• Home
  • Textbooks
  • Fundamentals of Thermodynamics
  • Gas Mixtures

Fundamentals of Thermodynamics

Claus Borgnakke, Richard E. Sonntag

Chapter 11

Gas Mixtures - all with Video Answers

Educators

Chapter Questions

01:12

Problem 1

Equal masses of argon and helium are mixed. Is the molecular mass of the mixture the linear average of the two individual ones?

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
02:02

Problem 2

Constant flows of pure argon and pure helium are mixed to produce a flow of mixture mole fractions 0.25 and $0.75,$ respectively. Explain how to meter the inlet flows to ensure the proper ratio, assuming inlet pressures are equal to the total exit pressure and all temperatures are the same.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
01:47

Problem 3

For a gas mixture in a tank, are the partial pressures important?

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
01:08

Problem 4

An ideal mixture at $T, P$ is made from ideal gases at $T, P$ by charging them into a steel tank. Assume heat is transferred, so $T$ stays the same as the supply. How do the properties $(P, v,$ and $u)$ for each component increase, decrease, or remain constant?

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
01:25

Problem 5

An ideal mixture at $T, P$ is made from ideal gases at $T, P$ by flow into a mixing chamber with no external heat transfer and an exit at $P$. How do the properties $(P, v,$ and $h)$ for each component increase, decrease, or remain constant?

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
01:32

Problem 6

If a certain mixture is used in a number of differ-- $-$ number of ent processes, is it necessary to consider partial pressures?

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
02:01

Problem 7

Why is it that a set of tables for air, which is a mixture, can be used without dealing with its composition?

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
01:08

Problem 8

Develop a formula to show how the mass fraction of water vapor is connected to the humidity ratio.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
00:36

Problem 9

Develop a formula to show how the mass fraction of water vapor is connected to the humidity ratio.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:00

Problem 10

Can moist air below the freezing point, say $-5^{\circ} \mathrm{C}$ have a dew point?

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
01:04

Problem 11

Why does a car with an air conditioner running often have water dripping out?

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
02:07

Problem 12

Moist air at $35^{\circ} \mathrm{C}, \omega=0.0175,$ and $\Phi=50 \%$
should be brought to a state of $20^{\circ} \mathrm{C}, \omega=0.01$ and $\Phi=70 \%$. Is it necessary to add or subtract water?

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
02:27

Problem 13

If oxygen is $21 \%$ by mole of air, what is the oxygen state $(P, T, v)$ in a room at $300 \mathrm{~K}, 100 \mathrm{kPa}$ with a total volume of $60 \mathrm{~m}^{3}$ ?

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
03:11

Problem 14

A 3-L liquid mixture is one-third each of water, ammonia, and ethanol by volume. Find the mass fractions and total mass of the mixture.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
04:27

Problem 15

A flow of oxygen and one of nitrogen, both at $300 \mathrm{~K}$, are mixed to produce $1 \mathrm{~kg} / \mathrm{s}$ air at $300 \mathrm{~K}$, $100 \mathrm{kPa}$. What are the mass and volume flow rates of each line?

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
03:13

Problem 16

A gas mixture at $20^{\circ} \mathrm{C}, 125 \mathrm{kPa}$ is $50 \% \mathrm{~N}_{2}, 30 \%$
$\mathrm{H}_{2} \mathrm{O},$ and $20 \% \mathrm{O}_{2}$ on a mole basis. Find the mass fractions, the mixture gas constant, and the volume for $5 \mathrm{~kg}$ of the mixture

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
03:39

Problem 17

A mixture of $60 \% \mathrm{~N}_{2}, 30 \% \mathrm{Ar},$ and $10 \% \mathrm{O}_{2}$ on a mass basis is in a cylinder at $250 \mathrm{kPa}, 310 \mathrm{~K}$ with a volume of $0.5 \mathrm{~m}^{3}$. Find the mole and the mass fractions and the mass of argon.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
02:27

Problem 18

A slightly oxygenated air mixture is $69 \% \mathrm{~N}_{2}, 1 \%$ Ar, and $30 \% \mathrm{O}_{2}$ on a mole basis. Assume a total pressure of $101 \mathrm{kPa}$ and find the mass fraction of oxygen and its partial pressure.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
05:49

Problem 19

A new refrigerant, $\mathrm{R}-407,$ is a mixture of $23 \%$ $\mathrm{R}-32,25 \% \mathrm{R}-125,$ and $52 \% \mathrm{R}-134 \mathrm{a}$ on a mass
basis. Find the mole fractions, the mixture gas constant, and the mixture heat capacities for the new refrigerant.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
02:15

Problem 20

In a car engine, gasoline (assume octane, $\mathrm{C}_{8} \mathrm{H}_{18}$ ) is evaporated and then mixed with air in a ratio of 1: 15 by mass. In the cylinder the mixture is at $750 \mathrm{kPa}, 650 \mathrm{~K}$ when the spark fires. For that time, find the partial pressure of the octane and the specific volume of the mixture.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
03:00

Problem 21

A $100-\mathrm{m}^{3}$ storage tank with fuel gases is at $20^{\circ} \mathrm{C}, 100 \mathrm{kPa}$ containing a mixture of acetylene $\left(\mathrm{C}_{2} \mathrm{H}_{2}\right),$ propane $\left(\mathrm{C}_{3} \mathrm{H}_{8}\right),$ and butane $\left(\mathrm{C}_{4} \mathrm{H}_{10}\right) . \mathrm{A}$
test shows that the partial pressure of the $\mathrm{C}_{2} \mathrm{H}_{2}$ is $15 \mathrm{kPa}$ and that of the $\mathrm{C}_{3} \mathrm{H}_{8}$ is $65 \mathrm{kPa}$. How much mass is there of each component?

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
03:44

Problem 22

A $2-\mathrm{kg}$ mixture of $25 \% \mathrm{~N}_{2}, 50 \% \mathrm{O}_{2},$ and $25 \%$
$\mathrm{CO}_{2}$ by mass is at $150 \mathrm{kPa}$ and $300 \mathrm{~K}$. Find the mixture gas constant and the total volume.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
01:01

Problem 23

A diesel engine sprays fuel (assume $n$ -dodecane, $\mathrm{C}_{12} \mathrm{H}_{26}, M=170.34 \mathrm{~kg} / \mathrm{kmol}$ ) into the combus-

Hast Aggarwal
Hast Aggarwal
Numerade Educator
03:47

Problem 24

A new refrigerant, $\mathrm{R}-410 \mathrm{a}$, is a mixture of $\mathrm{R}-32$ and $\mathrm{R}-125$ in a 1: 1 mass ratio. What are the overall molecular weight, the gas constant, and the ratio of specific heats for such a mixture?

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
02:52

Problem 25

Do Problem 11.24 for $\mathrm{R}-507 \mathrm{a}$, which has a 1: 1 mass ratio of $\mathrm{R}-125$ and $\mathrm{R}-143 \mathrm{a}$. The refrigerant R-143a has a molecular mass of $84.041 \mathrm{~kg} / \mathrm{kmol}$ and $C_{p}=0.929 \mathrm{~kJ} / \mathrm{kg}-\mathrm{K}$.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
03:32

Problem 26

A rigid container has $1 \mathrm{~kg} \mathrm{CO}_{2}$ at $300 \mathrm{~K}$ and $1 \mathrm{~kg}$ Ar at $400 \mathrm{~K}$, both at $150 \mathrm{kPa}$. Now they are allowed to mix without any heat transfer. What is the final $T, P ?$

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
04:33

Problem 27

At a certain point in a coal gasification process, a sample of the gas is taken and stored in a $1-\mathrm{L}$ cylinder. An analysis of the mixture yields the followings results:
Component $\begin{array}{lllll}\mathrm{H}_{2} & \mathrm{CO} & \mathrm{CO}_{2} & \mathrm{~N}_{2}\end{array}$
$\begin{array}{lllll}\text { Percent by mass } & 2 & 45 & 28 & 25\end{array}$
Determine the mole fractions and total mass in the cylinder at $100 \mathrm{kPa}, 20^{\circ} \mathrm{C}$. How much heat must be transferred to heat the sample at constant volume from the initial state to $100^{\circ} \mathrm{C} ?$

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
02:44

Problem 28

The mixture in Problem 11.22 is heated to $500 \mathrm{~K}$ with constant volume. Find the final pressure and the total heat transfer needed using Table A.5.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
02:52

Problem 29

The mixture in Problem 11.22 is heated to $500 \mathrm{~K}$ in a constant-pressure process. Find the final volume and the total heat transfer using Table A.5.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
02:18

Problem 30

A flow of $1 \mathrm{~kg} / \mathrm{s}$ argon at $300 \mathrm{~K}$ and another flow of $1 \mathrm{~kg} / \mathrm{s}$ carbon dioxide at $1600 \mathrm{~K}$, both at $150 \mathrm{kPa}$ are mixed without any heat transfer. What is the exit $T, P ?$

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
03:56

Problem 31

A flow of $1 \mathrm{~kg} / \mathrm{s}$ argon at $300 \mathrm{~K}$ and another flow of $1 \mathrm{~kg} / \mathrm{s}$ carbon dioxide at $1600 \mathrm{~K},$ both at $150 \mathrm{kPa}$ are mixed without any heat transfer. Find the exit T, $P$ using variable specific heats.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
01:35

Problem 32

A pipe flows $0.1 \mathrm{~kg} / \mathrm{s}$ of a mixture with mass fractions of $40 \% \mathrm{CO}_{2}$ and $60 \% \mathrm{~N}_{2}$ at $400 \mathrm{kPa}, 300 \mathrm{~K}$.
Heating tape is wrapped around a section of pipe with insulation added, and $2 \mathrm{~kW}$ electrical power is heating the pipe flow. Find the mixture exit temperature.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
03:16

Problem 33

A steady flow of $0.1 \mathrm{~kg} / \mathrm{s}$ carbon dioxide at $1000 \mathrm{~K}$ in one line is mixed with $0.2 \mathrm{~kg} / \mathrm{s}$ nitrogen at $400 \mathrm{~K}$ from another line, both at $100 \mathrm{kPa}$. The mixing chamber is insulated and has constant pressure of $100 \mathrm{kPa}$. Use constant heat capacity to find the mixing chamber's exit temperature.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
02:35

Problem 34

An insulated gas turbine receives a mixture of $10 \% \mathrm{CO}_{2}, 10 \% \mathrm{H}_{2} \mathrm{O},$ and $80 \% \mathrm{~N}_{2}$ on a mass basis
at $1000 \mathrm{kPa}, 500 \mathrm{kPa}$. The volume flow rate is $2 \mathrm{~m}^{3} / \mathrm{s}$ and its exhaust is at $700 \mathrm{~K}, 100 \mathrm{kPa}$. Find
the power output in $\mathrm{kW}$ using constant specific heat from Table $\mathrm{A} .5$ at $300 \mathrm{~K}$.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
02:13

Problem 35

Solve Problem 11.34 using the values of enthalpy from Table $A .8$

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
02:53

Problem 36

Solve Problem 11.33 assuming the flows are in $\mathrm{kmol} / \mathrm{s}$

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
01:44

Problem 37

Solve Problem 11.34 with the percentages on a mole basis and use Table A.9.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
02:35

Problem 38

A mixture of $0.5 \mathrm{~kg}$ nitrogen and $0.5 \mathrm{~kg}$ oxygen is at $100 \mathrm{kPa}, 300 \mathrm{~K}$ in a piston/cylinder maintaining constant pressure. Now $800 \mathrm{~kJ}$ is added by heating. Find the final temperature and the increase in entropy of the mixture using Table A. 5 values.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
08:50

Problem 39

A rigid insulated vessel contains $12 \mathrm{~kg}$ of oxygen at $200 \mathrm{kPa}, 280 \mathrm{~K}$ separated by a membrane from $26 \mathrm{~kg}$ carbon dioxide at $400 \mathrm{kPa}, 360 \mathrm{~K}$. The membrane is removed and the mixture comes to
a uniform state. Find the final temperature and pressure of the mixture.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
01:20

Problem 40

A new refrigerant, $\mathrm{R}-410 \mathrm{a}$, is a mixture of $\mathrm{R}-32$ and $\mathrm{R}-125$ in a 1: 1 mass ratio. A process brings $0.5 \mathrm{~kg} \mathrm{R}-410 \mathrm{a}$ from $270 \mathrm{~K}$ to $320 \mathrm{~K}$ at a constant
pressure of $250 \mathrm{kPa}$ in a piston/cylinder. Find the work and heat transfer.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:00

Problem 41

A piston/cylinder device contains $0.1 \mathrm{~kg}$ of a mixture of $40 \%$ methane and $60 \%$ propane gases by mass at $300 \mathrm{~K}$ and $100 \mathrm{kPa}$. The gas is now slowly compressed in an isothermal $(T=$ constant $)$ process to a final pressure of $250 \mathrm{kPa}$. Show the process in a $P-V$ diagram, and find both the work and the heat transfer in the process.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
02:04

Problem 42

A piston/cylinder device contains $0.1 \mathrm{~kg}$ of a mixture of $40 \%$ methane and $60 \%$ propane gases by mass at $300 \mathrm{~K}$ and $100 \mathrm{kPa}$. The gas is now slowly compressed in an isothermal $(T=$ constant $)$ process to a final pressure of $250 \mathrm{kPa}$. Show the process in a $P-V$ diagram, and find both the work and the heat transfer in the process.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
03:01

Problem 43

The refrigerant R-410a (see Problem 11.41 ) is at $100 \mathrm{kPa}, 290 \mathrm{~K}$. It is now brought to $250 \mathrm{kPa}$
$400 \mathrm{~K}$ in a reversible polytropic process. Find the change in specific volume, specific enthalpy, and the specific entropy for the process.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
02:51

Problem 44

Natural gas as a mixture of $75 \%$ methane and $25 \%$ ethane by mass is flowing to a compressor at $17^{\circ} \mathrm{C}, 100 \mathrm{kPa}$. The reversible adiabatic compressor brings the flow to $350 \mathrm{kPa}$. Find the exit temperature and the needed work per kilogram of flow

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
02:21

Problem 45

A compressor brings $\mathrm{R}-410 \mathrm{a}$ (see Problem 11.41 ) from $-10^{\circ} \mathrm{C}, 125 \mathrm{kPa}$ to $500 \mathrm{kPa}$ in an adiabatic reversible compression. Assume ideal gas behavior and find the exit temperature and the specific work.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
00:53

Problem 46

Two insulated tanks, $A$ and $B$, are connected by a valve. Tank A has a volume of $1 \mathrm{~m}^{3}$ and initially contains argon at $300 \mathrm{kPa}, 10^{\circ} \mathrm{C}$. Tank $\mathrm{B}$ has a volume of $2 \mathrm{~m}^{3}$ and initially contains ethane at $200 \mathrm{kPa}, 50^{\circ} \mathrm{C}$. The valve is opened and remains open until the resulting gas mixture comes to a uniform state. Determine the final pressure and temperature.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:53

Problem 47

A steady flow of $0.1 \mathrm{kmol} / \mathrm{s}$ carbon dioxide at 1000 $\mathrm{K}$ in one line is mixed with $0.2 \mathrm{kmol} / \mathrm{s}$ nitrogen at $400 \mathrm{~K}$ in another line, both at $100 \mathrm{kPa}$. The exit mixture at $100 \mathrm{kPa}$ is compressed by a reversible adiabatic compressor to $500 \mathrm{kPa}$. Use constant heat capacity to find the mixing chamber's exit temperature and the needed compressor power.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
03:10

Problem 48

A mixture of 2 kg oxygen and 2 kg argon is in an insulated piston/cylinder arrangement at $100 \mathrm{kPa}$ $300 \mathrm{~K}$. The piston now compresses the mixture to half of its initial volume. Find the final pressure, temperature, and the piston work.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
05:38

Problem 49

The gas mixture from Problem 11.27 is compressed in a reversible adiabatic process from the initial state in the sample cylinder to a volume of $0.2 \mathrm{~L}$. Determine the final temperature of the mixture and the work done during the process.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
07:26

Problem 50

A piston/cylinder has a $0.1-\mathrm{kg}$ mixture of $25 \%$ argon, $25 \%$ nitrogen, and $50 \%$ carbon dioxide by mass at a total pressure of $100 \mathrm{kPa}$ and $290 \mathrm{~K}$ Now the piston compresses the gases to volume seven times smaller in a polytropic process with $n=1.3 .$ Find the final pressure and temperature, the work, and the heat transfer for the process.

Rashmi Sinha
Rashmi Sinha
Numerade Educator
01:04

Problem 51

A flow of gas $A$ and a flow of gas $B$ are mixed in a 1: 2 mole ratio with the same $T$. what is the entropy generation per kmole flow out?

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
00:37

Problem 53

What is the entropy generation in Problem $11.26 ?$

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:00

Problem 54

A flow of $2 \mathrm{~kg} / \mathrm{s}$ mixture of $50 \%$ carbon dioxide and $50 \%$ oxygen by mass is heated in a constantpressure heat exchanger from $400 \mathrm{~K}$ to $1000 \mathrm{~K}$ by a radiation source at $1400 \mathrm{~K}$. Find the rate of heat transfer and the entropy generation in the process shown in Fig. P 11.54 .

Hast Aggarwal
Hast Aggarwal
Numerade Educator
05:51

Problem 55

A flow of $1.8 \mathrm{~kg} / \mathrm{s}$ steam at $400 \mathrm{kPa}, 400^{\circ} \mathrm{C}$ is
mixed with $3.2 \mathrm{~kg} / \mathrm{s}$ oxygen at $400 \mathrm{kPa}, 400 \mathrm{~K}$ in a steady-flow mixing chamber without any heat transfer. Find the exit temperature and the rate of entropy generation.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
01:21

Problem 56

Carbon dioxide gas at $320 \mathrm{~K}$ is mixed with nitrogen at $280 \mathrm{~K}$ in an insulated mixing chamber. Both flows are at $100 \mathrm{kPa}$, and the mass ratio of carbon dioxide to nitrogen is $2: 1 .$ Find the exit temperature and the total entropy generation per kilogram of the exit mixture.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:08

Problem 57

Carbon dioxide gas at $320 \mathrm{~K}$ is mixed with nitrogen at $280 \mathrm{~K}$ in an insulated mixing chamber. Both flows are coming in at $100 \mathrm{kPa}$, and the mole ratio of carbon dioxide to nitrogen is 2: 1 . Find the exit temperature and the total entropy generation per kmole of the exit mixture.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:52

Problem 58

A flow of $1 \mathrm{~kg} / \mathrm{s}$ carbon dioxide at $1600 \mathrm{~K}, 100 \mathrm{kPa}$ is mixed with a flow of $2 \mathrm{~kg} / \mathrm{s}$ water at $800 \mathrm{~K}$ $100 \mathrm{kPa},$ and after the mixing it goes through a heat exchanger, where it is cooled to $500 \mathrm{~K}$ by a $400 \mathrm{~K}$ ambient. How much heat transfer is taken
out in the heat exchanger? What is the entropy generation rate for the whole process?

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:57

Problem 59

The only known sources of helium are the atmosphere (mole fraction approximately $5 \times 10^{-6}$ ) and natural gas. A large unit is being constructed to separate $100 \mathrm{~m}^{3} / \mathrm{s}$ of natural gas, assumed to be 0.001 helium mole fraction and 0.999 methane. The gas enters the unit at $150 \mathrm{kPa}, 10^{\circ} \mathrm{C}$. Pure helium exits at $100 \mathrm{kPa}, 20^{\circ} \mathrm{C}$ and pure methane exits at $150 \mathrm{kPa}, 30^{\circ} \mathrm{C}$. Any heat transfer is with the surroundings at $20^{\circ} \mathrm{C}$. Is an electrical power input of $3000 \mathrm{~kW}$ sufficient to drive this unit?

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:20

Problem 60

Repeat Problem 11.44 for an isentropic compressor efficiency of $82 \%$.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:00

Problem 61

A steady flow of $0.3 \mathrm{~kg} / \mathrm{s}$ of $60 \%$ carbon dioxide and $40 \%$ water mixture by mass at $1200 \mathrm{~K}$, $200 \mathrm{kPa}$ is used in a constant-pressure heat exchanger where $300 \mathrm{~kW}$ is extracted from the flow. Find the exit temperature and rate of change in entropy using Table A.5.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:16

Problem 62

A steady flow of $0.3 \mathrm{~kg} / \mathrm{s}$ of $60 \%$ carbon dioxide and $40 \%$ water by mass at $1200 \mathrm{~K}, 200 \mathrm{kPa}$ is used in a heat exchanger where $300 \mathrm{~kW}$ is extracted from the flow. Find the flow exit temperature and the rate of change of entropy using Table $\mathrm{A} .8$.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
05:12

Problem 63

A mixture of $60 \%$ helium and $40 \%$ nitrogen by mass enters a turbine at $1 \mathrm{MPa}, 800 \mathrm{~K}$ at a rate of $2 \mathrm{~kg} / \mathrm{s}$. The adiabatic turbine has an exit pressure of $100 \mathrm{kPa}$ and an isentropic efficiency of $85 \%$. Find the turbine work.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
01:19

Problem 64

Three steady flows are mixed in an adiabatic chamber at $150 \mathrm{kPa}$. Flow one is $2 \mathrm{~kg} / \mathrm{s}$ oxygen at $340 \mathrm{~K}$, flow two is $4 \mathrm{~kg} / \mathrm{s}$ nitrogen at $280 \mathrm{~K}$, and flow three is $3 \mathrm{~kg} / \mathrm{s}$ carbon dioxide at $310 \mathrm{~K}$. All flows are at $150 \mathrm{kPa}$, the same as the total exit pressure. Find the exit temperature and the rate of entropy generation in the process.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:52

Problem 65

A tank has two sides initially separated by a diaphragm. Side A contains 1 kg water and side B contains $1.2 \mathrm{~kg}$ air, both at $20^{\circ} \mathrm{C}, 100 \mathrm{kPa}$. The diaphragm is now broken and the whole tank is heated to $600^{\circ} \mathrm{C}$ by a $700^{\circ} \mathrm{C}$ reservoir. Find the final total pressure, heat transfer, and total entropy generation.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
10:07

Problem 66

Reconsider Problem $11.64,$ but let the tanks have a small amount of heat transfer so that the final mixture is at $400 \mathrm{~K}$. Find the final pressure, the heat transfer, and the entropy change for the process.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
02:06

Problem 67

Atmospheric air is at $100 \mathrm{kPa}, 25^{\circ} \mathrm{C}$ and relative humidity $65 \%$. Find the absolute humidity and the dew point of the mixture. If the mixture is heated to $35^{\circ} \mathrm{C}$, what is the new relative humidity?

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
02:58

Problem 68

A flow of $1 \mathrm{~kg} / \mathrm{s}$ saturated moist air (relative humidity $100 \%$ ) at $100 \mathrm{kPa}, 10^{\circ} \mathrm{C}$ goes through a heat exchanger and comes out at $25^{\circ} \mathrm{C}$. What are the exit relative humidity and the heat transfer?

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
03:34

Problem 69

If I have air at $100 \mathrm{kPa}$ and $(\mathrm{a})-10^{\circ} \mathrm{C},$ (b) $45^{\circ} \mathrm{C}$
and (c) $110^{\circ} \mathrm{C}$, what is the maximum absolute humidity I can have?

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
00:46

Problem 70

A new high-efficiency home heating system includes an air-to-air heat exchanger that uses energy from outgoing stale air to heat the fresh incoming air. If the outside ambient temperature is $-10^{\circ} \mathrm{C}$ and the relative humidity is $50 \%,$ how much water will have to be added to the incoming air if it flows in at the rate of $1 \mathrm{~m}^{3} / \mathrm{s}$ and must eventually be conditioned to $20^{\circ} \mathrm{C}$ and $45 \%$ relative humidity?

Hast Aggarwal
Hast Aggarwal
Numerade Educator
03:42

Problem 71

Consider $100 \mathrm{~m}^{3}$ of atmospheric air which is an air-water vapor mixture at $100 \mathrm{kPa}, 15^{\circ} \mathrm{C}$ and $40 \%$ relative humidity. Find the mass of water and the humidity ratio. What is the dew point of the mixture?

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
04:22

Problem 72

A flow of $2 \mathrm{~kg} / \mathrm{s}$ completely dry air at $T_{1}, 100 \mathrm{kPa}$ is cooled down to $10^{\circ} \mathrm{C}$ by spraying liquid water at $10^{\circ} \mathrm{C}, 100 \mathrm{kPa}$ into it so that it becomes saturated moist air at $10^{\circ} \mathrm{C}$. The process is steady state with no external heat transfer or work. Find the exit moist air humidity ratio and the flow rate of liquid water. Also find the dry air inlet temperature $T_{1}$.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
00:50

Problem 73

The products of combustion are flowing through a heat exchanger with $12 \%$ carbon dioxide, $13 \%$ water, and $75 \%$ nitrogen on a volume basis at the rate $0.1 \mathrm{~kg} / \mathrm{s}$ and $100 \mathrm{kPa}$. What is the dew-point temperature? If the mixture is cooled $10^{\circ} \mathrm{C}$ below the dew-point temperature, how long will it take to collect $10 \mathrm{~kg}$ of liquid water?

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:10

Problem 74

Consider a $1-\mathrm{m}^{3} / \mathrm{s}$ flow of atmospheric air at $100 \mathrm{kPa}, 25^{\circ} \mathrm{C},$ and $80 \%$ relative humidity. Assume this mixture flows into a basement room where it cools to $15^{\circ} \mathrm{C}, 100 \mathrm{kPa}$. Find the rate of water condensing out and the exit mixture volume flow rate?

Hast Aggarwal
Hast Aggarwal
Numerade Educator
03:36

Problem 75

Ambient moist air enters a steady-flow airconditioning unit at $102 \mathrm{kPa}, 30^{\circ} \mathrm{C}$, with $60 \%$ relative humidity. The volume flow rate entering the unit is $100 \mathrm{~L} / \mathrm{s}$. The moist air leaves the unit at $95 \mathrm{kPa}, 15^{\circ} \mathrm{C},$ with a relative humidity of $100 \%$ liquid also leaves at $15^{\circ} \mathrm{C}$. Determine the rate of heat transfer for this process.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
01:08

Problem 76

A room with air at $40 \%$ relative humidity, $20^{\circ} \mathrm{C}$ having $50 \mathrm{~kg}$ of dry air is made moist by boiling water to a final state of $20^{\circ} \mathrm{C}$ and $80 \%$ humidity. How much water was added to the air?

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
03:16

Problem 77

Consider a 500 - $L$ rigid tank containing an airwater vapor mixture at $100 \mathrm{kPa}, 35^{\circ} \mathrm{C}$ with $70 \%$ relative humidity. The system is cooled until the water just begins to condense. Determine the final temperature in the tank and the heat transfer for the process.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
00:53

Problem 78

A saturated air-water vapor mixture at $20^{\circ} \mathrm{C}$, $100 \mathrm{kPa}$ is contained in a $5-\mathrm{m}^{3}$ closed tank in equilibrium with 1 kg liquid water. The tank is heated to $80^{\circ} \mathrm{C}$. Is there any liquid water in the final state? Find the heat transfer for the process.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
02:43

Problem 79

A flow of $0.2 \mathrm{~kg} / \mathrm{s}$ liquid water at $80^{\circ} \mathrm{C}$ is sprayed into a chamber together with $16 \mathrm{~kg} / \mathrm{s}$ dry air at $60^{\circ} \mathrm{C}$. All the water evaporates, and the air leaves at $40^{\circ} \mathrm{C}$. What is the exit relative humidity and the heat transfer?

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
07:42

Problem 80

A rigid container, $10 \mathrm{~m}^{3}$ in volume, contains moist air at $45^{\circ} \mathrm{C}, 100 \mathrm{kPa}, \phi=40 \% .$ The container is now cooled to $5^{\circ} \mathrm{C}$. Neglect the volume of any liquid that might be present and find the final mass of water vapor, the final total pressure, and the heat transfer.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
01:11

Problem 81

A water-filled reactor of $1 \mathrm{~m}^{3}$ is at $20 \mathrm{MPa}, 360^{\circ} \mathrm{C}$ and is located inside an insulated containment room of $100 \mathrm{~m}^{3}$ that contains air at $100 \mathrm{kPa}, 25^{\circ} \mathrm{C}$. Due to a failure, the reactor ruptures and the water fills the containment room. Find the final pressure.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
02:05

Problem 82

In the production of ethanol from corn, the solids left after fermentation are dried in a continuousflow oven. This process generates a flow of $15 \mathrm{~kg} / \mathrm{s}$ moist air, $90^{\circ} \mathrm{C}$ with $70 \%$ relative humidity, which contains some volatile organic compounds and some particles. To remove the organic gases and the particles, the flow is sent to a thermal oxidizer, where natural gas flames bring the mixture to $800^{\circ} \mathrm{C}$. Find the rate of heating by the natural gas burners.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
00:57

Problem 83

To reduce natural gas use in the previous problem, a suggestion is to take and cool the mixture and condense out some water before heating it again. So, the flow is cooled from $90^{\circ} \mathrm{C}$ to $50^{\circ} \mathrm{C}$ and the dryer mixture is heated to $800^{\circ} \mathrm{C}$. Find the amount of water condensed out and the rate of heating by the natural gas burners for this case.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:18

Problem 84

I want to bring air at $35^{\circ} \mathrm{C}, \Phi=40 \%$ to a state of $25^{\circ} \mathrm{C}, \omega=0.015 .$ Do I need to add or subtract water?

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
05:13

Problem 85

A flow of moist air at $100 \mathrm{kPa}, 40^{\circ} \mathrm{C}, 40 \%$ relative humidity is cooled to $15^{\circ} \mathrm{C}$ in a constant-pressure device. Find the humidity ratio of the inlet and the exit flow, and the heat transfer in the device per $\mathrm{kg}$ dry air.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
01:07

Problem 86

Use the formulas and the steam tables to find the missing property of $\phi, \omega,$ and $T_{\text {dry }} ;$ total pressure is $100 \mathrm{kPa}$. Repeat the answers using the psychometric chart.
a. $\phi=50 \%, \omega=0.010$
b. $T_{\mathrm{dry}}=25^{\circ} \mathrm{C}, T_{\text {wet }}=21^{\circ} \mathrm{C}$

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:37

Problem 87

The discharge moist air from a clothes dryer is at $40^{\circ} \mathrm{C}, 80 \%$ relative humidity. The flow is guided through a pipe up through the roof and a vent to the atmosphere. Due to heat transfer in the pipe, the flow is cooled to $24^{\circ} \mathrm{C}$ by the time it reaches the vent. Find the humidity ratio in the flow out of the clothes dryer and at the vent. Find the heat transfer and any amount of liquid that may be forming per $\mathrm{kg}$ dry air for the flow.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:32

Problem 88

A flow, $0.2, \mathrm{~kg} / \mathrm{s}$ dry air, of moist air at $40^{\circ} \mathrm{C}, 50 \%$ relative humidity flows from the outside, state 1 down into a basement, where it cools to $16^{\circ} \mathrm{C}$, state 2 . Then it flows up to the living room, where it is heated to $25^{\circ} \mathrm{C}$, state $3 .$ Find the dew point for state 1 , any amount of liquid that may appear, the heat transfer that takes place in the basement, and the relative humidity in the living room at state 3 .

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:00

Problem 89

A steady supply of $1.0 \mathrm{~m}^{3} / \mathrm{s}$ air at $25^{\circ} \mathrm{C}, 100 \mathrm{kPa}$
$50 \%$ relative humidity is needed to heat a building in the winter. The outdoor ambient is at $10^{\circ} \mathrm{C},$ $100 \mathrm{kPa}, 50 \%$ relative humidity. What are the required liquid water input and heat transfer rates for this purpose?

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:06

Problem 90

In a ventilation system, inside air at $34^{\circ} \mathrm{C}$ and $70 \%$ relative humidity is blown through a channel, where it cools to $25^{\circ} \mathrm{C}$ with a flow rate of $0.75 \mathrm{~kg} / \mathrm{s}$ dry air. Find the dew point of the inside air, the relative humidity at the end of the channel, and the heat transfer in the channel.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:19

Problem 91

Two moist air streams with $85 \%$ relative humidity, both flowing at a rate of $0.1 \mathrm{~kg} / \mathrm{s}$ dry air, are mixed in a steady setup. One inlet flowstream is at $32.5^{\circ} \mathrm{C}$ and the other is at $16^{\circ} \mathrm{C}$. Find the exit relative humidity

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:14

Problem 92

A combination air cooler and dehumidification unit receives outside ambient air at $35^{\circ} \mathrm{C}, 100 \mathrm{kPa}$ $90 \%$ relative humidity. The moist air is first cooled to a low temperature $T_{2}$ to condense the proper amount of water; assume all the liquid leaves at $T_{2}$. The moist air is then heated and leaves the unit at $20^{\circ} \mathrm{C}, 100 \mathrm{kPa},$ relative humidity $30 \%$ with volume flow rate of $0.01 \mathrm{~m}^{3} / \mathrm{s}$. Find the temperature $T_{2},$ the mass of liquid per kilogram of dry air, and the overall heat transfer rate.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:04

Problem 93

To make dry coffee powder, we spray $0.2 \mathrm{~kg} / \mathrm{s}$ coffee (assume liquid water) at $80^{\circ} \mathrm{C}$ in to a chamber, where we add $10 \mathrm{~kg} / \mathrm{s}$ dry air at $T$. All the water should evaporate, and the air should leave at a minimum $40^{\circ} \mathrm{C}$; we neglect the power. How high should $T$ in the inlet air flow be?

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:57

Problem 94

An insulated tank has an air inlet, $\omega_{1}=0.0084$ and an outlet, $T_{2}=22^{\circ} \mathrm{C}, \phi_{2}=90 \%,$ both at $100 \mathrm{kPa}$. A third line sprays $0.25 \mathrm{~kg} / \mathrm{s}$ water at $80^{\circ} \mathrm{C}, 100 \mathrm{kPa}$. For steady operation, find the outlet specific humidity, the mass flow rate of air needed, and the required air inlet temperature, $T_{1}$.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:58

Problem 95

An air flow of $2 \mathrm{~kg} / \mathrm{s}$ at $30^{\circ} \mathrm{C}$, relative humidity $80 \%$, is conditioned by taking half of the air flow, cooling it, and mixing it with the other half. Assume the outlet flow should have a water content that is $75 \%$ of the original flow. Find the temperature to cool to, the rate of cooling, and the final exit flow temperature.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:45

Problem 96

A water-cooling tower for a power plant cools $45^{\circ} \mathrm{C}$ liquid water by evaporation. The tower receives air at $19.5^{\circ} \mathrm{C}, \phi=30 \%, 100 \mathrm{kPa}$ that is
blown through/over the water such that it leaves the tower at $25^{\circ} \mathrm{C}, \phi=70 \%$. The remaining liquid water flows back to the condenser at $30^{\circ} \mathrm{C}$, having given off $1 \mathrm{MW}$. Find the mass flow rate of air and the amount of water that evaporates.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:49

Problem 97

Moist air at $31^{\circ} \mathrm{C}$ and $50 \%$ relative humidity flows over a large surface of liquid water. Find the adi abatic saturation temperature by trial and error Hint: it is around $22.5^{\circ} \mathrm{C}$.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:38

Problem 98

A flow of air at $10^{\circ} \mathrm{C}, \phi=90 \%$ is brought into a house, where it is conditioned to $25^{\circ} \mathrm{C}, 60 \%$ relative humidity. This is done with a combined heater-evaporator in which any liquid water is at $10^{\circ} \mathrm{C}$. Find any flow of liquid and the necessary heat transfer, both per kilogram of dry air flowing. Find the dew point for the final mixture.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
04:03

Problem 99

An air conditioner for an airport receives desert air at $45^{\circ} \mathrm{C}, 10 \%$ relative humidity and must deliver it to the building at $20^{\circ} \mathrm{C}, 50 \%$ relative humidity. The buildings have a cooling system with $\mathrm{R}-410 \mathrm{a}$ running with a high pressure of $3000 \mathrm{kPa}$ and a low pressure of $1000 \mathrm{kPa}$, and their tap water is $18^{\circ} \mathrm{C}$. What should be done to the air? Find the needed heating/cooling per $\mathrm{kg}$ dry air.

James Kiss
James Kiss
Numerade Educator
00:59

Problem 100

A flow of moist air from a domestic furnace, state 1 , is at $45^{\circ} \mathrm{C}, 10 \%$ relative humidity with a flow rate of $0.05 \mathrm{~kg} / \mathrm{s}$ dry air. A small electric heater adds steam at $100^{\circ} \mathrm{C}, 100 \mathrm{kPa}$ generated from tap water at $15^{\circ} \mathrm{C}$. Up in the living room the flow comes out at state $4: 30^{\circ} \mathrm{C}, 60 \%$ relative humidity. Find the power needed for the electric heater and the heat transfer to the flow from state 1 to state 4

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:46

Problem 101

One means of conditioning hot summer air is evaporative cooling, which is a process similar to the adiabatic saturation process. Consider outdoor ambient air at $35^{\circ} \mathrm{C}, 100 \mathrm{kPa}, 30 \%$ relative humidity. Find the lowest temperature this can generate and mention some disadvantage with this technique. Solve the problem with the energy equation and formulas and repeat it using the psychrometric chart, Fig. E.4.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:02

Problem 102

One means of conditioning hot summer air is evaporative cooling, which is a process similar to the adiabatic saturation process. Consider outdoor ambient air at $35^{\circ} \mathrm{C}, 100 \mathrm{kPa}, 30 \%$ relative humidity. Find the lowest temperature this can generate and mention some disadvantage with this technique. Solve the problem with the energy equation and formulas and repeat it using the psychrometric chart, Fig. E.4.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:04

Problem 103

Atmospheric air at $35^{\circ} \mathrm{C},$ relative humidity $10 \%$ is too warm and also too dry. An air conditioner should deliver air at $21^{\circ} \mathrm{C}$ and $50 \%$ relative humidity at a rate of $3600 \mathrm{~m}^{3} / \mathrm{h}$. Sketch a setup to accomplish this, and find any amount of liquid (at $20^{\circ} \mathrm{C}$ ) that is needed or discarded and any heat transfer.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
05:09

Problem 104

In a car's defrost/defog system atmospheric air, $21^{\circ} \mathrm{C},$ relative humidity $80 \%,$ is taken in and cooled such that liquid water drips out. The now dryer air is heated to $41^{\circ} \mathrm{C}$ and then blown onto the windshield, where it should have a maximum of $10 \%$ relative humidity to remove water from the windshield. Find the dew point of the atmospheric air, specific humidity of air onto the windshield, the lowest temperature, and the specific heat transfer in the cooler.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
00:56

Problem 105

A commercial laundry runs a dryer that has an exit flow of $0.5 \mathrm{~kg} / \mathrm{s}$ moist air at $48^{\circ} \mathrm{C}, 70 \%$ relative humidity. To reduce the heating cost, a counterflow stack heat exchanger is used to heat the incoming fresh air at $20^{\circ} \mathrm{C}$ with the exit flow, as shown in Fig. $\mathrm{P} 11.105 .$ Assume the outgoing flow can be cooled to $25^{\circ} \mathrm{C}$ and the two flows have the same mass flow rate of dry air. Is there a missing flow in the figure? Find the rate of energy recovered by this heat exchanger.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:57

Problem 106

A flow of moist air at $45^{\circ} \mathrm{C}, 10 \%$ relative humidity with a flow rate of $0.2 \mathrm{~kg} / \mathrm{s}$ dry air is mixed with a flow of moist air at $25^{\circ} \mathrm{C}$ and absolute humidity of $w=0.018$ with a rate of $0.3 \mathrm{~kg} / \mathrm{s}$ dry air. The mixing takes place in an air duct at $100 \mathrm{kPa}$, and there is no significant heat transfer. After the mixing, there is heat transfer to a final temperature of $25^{\circ} \mathrm{C}$. Find the temperature and relative humidity after mixing. Find the heat transfer and the final exit relative humidity.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:12

Problem 107

An indoor pool evaporates $1.512 \mathrm{~kg} / \mathrm{h}$ of water, which is removed by a dehumidifier to maintain $21^{\circ} \mathrm{C}, \phi=70 \%$ in the room. The dehumidifier, shown in Fig. $\mathrm{P} 11.107,$ is a refrigeration cycle in which air flowing over the evaporator cools such that liquid water drops out, and the air continues flowing over the condenser. For an air flow rate of $0.1 \mathrm{~kg} / \mathrm{s},$ the unit requires $1.4 \mathrm{~kW}$ input to a motor driving a fan and the compressor, and it has a cop of $\beta=Q_{L} / W_{C}=2.0 .$ Find the state of the air as it returns to the room and the compressor work $Q_{L}$ input.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:51

Problem 108

A moist air flow of $5 \mathrm{~kg} / \mathrm{min}$ at $30^{\circ} \mathrm{C}, \Phi=60 \%$
100 kPa goes through a dehumidifier in the setup shown in Problem $11.107 .$ The air is cooled down to $15^{\circ} \mathrm{C}$ and then blown over the condenser. The refrigeration cycle runs with $\mathrm{R}-134 \mathrm{a}$ with a low pressure of $200 \mathrm{kPa}$ and a high pressure of $1000 \mathrm{kPa}$. Find the COP of the refrigeration cycle, the ratio $\dot{m}_{R-134 \mathrm{a}} / m_{\text {air }},$ and the outgoing $T_{3}$ and $\Phi_{3}$

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:10

Problem 109

Use the psychrometric chart to find the missing property of $\phi, \omega, T_{\text {wet }}, T_{\text {dry }}$
a. $T_{\text {dry }}=25^{\circ} \mathrm{C}, \phi=80 \%$
b. $T_{\text {dry }}=15^{\circ} \mathrm{C}, \phi=100 \%$
c. $T_{\text {dry }}=20^{\circ} \mathrm{C}, \omega=0.010$
d. $T_{\text {dry }}=25^{\circ} \mathrm{C}, T_{\text {wet }}=23^{\circ} \mathrm{C}$

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:10

Problem 110

Use the psychrometric chart to find the missing property of $\phi, \omega, T_{\text {wet }}, T_{\text {dry }}$
a. $\phi=50 \%, \omega=0.014$
b. $T_{\text {wet }}=15^{\circ} \mathrm{C}, \phi=60 \%$
c. $\omega=0.008, T_{\text {wet }}=15^{\circ} \mathrm{C}$
d. $T_{\text {dry }}=10^{\circ} \mathrm{C}, \omega=0.006$

Hast Aggarwal
Hast Aggarwal
Numerade Educator
02:27

Problem 111

For each of the states in Problem $11.110,$ find the dew-point temperature.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
01:19

Problem 112

Use the formulas and the steam tables to find the missing property of $\phi, \omega,$ and $T_{\text {dry }} ;$ total pressure is $100 \mathrm{kPa}$. Repeat the answers using the psychrometric chart.
a. $\phi=50 \%, \omega=0.010$
b. $T_{\text {wet }}=15^{\circ} \mathrm{C}, \phi=50 \%$
c. $T_{\text {dry }}=25^{\circ} \mathrm{C}, T_{\text {wet }}=21^{\circ} \mathrm{C}$

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:16

Problem 113

An air conditioner should cool a flow of ambient moist air at $40^{\circ} \mathrm{C}, 40 \%$ relative humidity with $0.2 \mathrm{~kg} / \mathrm{s}$ flow of dry air. The exit temperature should be $20^{\circ} \mathrm{C},$ and the pressure is $100 \mathrm{kPa}$. Find the rate of heat transfer needed and check for the formation of liquid water.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:45

Problem 114

A flow of moist air at $21^{\circ} \mathrm{C}, 60 \%$ relative humidity should be produced by mixing two different moist air flows. Flow 1 is at $10^{\circ} \mathrm{C},$ relative humidity $80 \%$ and flow 2 is at $32^{\circ} \mathrm{C}$ and has $T_{\text {wet }}=27^{\circ} \mathrm{C}$. The mixing chamber can be followed by a heater or a cooler. No liquid water is added, and $P=100 \mathrm{kPa}$. Find the two controls; one is the ratio of the two mass flow rates $\dot{m}_{a 1} / \dot{m}_{a 2},$ and the other is the heat transfer in the heater/cooler per kg dry air.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:11

Problem 115

Consider a mixing process as in Fig. $\mathrm{P} 11.114$ where flow 1 comes in as cold and moist, $10^{\circ} \mathrm{C}$ $\phi=90 \%$. It is mixed with a flow 2 at $42^{\circ} \mathrm{C}$ $\mathrm{T}=31^{\circ} \mathrm{C}$. If the exit flow should be at $21^{\circ} \mathrm{C}$
$\phi=50 \%$ find the ratio $\dot{m}_{a 1} / \dot{m}_{a 2}$ and the heat transfer per $\mathrm{kg}$ dry air out.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:04

Problem 116

In a hot, dry climate, air enters an air-conditioner unit at $100 \mathrm{kPa}, 40^{\circ} \mathrm{C},$ and $5 \%$ relative humidity In a hot, dry climate, air enters an air-conditioner unit at $100 \mathrm{kPa}, 40^{\circ} \mathrm{C},$ and $5 \%$ relative humidity

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:36

Problem 117

Compare the weather in two places where it is cloudy and breezy. At beach $\mathrm{A}$ it is $20^{\circ} \mathrm{C}, 103.5$ $\mathrm{kPa}$, relative humidity $90 \%$; at beach $\mathrm{B}$ it is $25^{\circ} \mathrm{C}$ $99 \mathrm{kPa}$, relative humidity $40 \%$. Suppose you just took a swim and came out of the water. Where would you feel more comfortable and why?

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:14

Problem 118

Ambient air at $100 \mathrm{kPa}, 30^{\circ} \mathrm{C}, 40 \%$ relative humidity goes through a constant-pressure heat exchanger as a steady flow. In one case it is heated to $45^{\circ} \mathrm{C},$ and in another case it is cooled until it reaches saturation. For both cases, find the exit relative humidity and the amount of heat transfer per kilogram of dry air.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:09

Problem 119

A flow of moist air at $100 \mathrm{kPa}, 35^{\circ} \mathrm{C}, 40 \%$ relative humidity is cooled by adiabatic evaporation of liquid $20^{\circ} \mathrm{C}$ water to reach a saturated state. Find the amount of water added per $\mathrm{kg}$ dry air and the exit temperature.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:09

Problem 119

A flow of moist air at $100 \mathrm{kPa}, 35^{\circ} \mathrm{C}, 40 \%$ relative humidity is cooled by adiabatic evaporation of liquid $20^{\circ} \mathrm{C}$ water to reach a saturated state. Find the amount of water added per $\mathrm{kg}$ dry air and the exit temperature.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:07

Problem 120

A flow out of a clothes dryer of $0.1 \mathrm{~kg} / \mathrm{s}$ dry air is at $60^{\circ} \mathrm{C}$ and relative humidity $60 \% .$ It flows through a heat exchanger, where it exits at $20^{\circ} \mathrm{C}$. After exiting the heat exchanger, the flow combines with another flow of $0.03 \mathrm{~kg} / \mathrm{s}$ dry air at $30^{\circ} \mathrm{C}$ and relative humidity $40 \% .$ Find the dew point of state 1 (see Fig. $\mathrm{P} 11.120$ ), the heat transfer per $\mathrm{kg}$ dry air, and the final exit state humidity ratio and relative humidity.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:00

Problem 121

Consider two states of atmospheric air: (1) $40^{\circ} \mathrm{C}$, $\phi=50 \%$ and $(2) 25^{\circ} \mathrm{C}, T_{\text {wet }}=16^{\circ} \mathrm{C} .$ Suggest a
system of devices that will allow air in a steadyflow process to change from (1) to (2) and from
(2) to (1). Heaters, coolers, (de)humidifiers, liquid traps, and so on are available, and any liquid/solid flowing is assumed to be at the lowest temperature seen in the process. Find the specific and relative humidity for state 1 the dew point for state $2,$ and the heat transfer per $\mathrm{kg}$ dry air in each component in the system.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:27

Problem 122

To refresh air in a room, a counterflow heat exchanger (see Fig. $\mathrm{P} 11.122$ ) is mounted in the wall, drawing in outside air at $0.5^{\circ} \mathrm{C}, 80 \%$ relative humidity and pushing out room air at $40^{\circ} \mathrm{C}, 50 \%$ relative humidity. Assume an exchange of $3 \mathrm{~kg} / \mathrm{min}$ dry air in a steady-flow device, and also assume that the room air exits the heat exchanger at $23^{\circ} \mathrm{C}$ to the outside. Find the net amount of water removed from the room, any liquid flow in the heat exchanger, and $T, \phi$ for the fresh air entering the

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:58

Problem 123

Consider several flow processes with ideal gases:
(1) compression of a gas mixture from $100 \mathrm{kPa}$ to $200 \mathrm{kPa} ;$ (2) cooling a gas mixture from $50^{\circ} \mathrm{C}$ to ambient $20^{\circ} \mathrm{C}$ using ambient air; (3) mixing two different gases at $100 \mathrm{kPa} ;$ (4) throttling a gas mixture from $125 \mathrm{kPa}$ to $100 \mathrm{kPa}$. For each case, explain what happens to the exergy, whether there is any exergy destruction, and whether the composition is needed.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:51

Problem 124

Find the second-law efficiency of the heat exchanger in Problem $11.54 .$

Hast Aggarwal
Hast Aggarwal
Numerade Educator
08:34

Problem 125

Consider the mixing of a steam flow with an oxygen flow in Problem $11.55 .$ Find the rate of total inflowing availability and the rate of exergy destruction in the process.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
01:17

Problem 126

A mixture of $75 \%$ carbon dioxide and $25 \%$ water on a mole basis is flowing at $1600 \mathrm{~K}, 100 \mathrm{kPa}$ into a heat exchanger, where it is used to deliver energy to a heat engine. The mixture have leave the heat exchanger at $500 \mathrm{~K}$ with a mass flow rate of $2 \mathrm{~kg} / \mathrm{min}$. Find the rate of energy and the rate of exergy delivered to the heat engine.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:05

Problem 127

For flows with moist air where the water content is changed either by evaporation or by condensation, what happens to the exergy? Is the water vapor in air flowing over a lake in equilibrium with the liquid water?

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:07

Problem 128

A semipermeable membrane is used for the partial removal of oxygen from air that is blown through a grain elevator storage facility. Ambient air $(79 \%$ nitrogen, $21 \%$ oxygen on a mole basis) is compressed to an appropriate pressure, cooled to ambient temperature $25^{\circ} \mathrm{C}$, and then fed through a bundle of hollow polymer fibers that selectively absorb oxygen, so the mixture leaving at $120 \mathrm{kPa}, 25^{\circ} \mathrm{C}$ contains only $5 \%$ oxygen. The absorbed oxygen is bled off through the fiber walls at $40 \mathrm{kPa}, 25^{\circ} \mathrm{C}$ to a vacuum pump. Assume the process is reversible and adiabatic, and determine the minimum inlet air pressure to the fiber bundle.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:05

Problem 129

Weighing of masses gives a mixture at $60^{\circ} \mathrm{C}$, $225 \mathrm{kPa}$ with $0.5 \mathrm{~kg} \mathrm{O}_{2}, 1.5 \mathrm{~kg} \mathrm{~N}_{2},$ and $0.5 \mathrm{~kg}$ $\mathrm{CH}_{4} .$ Find the partial pressures of each component, the mixture specific volume (mass basis), mixture molecular weight, and the total volume.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
03:59

Problem 130

A carbureted internal combustion engine is converted to run on methane gas (natural gas). The air-fuel ratio in the cylinder is to be 20: 1 on a mass basis. How many moles of oxygen per mole of methane are there in the cylinder?

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
02:28

Problem 131

A mixture of $50 \%$ carbon dioxide and $50 \%$ water by mass is brought from $1500 \mathrm{~K}, 1 \mathrm{MPa}$ to $500 \mathrm{~K}$, $200 \mathrm{kPa}$ in a polytropic process through a steadystate device. Find the necessary heat transfer and work involved using values from Table A.5.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
01:06

Problem 132

The accuracy of calculations can be improved by using a better estimate for the specific heat. Reconsider the previous problem and use $C_{p}=\Delta h / \Delta T$ from Table A.8 centered at $1000 \mathrm{~K}$.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:51

Problem 133

A large air separation plant takes in ambient air $\left(79 \% \mathrm{~N}_{2}, 21 \% \mathrm{O}_{2}\right.$ by mole $)$ at $100 \mathrm{kPa}, 20^{\circ} \mathrm{C}$ at
a rate of $25 \mathrm{~kg} / \mathrm{s}$. It discharged a stream of pure $\mathrm{O}_{2}$ gas at $200 \mathrm{kPa}, 100^{\circ} \mathrm{C}$ and a stream of pure $\mathrm{N}_{2}$ gas at $100 \mathrm{kPa}, 20^{\circ} \mathrm{C}$. The plant operates on an electrical power input of $2000 \mathrm{~kW}$. Calculate the net rate of entropy change for the process.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:09

Problem 134

Take Problem 11.57 with inlet temperature of $1400 \mathrm{~K}$ for the carbon dioxide and $300 \mathrm{~K}$ for the nitrogen. Estimate the exit temperature with the specific heats from Table $A .5$ and use this to start iterations using Table A.9 to find the exit temperature.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:57

Problem 135

A piston/cylinder has $100 \mathrm{~kg}$ saturated moist air at $100 \mathrm{kPa}, 5^{\circ} \mathrm{C}$. If it is heated to $45^{\circ} \mathrm{C}$ in an isobaric process, find ${ }_{1} Q_{2}$ and the final relative humidity. If it is compressed from the initial state to $200 \mathrm{kPa}$ in an isothermal process, find the mass of water condensing.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:49

Problem 136

A piston/cylinder contains helium at $110 \mathrm{kPa}$ at ambient temperature $20^{\circ} \mathrm{C}$ and an initial volume of $20 \mathrm{~L}$, as shown in Fig. $\mathrm{P} 11.136 .$ The stops are mounted to give a maximum volume of $25 \mathrm{~L},$ and the nitrogen line conditions are $300 \mathrm{kPa}, 30^{\circ} \mathrm{C}$. The value is now opened, which allow nitrogen to flow in and mix with the helium. The valve is closed when the pressure inside reaches $200 \mathrm{kPa}$ at which point the temperature inside is $40^{\circ} \mathrm{C}$. Is this process consistent with the second law of thermodynamics?

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:00

Problem 137

A spherical balloon has an initial diameter of $1 \mathrm{~m}$ and contains argon gas at $200 \mathrm{kPa}, 40^{\circ} \mathrm{C}$. The balloon is connected by value to a $500-\mathrm{L}$ rigid tank containing carbon dioxide at $100 \mathrm{kPa}$, $100^{\circ} \mathrm{C}$. The valve is opened, and eventually the balloon and tank reach a uniform state in which the pressure is $185 \mathrm{kPa}$. The balloon pressure is directly proportional to its diameter. Take the balloon and tank as a control volume, and calculate the final temperature and the heat transfer for the process.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:59

Problem 138

An insulated rigid $2-\mathrm{m}^{3}$ tank A contains carbon dioxide gas at $200^{\circ} \mathrm{C}, 1 \mathrm{MPa}$. An uninsulated rigid $1-\mathrm{m}^{3}$ tank $\mathrm{B}$ contains ethane, $\left(\mathrm{C}_{2} \mathrm{H}_{6}\right),$ gas at $200 \mathrm{kPa}$, room temperature $20^{\circ} \mathrm{C}$. The two tanks are connected by a one-way check valve that will allow gas to flow from $\mathrm{A}$ to $\mathrm{B}$ but not from $\mathrm{B}$ to $\mathrm{A}$. The valve is opened, and gas flows from tank A to $\mathrm{B}$ until the pressure in $\mathrm{B}$ reaches $500 \mathrm{kPa}$ and the valve is closed. The mixture in $\mathrm{B}$ tank is kept at room temperature due to heat transfer. Find the total number of moles and the ethane mole fraction at the final state in $\operatorname{tank} \mathrm{B}$. Find the final temperature and pressure in tank $\mathrm{A}$ and the heat transfer to/from tank B.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:59

Problem 139

You have just washed your hair and you now blow dry it in a room with $23^{\circ} \mathrm{C}, \phi=60 \%,(1) .$ The dryer, $500 \mathrm{~W}$, heats the air to $49^{\circ} \mathrm{C},$ (2), blows it through your hair, where the air becomes saturated
(3), and then flows on to hit a window, where it cools to $15^{\circ} \mathrm{C}$ (4). Find the relative humidity at state $2,$ the heat transfer per kilogram of dry air in the dryer, the air flow rate, and the amount of water condensed on the window, if any.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:17

Problem 140

A $0.2-\mathrm{m}^{3}$ insulated rigid vessel is divided into two equal parts, $A$ and $B$, by an insulated partition, as shown in Fig. $\mathrm{P} 11.140 .$ The partition will support a pressure difference of $400 \mathrm{kPa}$ before breaking. Side A contains methane and side B contains carbon dioxide. Both sides are initially at $1 \mathrm{MPa}$ $30^{\circ} \mathrm{C}$. A valve on side $\mathrm{B}$ is opened, and carbon dioxide flows out. The carbon dioxide that remains in $\mathrm{B}$ is assumed to undergo a reversible adiabatic expansion while there is flow out. Eventually the partition breaks, and the valve is closed. Calculate the net entropy change for the process that begins when the valve is closed.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:10

Problem 141

Ambient air is at a condition of $100 \mathrm{kPa}, 35^{\circ} \mathrm{C}$ $50 \%$ relative humidity. A steady stream of air at $100 \mathrm{kPa}, 23^{\circ} \mathrm{C}, 70 \%$ relative humidity is to be produced by first cooling a flow of ambient air to an appropriate temperature to condense out the proper amount of water and then mix this stream adiabatically with another flow under ambient conditions. What is the ratio of the two flow rates? To what temperature must the first stream be cooled?

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:22

Problem 142

An air-water vapor mixture enters a steady-flow heater humidifier unit at state $1: 10^{\circ} \mathrm{C}, 10 \%$ relative humidity, at the rate of $1 \mathrm{~m}^{3} / \mathrm{s}$. A second air-vapor stream enters the unit at state $2: 20^{\circ} \mathrm{C}$, $20 \%$ relative humidity, at the rate of $2 \mathrm{~m}^{3} / \mathrm{s}$. Liquid water enters at state $3: 10^{\circ} \mathrm{C}$ at the rate of $400 \mathrm{~kg} / \mathrm{h}$. A single air-vapor flow exits the unit at state $4: 40^{\circ} \mathrm{C},$ as shown in Fig. $\mathrm{P} 11.142 .$ Calculate the relative humidity of the exit flow and the rate of heat transfer to the unit.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:46

Problem 143

A dehumidifier receives a flow of $0.25 \mathrm{~kg} / \mathrm{s}$ dry air at $35^{\circ} \mathrm{C}, 90 \%$ relative humidity, as shown in Fig. P11.107. It is cooled down to $20^{\circ} \mathrm{C}$ as it flows over the evaporator and then is heated up again as it flows over the condenser. The standard refrigeration cycle uses $\mathrm{R}-410 \mathrm{a}$ with an evaporator temperature of $-5^{\circ} \mathrm{C}$ and a condensation pressure of $3000 \mathrm{kPa}$. Find the amount of liquid water removed and the heat transfer in the cooling process. How much compressor work is needed? What is the final air exit temperature and relative humidity?

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:42

Problem 144

The air conditioning by evaporative cooling in Problem 11.101 is modified by adding a dehumidification process before the water spray cooling process. This dehumidification is achieved, as shown in Fig. $\mathrm{P} 11.144,$ by using a desiccant material, which absorbs water on one side of a rotating drum heat exchanger. The desiccant is regenerated by heating on the other side of the drum to drive the water out. The pressure is $100 \mathrm{kPa}$ everywhere, and other properties are indicated on the diagram. Calculate the relative humidity of the cool air supplied to the room at state 4 and the heat transfer per unit mass of air that needs to be supplied to the heater unit.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
02:06

Problem 145

If oxygen is $21 \%$ by mole of air, what is the oxygen state $(P, T, v)$ in a room at $540 \mathrm{R}$, 15 psia, with a total volume of $2000 \mathrm{ft}^{3} ?$

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
03:17

Problem 146

A flow of oxygen and one of nitrogen, both at $540 \mathrm{R},$ are mixed to produce $1 \mathrm{lbm} / \mathrm{s}$ air at $540 \mathrm{R}$ 15 psia. What are the mass and volume flow rates of each line?

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
01:05

Problem 147

A gas mixture at $250 \mathrm{~F}, 18 \mathrm{lbf} / \mathrm{in} .{ }^{2}$ is $50 \% \mathrm{~N}_{2}$,
$30 \% \mathrm{H}_{2} \mathrm{O},$ and $20 \% \mathrm{O}_{2}$ on a mole basis. Find the mass fractions, the mixture gas constant, and the volume for $10 \mathrm{lbm}$ of mixture.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:00

Problem 148

In a car engine, gasoline (assume octane, $\mathrm{C}_{8} \mathrm{H}_{18}$ ) is evaporated and then mixed with air in a ratio of 1: 15 by mass. In the cylinder the mixture is at 110 psia, $1200 \mathrm{R}$ when the spark fires. For that time, find the partial pressure of the octane and the specific volume of the mixture.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:03

Problem 149

A diesel engine sprays fuel (assume $n$ -dodecane, $\mathrm{C}_{12} \mathrm{H}_{26}, M=170.34 \mathrm{Ibm} / \mathrm{lbmol}$ ) into the com-
bustion chamber already filled with $1 \mathrm{~mol}$ fuel per $88 \mathrm{~mol}$ air. Find the fuel fraction on a mass basis and the fuel mass for a chamber that is $0.07 \mathrm{ft}^{3}$ at $1400 \mathrm{R}$ and a total pressure of 600 psia.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:13

Problem 150

A new refrigerant, $\mathrm{R}-410 \mathrm{a}$, is a mixture of $\mathrm{R}-32$
all molecular weight, the gas constant, and the ratio of specific heats for such a mixture?

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:57

Problem 151

Do the previous problem for $\mathrm{R}-507 \mathrm{a}$, which is
frigerant R-143a has a molecular mass of 84.041 $\mathrm{lbm} / \mathrm{lbmol}$, and $C_{p}=0.222 \mathrm{Btu} / \mathrm{lbm}-\mathrm{R}$.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:59

Problem 152

A rigid container has 1 lbm carbon dioxide at $540 \mathrm{R}$ and $1 \mathrm{lbm}$ argon at $720 \mathrm{R},$ both at 20 psia. Now they are allowed to mix without any heat transfer. What is the final $T, P ?$

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:55

Problem 153

A flow of $1 \mathrm{lbm} / \mathrm{s}$ argon at $540 \mathrm{R}$ and another flow of $1 \mathrm{lbm} / \mathrm{s}$ carbon dioxide at $2800 \mathrm{R},$ both at 20 psia, are mixed without any heat transfer. What is the exit $T, P ?$

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:08

Problem 154

Repeat the previous problem using variable specific heats.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:42

Problem 155

A pipe flows a $0.1-\mathrm{lbm} / \mathrm{s}$ mixture with mass fractions of $40 \% \mathrm{CO}_{2}$ and $60 \% \mathrm{~N}_{2}$ at $60 \mathrm{lbf} / \mathrm{in} .^{2}$
$540 \mathrm{R}$. Heating tape is wrapped around a section of pipe with insulation added, and $2 \mathrm{Btu} / \mathrm{s}$ electrical power is heating the pipe flow. Find the mixture exit temperature.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:47

Problem 156

An insulated gas turbine receives a mixture of $10 \% \mathrm{CO}_{2}, 10 \% \mathrm{H}_{2} \mathrm{O},$ and $80 \% \mathrm{~N}_{2}$ on a mass
basis at $1800 \mathrm{R}, 75 \mathrm{lbf} / \mathrm{in} .^{2} .$ The volume flow rate is $70 \mathrm{ft}^{3} / \mathrm{s}$, and its exhaust is at $1300 \mathrm{R}, 15$ $\mathrm{lbf} / \mathrm{in} .^{2} .$ Find the power output in $\mathrm{Btu} / \mathrm{s}$ using constant specific heat from Table $\mathrm{F} .4$ at $540 \mathrm{R}$.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:55

Problem 157

Solve Problem $11.156 \mathrm{E}$ using the values of $\mathrm{en}-$ thalpy from Table F.6.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:53

Problem 158

A piston/cylinder device contains $0.3 \mathrm{lbm}$ of mixture of $40 \%$ methane and $60 \%$ propane by mass at $540 \mathrm{R}, 15$ psia. The gas is now slowly compressed in an isothermal $(T=$ constant $)$ process to a final pressure of 40 psia. Show the process in a $P-V$ diagram, and find both the work and the heat transfer in the process.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:49

Problem 159

Two insulated tanks, $A$ and $B$, are connected by a valve. Tank A has a volume of $30 \mathrm{ft}^{3}$ and initially contains argon at $50 \mathrm{lbf} / \mathrm{in} .^{2}, 50 \mathrm{~F}$. Tank $\mathrm{B}$ has a volume of $60 \mathrm{ft}^{3}$ and initially contains ethane at $30 \mathrm{lbf} / \mathrm{in} .^{2}, 120 \mathrm{~F}$. The valve is opened and remains open until the resulting gas mixture comes to a uniform state. Find the final pressure and temperature.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
06:32

Problem 160

A mixture of 4 lbm oxygen and 4 lbm argon is in an insulated piston/cylinder arrangement at $14.7 \mathrm{lbf} / \mathrm{in.}^{2}, 540 \mathrm{R} .$ The piston now compresses
the mixture to half of its initial volume. Find the final pressure, final temperature, and piston work.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
00:42

Problem 161

A flow of gas $A$ and a flow of gas $B$ are mixed in a 1: 2 mole ratio with the same $T$. What is the entropy generation per lbmole flow out?

Hast Aggarwal
Hast Aggarwal
Numerade Educator
04:49

Problem 162

A rigid container has $1 \mathrm{lbm}$ argon at $540 \mathrm{R}$ and $1 \mathrm{lbm}$ argon at $720 \mathrm{R}$, both at 20 psia. Now they are allowed to mix without any external heat transfer. What is the final $T, P ?$ Is any $s$ generated?

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
01:08

Problem 163

What is the rate of entropy generation in Problem $11.153 \mathrm{E} ?$

Hast Aggarwal
Hast Aggarwal
Numerade Educator
10:20

Problem 164

Find the entropy generation for the process in Problem $11.159 \mathrm{E}$.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
08:45

Problem 165

Carbon dioxide gas at $580 \mathrm{R}$ is mixed with nitrogen at $500 \mathrm{R}$ in an insulated mixing chamber. Both flows are at $14.7 \mathrm{lbf} / \mathrm{in} .^{2}$ and the mole ratio of carbon dioxide to nitrogen is $2: 1 .$ Find the exit temperature and the total entropy generation per mole of the exit mixture.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
01:03

Problem 166

A steady flow of $0.6 \mathrm{lbm} / \mathrm{s}$ of a $60 \%$ carbon dioxide and $40 \%$ water mixture by mass at $2200 \mathrm{R}$ and 30 psia is used in a constant-pressure heat exchanger where $300 \mathrm{Btu} / \mathrm{s}$ is extracted from the flow. Find the exit temperature and rate of change in entropy using Table $\mathrm{F} .4$

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:37

Problem 167

Redo the previous problem using Table F.6.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:52

Problem 168

A mixture of $60 \%$ helium and $40 \%$ nitrogen by mole enters a turbine at $150 \mathrm{lbf} / \mathrm{in} .^{2}, 1500 \mathrm{R}$ at a rate of $4 \mathrm{lbm} / \mathrm{s}$. The adiabatic turbine has an exit pressure of $15 \mathrm{lbf} / \mathrm{in} .^{2}$ and an isentropic efficiency of $85 \% .$ Find the turbine work.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:18

Problem 169

A tank has two sides initially separated by a diaphragm. Side A contains 2 lbm water and side B contains $2.4 \mathrm{lbm}$ air, both at $68 \mathrm{~F}, 14.7 \mathrm{lbf} / \mathrm{in} .^{2}$
The diaphragm is now broken, and the whole tank is heated to $1100 \mathrm{~F}$ by a $1300 \mathrm{~F}$ reservoir. Find the final total pressure, heat transfer, and total entropy generation.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:09

Problem 170

A $1-\mathrm{lbm} / \mathrm{s}$ flow of saturated moist air (relative humidity $100 \%$ ) at 14.7 psia and 50 F goes through a heat exchanger and comes out at $77 \mathrm{~F}$. What is the exit relative humidity and how much power is needed?

Hast Aggarwal
Hast Aggarwal
Numerade Educator
03:07

Problem 171

If I have air at 14.7 psia and (a) $15 \mathrm{~F}$, (b) $115 \mathrm{~F}$, and (c) $230 \mathrm{~F}$, what is the maximum absolute humidity I can have?

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
02:56

Problem 172

Consider a volume of $2000 \mathrm{ft}^{3}$ that contains an air-water vapor mixture at $14.7 \mathrm{lbf} / \mathrm{in} .^{2}, 60 \mathrm{~F}$
and $40 \%$ relative humidity. Find the mass of water and the humidity ratio. What is the dew point of the mixture?

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
00:54

Problem 173

Consider a $35-\mathrm{ft}^{3} / \mathrm{s}$ flow of atmospheric air at 14.7 psia, $77 \mathrm{~F},$ and $80 \%$ relative humidity. Assume this flows into a basement room, where it 1 cools to $60 \mathrm{~F}$ at 14.7 psia. How much liquid will condense out?

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:02

Problem 174

Consider a $10-\mathrm{ft}^{3}$ rigid tank containing an airwater vapor mixture at $14.7 \mathrm{lbf} / \mathrm{in} .^{2}, 90 \mathrm{~F}, 70 \%$
relative humidity. The system is cooled until the water just begins to condense. Determine the final temperature in the tank and the heat transfer for the process.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:56

Problem 175

A water-filled reactor of $50 \mathrm{ft}^{3}$ is at $2000 \mathrm{lbf} / \mathrm{in} .^{2}$ $550 \mathrm{~F}$ and is located inside an insulated containment room of $5000 \mathrm{ft}^{3}$ that has air at $1 \mathrm{~atm}$ and $77 \mathrm{~F}$. Due to a failure, the reactor ruptures and the water fills the containment room. Find the final pressure.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:03

Problem 176

In the production of ethanol from corn, the solids left after fermentation are dried in a continuous-flow oven. This process generates a flow of $35 \mathrm{lbm} / \mathrm{s}$ moist air, $200 \mathrm{~F}$ with $70 \%$ relative humidity, which contains some volatile organic compounds and some particles. To remove the organic gases and the particles, the flow is sent to a thermal oxidizer (see Fig. P11.82), where natural gas flames bring the mixture to $1500 \mathrm{~F}$. Find the rate of heating by the natural gas burners.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:59

Problem 177

To reduce the natural gas use in the previous problem, a suggestion is to take and cool the mixture and condense out some water before heating it again. So, the flow is cooled from $200 \mathrm{~F}$ to $120 \mathrm{~F}$, as shown in Fig. $\mathrm{P} 11.83$, and the dryer mixture is heated to $1500 \mathrm{~F}$. Find the amount of water condensed out and the rate of heating by the natural gas burners for this case.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:07

Problem 178

Two moist air streams with $85 \%$ relative humidity, both flowing at a rate of $0.2 \mathrm{lbm} / \mathrm{s}$ of dry air, are mixed in a steady-flow setup. One inlet flowstream is at $90 \mathrm{~F}$ and the other is at $61 \mathrm{~F}$. Find
the exit relative humidity.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:11

Problem 179

A flow of moist air from a domestic furnace, state 1 in Fig. $\mathrm{P} 11.95,$ is at $120 \mathrm{~F}, 10 \%$ relative humidity with a flow rate of $0.1 \mathrm{lbm} / \mathrm{s}$ dry air. A small electric heater adds steam at $212 \mathrm{~F}$, 14.7 psia generated from tap water at 60 F. Up in the living room the flow comes out at state 4: $90 \mathrm{~F}, 60 \%$ relative humidity. Find the power needed for the electric heater and the heat transfer to the flow from state 1 to state 4 .

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:24

Problem 180

Atmospheric air at $95 \mathrm{~F}$, relative humidity $10 \%$ is too warm and also too dry. An air conditioner should deliver air at $70 \mathrm{~F}$ and $50 \%$ relative $\mathrm{hu}-$ midity at a rate of $3600 \mathrm{ft}^{3} / \mathrm{h}$. Sketch a setup to accomplish this, and find any amount of liquid (at $68 \mathrm{~F}$ ) that is needed or discarded, and any heat transfer.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
00:44

Problem 181

A commercial laundry runs a dryer that has an exit flow of $1 \mathrm{lbm} / \mathrm{s}$ moist air at $120 \mathrm{~F}, 70 \%$ relative humidity. To reduce the heating cost, a counterflow stack heat exchanger is used to heat the incoming fresh air at $68 \mathrm{~F}$ with the exit flow, as shown in Fig. $\mathrm{P} 11.105 .$ Assume the outgoing flow can be cooled to $77 \mathrm{~F}$ and the two flows have the same mass flow rate of dry air. Is there a missing flow in the figure? Find the rate of energy recovered by this heat exchanger.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:26

Problem 182

An indoor pool evaporates $3 \mathrm{lbm} / \mathrm{h}$ of water, which is removed by a dehumidifier to maintain $70 \mathrm{~F}, \Phi=70 \%$ in the room. The dehumidifier is a refrigeration cycle in which air flowing over the evaporator cools such that liquid water drops out, and the air continues flowing over the condenser, as shown in Fig. P11.107. For an air flow rate of $0.2 \mathrm{lbm} / \mathrm{s}$ the unit requires $1.2 \mathrm{Btu} / \mathrm{s}$ input to a motor driving a fan and the compressor, and it has a COP of $\beta=Q_{L} / W c=2.0$. Find the state of the air after the evaporator, $T_{2}, \omega_{2}, \Phi_{2}$ and the heat rejected. Find the state of the air as it returns to the room and the compressor work input.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
09:59

Problem 183

To refresh air in a room, a counterflow heat exchanger is mounted in the wall, as shown in Fig. P11.122. It draws in outside air at $33 \mathrm{~F}, 80 \%$ relative humidity and draws room air, $104 \mathrm{~F}, 50 \%$ relative humidity, out. Assume an exchange of $6 \mathrm{lbm} / \mathrm{min}$ dry air in a steady-flow device, and also assume that the room air exits the heat exchanger to the atmosphere at $72 \mathrm{~F}$. Find the net amount of water removed from room, any liquid flow in the heat exchanger, and $T, \phi$ for the fresh air entering the room.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
01:19

Problem 184

Weighing of masses gives a mixture at $80 \mathrm{~F}$ $35 \mathrm{lbf} / \mathrm{in} .^{2}$ with $1 \mathrm{lbm}$ oxygen, $3 \mathrm{lbm}$ nitrogen, and 1 lbm methane. Find the partial pressures of each component, the mixture specific volume (mass basis), mixture molecular weight, and the total volume.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:08

Problem 185

A mixture of $50 \%$ carbon dioxide and $50 \%$ water by mass is brought from $2800 \mathrm{R}$, $150 \mathrm{lbf} / \mathrm{in} .^{2}$ to $900 \mathrm{R}, 30 \mathrm{lbf} / \mathrm{in} .^{2}$ in a polytropic
process through a steady-flow device. Find the necessary heat transfer and work involved using values from Table $\mathrm{F} .4$

Hast Aggarwal
Hast Aggarwal
Numerade Educator
01:22

Problem 186

A large air separation plant takes in ambient air $(79 \%$ nitrogen, $21 \%$ oxygen by volume $)$ at 14.7 $\mathrm{lbf} / \mathrm{in} .^{2}, 70 \mathrm{~F},$ at a rate of $2 \mathrm{lb} \mathrm{mol} / \mathrm{s} .$ It discharges
a stream of pure oxygen gas at $30 \mathrm{lbf} / \mathrm{in} .^{2}, 200 \mathrm{~F}$ and a stream of pure nitrogen gas at $14.7 \mathrm{lbf} / \mathrm{in} .^{2}$ $70 \mathrm{~F}$. The plant operates on an electrical power input of $2000 \mathrm{~kW}$. Calculate the net rate of entropy change for the process.

Hast Aggarwal
Hast Aggarwal
Numerade Educator
02:06

Problem 187

Ambient air is at a condition of $14.7 \mathrm{lbf} / \mathrm{in} .^{2}$ $95 \mathrm{~F}, 50 \%$ relative humidity. A steady stream of air at $14.7 \mathrm{lbf} / \mathrm{in} .^{2}, 73 \mathrm{~F}, 70 \%$ relative humid-
ity is to be produced by first cooling one stream to an appropriate temperature to condense out the proper amount of water and then mixing this stream adiabatically with the second one under ambient conditions. What is the ratio of the two flow rates? To what temperature must the first stream be cooled?

Hast Aggarwal
Hast Aggarwal
Numerade Educator
09:02

Problem 188

Write a program to solve the general case of Problems $11.46 / 66$ in which the two volumes and the initial state properties of the argon and ethane are input variables. Use constant specific heat from Table A.5.

Mohammad Mehran
Mohammad Mehran
Numerade Educator
01:19

Problem 189

The setup in Problem 11.94 is similar to a process that can be used to produce dry powder from a slurry of water and dry material as coffee or milk. The water flow at state 3 is a mixture of $80 \%$ liquid water and $20 \%$ dry material on a mass basis with $C_{\mathrm{dry}}=0.4 \mathrm{~kJ} / \mathrm{kg} \mathrm{K}$. After the water is evaporated,
the dry material falls to the bottom and is removed in an additional line, $\dot{m}_{\text {dry }}$ exit at state 4 . Assume a reasonable $T_{4}$ and that state 1 is heated atmospheric air. Investigate the inlet flow temperature as a function of state 1 humidity ratio.

Penny Riley
Penny Riley
Numerade Educator
01:45

Problem 190

A dehumidifier for household applications is similar to the system shown in Fig. $\mathrm{P} 11.107 .$ Study the requirements of the refrigeration cycle as a function of the atmospheric conditions and include a worst case estimation.

Penny Riley
Penny Riley
Numerade Educator
01:07

Problem 191

A clothes dryer has a $60^{\circ} \mathrm{C}, \Phi=90 \%$ air flow out at a rate of $3 \mathrm{~kg} / \mathrm{min}$. The atmospheric conditions are $20^{\circ} \mathrm{C}$, relative humidity of $50 \% .$ How

Hast Aggarwal
Hast Aggarwal
Numerade Educator
13:58

Problem 192

Addition of steam to combustors in gas turbines and to internal-combustion engines reduces the peak temperatures and lowers emission of $\mathrm{NO}_{x}$. Consider a modification to a gas turbine, as shown in Fig. $\mathrm{P} 11.192$, where the modified cycle is called the Cheng cycle. In this example, it is used for a cogenerating power plant. Assume $12 \mathrm{~kg} / \mathrm{s}$ air with state 2 at $1.25 \mathrm{MPa}$, unknown temperature, is mixed with $2.5 \mathrm{~kg} / \mathrm{s}$ water at $450^{\circ} \mathrm{C}$ at constant pressure before the inlet to the turbine. The turbine exit temperature is $T_{4}=500^{\circ} \mathrm{C}$, and the pressure is $125 \mathrm{kPa}$. For a reasonable turbine efficiency, estimate the required air temperature at state 2 . Compare the result to the case where no steam is added to the mixing chamber and only air runs through the turbine.

Eric Mockensturm
Eric Mockensturm
Numerade Educator
02:47

Problem 193

Consider the district water heater acting as the condenser for part of the water between states 5 and 6 in Fig. $\mathrm{P} 11.192 .$ If the temperature of the mixture $(12 \mathrm{~kg} / \mathrm{s}$ air, $2.5 \mathrm{~kg} / \mathrm{s}$ steam $)$ at state 5 is $135^{\circ} \mathrm{C}$, study the district heating load, $\dot{Q}_{1},$ as a function of the exit temperature $T_{6} .$ Study also the sensitivity of the results with respect to the assumption that state 6 is saturated moist air.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
02:27

Problem 194

The cogeneration gas-turbine cycle can be augmented with a heat pump to extract more energy from the turbine exhaust gas, as shown in Fig. P11.194. The heat pump upgrades the energy to be delivered at the $70^{\circ} \mathrm{C}$ line for district heating. In the modified application, the first heat exchanger has exit temperature $T_{6 a}=T_{7 a}=45^{\circ} \mathrm{C},$ and the second one has $T_{6 b}=T_{7 b}=36^{\circ} \mathrm{C}$. Assume the district heating line has the same exit temperature as before, so this arrangement allows for a higher flow rate. Estimate the increase in the district heat- $-$ ing load that can be obtained and the necessary $y$ work input to the heat pump.

Banhishikha Sinha
Banhishikha Sinha
Numerade Educator
04:41

Problem 195

Several applications of dehumidification do not rely on water condensation by cooling. A desiccant with a greater affinity to water can absorb water directly from the air accompanied by a heat release. The desiccant is then regenerated by heating, driving the water out. Make a list of several materials such as liquids, gels, and solids and show examples of their use.

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator