放射形相变蓄热器的释热特性实验与数值研究

EXPERIMENTAL AND NUMERICAL STUDY ON HEAT DISCHARGE CHARACTERISTICS OF PHASE CHANGE HEAT ACCUMULATOR WITH RADIAL FINS

针对太阳能热利用的时空不匹配问题,设计并制备一种放射形相变蓄热器,通过实验与数值模拟研究了蓄热器释热功率及相变材料固相率在释热过程中的响应特性,探讨了冷却工质流量、进水方式、翅片型式对释热性能的影响规律。研究结果表明:蓄热器的释热过程可划分为液态显热区间、潜热区间、固态显热区间3个阶段,潜热区间相变材料的潜热作用使得释热功率下降相对缓慢;冷却工质流量越大,释热功率下降速率越快,完全凝固时间越短;不同进水方式对换热效果影响不明显,但可改善蓄热器的换热均匀性;与平板翅片相比,放射形翅片各翅片单元间相变材料的导热更均匀,凝固时间缩短31%,提高了换热速率。

Aiming at the problem of space-time mismatch of solar heat utilization,a kind of heat accumulator of phase change with radial fins is designed and fabricated.The characteristics of the heat discharge power of the heat accumulator and the solid fraction of the phase change material during the heat discharge process are studied experimentally and numerically.The effects of cooling water flow rate,water influent mode and fin type on the heat discharge performance are discussed.The results show that the heat discharge process of the heat accumulator can be divided into three stages:liquid sensible heat stage,latent heat stage and solid sensible heat stage.The latent heat release of phase change materials during the latent heat stage makes the heat discharge power decrease relatively slowly.The case with the higher flow rate of water behaves,the faster decrease rate of heat discharge power and the shorter solidification time.The effect of water influent mode on the heat transfer feature is not obvious,but it can improve the heat transfer uniformity of heat accumulator.Compared with the flat fin,the heat conduction of phase change material between each fin element for the radial fin is more uniform,the solidification time for that is reduced by 31%,and the heat transfer rate for that is improved.