UNIFIED ENGINEERING                                                                           Fall 2006

                                                                                                                        Ian A. Waitz

                       

 

Problem T21 (Unified Thermodynamics) (LO#4, LO#5)

 

Hydrogen at T1=300K and V1=100cm3 expands adiabatically in a piston-cylinder assembly to T2=270K and V2=200cm3. Assume that hydrogen behaves as an ideal gas with constant specific heats cv=10085 J/kg-K, cp=14209 J/kg-K, and R=4124 J/kg-K.

 

a) Find the change in entropy and the work done per kilogram of hydrogen.

 

b) If the expansion were adiabatic and quasi-static between the same volumes, what would be the final temperature, the work done and the change in entropy?

 

c) In homework problem T4 you calculated the difference in work for two adiabatic processes: one impulsive and the other quasi-static.  Calculate the change in entropy for each of these processes.