Frost formation, tube-fin evaporator, fan-coil, numerical model, visualization
This paper presents an experimental and numerical study to evaluate the thermal-hydraulic performance of light commercial capacity evaporators operating under frosting conditions. A tube-fin heat exchanger was tested on a closed-loop wind-tunnel considering the fan performance. A visual analysis of the frost formation processes was carried out to compare the frost layer morphology in different conditions. A mathematical model was developed and the numerical results were compared with the experimental accumulated mass of frost, air flow rate and cooling capacity, with all the predictions falling within the experimental band of uncertainties. Based on this comparison, a frost density correlation was proposed for a typical range of light commercial refrigeration applications. The results show evaporator cooling capacity reductions up to 40% due to frost formation process. Moreover, the effects of air flow reduction and low conductivity frost layer on the overall thermal resistance were analyzed, when it was found that the former is the main cause of the cooling capacity reduction under frosting conditions.