Overshoot temperature control on evaporator wall of loop heat pipe for space vehicle thermal control through bypass line under high thermal load

초록

This paper presents the experimental results of controlling an evaporator wall temperature overshoot problem under a high thermal load by applying a bypass line to the loop heat pipe (LHP). To solve the overshoot problem during the LHP start-up, any nucleation bubbles generated on the wick surface should be removed from the vapor channel as soon as possible. In special cases, a serious evaporator wall temperature overshoot problem at high thermal loads can cause start-up failure. The LHP must be operated stably within an appropriate temperature range during start-up because any sudden rise in the evaporator wall temperature may cause serious damage to the temperature control target. To control the evaporator wall temperature overshoot of the LHP with a flat evaporator and sintered metal wick, a bypass line was installed between the evaporator and the liquid reservoir. The bypass line was integrated into the LHP using a sintered metal wick and flat evaporator, of dimensions (width and length) 40 x 50 mm. The body of the LHP was made of stainless steel, and distilled water was used as the working fluid. The vapor generated in the evaporator was supplied to the vapor transport tube through inverted axial trapezoidal grooves. The inner diameters of the liquid and vapor transport tubes were 2 mm and 4 mm, respectively, and both tubes were 0.5 m long. The input thermal load ranged up to 270 W for a coolant temperature of 10 degrees C. The LHP was aligned at a favorite tilt angle of 15 degrees, where an evaporator wall temperature overshoot was observed. The experimental results demonstrated the ability of the bypass line to effectively control the evaporator wall temperature overshoot during start-up under high thermal loads.

키워드