Chapter 7, Problem 7.91P

10. Carnot cycle thermal efficiency is increased by reducing lower(sink) temperature 11. A system with higher exergy has more capacity to do work than a system with lower exergy. 12. A diffuser has low pressure at inlet and high pressure at outlet 13. Carnot efficiency equation can also be used to find efficiency of conversion of electrical and/or magnetic energy to work. 14. Quality factor of 0.75 indicates supersaturated vapor 15. Law of conservation of Mass and energy applied to Nozzles and Diffusers indicates that under ideal conditions, the change in kinetic energy of the fluid results in a complimentary change in enthalpy of the fluid

Determine the specific exergy of saturated water vapor at 137 °C, where To = 313K, Po = 101.3kPa. Assume the velocity and elevation is zero with reference to the environment. You must use following tables to solve this problem. (answer to 2 decimal) Saturated water temperature table Sat Liq. Temp., Sat Liq. Sat Liq. Sat Liq. vf uf hf sf °C m3/kg kJ/kg kJ/kg kJ/kg.K 30 0.001004 125.73 125.74 0.4368 35 0.001006 146.63 146.64 0.5051 40 0.001008 167.53 167.53 0.5724 45 0.00101 188.43 188.44 0.6386 Saturated water temperature table Temp., Sat. Vap. Sat. Vap. Sat. Vap. Sat. Vap. hg kJ/kg vg ug sg °C m3/kg kJ/kg kJ/kg.K 125 0.7508 2534.5 2713.5 7.0745 126 0.7358 2535.5 2714.8 7.0649 127 0.7208 2536.5 2716.1 7.0553 128 0.7058 2537.5 2717.4 7.0457 129 0.6908 2538.5 2718.7 7.0361 130 0.6758 2539.5 2720.0 7.0265 131 0.6608 2540.5 2721.4 7.0169 132 0.6458 2541.4 2722.7 7.0073 133 0.6308 2542.4 2724.0 6.9977 134 0.6158 2543.4 2725.3 6.9881 6.9785 135 0.6008 2544.4 2726.6 136 0.5858 2545.4 2727.9…

a (a) Air in (b) (c) Diffuser Compressor Combustors 2 State State 1 80 State 2 3300 State 3 3200 State 4 400 State 5 80 wwww Pressure (kPa) 3 Turbine 4 Figure 1: Figure for Problem 2. In a modern jet engine, air passes through the following states from the inlet to the outlet, as shown in Figure 1: Product gases out 260 780 1500 900 640 K 5 > Nozzle justify them) to find the compressor specific work. Temperature (K) For this problem, you may neglect any heat transfer, as well as neglect kinetic energy except at the outlet (state 5). Use the tables for obtaining properties (do not assume constant specific heat). Assume air is an ideal gas with ideal gas constant of R = 0.287 kJ/kg-K. Use the appropriate conservation equations and make approximations (and In a similar manner, find the turbine specific work. And finally, using similar arguments, find the nozzle exit velocity.

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

p89#11. the work required to compare a gas reversibly according to pV1.30=c is 67,790J, if there is no flow. Determine change of internal energy and Q if the gas is (a)air,(b) methane. for methane,k=1.321,R=518.45J/kgm.K, Cv=1.6187, Cp=2.1377kJ/kgm.K

Air as an ideal gas flows through the compressor and heat exchanger shown in the figure. A separate liquid stream also flows through the heat exchanger. The data given are for operation at steady state. Stray heat transfer to the surroundings can be neglected, as can all kinetic and potential energy changes. Determine the compressor power, in kW, and the mass flow rate of the cooling water, in kg/s.

ů EJERCICIO-2 9.66 WP A combined gas turbine-vapor power plant operates as shown in Fig. P9.66. Pressure and temperature data are given at prin- cipal states, and the net power developed by the gas turbine is 147 MW. Using air-standard analysis for the gas turbine, determine a. the net power, in MW, developed by the power plant. b. the overall thermal efficiency of the plant. T₂ = 690 K P₂= 13.6 bar 2- Air inlet Exhaust Compressor Ts = 400 K P5 = 1 bar P6 P7 FIGURE DO 66 6 Combustor T₁ = 300 K 1 P₁ = 1 bar Gas turbine ein www www Heat exchanger Pump 1p = 80% Steam cycle T3= 1580 K +3 P3= 13 bar Turbine -4 T4 = 900 K P4 = 1 bar T₁ = 520°C P = 100 bar Turbine Condenser 1₁ = 85% P9 = Ps= 0.08 bar W - gas 147 MW W vap Cook

Air enters a diesel engine with a density of 1.0 kg/m³. The compression ratio is 21. At steady state, the air intake is 30 x 10-3kg/s and the net work output is 15 kW. The mean effective pressure (in kPa)

An ideal air-standard Brayton cycle operating at steady state produces 50 MW of power. Operating data at principal states in the cycle are given in the table below. The states are numbered as in the figure below. State p(kPa) T(K) h (kJ/kg) 1 100 300 300 1200 603.5 610.5 3 1200 1450 1574 4 100 780.3 800 Heat exchanger cycle Compressor Turbine Heat exchanger Determine: (a) the mass flow rate of air, in kg/s. (b) the rate of heat transfer, in kW, to the working fluid passing through the heat exchanger. (c) the percent thermal efficiency.