定形相变材料回填下的地埋管换热器实验

Experimental analysis of ground tube heat exchanger with shape-stabilize phase change material backfill

为研究定形相变材料(SSPCM)作为地埋管回填材料的传热特性,以30 W圆柱形发热棒作为线热源模拟地埋管换热器,用膨胀石墨吸附石蜡制成SSPCM,并将其和普通回填沙以3:7的质量比混合制备成混合回填材料,分析在夏季间歇运行工况下,SSPCM混合回填下的传热特性。结果表明,在短期实验运行模式下,相对普通沙回填,SSPCM混合回填材料形成的温度场优势明显,温度波动较小,管壁附近过余温度差异可达到10℃;距离发热中心距离越近,减缓温度场变化的效果越明显;在2种回填条件下,恢复后稳定温度以及恢复所需时间无显著差异;在多周期间歇运行工况时,回填区域内温度明显低于连续运行状况;若运行时间导致的温升超过相变材料潜热利用阶段,SSPCM无法发挥出相变储能的优势。该实验现象对SSPCM实际应用有一定参考价值。

To investigate the heat transfer characteristics of a ground heat exchanger(GHE)with shape-stabilized phase change material(SSPCM)backfill,a 30 W cylindrical heating rod was used as a linear heat source in place of the GHE.Expanded graphite adsorbed paraffin was used to create SSPCM,which was then mixed with ordinary backfill sand at a mass ratio of 3:7 to prepare a mixed backfill material.The heat transfer characteristics of the SSPCM mixed backfill material were studied under intermittent operation during summer.The research results indicate that the temperature field formed by the SSPCM mixed backfill material had obvious advantages,with smaller temperature fluctuations.In short-term operation modes,the excess temperature difference near the pipe wall could reach about 10℃when compared with ordinary sand backfill.The effect of alleviating temperature fluctuations became more prominent as the distance from the heating center decreased.There were no significant differences in stable temperature and recovery time after recovery under the two backfill conditions.During intermittent and multi-cycle operation,the temperature in the backfill area was lower than in continuous operation.If the temperature rise caused by running time exceeded the latent heat utilization stage of phase change materials,SSPCM could not fully utilize the advantages of phase change energy storage.These experimental results hold valuable insights for the practical application of SSPCM.