Effects of Condensate and Initial Formation of Thin Frost Layer on Evaporator Coil Performance of Room Air-Conditioners

This study investigated experimentally and theoretically, how condensate and initial formation of a thin frost layer on the surface of the evaporator affects the evaporator performance of room air-conditioners compared to dry coil conditions. The theoretically obtained results were validated with the measured values in both wet and initial frost formation conditions and a good correlation was found. The results indicated that, at the same range of change in face velocity value, the total conductivity of a dry coil (UA) dry is increased by 38.8%. However, when it is combined with an increase in latent heat to the evaporator total cooling capacity ratio value (Qlat/Q) of 10.6%, the total conductivity of wet coil (UA) wet is 45.4%. These results clearly indicate that the evaporator coil is characterized by higher performance under wet conditions compared to dry coil conditions. The results also show that the total conductivity after initial formation of a thin frost layer (UA) Fr has a higher value by about 8.2% than the dry coil condition. Moreover, the degradation in the evaporator coil performance under thin frost with a thickness up to one mm is only about 6.7%.