x = 4 and y = 9, Consider a two-stage cascade refrigeration system operating between the pressure limits of 0.8 and 0.1x MPa. Each stage operates on the ideal vapor-compression refrigeration cycle with refrigerant-134a as the working fluid. Heat rejection from the lower cycle
x = 4 and y = 9,
Consider a two-stage cascade refrigeration system operating between the pressure limits of 0.8 and 0.1x MPa. Each stage operates on the ideal vapor-compression refrigeration cycle with refrigerant-134a as the working fluid. Heat rejection from the lower cycle to the upper cycle takes place in an adiabatic counterflow heat exchanger where both streams enter at about 0.4y MPa. If the mass flow rate of the refrigerant through the upper cycle is 0.24 kg/s, determine: (a) Sketch T-s diagram by listing all the entry and exit points to each refrigeration equipment as well as labelling the pressure lines, (b) the mass flow rate of the refrigerant through the lower cycle, (c) the rate of heat removal from the refrigerated space and the power input to the compressor, (d) the coefficient of performance of this cascade refrigerator. Calculate the work done by a single compressor if it is to deliver the cooling load as above by compressing refrigerant-134a from 0.1x MPa to 0.8 MPa. Repeat your calculation and compare their COP values.
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