Compact heat exchager, frost formation, porous medium, peripheral fins
The peripheral finned-tube (PFT) is a novel air-side geometry for compact heat exchangers. Previous studies (Pussoli et al., Int. J. Heat Mass Transfer 55, 2835â€“2843, 2012) dealt with the evaluation of the thermal-hydraulic performance of the PFT geometry under dry conditions (i.e., no frost or condensate formation on the air side). The present study is focused on quantifying the thermal-hydraulic perfomance of the PFT geometry under frosting conditions. PFT evaporators were tested in a closed loop wind tunnel calorimeter to quantify the influence of the tube wall temperature, air velocity and air psychrometric properties (temperature and relative humidity) on the air-side thermal conductance, friction factor and on the rate of frost buildup. A mathematical model was developed to predict the behavior of the evaporator under real operating conditions. The model treats the air flow paths as a porous medium, whose porosity, equivalent particle diameter and thermal properties change with time due to the frost accumulation. The time-dependent characters of rates of heat transfer and moisture deposition and of the air-side pressure drop were well correlated by the mathematical model.