Q1 Nitrogen is compressed in an axial-flow compressor operating at steady state from a pressure of 15 lbf/in.² and a temperature of 50°F to a pressure 60 lbf/in.². The gas enters the compressor through a 6-in.-diameter duct with a velocity of 30 ft/s and exit at 198 °F with a velocity of 80 ft/s. Using the ideal gas model, and neglecting stray heat transfer and potential energy effects, determine the compressor power input, in hp. [Hint: a. do not neglect kinetic energy change; b) ideal gas properties of N? could be found from Table A-23E] [Answer] -23.48 hp Q2 As shown in the following figure, air enters a pipe at 40°C, 100 kPa with a volumetric flow rate of 23 m³/h. On the outer pipe surface is an electrical resistor covered with insulation. With a voltage of 130 V, the resistor draws a current of 5 amps. Assuming the ideal gas model with c? = 1.005 kJ/(kg · K) for air and ignoring kinetic and potential energy effects. Determine (a) the mass flow rate of the air, in kg/h, and (b) the temperature of the air at exit, in °C. [Answer] (a) 25.54 kg/h; (b) 130.95°C Insulation Electrical resistor + Air 1 2 T? = 40°C T? = ? p? = 100 kPa (AV)? = 23 m³/h -
Added by Connie L.
Close
Step 1
For Q1: Show more…
Show all steps
Your feedback will help us improve your experience
Adi S and 55 other Physics 101 Mechanics educators are ready to help you.
Ask a new question
Labs
Want to see this concept in action?
Explore this concept interactively to see how it behaves as you change inputs.
Key Concepts
Recommended Videos
Problem 2 Air enters a compressor at a pressure of 1.0 bar and exits at 8.5 bar. The compressor inlet temperature is 37 °C. The compressor is not insulated. Kinetic and potential energy effects can be neglected. The compressor outlet temperature is 650 K and the power input to the compressor is 500 kW. The compressor is operating at steady-state, and the air can be modeled as an ideal gas. The air mass flow rate through the compressor is 1.8 kg/s. a. Determine the direction and rate of heat transfer, in kJ/kg. b. Determine the compressor isentropic efficiency. c. Draw the process on a T-s diagram (clearly indicate the direction of the process and label the states). d. Determine the entropy generation rate, in kJ/kg/K, assuming the boundary temperature is 100 °C, and state the nature of the process (reversible, irreversible, or impossible). Summarize you results in the table below a. heat transfer, kJ/kg (include direction, so in or out?) b. isentropic efficiency d. entropy generation rate, in kJ/kg/K, and is it reversible, irreversible, or impossible?
Madhur L.
Q. 15.1 : Compute the time necessary to raise the pressure of air in the storage vessel from 200 kPa to 900 kPa with the two-stage compression system shown in Fig. 15-48. Data and conditions in addition to those shown in Fig. 15-48 are as follows: Adiabatic compression efficiency of both compressors Ηc = (isentropic work / actual work) (100) = 75% Volumetric efficiency of both compressors Ηv, % = (volume rate measured at compressor suction / displacement rate of compressor) (100) = 100 - 12[(Pdisch/Psuction) - 1] Displacement rates low-stage compressor, 0.12 m3/s high-stage compressor, 0.075 m3/s Properties of air Rair = 287 J/(kg ∙ K) cp = 1.00 kJ/(kg ∙ K) cv = 0.712 kJ/(kg ∙ K) Assume no heat transfer between the environment and the compressor, intercooler, and storage vessel. The principles of filling processes apply to air entering the tank, namely, the temperature of air after entering is greater than before entering the tank. The air at point 1 is dry enough that no moisture condenses at either heat exchanger. Use a time step of 4 s.
Sri K.
A two-stage air compressor compresses 5 kg/s of air from 100 kPa to 1000 kPa (see figure below). The first compressor stage compresses the air to 500 kPa and it is then cooled to 40°C by an intercooler. Assume both stages of the compressor are adiabatic and reversible. Calculate: a) the power required by the compressor stages (-878.5 kW, -346.4 kW), b) the heat rejected from the intercooler (-803.2 kW), c) what is the percent difference between the work done by the two-stage compressor shown above and a single-stage compressor for the same pressure increase? Assume the single stage of the compressor is adiabatic and reversible (13.7%). Use: R = 0.287 kJ/kgK, Cv = 0.717 kJ/kgK, Cp = 1.004 kJ/kgK
Recommended Textbooks
University Physics with Modern Physics
Physics: Principles with Applications
Fundamentals of Physics
Transcript
Watch the video solution with this free unlock.
EMAIL
PASSWORD