AN EXPERIMENTAL STUDY OF THE EVAPORATOR PERFORMANCE OF A DOMESTIC REFRIGERATOR USING R-22

Abstract

The performance of a domestic refrigerator of 78 litres capacity has been studied with refrigerants R12 and R22. The evaporator of this fridge was the test evaporator which was a flat plate type aluminium evaporator, bent in a rectangular shape. The copper cooling coil of 6 mm diameter was spot welded on the outside surface of the test evaporator. The evaporator was tested in the following range of parameters: (1) Refrigerant mass flow rate: in (for R12) = 0.9 to 1.8 kg/hr m (for R22) = 0.8 to 1.6 kg/hr (2) Heat Load: Q (for R12) = 30 to 56 W Q (for R22) = 37 to 67 W (3) Saturation (Evaporating) Temperature: Tsat (both for R12 and R22) - 7°C to -23°C (4) Surface area (outer) of test evaporator': A = 0.25 m2 (5') Cabinet Temperature TC = 5°C (6) Degree of superheat = 4°C to 5°C Curves have been plotted to study the variation of wall temperatures, heat transfer coefficients, power consumption, COP and the compressor discharge pressure with the load and the saturation temperature keeping the cabinet temperature constant at (iv) about 5°C. The COP of the refrigerator working with R22 has been found to be greater than that with R12 at all the loads and evaporating temperatures. The increase is about 2% at constant evaporating temperature while it is.upto 25% maximum at constant loads. The compressor discharge pressure is much higher in the case of R22 than with R12 at all the test conditions. The heat transfer coefficients for R22 are found to be better than R12 at constant saturation temperature while they are better for R12 than R22 at constant load