Chapter 5, Problem 5.31P

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%

Problem 1 A power cycle operating between two reservoirs receives energy Qn by heat transfer from a hot reservoir at TH 1888 K and rejects energy Oc by heat transfer to a cold reservoir at Tc=377 K. For each of the following cases determine whether the cycle operates reversibly, irreversibly, or does not verify the second aw of thermodynamics (make all necessary calculation for each case): %3D a) QH=1700 kJ and Wrcle = 1600 b) QH=702 kJ and Qc= 351 kJ c) =94 % d) QH=1700 kJ and Wcl= 1800 kl %3D %3D

7. A power cycle operating between two thermal reservoirs receives energy QH by heat transfer from a hot reservoir at TH = 1600 K and rejects energy QC by heat transfer to a cold reservoir at TC = 400 K. For each of the following cases determine whether the cycle operates reversibly, operates irreversibly, or is impossible. a. QH = 1000 kJ, ŋ = 75% b. QH = 1100 kJ, Wcycle = 800 kJ c. QH = 900 kJ, QC = 300 kJ

C5 8.

Q.34

As shown in the figure, an air conditioner operating at steady state maintains a dwelling at 70°F on a day when the outside temperature is 103.5°F. The rate of heat transfer into the dwelling through the walls and roof is 30,000 Btu/h and the net power input to the air conditioner compressor is 3.45 hp. Step 1 B Inside, 70° F Determine the coefficient of performance for the air conditioner. = Evaporator i 30,000 Btu/h Determine the coefficient of performance of the air conditioner. Determine the power input required, in hp, and the coefficient of performance for a reversible air conditioner providing the same cooling effect while operating between the same cold and hot temperatures. Refrigerant loop Compressor Outside Q + Condenser

At steady state, a reversible heat pump cycle discharges energy at the rate Q˙H to a hot reservoir at temperature TH, while receiving energy at the rate Q˙C from a cold reservoir at temperature TC.(a) If TH = 10°C and TC = 2°C, determine the coefficient of performance.(b) If Q˙H= 15 kW, Q˙C= 8.75 kW, and TC = 0°C, determine TH, in °C.(c) If the coefficient of performance is 5 and TH = 27°C, determine TC, in °C.

5.9

Q: The working fluid, in a steady flow process flows at a rate of 220 kg/min. The fluid rejects 100 kJ/s passing through the system. The conditions of the fluid at inlet and outlet are given as : C1 = 320 m/s, p1 = 6.0 bar, u1 = 2000 kJ/kg, v1 = 0.36 m3/kg and C2 = 140 m/s, p2 1.2 bar, u2 = 1400 kJ/kg, v2 = 1.3 m3/kg. The suffix 1 indicates the condition at inlet and 2 indicates at outlet of the system. Determine the power capacity of the system in MW. The change in potential energy may be neglected. Fluid Fluid leaves System enters