Frost Formation and Heat Transfer over Flat Plate Evaporator

Abstract

In the present study, numerical and experimental investigations of heat and mass transfer characteristics of a plate type evaporator immersed in a still humid air environment with the presence of frost formation is carried out. In the numerical investigation, the suggested model considered the frost layer as a porous medium. The solution of a set of partial differential equations characterizing frost formation taking into consideration the variation of air ambient conditions during frost formation process and a diffusion term is preceded. In experimental investigation, the ambient air temperature is changed over a range of 20°C to 25°C and the relative humidity is varied from 41% to 56% while maintaining the plate type evaporator average temperature at nearly -10°C. Also, Rayleigh number was varied from 104 to 1.2x106 and the dimensionless time from zero to 1. The results show that the system coefficient of performance decreases within a range of (10% - 15%), the average Nusselt number varies within a range of (15% - 30%) and the average Sherwood number varies within a range of (25% - 40%).