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 MW10 lb /s, m3 15 b /s, en = 1000 Btu/Ib, eg = 50 Btu/Ib, eg = 400 Btu/lbd. Direct contact heat exchanger: m1

a)Write the expression for exergetic efficiency for the turbine.

Answered: 7.66 Referring to the discussion of…

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

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6.107 Figure P6.107 provides the schematic of a heat pump using Refrigerant 134a as the working fluid, together with steady-state data at key points. The mass flow rate of the refrigerant is 7 kg/min, and the power input to the compressor is 5.17 kW. (a) Determine the co- efficient of performance for the heat pump. (b) If the valve were re- placed by a turbine, power could be produced, thereby reducing the power requirement of the heat pump system. Would you recommend this power-saving measure? Explain. She P2 = P3 = 9 bar Tz = 60°C Saturated liquid Condenser Expansion W = 5.17 kW Compressor valve Evaporator m= 7 kg/min P1 =P4 = 2.4 bar FIGURE P6.107
Steam at 44 bar and a dryness fraction, x = 0.9 is throttled to a pressure of 12 bar. Calculate thedifference in power output in kilowatts between the following two expansion processes:a) Steam at the initial pressure of 44 bar and x = 0.9 at State 1 is expanded in a turbine to State 3 at 0.12 bar.b) Steam at the reduced pressure of 12 bar after throttling at State 2 is expanded in another turbine to State 4 at the same exhaust pressure of 0.12 bar.The mass flow rate of steam is 8 kg/sec in both cases and the expansion in both turbines can be assumed to be reversible and adiabatic. Sketch both expansion processes on the same T-s diagram using the respective initial and final state points as described above.Explain the reason for the difference in power output.Calculate the mass flow rate of steam for the turbine operating at the throttled/reduced pressure to generate the same output as the turbine operating at the pressure before throttling.NOTE: You are required to number the state…
6.111 Steam enters a two-stage turbine with reheat operating at steady state as shown in Fig. P6.111. The steam enters turbine 1 with a mass flow rate of 120,000 lb/h at 1000 lbf/in.², 800°F and expands to a pressure of 60 lbf/in. From there, the steam enters the reheater where it is heated at constant pressure to 350°C before entering tur- bine 2 and expanding to a final pressure of 1 lbf/in.? The turbines operate adiabatically with isentropic efficiencies of 88% and 85%, respectively. Kinetic and potential energy effects can be neglected. Determine the net power developed by the two turbines and the rate of heat transfer in the reheater, each in Btu/h. Qin P3 = 60 lbf/in.2 T = 350°C P2 = 60 lbf/in.2 Reheater W net Turbine 1 Turbine 2 Nu = 88% Ni2 = 85% P4 =1 lbf/in.2 P1 = 1000 Ibf/in.2 T = 800°F m = 120,000 lb/h FIGURE P6.111
As shown in the figure below, two reversible cycles arranged in series each produce the same net work, Wcycle. The first cycle receives energy QH by heat transfer from a hot reservoir at TH = 1000°R and rejects energy Q by heat transfer to a reservoir at an intermediate temperature, T. The second cycle receives energy Q by heat transfer from the reservoir at temperature T and rejects energy Qc by heat transfer to a reservoir at Tc = 500°R. All energy transfers are positive in the directions of the arrows. Determine: Hot reservoir at TH QH Reservoir at T R1 lo ali R2 Qc Cold reservoir at Te W. cycle W cycle (a) the intermediate temperature T, in °R, and the thermal efficiency for each of the two power cycles. (b) the thermal efficiency of a single reversible power cycle operating between hot and cold reservoirs at 1000°R and 500°R. respectively. Also, determine the ratio of the net work developed by the single cycle to the net work developed by each of the two cycles, Wcycle.
As shown in the figure below, two reversible cycles arranged in series each produce the same net work, Wcycle. The first cycle receives energy QH by heat transfer from a hot reservoir at TH = 1500°R and rejects energy Q by heat transfer to a reservoir at an intermediate temperature, T. The second cycle receives energy Q by heat transfer from the reservoir at temperature T and rejects energy QC by heat transfer to a reservoir at TC = 450°R. All energy transfers are positive in the directions of the arrows. Determine:(a) the intermediate temperature T, in °R, and the thermal efficiency for each of the two power cycles.(b) the thermal efficiency of a single reversible power cycle operating between hot and cold reservoirs at 1500°R and 450°R, respectively. Also, determine the ratio of the net work developed by the single cycle to the net work developed by each of the two cycles, Wcycle.
As shown in the figure below, two reversible cycles arranged in series each produce the same net work, Wcycle. The first cycle receives energy QH by heat transfer from a hot reservoir at TH-1000°R and rejects energy Q by heat transfer to a reservoir at an intermediate temperature, T. The second cycle receives energy Q by heat transfer from the reservoir at temperature T and rejects energy Qc by heat transfer to a reservoir at Te - 500°R. All energy transfers are positive in the directions of the arrows. Determine: Hot reservoir at TH lH R1 Reservoir Q at T 20 R2 lc Cold reservoir at Tc We cycle W Wcycle (a) the intermediate temperature T, in °R, and the thermal efficiency for each of the two power cycles. (b) the thermal efficiency of a single reversible power cycle operating between hot and cold reservoirs at 1000°R and 500°R, respectively. Also, determine the ratio of the network developed by the single cycle to the network developed by each of the two cycles, Wcycle-
As shown in the figure below, two reversible cycles arranged in series each produce the same net work, Weycle: The first cycle receives energy QH by heat transfer from a hot reservoir at TH = 1000°R and rejects energy Q by heat transfer to a reservoir at an intermediate temperature, T. The second cycle receives energy Q by heat transfer from the reservoir at temperature Tand rejects energy Qc by heat transfer to a reservoir at Tc = 450°R. All energy transfers are positive in the directions of the arrows. Hot reservoir at TH R1 W cycle Reservoir at T W cycle R2 Cold reservoir at Te Determine: (a) the intermediate temperature T, in °R, and the thermal efficiency for each of the two power cycles. (b) the thermal efficiency of a single reversible power cycle operating between hot and cold reservoirs at 1000°R and 450°R, respectively. Also, determine the ratio of the net work developed by the single cycle to the net work developed by each of the two cycles, Wcycle
Two reversible cycles are in series, each process doing the same net work, Wcycle. The first cycle receives energy QH by heat transfer from a hot reservoir at 1000°R and energy Q is reinjected by heat transfer to a reservoir at an intermediate temperature, T. The second cycle receives energy Q by heat transfer from the reservoir at temperature T and reinjects the QC energy by heat transfer to the reservoir at a temperature of 400°R. All energy transferred is positive in the direction of the arrow. Determine: a) the intermediate temperature T, in °R, and the thermal efficiency for each of the two cycles; b) the thermal efficiency of a simple reversible cycle operating between the hot and cold reservoirs at 1000°R and 400°C, respectively. Then determine the net work done by the simple cycle, expressed in terms of the net work done by each of the two cycles, Wcycle.
Q.8 A reversible cycle receives 40 kJ of heat from one heat source at a temperature of 127 °C and 37 kJ from another heat source at 97 °C. The heat rejected (in kJ) to the heat sink at 47 °Cis A 36 В 49 C 64 D 81
As shown in the figure below, two reversible cycles arranged in series each produce the same net work, Weycle. The first cycle receives energy QH by heat transfer from a hot reservoir at TH = 1500°R and rejects energy Q by heat transfer to a reservoir at an intermediate temperature, T. The second cycle receives energy Q by heat transfer from the reservoir at temperature T and rejects energy Qc by heat transfer to a reservoir at Tc = 500°R. All energy transfers are positive in the directions of the arrows. Hot reservoir at T RI W. cycle Reservoir at T R2 Wcycle Cold reservoir at Te Determine: (a) the intermediate temperature T, in °R, and the thermal efficiency for each of the two power cycles. (b) the thermal efficiency of a single reversible power cycle operating between hot and cold reservoirs at 1500°R and 500°R, respectively. Also, determine the ratio of the net work developed by the single cycle to the net work developed by each of the two cycles, Woycle-
2. A power cycle receives energy QH by heat transfer from a hot reservoir at TH = 1200 R and rejects energy QC by heat transfer to a cold reservoir at TC = 400 R. For each of the following cases, determine whether the cycle operates reversibly, operates irreversibly, or is impossible. (a) QH = 900 Btu, Wcycle = 450 Btu (b) QH = 900 Btu, QC = 300 Btu (c) Wcycle = 600 Btu, QC = 400 Btu (d) Eff. = 70%
Current Attempt in Progress A pump is used to circulate hot water in a home heating system. Water enters the well-insulated pump operating at steady state at a rate of 0.42 gal/min. The inlet pressure and temperature are 14.7 Ibf/in.?, and 180°F, respectively; at the exit the pressure is 90 Ibf/in.2 The pump requires 1/25 hp of power input. Water can be modeled as an incompressible substance with constant density of 60.58 Ib/ft and constant specific heat of 1 Btu/lb · °R. Neglecting kinetic and potential energy effects, determine the temperature change, in °R, as the water flows through the pump. AT = i °R

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