Question: 2. (31 Marks) The two-stage compression refrigeration system shown below is used to remove heat from refrigerated space using R-410a as the coolant. The R-410a

2. (31 Marks) The two-stage compression refrigeration system shown below is used to remove heat from refrigerated space using R-410a as the coolant. The R-410a leaves the evaporator at state 1 and is first compressed in a low-pressure compressor (W.Pc=-250 kW) to an intermediate pressure of 933.9 kPa before it is mixed with saturated vapor and then further compressed in a high-pressure compressor to 3000 kPa. Heat is then removed from the R-410a as it passes through the heat exchanger and exchanges heat with cooling water. The R-410a is then expanded in the throttling valve to the intermediate pressure and passed through a type of mixing chamber called a flash chamber where it is separated into a saturated vapor leaving at state 7 and a saturated liquid leaving at state 8. Finally, the liquid is expanded before entering the evaporator at state 9. Note that the mass flow rate of R-410a leaving the mixing chamber is PC = 10 kg/s. Neglect changes in kinetic and potential energy across all devices and assume the compressors, mixing chamber, flash chamber and throttling valves are well insulated. Refer to the figure for additional information. a) Determine the rate of heat transfer to the R-410a in the Heat Exchanger, One: (5 Marks) b) Determine the rate of heat transfer to the R-410a in the Evaporator, QE (9 Marks) c) Determine the specific enthalpies at states 2 and 3, h, and hz, and the work of the High-Pressure Compressor, WwPc: (7 Marks) d) Determine the Coefficient of Performance of the refrigeration cycle. (2 Marks) e) Determine the mass flow rate of water through the Heat Exchanger, mw, and the pump work, w.. (8 Marks) Water T=10C Po= 100 kPa T2-20C Pump 12 UP,P2-500 kPa T:+25C Heat Exchanger P.P-3000 kPa T. +60C High-Press. Comp. - Watc Throttling Valve mrc=10 kg's m, P =P =P =933.9 kPa Flash Separator Mixing Chamber P-P-P,=933.9 kPa sat. vapor mpc sat. liquid Throttling Valve Low-Press Comp. Wc-250 kW Evaporator t P, P =175 kPa X=0.95
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