Capillarity of Rectangular Micro Grooves and Their Application to Heat Pipes

Abstract

The capillarity of micro grooves with rectangular cross-section is studied theoretically and experimentally in this paper. The Helmholtz free energy method is used to predict the capillarity as the groove is placed vertically and inserted the bottom end into the liquid. In the experiment, micro grooves are first constructed by the thick photoresist patterned by photolithography method and then a thin copper layer is deposited on their surface to improve the hydrophilic property of liquid-solid interface. It is shown that the theoretical and experimental results are in good agreement. Furthermore, the capillary limits of micro grooved heat pipes are investigated. The effects of groove’s width and number on the capillary limit contributed from the maximum capillary pumping pressure and the pressure drops due to the friction and gravitational force are calculated. A workable geometry range of micro grooves for a heat pipe designed to transport a specific heat rate can be determined by these developed tools.