naman Kumar
Naman Kumar
Numerade Educator
02:26

Problem 154

Cold water enters a steam generator at $20^{\circ} \mathrm{C}$ and leaves as saturated vapor at $200^{\circ} \mathrm{C}$. Determine the fraction of heat used in the steam generator to preheat the liquid water from $20^{\circ} \mathrm{C}$ to the saturation temperature of $200^{\circ} \mathrm{C}$.

Dading Chen
Dading Chen
Numerade Educator
01:23

Problem 155

An ideal gas expands in an adiabatic turbine from $1200 \mathrm{~K}$ and $900 \mathrm{kPa}$ to $800 \mathrm{~K}$. Determine the turbine inlet volume flow rate of the gas, in $\mathrm{m}^{3} / \mathrm{s},$ required to produce turbine work output at the rate of $650 \mathrm{~kW}$. The average values of the specific heats for this gas over the temperature range and the gas constant are $c_{p}=1.13 \mathrm{~kJ} / \mathrm{kg} \cdot \mathrm{K}, c_{u}=0.83 \mathrm{~kJ} / \mathrm{kg} \cdot \mathrm{K},$ and $R=0.30 \mathrm{~kJ} / \mathrm{kg} \cdot \mathrm{K}$

Naman Kumar
Naman Kumar
Numerade Educator
01:10

Problem 156

Determine the power input for a compressor that compresses helium from $110 \mathrm{kPa}$ and $20^{\circ} \mathrm{C}$ to $400 \mathrm{kPa}$ and $200^{\circ} \mathrm{C}$. Helium enters this compressor through a $0.1-\mathrm{m}^{2}$ pipe at a velocity of $7 \mathrm{~m} / \mathrm{s}$.

Naman Kumar
Naman Kumar
Numerade Educator
01:09

Problem 157

Chickens with an average mass of $2.2 \mathrm{~kg}$ and average specific heat of $3.54 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}$ are to be cooled by chilled water that enters a continuous-flow-type immersion chiller at $0.5^{\circ} \mathrm{C}$. Chickens are dropped into the chiller at a uniform temperature of $15^{\circ} \mathrm{C}$ at a rate of 500 chickens per hour and are cooled to an average temperature of $3^{\circ} \mathrm{C}$ before they are taken out. The chiller gains heat from the surroundings at a rate of $200 \mathrm{~kJ} / \mathrm{h}$ Determine $(a)$ the rate of heat removal from the chickens, in $\mathrm{kW},$ and $(b)$ the mass flow rate of water, in $\mathrm{kg} / \mathrm{s},$ if the temperature rise of water is not to exceed $2^{\circ} \mathrm{C}$.

Naman Kumar
Naman Kumar
Numerade Educator
03:16

Problem 158

Repeat Prob. 5-157 assuming heat gain of the chiller is negligible.

Naman Kumar
Naman Kumar
Numerade Educator
01:23

Problem 159

A refrigeration system is being designed to cool eggs $\left(\rho=67.4 \mathrm{lbm} / \mathrm{ft}^{3}\right.$ and $\left.c_{p}=0.80 \mathrm{Btu} / \mathrm{lbm} \cdot{ }^{\circ} \mathrm{F}\right)$ with an average mass of 0.14 lbm from an initial temperature of $90^{\circ} \mathrm{F}$ to a final average temperature of $50^{\circ} \mathrm{F}$ by air at $34^{\circ} \mathrm{F}$ at a rate of 3000 eggs per hour. Determine $(a)$ the rate of heat removal from the eggs, in $\mathrm{Btu} / \mathrm{h}$ and $(b)$ the required volume flow rate of air, in $\mathrm{ft}^{3} / \mathrm{h},$ if the temperature rise of air is not to exceed $10^{\circ} \mathrm{F}$.

Naman Kumar
Naman Kumar
Numerade Educator
01:09

Problem 160

A glass bottle washing facility uses a well-agitated hot-water bath at $50^{\circ} \mathrm{C}$ that is placed on the ground. The bottles enter at a rate of 450 per minute at an ambient temperature of $20^{\circ} \mathrm{C}$ and leave at the water temperature. Each bottle has a mass of $150 \mathrm{~g}$ and removes $0.2 \mathrm{~g}$ of water as it leaves the bath wet. Make-up water is supplied at $15^{\circ} \mathrm{C}$. Disregarding any heat losses from the outer surfaces of the bath, determine the rate at which $(a)$ water and $(b)$ heat must be supplied to maintain steady operation.

Dominador Tan
Dominador Tan
Numerade Educator
01:40

Problem 161

In a dairy plant, milk at $4^{\circ} \mathrm{C}$ is pasteurized continuously at $72^{\circ} \mathrm{C}$ at a rate of $20 \mathrm{~L} / \mathrm{s}$ for $24 \mathrm{~h}$ a day and 365 days a year. The milk is heated to the pasteurizing temperature by hot water heated in a natural-gas-fired boiler that has an efficiency of 90 percent. The pasteurized milk is then cooled by cold water at $18^{\circ} \mathrm{C}$ before it is finally refrigerated back to $4^{\circ} \mathrm{C}$. To save energy and money, the plant installs a regenerator that has an effectiveness of 82 percent. If the cost of natural gas is $\$ 1.10 /$ therm $(1$ therm $=105.500 \mathrm{~kJ}),$ determine how much energy and money the regenerator will save this company per year.

Naman Kumar
Naman Kumar
Numerade Educator
03:30

Problem 162

Long aluminum wires of diameter $5 \mathrm{~mm}(\rho=$ $2702 \mathrm{~kg} / \mathrm{m}^{3}$ and $c_{p}=0.896 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}$ ) are extruded at a temperature of $350^{\circ} \mathrm{C}$ and are cooled to $50^{\circ} \mathrm{C}$ in atmospheric air at $25^{\circ} \mathrm{C} .$ If the wire is extruded at a velocity of $8 \mathrm{~m} / \mathrm{min},$ determine the rate of heat transfer from the wire to the extrusion room.

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
01:20

Problem 163

Repeat Prob. $5-162$ for a copper wire $\left(\rho=8950 \mathrm{~kg} / \mathrm{m}^{3}\right.$ and $\left.c_{p}=0.383 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\right)$

Naman Kumar
Naman Kumar
Numerade Educator
04:07

Problem 164

Steam at 80 psia and $400^{\circ} \mathrm{F}$ is mixed with water at $60^{\circ} \mathrm{F}$ and 80 psia steadily in an adiabatic device. Steam enters the device at a rate of $0.05 \mathrm{lbm} / \mathrm{s},$ while the water enters at $1 \mathrm{lbm} / \mathrm{s} .$ Determine the temperature of the mixture leaving this device when the outlet pressure is 80 psia.

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
01:55

Problem 165

A constant-pressure R-134a vapor separation unit separates the liquid and vapor portions of a saturated mixture into two separate outlet streams. Determine the flow power needed to pass $6 \mathrm{~L} / \mathrm{s}$ of $\mathrm{R}-134 \mathrm{a}$ at $320 \mathrm{kPa}$ and 55 percent quality through this unit. What is the mass flow rate, in $\mathrm{kg} / \mathrm{s}$, of the two outlet streams?

Naman Kumar
Naman Kumar
Numerade Educator
01:20

Problem 166

It is well established that indoor air quality (IAQ) has a significant effect on general health and productivity of employees at a workplace. A study showed that enhancing IAQ by increasing the building ventilation from $5 \mathrm{cfm}$ (cubic feet per minute) to 20 cfm increased the productivity by 0.25 percent, valued at $\$ 90$ per person per year, and decreased the respiratory illnesses by 10 percent for an average annual savings of $\$ 39$ per person while increasing the annual energy consumption by $\$ 6$ and the equipment cost by about $\$ 4$ per person per year (ASHRAE Journal, December 1998). For a workplace with 120 employees, determine the net monetary benefit of installing an enhanced IAQ system to the employer per year.

Naman Kumar
Naman Kumar
Numerade Educator
01:18

Problem 167

The average atmospheric pressure in Spokane, Washington (elevation $=2350 \mathrm{ft}$ ), is 13.5 psia, and the average winter temperature is $36.5^{\circ} \mathrm{F}$. The pressurization test of a 9-ft-high, $4500-\mathrm{ft}^{2}$ older home revealed that the seasonal average infiltration rate of the house is 2.2 air changes per hour $(\mathrm{ACH}) .$ That is, the entire air in the house is replaced completely 2.2 times per hour by the outdoor air. It is suggested that the infiltration rate of the house can be reduced by half to 1.1 ACH by winterizing the doors and the windows. If the house is heated by natural gas whose unit cost is $\$ 1.24 /$ therm and the heating season can be taken to be six months, determine how much the homeowner will save from the heating costs per year by this winterization project. Assume the house is maintained at $72^{\circ} \mathrm{F}$ at all times and the efficiency of the furnace is $0.92 .$ Also assume the latent heat load during the heating season to be negligible.

Naman Kumar
Naman Kumar
Numerade Educator
04:18

Problem 168

The ventilating fan of the bathroom of a building has a volume flow rate of $30 \mathrm{~L} / \mathrm{s}$ and runs continuously. The building is located in San Francisco, California, where the average winter temperature is $12.2^{\circ} \mathrm{C},$ and it is maintained at $22^{\circ} \mathrm{C}$ at all times. The building is heated by electricity whose unit cost is $\$ 0.12 / \mathrm{kWh}$. Determine the amount and cost of the heat "vented out" per month in winter.

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
01:04

Problem 169

A small positioning control rocket in a satellite is driven by a $2-\mathrm{ft}^{3}$ container filled with $\mathrm{R}-134 \mathrm{a}$ at $-10^{\circ} \mathrm{F}$. Upon launch, the container is completely filled with saturated liquid R-134a. The rocket is designed for short bursts of 5 -s duration. During each burst, the mass flow rate leaving the rocket is $0.05 \mathrm{lbm} / \mathrm{s} .$ How many such bursts can this rocket experience before the quality in the container is 90 percent or more, presuming that the temperature of the container contents is maintained at $-10^{\circ} \mathrm{F}$ ?

Naman Kumar
Naman Kumar
Numerade Educator
03:01

Problem 170

Determine the rate of sensible heat loss from a building due to infiltration if the outdoor air at $-5^{\circ} \mathrm{C}$ and $95 \mathrm{kPa}$ enters the building at a rate of $60 \mathrm{~L} / \mathrm{s}$ when the indoors is maintained at $25^{\circ} \mathrm{C}$

Dading Chen
Dading Chen
Numerade Educator
01:00

Problem 171

Consider a large classroom on a hot summer day with 150 students, each dissipating $60 \mathrm{~W}$ of sensible heat. All the lights, with $6.0 \mathrm{~kW}$ of rated power, are kept on. The room has no external walls, and thus heat gain through the walls and the roof is negligible. Chilled air is available at $15^{\circ} \mathrm{C},$ and the temperature of the return air is not to exceed $25^{\circ} \mathrm{C}$. Determine the required flow rate of air, in $\mathrm{kg} / \mathrm{s},$ that needs to be supplied to the room to keep the average temperature of the room constant.

Naman Kumar
Naman Kumar
Numerade Educator
03:35

Problem 172

An air-conditioning system requires airflow at the main supply duct at a rate of $130 \mathrm{~m}^{3} / \mathrm{min}$. The average velocity of air in the circular duct is not to exceed $8 \mathrm{~m} / \mathrm{s}$ to avoid excessive vibration and pressure drops. Assuming the fan converts 80 percent of the electrical energy it consumes into kinetic energy of air, determine the size of the electric motor needed to drive the fan and the diameter of the main duct. Take the density of air to be $1.20 \mathrm{~kg} / \mathrm{m}^{3}$

Dading Chen
Dading Chen
Numerade Educator
04:40

Problem 173

A building with an internal volume of $400 \mathrm{~m}^{3}$ is to be heated by a $30-\mathrm{kW}$ electric resistance heater placed in the duct inside the building. Initially, the air in the building is at $14^{\circ} \mathrm{C}$ and the local atmospheric pressure is $95 \mathrm{kPa}$. The building is losing heat to the surroundings at a steady rate of $450 \mathrm{~kJ} / \mathrm{min}$. Air is forced to flow through the duct and the heater steadily by a $250-\mathrm{W}$ fan, and it experiences a temperature rise of $5^{\circ} \mathrm{C}$ each time it passes through the duct, which may be assumed to be adiabatic.
(a) How long will it take for the air inside the building to reach an average temperature of $24^{\circ} \mathrm{C} ?$
(b) Determine the average mass flow rate of air through the duct.

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
06:20

Problem 174

The maximum flow rate of standard shower heads is about 3.5 gpm $(13.3 \mathrm{~L} / \mathrm{min})$ and can be reduced to 2.75 gpm (10.5 L/min) by switching to low-flow shower heads that are equipped with flow controllers. Consider a family of four, with each person taking a 5 -min shower every morning. City water at $15^{\circ} \mathrm{C}$ is heated to $55^{\circ} \mathrm{C}$ in an electric water heater and tempered to $42^{\circ} \mathrm{C}$ by cold water at the $\mathrm{T}$ -elbow of the shower before being routed to the shower heads. Assuming a constant specific heat of $4.18 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}$ for water, determine $(a)$ the ratio of the flow rates of the hot and cold water as they enter the T-elbow and ( $b$ ) the amount of electricity that will be saved per year, in $\mathrm{kWh}$, by replacing the standard shower heads with the low-flow ones.

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
01:43

Problem 175

Reconsider Prob. 5-174. Using appropriate software, investigate the effect of the inlet temperature of cold water on the energy saved by using the lowflow shower head. Let the inlet temperature vary from $10^{\circ} \mathrm{C}$ to $20^{\circ} \mathrm{C} .$ Plot the electric energy savings against the water inlet temperature, and discuss the results.

Naman Kumar
Naman Kumar
Numerade Educator
05:18

Problem 176

Submarines change their depth by adding or removing air from rigid ballast tanks, thereby displacing seawater in the tanks. Consider a submarine that has a $700-\mathrm{m}^{3}$ air-ballast tank originally partially filled with $100 \mathrm{~m}^{3}$ of air at $1500 \mathrm{kPa}$ and $15^{\circ} \mathrm{C} .$ For the submarine to surface, air at $1500 \mathrm{kPa}$ and $20^{\circ} \mathrm{C}$ is pumped into the ballast tank until it is entirely filled with air. The tank is filled so quickly that the process is adiabatic, and the seawater leaves the tank at $15^{\circ} \mathrm{C}$. Determine the final temperature and mass of the air in the ballast tank.

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
02:05

Problem 177

In Prob. 5-176, presume that air is added to the tank in such a way that the temperature and pressure of the air in the tank remain constant. Determine the final mass of the air in the ballast tank under this condition. Also determine the total heat transfer while the tank is being filled in this manner.

Naman Kumar
Naman Kumar
Numerade Educator
04:08

Problem 178

Steam enters a turbine steadily at $7 \mathrm{MPa}$ and $600^{\circ} \mathrm{C}$ with a velocity of $60 \mathrm{~m} / \mathrm{s}$ and leaves at $25 \mathrm{kPa}$ with a quality of 95 percent. A heat loss of $20 \mathrm{~kJ} / \mathrm{kg}$ occurs during the process. The inlet area of the turbine is $150 \mathrm{~cm}^{2},$ and the exit area is $1400 \mathrm{~cm}^{2}$. Determine $(a)$ the mass flow rate of the steam, (b) the exit velocity, and $(c)$ the power output.

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
03:21

Problem 179

Reconsider Prob. 5-178. Using appropriate software, investigate the effects of turbine exit area and turbine exit pressure on the exit velocity and power output of the turbine. Let the exit pressure vary from 10 to $50 \mathrm{kPa}$ (with the same quality), and let the exit area vary from 1000 to $3000 \mathrm{~cm}^{2}$. Plot the exit velocity and the power outlet against the exit pressure for the exit areas of $1000,2000,$ and $3000 \mathrm{~cm}^{2},$ and discuss the results.

Naman Kumar
Naman Kumar
Numerade Educator
03:31

Problem 180

It is proposed to have a water heater that consists of an insulated pipe of 7.5 -cm diameter and an electric resistor inside. Cold water at $20^{\circ} \mathrm{C}$ enters the heating section steadily at a rate of $24 \mathrm{~L} / \mathrm{min} .$ If water is to be heated to $48^{\circ} \mathrm{C},$ determine
(a) the power rating of the resistance heater and $(b)$ the average velocity of the water in the pipe.

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
06:38

Problem 181

A liquid $R-134 a$ bottle has an internal volume of $0.0015 \mathrm{~m}^{3} .$ Initially it contains $0.55 \mathrm{~kg}$ of $\mathrm{R}-134 \mathrm{a}$ (saturated mixture) at $26^{\circ} \mathrm{C}$. A valve is opened and R-134a vapor only (no liquid) is allowed to escape slowly such that temperature remains constant until the mass of R-134a remaining is $0.15 \mathrm{~kg} .$ Find the heat transfer with the surroundings that is needed to maintain the temperature and pressure of the $\mathrm{R}-134 \mathrm{a}$ constant.

Naman Kumar
Naman Kumar
Numerade Educator
05:18

Problem 182

A piston-cylinder device initially contains $2 \mathrm{~kg}$ of refrigerant- $134 \mathrm{a}$ at $800 \mathrm{kPa}$ and $80^{\circ} \mathrm{C}$. At this state, the piston is touching on a pair of stops at the top. The mass of the piston is such that a 500 -kPa pressure is required to move it. A valve at the bottom of the cylinder is opened, and R-134a is withdrawn from the cylinder. After a while, the piston is observed to move and the valve is closed when half of the refrigerant is withdrawn from the cylinder and the temperature in the tank drops to $20^{\circ} \mathrm{C}$. Determine $(a)$ the work done and $(b)$ the heat transfer.

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
06:50

Problem 183

A piston-cylinder device initially contains $1.2 \mathrm{~kg}$ of air at $700 \mathrm{kPa}$ and $200^{\circ} \mathrm{C}$. At this state, the piston is touching on a pair of stops. The mass of the piston is such that $600-\mathrm{kPa}$ pressure is required to move it. A valve at the bottom of the tank is opened, and air is withdrawn from the cylinder. The valve is closed when the volume of the cylinder decreases to 80 percent of the initial volume. If it is estimated that $40 \mathrm{~kJ}$ of heat is lost from the cylinder, determine $(a)$ the final temperature of the air in the cylinder, $(b)$ the amount of mass that has escaped from the cylinder, and $(c)$ the work done. Use constant specific heats at the average temperature.

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
06:33

Problem 184

A pressure cooker is a pot that cooks food much faster than ordinary pots by maintaining a higher pressure and temperature during cooking. The pressure inside the pot is controlled by a pressure regulator (the petcock) that keeps the pressure at a constant level by periodically allowing some steam to escape, thus preventing any excess pressure buildup. Pressure cookers, in general, maintain a gage pressure of 2 atm (or 3 atm absolute) inside. Therefore, pressure cookers cook at a temperature of about $133^{\circ} \mathrm{C}$ instead of $100^{\circ} \mathrm{C}$, cutting the cooking time by as much as 70 percent while minimizing the loss of nutrients. The newer pressure cookers use a spring valve with several pressure settings rather than a weight on the cover.

A certain pressure cooker has a volume of $6 \mathrm{~L}$ and an operating pressure of 75 kPa gage. Initially, it contains $1 \mathrm{~kg}$ of water. Heat is supplied to the pressure cooker at a rate of $500 \mathrm{~W}$ for 30 min after the operating pressure is reached. Assuming an atmospheric pressure of $100 \mathrm{kPa}$, determine $(a)$ the temperature at which cooking takes place and $(b)$ the amount of water left in the pressure cooker at the end of the process.

Naman Kumar
Naman Kumar
Numerade Educator
11:29

Problem 185

A tank with an internal volume of $1 \mathrm{~m}^{3}$ contains air at $800 \mathrm{kPa}$ and $25^{\circ} \mathrm{C}$. A valve on the tank is opened, allowing air to escape, and the pressure inside quickly drops to $150 \mathrm{kPa}$ at which point the valve is closed. Assume there is negligible heat transfer from the tank to the air left in the tank.
(a) Using the approximation $h_{e} \approx$ constant $=h_{e, \mathrm{avg}}=0.5$ $\left(h_{1}+h_{2}\right),$ calculate the mass withdrawn during the process.
(b) Consider the same process but broken into two parts. That is, consider an intermediate state at $P_{2}=400 \mathrm{kPa}$ calculate the mass removed during the process from $P_{1}=800 \mathrm{kPa}$ to $P_{2}$ and then the mass removed during the process from $P_{2}$ to $P_{3}=150 \mathrm{kPa},$ using the type of approximation used in part $(a),$ and add the two to get the total mass removed.
(c) Calculate the mass removed if the variation of $h_{e}$ is accounted for.

Vidhi Bhatt
Vidhi Bhatt
Numerade Educator
06:41

Problem 186

In a single-flash geothermal power plant, geothermal water enters the flash chamber (a throttling valve) at $230^{\circ} \mathrm{C}$ as a saturated liquid at a rate of $50 \mathrm{~kg} / \mathrm{s}$. The steam resulting from the flashing process enters a turbine and leaves at $20 \mathrm{kPa}$ with a moisture content of 5 percent. Determine the temperature of the steam after the flashing process and the power output from the turbine if the pressure of the steam at the exit of the flash chamber is $(a) 1 \mathrm{MPa}$. (b) $500 \mathrm{kPa}$ (c) $100 \mathrm{kPa},$ (d) $50 \mathrm{kPa}$.

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
04:25

Problem 187

An adiabatic air compressor is to be powered by a direct-coupled adiabatic steam turbine that is also driving a generator. Steam enters the turbine at $12.5 \mathrm{MPa}$ and $500^{\circ} \mathrm{C}$ at a rate of $25 \mathrm{~kg} / \mathrm{s}$ and exits at $10 \mathrm{kPa}$ and a quality of $0.92 .$ Air enters the compressor at $98 \mathrm{kPa}$ and $295 \mathrm{~K}$ at a rate of $10 \mathrm{~kg} / \mathrm{s}$ and exits at $1 \mathrm{MPa}$ and $620 \mathrm{~K}$. Determine the net power delivered to the generator by the turbine.

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
03:36

Problem 188

The turbocharger of an internal combustion engine consists of a turbine and a compressor. Hot exhaust gases flow through the turbine to produce work, and the work output from the turbine is used as the work input to the compressor. The pressure of ambient air is increased as it flows through the compressor before it enters the engine cylinders. Thus, the purpose of a turbocharger is to increase the pressure of air so that more air gets into the cylinder. Consequently, more fuel can be burned and more power can be produced by the engine.

In a turbocharger, exhaust gases enter the turbine at $400^{\circ} \mathrm{C}$ and $120 \mathrm{kPa}$ at a rate of $0.02 \mathrm{~kg} / \mathrm{s}$ and leave at $350^{\circ} \mathrm{C}$. Air enters the compressor at $50^{\circ} \mathrm{C}$ and $100 \mathrm{kPa}$ and leaves at $130 \mathrm{kPa}$ at a rate of $0.018 \mathrm{~kg} / \mathrm{s}$. The compressor increases the air pressure with a side effect: It also increases the air temperature, which increases the possibility that a gasoline engine will experience an engine knock. To avoid this, an aftercooler is placed after the compressor to cool the warm air with cold ambient air before it enters the engine cylinders. It is estimated that the aftercooler must decrease the air temperature below $80^{\circ} \mathrm{C}$ if $\mathrm{knock}$ is to be avoided. The cold ambient air enters the aftercooler at $30^{\circ} \mathrm{C}$ and leaves at $40^{\circ} \mathrm{C}$. Disregarding any frictional losses in the turbine and the compressor and treating the exhaust gases as air, determine $(a)$ the temperature of the air at the compressor outlet and $(b)$ the minimum volume flow rate of ambient air required to avoid knock.

Naman Kumar
Naman Kumar
Numerade Educator
05:25

Problem 189

A $D_{0}=10$ -m-diameter tank is initially filled with water $2 \mathrm{~m}$ above the center of a $D=10-\mathrm{cm}$ -diameter valve near the bottom. The tank surface is open to the atmosphere, and the tank drains through a $L=100$ -m-long pipe connected to the valve. The friction factor of the pipe is given to be $f=0.015,$ and the discharge velocity is expressed as $V=\sqrt{\frac{2 g z}{1.5+f L / D}}$ where $z$ is the water height above the center of the valve. Determine (a) the initial discharge velocity from the tank and $(b)$ the time required to empty the tank. The tank can be considered to be empty when the water level drops to the center of the valve.

Hariprasad Annamalai
Hariprasad Annamalai
Numerade Educator
04:22

Problem 190

Consider an evacuated rigid bottle of volume $V$ that is surrounded by the atmosphere at pressure $P_{0}$ and temperature $T_{0} .$ A valve at the neck of the bottle is now opened and the atmospheric air is allowed to flow into the bottle. The air trapped in the bottle eventually reaches thermal equilibrium with the atmosphere as a result of heat transfer through the wall of the bottle. The valve remains open during the process so that the trapped air also reaches mechanical equilibrium with the atmosphere. Determine the net heat transfer through the wall of the bottle during this filling process in terms of the properties of the system and the surrounding atmosphere.

Naman Kumar
Naman Kumar
Numerade Educator
02:22

Problem 191

An adiabatic heat exchanger is used to heat cold water at $15^{\circ} \mathrm{C}$ entering at a rate of $5 \mathrm{~kg} / \mathrm{s}$ with hot air at $90^{\circ} \mathrm{C}$ entering also at a rate of $5 \mathrm{~kg} / \mathrm{s}$. If the exit temperature of hot air is $20^{\circ} \mathrm{C},$ the exit temperature of cold water is
(a) $27^{\circ} \mathrm{C}$
(b) $32^{\circ} \mathrm{C}$
(c) $52^{\circ} \mathrm{C}$
(d) $85^{\circ} \mathrm{C}$
(e) $90^{\circ} \mathrm{C}$

Dading Chen
Dading Chen
Numerade Educator
04:04

Problem 192

A heat exchanger is used to heat cold water at $15^{\circ} \mathrm{C}$ entering at a rate of $2 \mathrm{~kg} / \mathrm{s}$ with hot air at $85^{\circ} \mathrm{C}$ entering at a rate of $3 \mathrm{~kg} / \mathrm{s}$. The heat exchanger is not insulated and is losing heat at a rate of $25 \mathrm{~kJ} / \mathrm{s}$. If the exit temperature of hot air is $20^{\circ} \mathrm{C},$ the exit temperature of cold water is
(a) $28^{\circ} \mathrm{C}$
(b) $35^{\circ} \mathrm{C}$
(c) $38^{\circ} \mathrm{C}$
(d) $41^{\circ} \mathrm{C}$
(e) $80^{\circ} \mathrm{C}$

Naman Kumar
Naman Kumar
Numerade Educator
02:28

Problem 193

An adiabatic heat exchanger is used to heat cold water at $15^{\circ} \mathrm{C}$ entering at a rate of $5 \mathrm{~kg} / \mathrm{s}$ with hot water at $90^{\circ} \mathrm{C}$ entering at a rate of $4 \mathrm{~kg} / \mathrm{s}$. If the exit temperature of hot water is $50^{\circ} \mathrm{C}$, the exit temperature of cold water is
(a) $42^{\circ} \mathrm{C}$
(b) $47^{\circ} \mathrm{C}$
(c) $55^{\circ} \mathrm{C}$
(d) $78^{\circ} \mathrm{C}$
(e) $90^{\circ} \mathrm{C}$

Dading Chen
Dading Chen
Numerade Educator
02:13

Problem 194

In a shower, cold water at $10^{\circ} \mathrm{C}$ flowing at a rate of $5 \mathrm{~kg} / \mathrm{min}$ is mixed with hot water at $60^{\circ} \mathrm{C}$ flowing at a rate of $2 \mathrm{~kg} / \mathrm{min}$. The exit temperature of the mixture is
(a) $24.3^{\circ} \mathrm{C}$
(b) $35.0^{\circ} \mathrm{C}$
(c) $40.0^{\circ} \mathrm{C}$
(d) $44.3^{\circ} \mathrm{C}$
(e) $55.2^{\circ} \mathrm{C}$

Dading Chen
Dading Chen
Numerade Educator
05:49

Problem 195

In a heating system, cold outdoor air at $7^{\circ} \mathrm{C}$ flowing at a rate of $4 \mathrm{~kg} / \mathrm{min}$ is mixed adiabatically with heated air at $70^{\circ} \mathrm{C}$ flowing at a rate of $5 \mathrm{~kg} / \mathrm{min}$. The exit temperature of the mixture is
(a) $34^{\circ} \mathrm{C}$
(b) $39^{\circ} \mathrm{C}$
(c) $42^{\circ} \mathrm{C}$
(d) $57^{\circ} \mathrm{C}$
(e) $70^{\circ} \mathrm{C}$

Prabhat Tyagi
Prabhat Tyagi
Numerade Educator
01:44

Problem 196

Refrigerant-134a expands in an adiabatic turbine from $1.2 \mathrm{MPa}$ and $100^{\circ} \mathrm{C}$ to $0.18 \mathrm{MPa}$ and $50^{\circ} \mathrm{C}$ at a rate of $1.25 \mathrm{~kg} / \mathrm{s}$. The power output of the turbine is
(a) $44.7 \mathrm{~kW}$
(b) $66.4 \mathrm{~kW}$
(c) $72.7 \mathrm{~kW}$
(d) $89.2 \mathrm{~kW}$
(e) $112.0 \mathrm{~kW}$

Dading Chen
Dading Chen
Numerade Educator
View

Problem 197

Hot combustion gases (assumed to have the properties of air at room temperature) enter a gas turbine at $1 \mathrm{MPa}$ and $1500 \mathrm{~K}$ at a rate of $0.1 \mathrm{~kg} / \mathrm{s},$ and exit at $0.2 \mathrm{MPa}$ and $900 \mathrm{~K}$
If heat is lost from the turbine to the surroundings at a rate of $15 \mathrm{~kJ} / \mathrm{s},$ the power output of the gas turbine is
(a) $15 \mathrm{~kW}$
(b) $30 \mathrm{~kW}$
(c) $45 \mathrm{~kW}$
(d) $60 \mathrm{~kW}$
(e) $75 \mathrm{~kW}$

Susan Hallstrom
Susan Hallstrom
Numerade Educator
02:34

Problem 198

Steam expands in a turbine from $4 \mathrm{MPa}$ and $500^{\circ} \mathrm{C}$ to $0.5 \mathrm{MPa}$ and $250^{\circ} \mathrm{C}$ at a rate of $1350 \mathrm{~kg} / \mathrm{h}$. Heat is lost from the turbine at a rate of $25 \mathrm{~kJ} / \mathrm{s}$ during the process. The power output of the turbine is
(a) $157 \mathrm{~kW}$
(b) $207 \mathrm{~kW}$
(c) $182 \mathrm{~kW}$
(d) $287 \mathrm{~kW}$
(e) $246 \mathrm{~kW}$

Dading Chen
Dading Chen
Numerade Educator
01:48

Problem 199

Steam is compressed by an adiabatic compressor from $0.2 \mathrm{MPa}$ and $150^{\circ} \mathrm{C}$ to $0.8 \mathrm{MPa}$ and $350^{\circ} \mathrm{C}$ at a rate of $1.30 \mathrm{~kg} / \mathrm{s} .$ The power input to the compressor is
(a) $511 \mathrm{~kW}$
(b) $393 \mathrm{~kW}$
(c) $302 \mathrm{~kW}$
(d) $717 \mathrm{~kW}$
(e) $901 \mathrm{~kW}$

Dading Chen
Dading Chen
Numerade Educator
02:27

Problem 200

Refrigerant-134a is compressed by a compressor from the saturated vapor state at $0.14 \mathrm{MPa}$ to $0.9 \mathrm{MPa}$ and $60^{\circ} \mathrm{C}$ at a rate of $0.108 \mathrm{~kg} / \mathrm{s} .$ The refrigerant is cooled at a rate of $1.10 \mathrm{~kJ} / \mathrm{s}$ during compression. The power input to the compressor is
(a) $4.94 \mathrm{~kW}$
(b) $6.04 \mathrm{~kW}$
(c) $7.14 \mathrm{~kW}$
(d) $7.50 \mathrm{~kW}$
(e) $8.13 \mathrm{~kW}$

Dading Chen
Dading Chen
Numerade Educator
07:54

Problem 201

Refrigerant-134a at $1.4 \mathrm{MPa}$ and $70^{\circ} \mathrm{C}$ is throttled to a pressure of 0.6 MPa. The temperature of the refrigerant after throttling is
(a) $70^{\circ} \mathrm{C}$
(b) $66^{\circ} \mathrm{C}$
(c) $57^{\circ} \mathrm{C}$
(d) $49^{\circ} \mathrm{C}$
(e) $22^{\circ} \mathrm{C}$

Naman Kumar
Naman Kumar
Numerade Educator
05:52

Problem 202

Steam enters a diffuser steadily at $0.5 \mathrm{MPa}, 300^{\circ} \mathrm{C}$ and $90 \mathrm{~m} / \mathrm{s}$ at a rate of $3.5 \mathrm{~kg} / \mathrm{s}$. The inlet area of the diffuser is
(a) $22 \mathrm{~cm}^{2}$
(b) $53 \mathrm{~cm}^{2}$
(c) $126 \mathrm{~cm}^{2}$
(d) $175 \mathrm{~cm}^{2}$
(e) $203 \mathrm{~cm}^{2}$

Naman Kumar
Naman Kumar
Numerade Educator
01:44

Problem 203

Steam is accelerated by a nozzle steadily from a low velocity to a velocity of $280 \mathrm{~m} / \mathrm{s}$ at a rate of $2.5 \mathrm{~kg} / \mathrm{s}$. If the temperature and pressure of the steam at the nozzle exit are $400^{\circ} \mathrm{C}$ and $2 \mathrm{MPa}$, the exit area of the nozzle is
(a) $8.4 \mathrm{~cm}^{2}$
(b) $10.7 \mathrm{~cm}^{2}$
(c) $13.5 \mathrm{~cm}^{2}$
(d) $19.6 \mathrm{~cm}^{2}$
(e) $23.0 \mathrm{~cm}^{2}$

Narayan Hari
Narayan Hari
Numerade Educator
00:51

Problem 204

Air at $27^{\circ} \mathrm{C}$ and 5 atm is throttled by a valve to 1 atm. If the valve is adiabatic and the change in kinetic energy is negligible, the exit temperature of air will be
(a) $10^{\circ} \mathrm{C}$
(b) $15^{\circ} \mathrm{C}$
(c) $20^{\circ} \mathrm{C}$
(d) $23^{\circ} \mathrm{C}$
(e) $27^{\circ} \mathrm{C}$

Dading Chen
Dading Chen
Numerade Educator
02:25

Problem 205

Steam at $1 \mathrm{MPa}$ and $300^{\circ} \mathrm{C}$ is throttled adiabatically to a pressure of 0.4 MPa. If the change in kinetic energy is negligible, the specific volume of the steam after throttling is
(a) $0.358 \mathrm{~m}^{3} / \mathrm{kg}$
(b) $0.233 \mathrm{~m}^{3} / \mathrm{kg}$
(c) $0.375 \mathrm{~m}^{3} / \mathrm{kg}$
(d) $0.646 \mathrm{~m}^{3} / \mathrm{kg}$
(e) $0.655 \mathrm{~m}^{3} / \mathrm{kg}$

Dading Chen
Dading Chen
Numerade Educator
01:25

Problem 206

Air is to be heated steadily by an $8-\mathrm{kW}$ electric resistance heater as it flows through an insulated duct. If the air enters at $50^{\circ} \mathrm{C}$ at a rate of $2 \mathrm{~kg} / \mathrm{s},$ the exit temperature of air is
(a) $46.0^{\circ} \mathrm{C}$
(b) $50.0^{\circ} \mathrm{C}$
(c) $54.0^{\circ} \mathrm{C}$
(d) $55.4^{\circ} \mathrm{C}$
(e) $58.0^{\circ} \mathrm{C}$

Dading Chen
Dading Chen
Numerade Educator
01:47

Problem 207

Saturated water vapor at $40^{\circ} \mathrm{C}$ is to be condensed as it flows through a tube at a rate of $0.20 \mathrm{~kg} / \mathrm{s} .$ The condensate leaves the tube as a saturated liquid at $40^{\circ} \mathrm{C}$. The rate of heat transfer from the tube is
(a) $34 \mathrm{~kJ} / \mathrm{s}$
(b) $481 \mathrm{~kJ} / \mathrm{s}$
(c) $2406 \mathrm{~kJ} / \mathrm{s}$
(d) $514 \mathrm{~kJ} / \mathrm{s}$
(e) $548 \mathrm{~kJ} / \mathrm{s}$

Naman Kumar
Naman Kumar
Numerade Educator
06:05

Problem 208

Pneumatic nail drivers used in construction require $0.02 \mathrm{ft}^{3}$ of air at 100 psia and 1 Btu of energy to drive a single nail. You have been assigned the task of designing a compressed-air storage tank with enough capacity to drive 500 nails. The pressure in this tank cannot exceed 500 psia, and the temperature cannot exceed that normally found at a construction site. What is the maximum pressure to be used in the tank and what is the tank's volume?

Naman Kumar
Naman Kumar
Numerade Educator
02:16

Problem 209

You have been given the responsibility of picking a steam turbine for an electrical-generation station that is to produce $300 \mathrm{MW}$ of electrical power that will sell for $\$ 0.08$ per kilowatt-hour. The boiler will produce steam at 700 psia and $700^{\circ} \mathrm{F},$ and the condenser is planned to operate at $80^{\circ} \mathrm{F}$. The cost of generating and condensing the steam is $\$ 0.015$ per kilowatt-hour of electricity produced. You have narrowed your selection to the three turbines in the following table. Your criterion for selection is to pay for the equipment as quickly as possible. Which turbine should you choose?

Naman Kumar
Naman Kumar
Numerade Educator
03:34

Problem 210

You are to design a small, directional control rocket to operate in space by providing as many as 100 bursts of 5 seconds each with a mass flow rate of $0.5 \mathrm{lbm} / \mathrm{s}$ at a velocity of $400 \mathrm{ft} / \mathrm{s}$. Storage tanks that will contain up to 3000 psia are available, and the tanks will be located in an environment whose temperature is $40^{\circ} \mathrm{F}$. Your design criterion is to minimize the volume of the storage tank. Should you use a compressed-air or an R-134a system?

Naman Kumar
Naman Kumar
Numerade Educator
02:35

Problem 211

An air cannon uses compressed air to propel a projectile from rest to a final velocity. Consider an air cannon that is to accelerate a 10 -gram projectile to a speed of $300 \mathrm{m} / \mathrm{s}$ using compressed air, whose temperature cannot exceed $20^{\circ} \mathrm{C}$. The volume of the storage tank is not to exceed $0.1 \mathrm{m}^{3} .$ Select the storage volume size and maximum storage pressure that requires the minimum amount of energy to fill the tank.

Naman Kumar
Naman Kumar
Numerade Educator
04:24

Problem 212

Design a $1200-\mathrm{W}$ electric hair dryer such that the air temperature and velocity in the dryer will not exceed $50^{\circ} \mathrm{C}$ and $3 \mathrm{~m} / \mathrm{s},$ respectively

Dading Chen
Dading Chen
Numerade Educator
02:54

Problem 213

To maintain altitude, the temperature of the air inside a hot-air balloon must remain within a $1^{\circ} \mathrm{C}$ band, while the volume cannot vary by more than 1 percent. At a 300 -m altitude, the air in a $1000 \mathrm{~m}^{3}$ hot-air balloon needs to maintain a $35^{\circ} \mathrm{C}$ average temperature. This balloon loses heat at a rate of $3 \mathrm{~kW}$ through the fabric. When the burner is activated, it adds $30 \mathrm{~kg} / \mathrm{s}$ of air at $200^{\circ} \mathrm{C}$ and $100 \mathrm{kPa}$ to the balloon. When the flap that allows air to escape is opened, air leaves the balloon at a rate of $20 \mathrm{~kg} / \mathrm{s}$. Design the burner and exhaust-flap control cycles (on time and off time) necessary to maintain the balloon at a 300 -m altitude.

Naman Kumar
Naman Kumar
Numerade Educator