套管式相变蓄热器内管排列方式和壁温的影响

Influence of Inner Tube Arrangement and Wall Temperature of Casing-type Phase-change Heat Accumulator

以卧式套管式相变蓄热器为研究对象,该装置由外管、4根相同的内管、相变材料石蜡组成。外管半径为50 mm,长度为480 mm,内管半径为10 mm,长度为500 mm。外管套在4根内管外面,内管两端连接传热流体,外管和内管之间的封闭空间封装着石蜡。由于管长较短,假设传热流体进出口温度基本相同,将蓄热器简化为二维模型。通过COMSOL Multiphysics软件对二维模型进行求解,模拟当内管以正方形、菱形1、菱形2排列时,观察石蜡的熔化过程和凝固过程,分析不同排列方式对相变蓄热器传热的影响。选取传热效果最好的正方形排列方式,模拟不同内管壁温对石蜡熔化和凝固过程的影响,分析不同内管壁温对相变蓄热器传热的影响。结果表明:内管不同排列方式时,正方形排列石蜡熔化和凝固所需时间最短;正方形排列的内管壁温从313 K增加到323 K、333 K时,完全熔化时间分别缩短了43. 57%、57. 14%,内管壁温从293 K下降到283 K、273K时,完全凝固时间分别缩短了47. 57%、59. 97%。

The horizontal casing-type phase-change heat accumulator is used as the research object which consists of the outer tube,four same inner tubes and the phase change material paraffin. The outer tube has a radius of 50 mm and a length of 480 mm,and the inner tube has a radius of 10 mm and a length of 500 mm. The outer tube is placed on the outside of the 4 inner tubes,and the heat transfer fluid is connected at both ends of the inner tube. The enclosed space between the outer tube and the inner tube is sealed with paraffin. Since the tube length is short,it is assumed that the heat transfer fluid inlet and outlet temperatures are substantially the same,and the heat accumulator is simplified to a two-dimensional model. The two-dimensional model was solved by COMSOL Multiphysics software. When the inner tubes are arranged in square,diamond 1 and diamond 2,the melting process and solidification process of paraffin were observed,and the effects of different arrangements on the heat transfer of the phase-change heat accumulator were analyzed. The square arrangement with best heat transfer effect was selected to simulate the influence of different inner tube wall temperatures on paraffin melting and solidification process,and the effects of different inner tube wall temperatures on heat transfer of phase-change heat accumulator were analyzed. The results show that when the inner tubes are arranged in different ways,the time required for the melting and solidification of paraffin in the square arrangement is the shortest;when the wall temperature of the inner tube arranged in square increases from 313 K to 323 K and 333 K,the complete melting time decreases by 43.57% and 57.14 %,respectively. When the inner tube wall temperature decreases from 293 K to 283 K and 273 K,the complete solidification time is shortened by 47.57% and 59.97%, respectively.