Q3. The cooling load in a vapour compression refrigeration plant using CO2 is 50 kW.
At this load, the refrigerant enters the compressor at a pressure of 17.314 bar and temperature of -14℃. It is then compressed isentropically to a pressure of 54.65 bar and temperature of 68℃.
After cooling the refrigerant enters the expansion valve as a saturated liquid.
The density of the CO2 at the compressor suction is 34.66 kg/m3.
The four cylinder single acting compressor has a bore and stroke of 100 mm with a volumetric efficiency of 85%.
(a) Sketch the cycle on Pressure-specific enthalpy and Temperature-specific entropy diagrams. (4)
(b) Using Datasheet Q6, calculate EACH of the following:
(i) the mass flow rate of refrigerant; (3)
(ii) the compressor power; (2)
(iii) the coefficient of performance; (2)
(iv) the compressor speed of rotation (5)
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