Modeling of Non-Uniform Frost Accretion on ‘No-Frost’ Tube-Fin Evaporators
This study presents a transient two-dimensional model devised to predict frost build-up, pressure drop, and sensible and latent heat transfer rates in tube-fin evaporators, commonly used in ‘frost-free’ refrigerators. Based on the first principles of mass, momentum, and energy conservation for the airflow and the frost layer, the model accurately simulates evaporator blockage over time. Furthermore, it incorporates the interaction between the heat exchanger air-side impedance and the fan performance characteristic curve, using an iterative fluid-dynamic sub-model that predicts airflow reduction and redistribution in an evaporator with three fin densities. Frost accretion experiments were conducted using a purpose-built test setup consisting of a bottom-mount refrigerator cabinet maintained at controlled temperature and humidity in both the fresh and frozen-food compartments. Model validation demonstrated that the predicted results closely matched experimental observations. The results show that localized frost accumulation at fin density transitions causes severe airflow blockage, resulting in a 75% reduction in effective heat transfer area due to uneven air distribution. Finally, an analysis of two dimensionless competing indices demonstrates that fin density selection involves a critical trade-off between the initial cooling capacity and long-term frost resilience.