Part A: 20 marks A refrigerator operates using R134a. The evaporator and condenser pressures are 2 and 8 bar respectivel

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Part A 20 Marks A Refrigerator Operates Using R134a The Evaporator And Condenser Pressures Are 2 And 8 Bar Respectivel 1 (86.29 KiB) Viewed 57 times

Part A 20 Marks A Refrigerator Operates Using R134a The Evaporator And Condenser Pressures Are 2 And 8 Bar Respectivel 2 (111.46 KiB) Viewed 57 times

Part A: 20 marks A refrigerator operates using R134a. The evaporator and condenser pressures are 2 and 8 bar respectively. A P-H diagram is enclosed on the next page (a copy or sketch of which should be included with the hand in). i) Draw the ideal cycle for the system on the chart provided (next page), and determine the enthalpy at the 4 main points of the cycle, as well as the dryness fraction at the throttle valve exit [7] In practice, due to additional heat gain from surroundings, the gas exits the compressor at a pressure of 8 bar and a temperature of 50°C. The compressor volumetric capacity remains unchanged. Determine: ii) The enthalpy at compressor outlet, and the degree of superheat. [3] iii) The compressor isentropic efficiency and plant CoP [6] iv) Determine the density of the working fluid at evaporator exit. If the required cooling load is 5 kW's, what is the required compressor capacity (in m3/h) and the mass flowrate (in kg/s) to achieve this desired cooling load? [4]
200 250 300 350 400 450 500 550 600 20 100 150 20 R-134a 11.1.12 10 Reference - 2000 - 100 g 8 for oud 6 1300 200 1150 -- 1100 700 1050 1000 500 P500 kg 400 300 10 8 6 48.983 200 150 4 4 OSTEOS -40°C 100 80 70 2 60 2 60 40 40 30 1 0.8 1 0.8 30 20 0.6 20 IR 0.6 15 PRESSURE, MPa 0.4 10 0.4 1 10 8.0 6.0 0.2 -T=10°C 0.2 40 3.0 0.1 0.08 -30 LO 20 Leo PO *50 0.1 0.08 0.06 06 0.7 0.06 2 5 Po 0.04 0.04 10 0.80 080 -100- 120 080 - 0.02 220 150 8-130- 0.60 -3230 kg 11.10 0.02 240 0.40 0.01 100 0.01 600 150 200 250 450 300 350 400 ENTHALPY, KJ/kg Figure Q4.1 500 550 Based on foron of Tire Ron and Properties come with NIST REFPROP www/