Development of a Miniature Loop Heat Pipe for High Heat Flux Devices and Evaluation of Its Heat Transport Performance

Abstract

This paper describes the design, fabrication, and the heat transfer performance of a miniature loop heat pipe (mLHP) aiming for cooling a small and high heat flux devices. For the design process, a one-dimensional numerical model was developed. Based on the numerical model, an mLHP was fabricated. The mLHP comprises an evaporator (15×16×t3 mm3), a condenser (12×12.5×t2 mm3) and transport lines (O.D.=1.6 mm, L=100 mm). The mLHP uses Shirasu porous glass (SPG) as a wick and is mainly made of stainless steel. The heat transport performance was investigated in horizontal attitude, anti-gravity (top heat mode) and gravity-assisted (bottom heat mode) with working fluid of water. When the condenser was dissipated by natural air convection, the mLHP performed 5-W (20-W/cm2) heat transport at 170-℃ heat source temperature in horizontal attitude. The thermal resistance was 7.9℃/W. In the bottom heat mode, the lowest thermal resistance of 2.6℃/W was obtained due to the gravity assist. Additionally, the mLHP was tested under the condition that the evaporator side was kept horizontal but the condenser side was bent upwards by 90 degree around the middle of transport lines. Consequently, in low heat load condition the bent mLHP showed the same performance with the bottom heat mode, but shifted to the horizontal mode as the heat load increased. Thus, the heat transport performance was comprehensively investigated for considering various uses.