ELECTROHYDRODYNAMIC MINI FLAT HEAT PIPE FOR ADVANCED ELECTRONICS COOLING

Abstract

Mini-grooved flat heat pipe with small size, compact structure, high thermal conductivity, and close contact with chips is very promising to be applied for electronic devices cooling under small space and high heat flux condition. However, capillary limit always restricts the heat transfer capacity of heat pipe. Adopting electrohydrodynamic (EHD) technology with simple structure, sensitive control, and low-energy consumption to the heat pipe can lower the reliance of heat pipe on capillary force and improve the heat transfer performance of heat pipe. In this paper, a one-dimensional mathematical model is established for mini-grooved flat heat pipe under dielectrophoretic force to study the working fluid flow and heat transfer along axial direction under EHD effect. The performance of mini-grooved flat heat pipe under different electric field intensity and electrodes distribution is analyzed. It is found that adding electric field to the mini-grooved flat heat pipe can lessen the demand for capillary force on the heat pipe, reduce the required working fluid filling amount, improve the wall temperature uniformity, and enlarge the range of negative working inclined angle, which enhances the heat transfer performance of heat pipe significantly. Under the electric field intensity 5 kV·mm-1, the critical input heat of Case 1 heat pipe is 4.8 times higher than that without electric field. And, when electrodes are arranged at the whole heat pipe with Case 2 convex gradient V-type grooved wick, the heat transfer performance of heat pipe is optimal. Considering the practical condition, fabricating sloped grooved heat pipe under EHD is more convenient. However, the electric field intensity cannot be larger than 5.5 kV·mm-1 in case of reaching entrainment limit and electrical properties of working fluid being destroyed.