Effective thermal conductivity of heat pipes

Several heat pipes were designed and manufactured to study the effect of the working fluids, container materials, and the wick structures on the heat transfer mechanism of the heat pipes. Also, the effect of the number of wick layers on the effective thermal conductivity and the heat transfer characteristics of the heat pipes have been investigated. It was found that the flow behavior of the working fluid depends on the wicking structures and the number of wick layers. The heat transfer characteristics and the effective thermal conductivity are related directly to the flow behavior. Increasing the number of wick layers (up to 16 layers) increases the heat flux with smaller temperature differences. The flattening phenomena of the thermal resistance was observed after 16 wicks layers due to the entrainment limit.