SBIR-STTR Award

Cooling electronic components in the space environment still remains a challenge for thermal engineers. In the current design practice, copper straps are used to transfer the waste heat from various high-power dissipating components to the side walls of the electronic box. Another heat transport device then collects the waste heat from the box mounting plate and carries it the space radiators for rejection. As the heat load of next generation electronics increases at a very fast rate, a more efficient heat transfer mechanism at the box level must be developed. Loop Heat Pipes (LHP) become popular heat transport devices for space-based thermal control systems for they are highly reliable and maintenancefree. Almost all LHPs in service at the present time contain one capillary pump. Thus one LHP provides only a "single point" heat acquisition. In addition, when redundancy is required for the mission long lifetime, many LHPs are therefore needed to provide adequate cooling for the electronic components. Miniature LHPs with multiple evaporators and multiple condensers will solve the aforementioned cooling problem without complicating the integration process.

Loop Heat Pipe (LHP) is a high performance heat transport device using capillary forces to circulate the working fluid in a closed loop. Conventional LHPs usually have one capillary pump (evaporator) to acquire waste heat from a heat source. Recent efforts have focused the development of LHPs that contain two or more evaporators. Even though two-evaporator LHPs performed very well, the volume of each compensation chamber (CC) became much larger than that of the single-evaporator counterpart. The reason was that all but one CC would be liquid-filled during normal operation. The one that was not liquid-filled had to be large enough to accommodate the system liquid expansion at maximum temperature. As a result, LHPs with more than 3 evaporators were not feasible for practical applications simply because the CCs became prohibitively large. In the current research, the CCs of a multiple-evaporator LHP were capillarily-linked. In other words, the CCs always contained a mixture of liquid and vapor (two-phase), allowing the loop to operate with a much smaller fluid charge. Consequently the required CC volume was also reduced.