AN ALL-METAL COMPACT HEAT EXCHANGER FOR SPACEBORNE 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, ONLYHEAT EXCHANGERS EMPLOYING ORGANIC MATERIALS HAVE BEEN ABLE TO ACHIEVE THE HIGH THERMAL EFFECTIVENESS VALUES REQUIRED FOR THESE SYSTEMS WITHIN THE ALLOWED SIZE AND WEIGHT LIMITATIONS. HOWEVER, HEAT EXCHANGERS WITH ORGANIC MATERIALS DEGRADE CYCLE PERFORMANCE BY LEAKAGE AND SYSTEM CONTAMINATION. THEREFORE, A COMPACT ALL-METAL HEAT EXCHANGER WITH HIGH THERMAL EFFECTIVENESS IS HIGHLY DESIRABLE. THIS PROPOSAL DESCRIBES A PROGRAM TO DEVELOP A HIGH PERFORMANCE, ALL METAL HEAT EXCHANGER. TWO HEAT EXCHANGER CONCEPTS WILL BE EVALUATED WITH RESPECT TO SIZE AND WEIGHT WITH THE AIM OF ACHIEVING A THERMAL EFFECTIVENESS IN EXCESS OF 0.98 WITH MINIMAL PRESSURE DROP. PHASE I WILL EXTEND EXISTING THEORETICAL MODELS AND OPTIMIZE THE EXCHANGER GEOMETRY WITH CONSIDERATION TO EFFECTIVENESS, PRESSURE DROP,WEIGHT, AND SIZE. FABRICATION AND ASSEMBLY TECHNIQUES OF KEY EXCHANGER ELEMENTS WILL ALSO BE DEMONSTRATED DURING PHASE I.