A 2-stage multi-evaporator system with a single compressor and multi-expansion valves operates between pressure limits of 1200kPa and 30kPa. If the two evaporators will operate with an equal refrigerating effect, and the flow of refrigerant (R134a) in the compressor is 0.35kg/s, determine the following: a. b. C. d. Optimum operating pressure (kPa) of the high-pressure evaporator (1pts) Individual and combined refrigerating effect (TOR) of the evaporators (4pts) Work of compressor in kW (5pts) The COP of the system in % (5pts) A refrigerating system having a 2-Stage Compression with Flash gas removal and intercooling (without water intercooler) operates under pressure limits of 1200kPa and 30kPa and uses R22 as a refrigerant. If the heat to be rejected by the condenser is equal to 185kJ/s and the COP of the system is 327%, determine the following: a. b. C. d. e. Total work of Compression in kW (5pts) Individual work of compressor kW (5pts) Refrigerating Effect in TOR (5pts) Mass flowrate in the high-pressure and low-pressure loop of the system in kg/s (5pts) Mass flow rate (kg/s) flowing in the high lower pressure loops of the system (5pts) A 2-stage cascade system that uses ammonia and R134a as a refrigerant has the following operating saturation temperatures: High pressure loop: Tsat at condenser = 30C Tsat at evaporator = 0C Low pressure loop: Tsat at condenser = 5C Tsat at evaporator = -20C If the load to be served by the system is 200TOR, analyze which refrigerant should be placed in the high and pressure loop to minimize the compressor work. After concluding the proper placement of refrigerant, determine the following: a. b. c. d. COP of the system (5pts) Heat to be Rejected by the Condenser in kJ/s (5pts) Individual Compressor work in kW (10pts) Mass flowrates of refrigerant in the low-pressure and high-pressure loops in kg/s (5pts) PROBLEM 5 A two-stage cascade refrigeration system uses R22 as the working substance. The evaporator is at -35C and the high-pressure condenser is at 1500 kPa. The cascade condenser is a direct contract type. The refrigeration load is 1200 BTU/hr. Determine the optimum operating intermediate pressure of the system to determine the following: a. Mass flowrate of the refrigerant in the low-pressure loop (5pts) b. Mass flowrate of the refrigerant in the low-pressure loop (5pts) C. Power required by the compressor in kW (10pts) d. COP of the system (5pts)