HW#5 Summer 2020-1 - homework 5 PDF

Preview

Summary

homework 5...

Description

MAE 3310: Thermodynamics I HW#5 Summer 2020 DUE:08/04/2020

1. Air is expanded from 2000 kPa and 500°C to 100 kPa and 50°C. Assuming constant specific heats, determine the change in the specific entropy of air. 2. A piston–cylinder device contains 0.75 kg of nitrogen gas at 140 kPa and 37 °C. The gas is now compressed slowly in a polytropic process during which P𝑉 1.3 = constant. The process ends when the volume is reduced by one-half.Determine the Entropy change of Nitrogen during this process. 3. Air is compressed in an isentropic compressor from15 psia and 70°F to 200 psia. Determine the outlet temperature and the work consumed by this compressor per unit mass of air.

4. Water enters the pump of a steam power plant as saturated liquid at 20 kPa at a rate of 45 kg/s and exits at 6 MPa. Neglecting the changes in kinetic and potential energies and assuming the process to be reversible, determine the power input to the pump.

5. Helium gas is compressed from 16 psia and 85 °F to 120 psia at a rate of 10 f𝑡 3 /s. Determine the power input to the compressor, assuming the compression process to be(a) isentropic, (b) polytropic with n =1.2, (c) isothermal.

6. Steam at 4 MPa and 350 °C is expanded in an adiabatic turbine to 120 kPa. What is the isentropic efficiency of this turbine if the steam is exhausted as a saturated vapor?

7. Carbon dioxide enters an adiabatic compressor at100 kPa and 300 K at a rate of 1.8 kg/s and exits at 600 kPa and 450 K. Neglecting the kinetic energy changes, determine the isentropic efficiency of the compressor.

8. Air enters a compressor steadily at the ambient conditions of 100 kPa and 22°C and leaves at 800 kPa. Heat is lost from the compressor in the amount of 120 kJ/kg and the air experiences an entropy decrease of 0.40 kJ/kg ∙K. Using constant specific heats, determine ( a) the exit temperature of the air, (b) the work input to the compressor, and (c) the entropy generation during this process....