Chapter 5, Problem 5.3CU

Three sub steps of a thermodynamic cycle are employed in order to change the state of a gas from 1 bar, 1.5 cubic meter and internal energy of 512 kJ. The processes are: 1st step: Compression at constant PV to a pressure of 2 bar and internal energy of 690 kJ. 2nd step: A process where work transferred is zero and heat transferred is - 150 kJ. 3rd step: A process where work transferred is -50 kJ. without KE and PE changes, determine: a. heat transferred during 1st step (kJ) b. heat transferred during 3rd step (kJ)

7.66 Referring to the discussion of Sec. Z.6.2 as required, evaluate the exergetic efficiency for each of the following cases, assuming steady-state operation with negligible effects of heat transfer with the surroundings: a. Turbine: Wer 1200 hp, e 250 Btu//lb, eg = 15 Btu/lb, m 240 lb/min. b. Compressor: Wev/m=-105 kJ /kg, e = 5 kJ/kg, eg = 90 kJ/kg, m 2 kg /s. c. Counterflow heat exchanger: mh = 3 kg/s, me 10 kg /s, ef = 2100 kJ/kg, e = 300 kJ/kg, É = 3.4 MW 10 lb /s, m3 15 b /s, en = 1000 Btu/Ib, eg = 50 Btu/Ib, eg = 400 Btu/lb d. Direct contact heat exchanger: m1

Air enters the compressor of a simple gas turbine at 14.5 lbf/in.2, 80°F, and exits at 87 lbf/in.2, 514°F. The air enters the turbine at 1540°F, 87 lbf/in.2 and expands to 917°F, 14.5 lbf/in.2 The compressor and turbine operate adiabatically, and kinetic and potential energy effects are negligible. On the basis of an air-standard analysis, a. develop a full accounting of the net exergy increase of the air passing through the gas turbine combustor, in Btu/lb. b. devise and evaluate an exergetic efficiency for the gas turbine cycle. Let T0 = 80°F, p0 = 14.5 lbf/in.2