1. A gas is at some initial P, V, and T.
Rank the following processes
by the change in the entropy of the gas as it increase in T by a small
dT. Explain using equations. (a) constant pressure
process (b) adiabatic process (c) constant volume process
2. Suppose that an inventor claims that a new engine has an efficiency of 0.61. The engine operates between energy reservoirs at 4 degrees C and 0 degrees C. It is a complicated device, with many pistons, gears, and pulleys, and the cycle involves freezing and melting. Does the claim of e=0.61 seem reasonable? Prove or disprove the claim.
3. Examine this
PV Diagram of a Stirling Engine (from a Uni. Karlsruhe study). The green line shows the idealized
Stirling process and the red line shows a simulation of a real Stirling engine,
taking irreversible processes into account. The pressure is in units of
bar ~ atmosphere ~ 105Pa.
(a) Identify the proceeses in the idealized Stirling engine, starting from
upper left point. If necessary, prove your identification with a calculation.
Assume that the gas used is air.
(b) Find the values of NkT at the extremes of the cycles
(highest and lowest temperatures).
(c) What is the Carnot efficiency of the cycle?
(d) What is the net work of the idealized Stirlig cycle?
(e) How much energy flowed into the system?
(f) What is the efficiency of the idealized Stirling cycle?
(g) What is the net work of the actual Stirling cycle?
(h) What is the efficiency of the actual Stirling cycle?
From the textbook:
12.X.11-15
12.RQ.24
12.P.33
Last updated November 15, 2009
