Experimental analysis of ground tube heat exchanger with shape-stabilize phase change material backfill
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Abstract:
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.
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Supported by Open Fund Project of Chongqing Shallow Geothermal Energy Field Scientific Observation and Research Station（GCZ-202112）.
