Fractal Loop Heat Pipe performance testing with a compressed carbon foam wick structure

This study investigates heat flux performance for a prototype wick structure fabricated from compressed carbon foam when used with a Loop Heat Pipe (LHP) containing a fractal-based evaporator design. The prototype wick structure geometry was based on a previous soda lime glass wick structure designed and manufactured by Mikros Manufacturing Inc., for use with the Fractal Loop Heat Pipe (FLHP). The compressed carbon foam wick structure was manufactured by ERG Aerospace Inc., and machined to specifications comparable to that of the initial soda lime glass wick structure. Machining of the compressed foam as well as performance testing were performed at the United States Naval Academy's School of Engineering. Heat input to the FLHP was supplied via cartridge heaters mounted in a copper block. The copper heater block was placed in intimate contact with the evaporator. The evaporator had a circular cross-sectional area of 0.88 cm2. Twice distilled, deionized water was used as the working fluid. Thermal performance data was obtained for three different Condenser/Subcooler temperatures under degassed conditions (Psat of 10.5 kPa at 23 °C). The compressed carbon foam wick structure demonstrated successful start-ups in each of the test cases performed and had a maximum heat flux of 70 W/cm2.