| The thermal design and structure optimization for the sub-atmospheric heat exchangers, key components of the superfluid refrigeration system with hundred-watt cooling capacity, were studied in this paper.The Giaque-Hampson type counterflow heat exchanger (coiled tubular heat exchanger) is chosen for the design of two sub-atmospheric heat exchangers. One is JT exchanger working at the temperature range from 2K to 4.5K. The other is large sub-atmospheric heat exchange, which works at the temperature range from 3K-300K. The numerical thermal design method and the structure optimization method for the superfluid sub-atmospheric heat exchangers respectively made of coiled tubes and of coiled finned-tubes were presented in order to meet the required of miner pressure drop.The effects of structure sizes on the performance of both types of heat exchangers were analyzed in detail. Optimization design of the geometric parameter of coiled tubular heat exchanger was carried out using heat-transfer volume per temperature difference regarding the volume of coiled tubular heat exchanger as objective function.The optimized structure parameters of two types of sub-atmospheric heat exchangers were presented finally. For JT heat exchanger, the pressure drop is kept within 30 Pa. For large sub-atmospheric heat exchanger, the pressure drop is kept within 900 Pa.Based on the optimized structure parameters, the influence of pressures, temperatures and mass flow rates of hot and cold streams on the configuration of sub-atmospheric heat exchanger were also analyzed.The method to design and optimize the sub-atmospheric heat exchanger in the hundreded-watt superfluid refrigeration system may be adapted for the same type heat exchanger. |
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