الفهرس 
Introduction and literature reviewOnly 14 pages are availabe for public view
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Abstract
When the air is cooled to a temperature below the dew point, the condensed moisture forms a layer of frost as a direct result of combined heat and mass transfer. The promotion of such layer increases thermal resistance, thereby lowering the coefficient of heat transfer and causes periodicity of cooling equipment operation and requiring the expenditure associated with the need to defrost equipment. Knowledge of the laws governing frost formation is a required prerequisite for efficient design of air coolers working under frost. A number of theoretical models dealing with the growth of frost are seemed to be inadequate. These models considered specified operating conditions, therefore considerable error predicting in the frost thickness raised when following their correlations. 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 are carried out. In the numerical investigation, the suggested model considered the frost layer as a porous media. 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 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 from 41% to 56% while maintaining the plate type evaporator average temperature at nearly -10°C. Also, Rayleigh number ranges from 104 to 1.2x106 and dimensionless time from zero to 1. The obtained results are summarized as follows: 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%).