Sung Jhee

Prediction of the frost formation on a cold flat surface

Abstract A mathematical model is presented to predict the behavior of frost formation by simultaneously considering the air flow and the frost layer. The present model is validated by comparing with several other analytical models and our experiments. It is found that most of the previous models cause considerable errors depending on the working conditions or the correlations used in predicting the frost thickness growth, whereas the model in this work estimates the thickness, density, and surface temperature of the frost layer more accurately within an error of 10% except the early stage of frosting in comparison with the experimental data. Numerical results are presented for the variations of heat and mass transfer during the frost formation and for the behavior of frost layer growth along the direction of air flow. Also, a correlation between the convective heat and mass transfer is obtained as Le(1−n)=0.905±0.005 in this work.

Effect of surface treatments on the frosting/defrosting behavior of a fin-tube heat exchanger

The effects of the heat exchanger surface treatment on the frosting/defrosting behavior in a fin-tube heat exchanger are investigated experimentally. It is found that the hydrophilic surface mainly influences the frosting behavior, while the hydrophobic surface has some influence on the defrosting behavior. In view of the frosting, a surface-treated heat exchanger with either hydrophilic or hydrophobic characteristic shows little improvement in the thermal performance rather than the bare aluminum heat exchanger. The results reveal that the heat exchanger with a hydrophobic surface treatment is more effective in view of the defrosting efficiency and time. The amount of residual water on the surface-treated heat exchangers is shown to be smaller than that of the bare heat exchanger. Therefore further improvements on the performance of re-operations are expected.

An Experimental Study of the Surface Treatment Effect on the Frosting/Defrosting Behavior of a Fin-Tube Heat Exchanger

The effect of heat exchanger surface treatment on the frosting/defrosting behavior in a fin-tube heat exchanger is investigated experimentally. It is found that the hydrophilic surface mainly influences on the frosting behavior, however, the hydrophobic surface gives some influence on the defrosting behavior. In view of frosting performance, surface-treated heat exchanger with either hydrophilic or hydrophobic characteristic shows a little improvement in the thermal performance than the aluminium heat exchanger with no surface treatment. The result reveals that the heat exchanger with hydrophobic surface treatment is more effective in view of the defrosting efficiency and time. The amounts of residual water on the surface-treated heat exchangers are shown to be smaller than those of the bare heat exchanger, therefore further improvements on the performance of re-operations are expected