Experimental Investigation on a Thin-Loop Heat Pipe With New Evaporator Structure

Abstract

This paper presents thin-loop heat pipes (tLHPs) with evaporator thickness of 1 mm and a one-way transport length of 200 mm. Grooves and liquid cores are mounted on the evaporator case in the design of a flat evaporator. Liquid cores play a critical role in reducing the pressure drop in the wick and in increasing the path length for heat transfer. A one-dimensional steady model was applied to the design of the tLHP. New tLHPs with thin evaporator (26 × 24 × t1 mm3) were fabricated by a three-dimensional printer. First, two kinds of tLHP systems were (type-1) fabricated with different wick materials—microglass paper (MGP) and Shirasu porous glass (SPG). Ethanol was selected as a working fluid. The experimental results showed the both LHPs can transport heat up to 12 W. Second, the evaporator structure was modified based on the experimental results with the type-1 tLHP, and the tLHP with SPG wick (type-2) was fabricated. The experimental results demonstrated the stable operation. The operation temperature was 83 °C, and the thermal resistance became 1.98 °C/W. The power cycle test at the range of a heat load from 5 to 10 W was also conducted. No temperature hysteresis was observed during three cycles.