Wicked heat pipe is well-known heat transfer device, operated with a two-phase working fluid. This operating principle is based on evaporation and condensation of working fluid, and circulation by capillary force. In this study, we visualized the fluid behavior inside the flat-plate heat pipe, especially at the evaporation region. The heat pipe performance depends on a number of factors, then we focus on the inner wall wettability and made different degrees of wetting conditions by coating the hydrophilic material. We will discuss how the wettability at the evaporation region affect the heat pipe performance.
