双层填充床储热器储热性能实验研究

Experimental Study on the Thermal Performance of a Thermal Storage with Double-Layered Packed Bed

为提高相变储热球填充床储热器的储热性能,提出了一种沿流动方向减小相变球球径的双层填充床储热器结构,并开展了储热器储热性能的实验研究,获得了储热器内的空气及储热球温度的变化规律。结果表明,沿换热流体流动方向的空气温度逐渐降低,采用双层变球径相变球填充床储热器结构后,填充床下层的储热球能够较快熔化,提高了填充床下层的换热效果,改善了储热器的换热温度不均匀性,从而提高了储热性能。其次,研究了不同空气进口温度和质量流量对该储热器储热速率及储热效率的影响规律,结果表明:当空气进口温度从425℃增加到465℃时,储热速率提高了60.5%,储热效率从84.8%提高到了91.1%;当质量流量从180kg·h-1增加到260kg·h-1时,储热速率提高了23.5%,储热效率略有下降。最后,对比了双层储热器与单层储热器的储热性能,结果表明,在相同进口温度和质量流量下,双层储热器的储热速率优于单层储热器,储热速率最大可比单层储热器提高12.4%。该研究可为高温熔盐相变球填充床储热器的设计及性能优化提供实验参考。

A new thermal storage packed with double-layered diameter-variable phase change material（PCM）capsules is presented to improve its thermal performance.First,the temperature evolution of air and PCM capsules are studied.The temperature of air decreases gradually along its flow direction.The lower-layer PCM capsules with smaller diameters can be quickly melted than the upper-layer capsules with larger diameters,which improves the heat exchange effect and heat exchange non-uniformity of this new thermal storage and hence leads to the enhancement of thermal performance.Moreover,the influences of different inlet temperatures and mass flow rates on the heat charging rate and efficiency are discussed.The results show that the charging rate is increased by 60.5% when inlet temperature is raised from 425℃to 465℃.The charging efficiency is also improved from 84.8%to 91.1%.The charging rate can be increased by 23.5%when the mass flow rate is raised from 180 kg·h^-1 to 260 kg·h^-1.Finally,the thermal performance of this thermal storage packed with double-layered diameter-variable PCM capsulesis further compared with that of single-layered thermal storage.The maximum charging rate of former increases by 12.4% compared with that of latter.This study may provide a design reference for the thermal storage systems taking high-temperature molten salt as phase change material.