Determine the entropy change and the heat transfer. Problem 7.8: 3 kg of steam initially at a quality of 40 % and a pressure of 4 MPa is expanded in a cylinder at constant temperature until the pressure is halved.
Calculate the work necessary (a) assuming a constant specific heat, and (b) the gas table. Problem 7.7: A piston cylinder arrangement is used to compress 0.1 kg of air isentropically from initial conditions of 200 kPa and 17 ☌ to 3.0 MPa. Compute the heat transfer and entropy change if the gas is (a) air, (b) helium, or (c) carbon dioxide. Problem 7.6: The temperature of a gas changes from 17 to 487 ☌ while the pressure remains constant at 0.2 MPa.
What is the entropy change of the gas if the gas is (a) helium, (b) hydrogen, (c) nitrogen, (d) air, (e) carbon dioxide? The gas is heated and reaches a gage pressure of 0.9 MPa. Problem 7.5: Gas is stored in a rigid container at 7 ☌. If the high temperature reservoir provides 50 kW of heat, what is the power produced and the temperature of the high temperature reservoir? Problem 7.4: A Carnot engine rejects 100 MJ of heat every hour to a low temperature reservoir at 5 ☌. Problem 7.3: An industrial proposer claims that he can extract 50 kw power by drawing 3000 kJ of heat per minute from a high temperature reservoir at 950 ☌ and dumping heat to a reservoir at 25 ☌. What is the maximum power that can be generated? Assume that a supply of water at 1.0 lbm/s is available.
The maximum temperature of the ground water is 200 ☏, and the average atmospheric temperature is 60 ☏. Problem 7.2: A industrial plant wants to use hot groundwater from a hot spring to power a heat engine. Calculate the rate of heat transfer from the high temperature reservoir and the rate of heat transfer to the low temperature reservoir.
Problem 7.1: A Carnot heat engine produces 1 MW by transferring energy between two reservoirs at 100 and 5 ☌.
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