1- Consider a Steam Power Plant Operating on the Simple Ideal Rankine Cycle. Steam Enters

1- Consider a steam power plant operating on the simple ideal Rankine cycle. Steam enters the turbine at 3 MPa and 350°C and is condensed in the condenser at a pressure of 75 kPa. Determine the thermal efficiency of this cycle.

2- A commercial refrigerator with refrigerant-134a as the working fluid is used to keep the refrigerated space at _30°C by rejecting its waste heat to cooling water that enters the condenser at 18°C at a rate of 0.25 kg/s and leaves at 26°C. The refrigerant enters the condenser at 1.2 MPa and 65°C and leaves at 42°C. The inlet state of the compressor is 60 kPa and _34°C and the compressor is estimated to gain a net heat of 450 W from the surroundings. Determine (a) the quality of the refrigerant at the evaporator inlet, (b) the refrigeration load, (c) the COP of the refrigerator.

3- In a refrigeration system, would you recommend condensing the refrigerant-134a at a pressure of 0.7 or 1.0 MPa if heat is to be rejected to a cooling medium at 15°C? Why?

4- Carnot refrigerator operates between temperature limits of -20 ℃ and 50 ℃. Calculate the C.O.P. What will be the C.O.P. if the cycle is used as a heat pump?

5- An inventor claims to have developed a refrigerator which maintains the cold store at -13 ℃ where the ambient temperature 300 K and has a C.O.P. of 7, can he achieve that?

6- A Carnot refrigerator requires 1.2 kW to produce one ton refrigerant (TR) to maintain the lower temperature at -40 ℃. Determine the higher temperature and the heat rejected.

7- Reversed Carnot cycle has a C.O.P. = 4 and consumed 12 kW. Determine the ratio TH /TL and the capacity in TR.

8- A steady-flow Carnot refrigeration cycle uses refrigerant-134a as the working fluid. The refrigerant changes from saturated vapor to saturated liquid at 30°C in the condenser as it rejects heat. The evaporator pressure is 160 kPa. Show the cycle on a T-s diagram relative to saturation lines, and determine (a) the coefficient of performance, (b) the amount of heat absorbed from the refrigerated space, and (c) the net work input.

9- R-134a ideal VCC and Carnot refrigerator operate between condensing and evaporating temperatures of 60 ℃ and -20 ℃. Determine:

a- The work and the refrigeration effect of Carnot.

b- The excess work due to throttling.

c- The loss in refrigeration effect due to throttling.

10- A heat pump that operates on the ideal vapor compression cycle with refrigerant-134a is used to heat a house and maintain it at 75°F by using underground water at 50°F as the heat source. The house is losing heat at a rate of 60,000 Btu/h. The evaporator and condenser pressures are 50 and 120 psi, respectively. Determine the power input to the heat pump and the electric power saved by using a heat pump instead of a resistance heater.