Give expressions for variation of CP with temperature (T) for Air, CO2, O2 and He. Assume Air, CO2, O2 and He to be ideal gases

Give expressions for variation of CP with temperature (T) for Air, CO2, O2
and He. Assume Air, CO2, O2 and He to be ideal gases

ME 291 (Spring 2017) – Homework 4
Submission Deadline
ME291-001: 27th February (Monday) before Class
ME291-002: 28st February (Tuesday) before Class
Write your name, course name or number at the top right hand corner of the first page of your
homework.
Homework Problem 1: Give expressions for variation of CP with temperature (T) for Air, CO2, O2
and He. Assume Air, CO2, O2 and He to be ideal gases.
Homework Problem 2: What are the enthalpy (h) and internal energy (u) values for Air, CO2 and
O2 at 350K, 600K and 900K? What are the units for h and u? Assume Air, CO2 and O2 to be ideal
gases.
Homework Problem 3: Is ‘h’ and ‘u’ an extensive or an intensive property? Why?
Homework Problem 4: What are the enthalpy (h) and internal energy (u) values for CO2 and O2 at
0K set to?
Homework Problem 5: A well-insulated ‘rigid’ tank holds 2 kg of Air at 300K and 5 atm. Due to
a fire event inside the tank, the Air inside the tank gets heated at a rate of 1.5 kW for 10 minutes.
Assuming Air to be an ideal gas, calculate the final temperature and final pressure of Air in the
tank.
Homework Problem 6: Convert units – For N2 at T=300K, u=6229 kJ/kmol. Convert u to kJ/kg.
Homework Problem 7: As shown in the figure below, a well-insulated tank fitted with an electrical
resistor of negligible mass holds 2.5 Kg of nitrogen (𝑁2), initially at 300 K, 2 bar. Over a period
of 15 minutes, electricity is provided to the resistor at a constant voltage of 150 volts and with a
constant current of 1 ampere. Assuming ideal gas behavior, determine the nitrogen’s final
temperature, in K, and the final pressure, in bar.
2/2
Homework Problem 8: Two-tenths kmol of nitrogen (𝑁2) in a piston-cylinder assembly undergoes
two processes in series as follows:
Process 1-2 􀃆 Constant pressure at 5 bar from 𝑉1 = 1𝑚3 to 𝑉2 = 1.1 𝑚3.
Process 2-3 􀃆 Constant volume to 𝑝3 = 4.5 𝑏𝑎𝑟
Assuming ideal gas behavior and neglecting kinetic and potential energy effects, determine the
work and heat transfer for each process, in kJ.
Homework Problem 9: What are the critical temperatures and pressures for Air, Ammonia, CO2
and Propane?
Homework Problem 10: Determine the specific volume of Air, Ammonia, CO2 and Propane at
1000C and 20 bar assuming it to be an ideal gas.
Homework Problem 11: Determine the compressibility factor of Air, Ammonia, CO2 and
Propane at 1000C and 20 bar. Do any of the gases behave like an ideal gas at 1000C and 20 bar?
Homework Problem 12: Determine the specific volume of Air, Ammonia, CO2 and Propane at
1000C and 20 bar.
Homework Problem 13: What is the quality of mixture for:
a) u = 1500 kJ/kg for saturated water at T=1000C and P=1.014 bar
b) h = 2000 kJ/kg for saturated water at P=10 bar and T=179.90C
c) h = 3483.9 kJ/kg for superheated water at P=5 bar and T=5000C
Homework Problem 14: For mixtures of quality 0.7, determine the ν, h and u values for
saturated:
a) water at 300C
b) Refrigerant 134a at 300C
c) Propane at 300C
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