Cool-down studies on vacuum insulated cryogenic transfer lines

Analytical and experimental studies on the cool-down of vacuum insulated cryogenic transfer lines have been carried out. An expression for estimating the cool-down history is derived taking into account the gas conduction effects. Experiments were carried out for LN2 flow in glass lines. The cool-down time decreases with increasing vacuum up to 10-2 torr. Beyond this there is no significant change in cool-down time. The outer jacket size has no appreciable influence on the cool-down process. Higher mass flow rates result in faster cooling of the pipe line. The experimental and theoretical cool-down curves agree well, particularly at higher jacket vacuums and at higher mass flow rates. © 1976.