EFFECT OF POROSITY AND EVAPORATION TEMPERATURE ON THE PERFORMANCE OF A REFRIGERATION SYSTEM USING POROUS EVAPORATOR: R422A CASE STUDY
The effect of using porous materials in flow passages of refrigerants during the evaporation process on the performance of a refrigeration systems is experimentally investigated. The effect of changing the evaporation temperature and the evaporator porosity on the behavior of the refrigeration cycle is studied. Refrigeration capacity, condenser capacity, power of compression, coefficient of performance, volumetric refrigeration capacity, compressor discharge temperature, pressure drop and the power consumption per ton of refrigeration were studied for different evaporation temperatures and different evaporator porosities. Empty tube evaporator and porous tube evaporator with porosities of 48%, 43% and 39% were used during the experimental tests. Small metallic spheres were used as porous inserts in the evaporator. The evaporation temperature was changed in the range of (-31.5 ° C to -19.1 ° C). Condensing temperature, degree of subcooling and degree of superheating were kept constants at 38 ° C, 6 ° C, 6 ° C, respectively. The performance analysis showed that, the refrigeration capacity, condenser capacity, volumetric refrigeration capacity as well as coefficient of performance of the refrigeration cycle can be enhanced by increasing the evaporation temperature and by decreasing the evaporator porosity. The Refrigeration capacity, condenser capacity, coefficient of performance, volumetric refrigeration capacity when using R422A as refrigerant in the refrigeration cycle showed percentages of increase of about 166%, 48.9%, 283%, 64.7%, respectively when changing the porosity of the evaporator from empty tube evaporator to 39% porous evaporator and increasing the evaporation temperature from (-31.5 ° C to -19.1 ° C). Low values of compressor power consumption and power consumption per ton of refrigeration were recorded at lower evaporator porosity and higher evaporation temperature. Low compressor discharge temperatures were detected at higher evaporation temperature and lower evaporator porosity.