Vital to the LHP operation is the evaporator/reservoir assembly where waste heat from a heat-dissipating source is absorbed through the metal casing to vaporize the liquid on the outer surface of the primary wick. To compel the vapor to vent into the vapor line to be transported to the condenser for heat rejection and not to percolate into the wick core, a liquid-vapor (LV) “seal” is established. A knife-edge seal is formed by using a hydraulic press to “incision” join a tube with sharp edges into the primary wick. It requires tedious manufacturing steps driving up the hardware cost. The knife edge introduces hidden micro-cracks in the primary wick, which cannot be detected if the cracks do not propagate all the way through the wick. The wick may produce a satisfactory pressure head initially but, when exposed to an excessive shock/vibration environment or recurring thermal cycling, the micro-cracks become larger and progressively advance all the way to the core. To make matters worse, the cost of LHP manufacturing has risen significantly, mainly because of the intricate design and “hand-made” fabrication/assembly process of the wick structure inside the evaporator/reservoir. The wick sintering, machining, insertion into the metal casing, and forming the knife-edge seal require expensive specialized tooling with tight tolerances and highly-skilled technicians many hours to carry out, contributing to the overall LHP price tag. However, the consistency/reproducibility of identical design LHPs in terms of performance have always been at issue with the users. TTH Research proposes to modify the existing LHP design and manufacturing process to (i) do away with the knife-edge L-V seal, (ii) simplify/modify the evaporator design to reduce the amount of tight-tolerance machining of the wicks and casing, and (iii) automate the wick fabrication and insertion methods for consistent quality assurance.
As the thermal requirements continues to increase at a fast rate due to advances in space electronics. Every NASA satellite and spacecraft in the future needs high-performance heat transports like the LHPs. Room-temperature TCS would welcome, in earnest, the proposed construction method to manufacture less costly LHPs. Nevertheless, thermal management in other temperature ranges such as cryogenic cooling for IR instruments is also benefited from the reduction in the overall LHP price tag.
The high cost of LHPs is driven by unnecessarily complicated fabrication of the evaporator. Thermal engineers often opt for less capable thermal devices. The terrestrial usage of the technology is nearly non-existent despite the many operational benefits of LHPs. Buy significantly reducing the LHP fabrication cost, the technology is expected to take off in the commercial electronic devices.