Bypass line assisted start-up of a loop heat pipe with a flat evaporator

Loop heat pipes often experience start-up problems especially under low thermal loads. A bypass line was installed between the evaporator and the liquid reservoir to alleviate the difficulties associated with start-up of a loop heat pipe with flat evaporator. The evaporator and condenser had dimensions of 40 mm (W) by 50 mm (L). The wall and tube materials were stainless steel and the working fluid was methanol. Axial grooves were provided in the flat evaporator to serve as vapor passages. The inner diameters of liquid and vapor transport lines were 2 mm and 4 mm, respectively, and the length of the two lines was 0.5 m each. The thermal load range was up to 130 W for horizontal alignment with the condenser temperature of 10°C. The experimental results showed that the minimum thermal load for start-up was lowered by 37% when the bypass line was employed. This paper was recommended for publication in revised form by Associate Editor Dae Hee Lee Joon Hong Boo received his B.S. degree in Mechanical Engineering from Seoul National University in 1978. He then received his M.S.M.E. and Ph.D. degrees from Georgia Institute of Technology in 1984 and 1989, respectively. Dr. Boo is currently a Professor in the School of Aerospace and Mechanical Engineering at Korea Aerospace University, where he joined in 1989. His research interests include heat transfer, heat pipes, and energy systems. He conducted joint research with Texas A&M University and Waseda University in 1994 and 2008, respectively, as Visiting Professor. Dr. Boo is an active member of the International Heat Pipe Conference Committee. Eui Guk Jung received his B.S. and M.S. degrees in Aerospace and Mechanical Engineering from Korea Aerospace University, in 2002 and 2004, respectively. He is currently a Ph.D. candidate in the Graduate School at Korea Aerospace University. His research interests include applications of heat pipes and loop heat pipes.