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- 2016
液氦/超流氦制冷系统负压换热器仿真及优化设计
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Abstract:
针对液氦/超流氦制冷系统负压换热器,开发了一种基于分布参数微元法的准一维换热器计算模型,并采用该模型对换热器进行了仿真计算及优化设计。在传统换热器设计方法的基础上,该模型进行了分块考虑,加入了低温下变物性和轴向热损失等因素的影响,并对换热器进行温度、压力耦合计算,准确得出了换热器内部的温度和压力场。最后,针对一个实际工况下的液氦/超流氦换热器进行了传热、流动设计和材料、翅片结构优化,结果表明:处于临界状态附近的换热器设计需要更加准确的工质物性,当换热器材料的热导率在4～10 W/(m？K)之间时,轴向导热效应对换热器长度和性能影响较小。该设计工况中采用的板翅式换热器材料为Al6061,5层排列结构(CHCHC),翅片结构为JC654202/JC474202,能够满足设计需求。该研究工作为后续实际液氦/超流氦制冷系统负压换热器优化设计提供理论和技术支持。
For simulating and optimizing sub？？atmospheric heat exchanger of liquid helium/superfluid helium refrigeration system, a quasi？？one？？dimensional heat exchanger model is developed with distributed parameter differential method. Compared with the traditional heat exchanger design, this model enables to obtain the temperature and pressure fields by the coupling calculation. It takes the variable physical properties at liquid helium temperature and the axial heat loss of the heat exchanger into consideration to achieve a more accurate simulation of the temperature and pressure fields inside the heat exchanger. A liquid helium/superfluid helium heat exchanger, whose material and fin structure are optimally determined, is designed for a practical system with the proposed model, The results suggest that more accurate physical properties are necessary for the designed heat exchanger at liquid helium temperatures. When the material thermal conductivity is within the range from 4 to 10 W/(m？K), the minimum heat exchanger length can be obtained with a smaller effect of axial heat conduction on the heat transfer performance. The five？？layer (CHCHC) plate？？fin heat exchanger with the material Al6061 and fin structure JC654202/JC474202 completely meets the requirements for the working conditions of the liquid helium/superfluid helium refrigeration system
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