frost, air-cooler, experiment, vegetables
The ﬁn-and-tube heat exchanger has been extensively used in many fields, especialy in HVACR (heat, ventilation, air-conditioning and refrigeration systems). When such heat exchangers is operating as an air-cooler, in most of the cases, it usually deals with lower temperature. When moist air ﬂows across cold surfaces of heat exchanger whose temperatures are lower than the freezing point the frost formation will occur. This frost accumulation is undesirable in most cases since it negatively affects heat transfer due to the insulation of frost layer and causes pressure loss by the blockage of air ﬂow as the frost grows. This will lead to an undesirable degradation of heat exchanger’s overall performance. In the paper analysis of effect of frosting process on the finned tube air cooler performance will be presented. On the basis of long-term experimental investigation of the air-cooler applied in the cold storage chamber, the general degradation of the heat exchanger performance will be discussed. The influence of the frost on the cooling capacity, by-pass factor and thermal resistance will be shown. Temperature distribution of the air passing though the air-cooler before and after defrost will be presented and discussed. A method of assessment of the amount of frost formed on the exchanger surface based on visualisation of the cooler surface during operation and synchronised with the thermal measurements was developed. Analysis carried out with application of the proposed approach revealed that frosting causes deterioration of the tested air cooler refrigeration capacity up to 40%. Proposed method was positively validated for investigations of the finned air coolers.