An experimental investigation of heat transfer performance of a flat plate heat pipe with a combined capillary structure

In this work it is conducted an experimental study to evaluate the thermal performance of a new design flat plate heat pipe (FPHP), which can be applied to cooling of electronic equipment or devices. The FPHP uses a 500 PPI (pores per inch) screen mesh as the capillary wick and some micro-channels are located on the condensation surface and the surfaces of internal fins. The experiments, under different heating loads, indicate superior performance of the FPHP in terms of start-up time and temperature uniformity on the condensation surface. In addition, the effects of working fluid, charging ratio, angle of incline, screen mesh material, and the number of screen mesh layers and of internal support plates on the thermal performance of the FPHP are studied. The results indicate that using distilled water as the FPHP working fluid gives better thermal performance than using acetone or ethanol. The optimum charging ratio is found to be 25%; the screen mesh material and the geometric structures of the wick and the micro-fins show important effects on the thermal performance of the FPHP. Different placement of the FPHP also leads to change at its thermal performance. A minimum thermal resistance of 0.231 °C/W is measured when the angle of incline is 0° (horizontal placement) and the heating load is 40 W.