Influence of wick characteristics on heat pipe performance

The performance of a heat pipe depends on several factors, one of which is the nature of the wick structure. Optimization of heat pipe performance requires wick structures that can provide high capillary pressure, and yet still offer low resistance to fluid flow. The current level of technology being developed in our laboratory makes it possible to engineer desired wick structures both micro‐ and macroscopically, especially tailored to optimize heat pipe performance. In order to assist the fabrication of unique wick structure, the influence of wick structure characteristics on heat pipe performance is numerically investigated in this work. Numerical methods are an effective tool to significantly reduce the number of experimental trials. Comparisons are made between performances of heat pipe with different wick structures; coarse pore sizes, fine pore sizes and a composite comprised of coarse and fine pore sizes. Results indicate superior performance, with a factor of up to 2, for heat pipe with composite structure combining coarse/fine wick. Validation of the simulation result presented using experimental data is being carried out. Copyright © 2005 John Wiley & Sons, Ltd.     

Validated Numerical Analysis of CaSO4 Fouling

In scaling experiments, the formation of fouling layers on heat transfer surfaces usually proceeds in a non-uniform manner. The result is a non-uniform layer, and hence a varying thermal resistance over the area covered with scale. Consequently, a non-uniform heat flux distribution results over the heat transfer surface. To evaluate the changes in the heat flow distribution resulting from a non-uniform scale layer, numerical calculations have been performed using a case where CaSO₄ scales form on a heated copper plate subjected to a shear flow. The calculated heat flux is used to calculate fouling resistances from measured temperatures. The results of the numerical calculations confirm that a non-uniform heat flux distribution occurs over the surface when the plate is partially covered with scale. Further, it is seen that the heat flux, the surface temperature, and the driving force all decrease with increase in scale accumulation.