Spot-Cooling with a Cryogenic Pump

Abstract

Many cryogenic designs have recently been proposed to provide cooling down to 150°K. The conventional methods listed below have many faults when used for “spot-cooling”:

• 1. Dip-type cooling: This is the simplest method of cooling, which involves submerging the object to be cooled in a bath of coolant. For spot-cooling, unnecessary quantities of the coolant are expended in cooling down an object and its supporting components.

• 2. Conduction cooling: This is an indirect method by which the object is cooled through a conductor connecting the cooled object with the cooling medium. It is difficult to utilize the entire capacity of the cooling medium because of the thermal resistance of the conductor. Moreover, it is difficult to attain an equilibrium temperature when the cooled object is subjected to a rising temperature.

• 3. Cold-gas-flow cooling: This is the normal method of cooling an object by flowing gas through a heat exchanger submerged in the coolant. However, complete heat exchange is not likely to occur, so that the temperature of the cooled object does not reach that of the coolant. It is difficult to obtain good temperature control and an equilibrium temperature of the cooled object under conditions of rising temperature.