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Thermodynamics Problem Set

1. Air in a piston/cylinder expands reversibly and adiabatic. The initial temperature is 507K and the pressure is 600Kpa. The final pressure is 120Kpa. Find
a) Final temperature assuming constant specific heat.
b) Work
c) Mass of the air in kg

2. 30,000 kj/h is needed for a heat pump to maintain a building at 20 degrees Celsius with an outside temperature of 0 degrees Celsius. Find
a) The minimum power to operate heat pump in KW
b) The maximum COP for heat pump

Solution Preview

Question 1(a):
Let initial pressure P1=600 Kpa
Final Pressure P2 = 120 Kpa
Initial Temperature T1=507 K
Let Final Temperature = T2
T2 / T1 = (P2 /P1)^(K-1)/K
T2 = ((120/600)^(0.286) )* 507
T2= 202 K
Final Temperature is ...

Solution Summary

Full solution. 300 words.
Temperature: T2 / T1 = (P2 /P1)^(K-1)/K
Work: W = n Cv (T2 -T1)
COP = Th / ( Th - Tc)

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