Development of cryogenic loop heat pipes

Since the loop heat pipe was invented in 1987 in Japan, efforts have been made to extend it for cryogenic use. In 1991, a loop heat pipe was demonstrated to work at liquid nitrogen temperature. The present work has taken these efforts still further. This work shows that loop heat pipes can be made to function at any cryogenic temperature, right down to 4 K. This was made possible because of the selection of heat pipe diameters based on the Laplace constant for the working fluid.