FROST FORMATION AND HEAT-TRANSFER ON CIRCULAR-CYLINDERS IN CROSS-FLOW

When humid air comes into contact with a surface whose temperature is below the dew point of water vapour in air and also below the freezing point, frost deposition takes place over the surface. Previous studie s indicate that the heat transfer rate increases at the initial stages of deposition since the rough frost surface acts as a finned one. As the frost thickens, however, the insulating effect of the frost layer predominates resulting in a reduction in the heat transfer rate. This paper presents a transient model to predict the frosting process over a circular cylinder in a cross-flow of humid air. The transfer paramet ers are computed employing a numerical solution of the momentum, energ y and diffusion boundary-layer equations along with the continuity equ ation, using a finite difference scheme. Empirical correlations for th ermal conductivity and density are utilized for closure purposes. Mode l results are compared with existing experimental data and with numeri cal data of previous investigators and are found to agree well in the applicable temperature and humidity ranges of the frost he and conduct ivity correlations.