PHASE-CHANGE COMPOSITE THERMAL ENERGY STORAGE FOR NI-H2 BATTERY.

THERMAL CONTROL IS A DESIGN DRIVER FOR SPACE APPLICATIONS OF NI-H2 BATTERY SYSTEMS. COMPARED WITH THE NI-CD BATTERIES THEY ARE REPLACING, THE NI-H2 BATTERIES REQUIRE LOWER OPERATING TEMPERATURES AND GENERATE HIGHER HEAT LOADS THAT INCREASE COOLING NEEDS. THE SPACE RADIATORS USED FOR COOLING ARE GENERALLY SIZED FOR THE PEAK HEAT LOADS DURING BATTERY DISCHARGE TO AVOID EXCESSIVELY HIGH TEMPERATURES THAT SHORTEN BATTERY LIFE. THE RADIATORS ARE THEN OVERSIZED AT OTHER PHASES OF THE CYCLE, NECESSITATING BACK-UP HEATERS TO AVOID EXCESSIVELY LOW TEMPERATURES. THERMAL ENERGY STORAGE IMPROVES BATTERY SYSTEM PERFORMANCE BY PASSIVELY ABSORBING AND STORING REJECT HEAT FOR RELEASE DURING LOW LOAD PHASES OF THE CYCLE, THEREBY PERMITTING THE RADIATOR TO BE SIZED FOR THE AVERAGE HEAT LOAD AND REDUCING THE SYSTEM WEIGHT AND SIZE. IN THIS PROJECT ESLI WILL DESIGN, FABRICATE AND TEST A PHASE-CHANGE COMPOSITE PASSIVE THERMAL ENERGY STORAGE UNIT FOR A GENERIC NI-H2 BATTERY DESIGN. THE COMPOSITE CONSISTS OF A HEAT CONDUCTOR FINELY DISPERSED IN A ORGANIC PHASE-CHANGE MATRIX THAT HAS HIGH HEAT CAPACITY IN THE TEMPERATURE RANGE OF INTEREST. THE UNIT IS DESIGNED FOR LOW WEIGHT, HIGH OVERALL THERMAL CONDUCTANCE, AND CAPILLARY CONTROL OF VOID DISTRIBUTION TO RELIEVE EXPANSION STRESS. PHASE I EFFORT WILL STUDY MATERIALS AND DESIGN OPTIONS, AS WELL AS TEST THE BEHAVIOR OF COMPOSITE SAMPLES UNDER RELEVANT CONDITIONS. PHASE II WOULD DEVELOP AND CYCLE-TEST A PROTOTYPE IN RELEVANT GEOMETRY LEADING TOWARD SUBSEQUENT FLIGHT QUALIFICATION.