Consider a two-stage cascade refrigeration system operatingbetween the pressure limits of 1.2 MPa and 200 kPa with refrigerantR717 (Ammonia) a as the working fluid. The refrigerant leaves thecondenser as a saturated liquid and is throttled to a flash chamberoperating at 0.45 MPa. Part of the refrigerant evaporates duringthis flashing process, and this vapor is mixed with the refrigerantleaving the low-pressure compressor. The mixture is then compressedto the condenser pressure by the high-pressure compressor. Theliquid in the flash chamber is throttled to the evaporator pressureand cools the refrigerated space as it vaporizes in the evaporator.The mass flow rate of the refrigerant through the low-pressurecompressor is 0.15 kg/s. Assuming the refrigerant leaves theevaporator as a saturated vapor and the isentropic efficiency is 80percent for both compressors, determine (a) the enthalpy at theexit of the high pressure compressor, (b) the entropy at exit oflow pressure compressor , (c) the mass flow rate of the refrigerantthrough the high-pressure compressor, (d) the rate of heat removalfrom the refrigerated space, and (e) the COP of this refrigerator.Also, determine (f) the rate of heat removal and (g) the COP ifthis refrigerator operated on a single-stage cycle between the samepressure limits with the same compressor efficiency and the sameflow rate as in part (c)
