First-principles modeling of frost accumulation on fan-supplied tube-fin evaporators

The present paper investigates the frost formation on air-supplied tube-fin evaporator coils under typical operating conditions of light commercial refrigerating appliances. To this end, a first-principles simulation model based on air-side mass, energy and momentum balances was put forward to predict the evaporator frosting over time. Experiments were also carried out to gather key data for the model validation exercise. The numerical results were compared with the experimental air-side pressure drop, air-flow rate, cooling capacity, and accumulated frost mass, with all predictions falling within the experimental uncertainty range. The model was then used to investigate the evaporator thermal-hydraulic performance under frosting conditions accounting for the non-linear effect induced by the combination of the frosted evaporator and the fan-supplied air-flow rate. The effects of progressive frost clogging and low conductivity frost layer on the overall thermal resistance were also assessed. It was found that the former is the main cause of cooling capacity reduction under frosting conditions.