EFFECTIVENESS OF COMBINED SUBCOOLER-CAPILLARY BLOCKER DEVICE IN LHP FOR SPACE APPLICATIONS

摘要

The critical condition of reliable and stable operation of a loop heat pipe is complete condensation of a working fluid in a condenser with subsequent subcooling of the liquid before entering in a compensation chamber. Usually, the final part of the condenser operates as a subcooler. The design of the loop heat pipe with separated subcooler acting also as a vapor/gas bubbles stopper (capillary blocker) is proposed. The subcooler-capillary blacker (SCB) is installed after the condenser. Its purpose is to capture noncondensed vapor bubbles, subcool the working fluid below the saturation temperature, and to eliminate a countercurrent in the loop heat pipe. A model of an SCB was developed and thermal-hydraulic calculations of the efficiency of the proposed SCB in comparison with a smooth-wall subcooler (geometric efficiency coefficient) were performed. Influence of the mass flow rate (Reynolds number), diameter of the channel, and of the porosity of a capillary structure on the SCB efficiency has been investigated. Emission in a vacuum was used as the boundary condition (modeling of space environment). It was proposed to use aluminum or silver fibers as an SCB capillary structure material to facilitate heat exchange (subcooling) and to minimize the pressure drop in SCB. The LHPs working fluid ammonia, typical of space applications, was selected for analysis.