Performance tests on triple composite mesh-groove-powder wicks in a visualizable flat-plate heat pipe

Abstract

Two types of novel triple composite mesh-groove-powder wicks are proposed and tested in a visualizable flat-plate heat pipe. The powders are only added in the evaporator in the triple composite wicks to increase the capillarity therein. Outside the evaporator is the mesh-groove wick, with a layer of 200-mesh copper screen sintered over parallel grooves, which has been shown to exhibit high permeability and anti-gravity ability. The first type (Triple A) is to add powders in the mesh-groove wick at the evaporator section, while the second type (Triple B) contains an evaporator with only copper powders. The parallel grooves have a semi-elliptic cross-section with a width of 0.18 mm and a depth of 0.075 mm. According to visualization, the powders in the mesh-groove evaporator appear to increase the flow resistance and prompt partial dry-out in some grooves at high heat loads. The experiment results for the Triple B wick with a powder-only evaporator demonstrate a maximum heat load (Qmax) 20 % higher than that for the double mesh-groove wick at the horizontal orientation, with evaporator resistances also slightly higher. However, the Triple A wick, with powders added in the mesh-groove evaporator, displays a slightly lower Qmax than the original mesh-groove evaporator due to the excessive flow resistance associated with powder-filled meshed grooves.