Abstract
The thermal performance of heat pipes and the capillary structure parameters such as the pore radius, the permeability and the porosity are investigated experimentally in this work. In addition, there is a preliminary result of flow visualization available in the plate heat pipe. For the measurement of performance of heat pipes, the middle point of heat pipes is maintained at constant temperature by adjusting the cooling capacity, and then the thermal resistance is recorded at varied power level. When the thermal resistance suddenly rises to a great value, the dry-out phenomena will occur in the heat pipes. Based on this measurement method, we can obtain the maximum heat transfer rate of heat pipes and compare with each other. The wick structures are made by a sintering process with spherically loose copper powders of different sizes. The results show that the process with fine particles gives a small pore radius and permeability respectively. The heat transfer rates of heat pipes are greater for the wick with larger particle sizes. According to the present results, the performance of heat pipes mainly depends on the permeability rather than the capillary pressure especially for long heat pipes.