Development of a Miniaturized High Intensity Cryogenic Flow Boiler 2002-01-2408

An extremely compact heat exchanger is being developed which can boil cryogenic fluids with a liquid heat source at temperatures close to its freezing point. Freezing of the heat source fluid, e.g. water is precluded by the normal flow arrangement. Boiling and superheating of the cryogen occurs as the fluid approaches the heat source in a stack of bonded jet-array laminations.

This heat exchanger technology is important in many applications where the storage of fluids at cryogenic temperatures offers substantial advantages in terms of system weight and volume. Often, as in several advanced portable life support system concepts, the advantages include the use of the cryogen as a heat sink in system thermal management. Realizing this benefit and safely conditioning the stored fluid for use requires effective heat transfer between the cryogen and a secondary heat transport fluid. Historically, this has resulted in a need for relatively large heat exchange devices and operational problems associated with the tendency of common heat transport media to freeze at temperatures well above the cryogenic fluid storage conditions. Hamilton Sundstrand has been developing an advanced high intensity heat exchanger design that simultaneously achieves dramatic reductions in the heat exchanger size and eliminates secondary fluid freezing problems. Preliminary testing has demonstrated the ability of this device to boil and thermally condition cryogenic nitrogen or oxygen with circulating water over a wide range of flow conditions without risk of freezing water in the device.

This paper presents the design concept for a prototype and a brief summary of its development from an earlier sub-scale compact high intensity cooler for electronics (CHIC). We will also describe the design, analysis, and manufacturing work being performed on the prototype heat exchanger.