Speaker
Description
Loop Heat Pipes (LHPs) are considered advantageous thermal management systems for various types of spacecraft, capable of transferring heat from source to sink in microgravity with low temperature drop, no external power input, and typical lifetimes of up to 15 years. However, as communication satellites evolve into the high-throughput and very-high-throughput categories, the need arises to dissipate tens of kilowatts of power into space. In this context, LHP technology loses ground to actively pumped two-phase loops (also known as Mechanically Pumped Loops, MPLs), primarily due to limitations in the effective area of capillary pumps and the maximum heat flux (W/cm²) they can sustain.
Higher throughput can now be achieved using a multi-evaporator LHP, in much the same way that multi-core CPUs overcame the limitations of single-core processing power a decade ago. The newly developed type of evaporator, which incorporates multiple capillary pumps and functions as a two-phase cold plate (Multi-Evaporator Cold Plate, MECOP), offers a compelling alternative to MPL.
An LHP equipped with a MECOP evaporator, assembled from 8 rather compact capillary pumps (approximately D15x110mm), 6m transport lines and a cold plate condenser, was stress tested for maximum heat transfer capability within the typical electronics temperature limit of 70°C at the thermal interface. Ammonia was used as the working fluid due to its high performance among a broad range of refrigerants that are compatible with the presented LHP and frequent use in MPLs.
The tests demonstrated that a passive heat transfer system with MECOP evaporator can overcome the typical heat flux limitations of conventional LHPs, transferring kilowatts of thermal power over a distance of 6 meters within the specified temperature range. Additionally, a series of experiments enabled the verification of the MECOP LHP mathematical model used to predict maximum heat transfer capacity and other LHP characteristics, thereby expanding the design capabilities for multi-evaporator heat transfer systems with alternative evaporator configurations.
