HEAT EXCHANGER FOR SENSOR SYSTEM CRYOCOOLERS

THE OVERALL CYCLE EFFICIENCY (HENCE, INPUT POWER REQUIREMENTS) OF REVERSE-BRAYTON CRYOCOOLERS FOR SPACE APPLICATIONS IS HIGHLY SENSITIVE TO THE THERMAL EFFECTIVENESS OF THE HEAT EXCHANGERS. APPLICATIONS FOR THESE CRYOCOOLERS IN SPACE DICTATE THAT THESE HEAT EXCHANGERS BE AS SMALL AND LIGHT AS POSSIBLE. TO DATE, ONLY HEAT EXCHANGERS EMPLOYING ORGANIC MATERIALS HAVE BEEN ABLE TO ACHIEVE THE HIGH THERMAL EFFECTIVENESS VALUES REQUIRED FOR THESE SYSTEMS WITHIN THE DESIRED SIZE AND WEIGHT LIMITATIONS. HOWEVER, HEAT EXCHANGERS WITH ORGANIC MATERIALS DEGRADE CYCLE PERFORMANCE BY LEAKAGE AND SYSTEM CONTAMINATION THUS LIMITING THE LIFE OF THE SYSTEM. THEREFORE, A COMPACT, ALL-METAL EXCHANGER WITH HIGH THERMAL EFFECTIVENESS IS HIGHLY DESIRABLE. THIS PROPOSAL DESCRIBES A PROGRAM TO DEVELOP AN ULTRA-LIGHT, HIGH PERFORMANCE HEAT EXCHANGER FOR SPACE-BORNE CRYOCOOLERS. THE PROPOSED HEAT EXCHANGER WOULD HAVE ALL-METAL CONSTRUCTION TO AVOID CONTAMINATION OF THE WORKING GAS AND WOULD BE CAPABLE OF ACHIEVING EFFECTIVENESS BETTER THAN 0.99 WITH A SPECIFIC MASS OF LESS THAN 0.1 KG/(W/K). THIS REPRESENTS A FACTOR OF TWO REDUCTION IN THERMAL LOSSES OVER THE BEST ALL-METAL HEAT EXCHANGER BUILT TO DATE AND TWO ORDERS OF MAGNITUDE REDUCTION IN SPECIFIC MASS. IN PHASE I WE WILL DEMONSTRATE THE FEASIBILITY OF FABRICATING THE PROPOSED HEAT EXCHANGER AND DESIGN A PROTOTYPE HEAT EXCHANGER TO BE BUILT AND TESTED IN PHASE II.