Refrigerant R12 is used in a vapour compression cycle. The saturated vapour enters the compressor at -18.8°C, and subsequently leaves at 75°C and 10 bar. The saturated liquid leaving the condenser is at 10 bar. The resulting stream is throttled and evaporated before being fed back to the compressor.  a) Determine the coefficient of performance of the refrigerator. Take the specific enthalpy, h, at 10 bar and 36 K of superheat to be 163.7 kJ/kg b) Obtain the isentropic efficiency of the compressor. Take the specific entropy, s, at 10 bar to be 1.188 kJ/kg

An r-134a refrigerator operates a simple vapor compression cycle (SVCC). The evaporatoroperates at -10 °C, while the condenser operates at 1 MPa. R-134a flows around the system at 10 g/s.a. Graph the cycle in a P-h diagram and calculate the temperature at the exit of the compressor, assuming it is 100% isentropicallyefficient.b. Calculate the power required by the compressor (in W) and the cooling effect of the refrigerator (in kW) c. Compute for the COP of the system. What is its percent difference from the reversible efficiency?

Q 4) A simple vapour compression plant produces (5 tonnes) of refrigeration. The enthalpy values at inlet to compressor, at exit from the compressor, and at exit from the condenser are (183.19, 209.41 and 74.59 kJ/kg) respectively. Determine :- (i) The refrigerant flow rate, (ii) The C.O.P. (ii) The power required to drive the compressor. (iv) The rate of heat rejection to the condenser.

ercise 6 6.1 A surface condenser is fitted with separate air and condensate outlets. A portion of the cooling surface is screened from the incoming steam and the air is passes over these screened tubes to the air extraction and becomes cooled below the condensate temperature. The condenser receives 20 000kg/hr of dry saturated steam at 36.2°C. At the condensate outlet the temperature is 34.6°C TK and at the air extraction the temperature is 29°C. The volume of air and vapour leaving the condenser is 3.8m3/min. Assume constant pressure throughout the condenser, calculate: 6.1.1 the mass of air removed per 10 000kg of steam (2.63kg); 6.1.2 the mass of steam condensed in the air cooler per minute (0.5kg/min)%3B 6.1.3 the heat rejected to the cooling water (13451kW).

b- An evacuated tank ,shown if fig of 1 ft3 is coupled to air supply line through valve .When the valve is opened, the air flow from supply line at 70°F,120 psi until the pressure reaches 90psi . calculate the final temperature and mass inside tank ,assuming the process is adiabatic. R= 53.34 Ibf-ft/lbm °R use the table below in case. Alr supply line Tank Idcat-Gas Propertiles of Air (English Units)0, Standard Entropy at 1 atm = 161.325 kPa = 14.696 1bf/in.² (R) (Btulbm) (Btu/lbm) (Btu/lbm R) (R) (Btu/lbm) (Btu/lbm) (Btu/Ibm R) 400 68.212 95.634 1.56788 1950 357.243 490.928 1.96404 440 75.047 105.212 1.59071 2000 367.642 504.755 1.97104 480 81.887 114.794 1.61155 2050 378.096 S18.636 1.97790 520 88.733 124.383 1.63074 2100 388.602 532.570 1.98461 536.67 91.589 128.381 1.63831 2150 399.158 546.554 1.99119 540 92.160 129.180 1.63979 2200 409.764 560.588 1.99765 560 95.589 133.980 1.61852 2300 431.114 588.793 2.01018 600 102.457 143.590 1.66510 2400 452.640 617.175 2.02226 1000 172.564…

Q.6 A vapor compression cycle uses R134a as the refrigerant . The vapor condenses at 40 degrees * C and is subcooled to 35 degrees * C before entering the expansion valve . The evaporating temperature is - 5 degrees * C . The vapor leaving the evaporator is superheated to 5 degrees * C at entry to the compressor . The heat absorption rate is 13 kW and the compression process is isentropic . Calculate (i) the refrigerant flow rate, (ii ) the work input , and ( iii ) the COP . Answers: () 0.0837kg * s ^ - 1 , (ii) 2.63 kW , (iii) 4.95

4. A refrigerating plant having R-12 as the working fluid, comprises three evaporators of 10 TR at -10°C, 20 TR at 5°C and 30 TR at 10°C. Each of the evaporators is having the individual expansion valve arrangement. The refrigerant from the higher stage expansion valve is bled and mixed with delivery from the lower stage compressor and sent to the higher stage compressor suction thus effecting intercooling of the delivery gas from the lower stage and bringing the suction of the higher stage compressor to dry and saturated conditions. There is only one condenser operating at 40°C and sub- cooling the liquid refrigerant to 30°C. The compression during each stage of compression may be assumed isentropic. The evaporator discharge is dry saturated in cach of the evaporators. Determine the power required by the entire system. 5. A refrigeration system using R-12 as refrigerant consists of three evaporators of capacities 20 TR at - 5°C, 30 TR at 0°C and 10 TR at 5°C. The vapours leaving the…

13. A plant using R-134a is used to chill water for warship systems. The condenser is also cooled by water. Assume no undercooling in the condenser. The following data is to be used: 50L/s Water flowrate through evaporator Water inlet temperature to evaporator Water outlet temperature from evaporator -10°C 20°C 140L/s 350kPa 1100kPa Water flowrate through condenser Compressor suction pressure Compressor discharge pressure Compressor suction temperature Compressor discharge temperature Specific heat capacity of water Calculate: -10°℃ 60°C 4.2kJ/kgK a. Coefficient of Performance b. refrigerant cooling load c. refrigerant mass flowrate d. compressor power e. heat removed in condenser f. temperature change in condenser cooling water

11. A vapour compression refrigeration plant uses ammonia. The compressor takes vapour from the evaporator at 207.7kPa and -8°C and delivers to the condenser at 1470kPa and 113°C. The temperature of the liquid leaving the condenser at a rate of 12kg/min is 38°C. Calculate: (a). the dryness of the refrigerant entering the evaporator (b). the cooling load (c). the power to the compressor (d). coefficient of performance (e). plant capacity

The evaporator (a heat exchanger) in an A/C unit has R-410A entering at -20 °C and a quality of 30% and leaves at the same temperature and a quality of 100%. The COP of the air conditioner is known to be 1.3 and the mass flow rate is given as 0.013 kg/s. Find the power input to the cycle. (Note that, here, the evaporator is the part of the A/C unit that accepts [i.e., withdraws] heat from the room maintained at a cold temperature)