Towards the pseudo-2D modeling of frost growth between cold parallel plates

When a heat recovery ventilator is operating under winter conditions, the water vapor present in the exhaust airflow can lead to frost formation that depends on the outside air temperature, the heat exchanger plate temperature and their spacing, the exhaust air flow and its humidity. In this study, an available 1D frost formation model, based on frost growth and its densification, is improved and validated using experimental data available in the literature and measurements performed on a new test bench before extending the model on a 2D geometry. The objective of this study is to evaluate accurately the frost growth between cold parallel plates. The frost densification depends on the square root of time and the ratio of supercooling and supersaturation degrees. An energy balance equation for the heat conduction through the frost layer is solved and the heat and mass transfer from the moist air to the frost layer is used as a convergence criterion to predict the frost surface temperature. The proposed pseudo-2D model shows that the airflow from a 2.5 mm parallel plate spacing heat exchanger is reduced by 33% over a 25 min period due to frost growth. Using a 4.0 mm spacing, the airflow reduction gets only 5% over the same time period. It shows that larger plate spacing airflow are less affected by frost growth. After 25 min, the 2.5 mm spacing heat recovery efficiency decreases from 87% to 77% while for the 4.0 mm spacing, it decreases from 60% to 55%.