Efficiency analysis of utilizing phase change materials as grout for a vertical U-tube heat exchanger coupled ground source heat pump system

Laboratory investigation on the use of thermally enhanced phase change material to improve the performance of borehole heat exchangers for ground source heat pumps

“…There are a few modeling studies, which analyzed the use of PCMs as grouting or in other words backfilling material in BHE of GSHP . Lei and Zhu selected different PCMs for use as grouting and showed that the number of boreholes may be decreased for a fixed energy demand.…”

“…As stated by Chen et al, PCM should not start to melt early and avoid prolonged use of latent heat. In their simulation study, Chen et al tested fictitious PCM grouts having the same thermal conductivity and latent heat, but with varying melting points of 19.9°C, 20.4°C, 20.9°C, 21.4°C, and 21.9°C.…”

“…Low thermal conductivity of PCM may delay heat transfer to the soil and cause buildup of heat in the borehole, which causes poor performance of the heat pump . Thermal conductivity of PCM is as important as the melting point choice of PCM.…”

“…Considerable amount of work has already been done regarding coupling PCM through LHTES with GSHP . There are only a few studies that investigate using PCMs as grouting of BHE in GSHPs numerically as given in the previous paragraph . In these numerical modeling studies done so far, the effects of using fictitious PCMs with constant properties were considered.…”

“…There are a few modeling studies, which analyzed the use of PCMs as grouting or in other words backfilling material in BHE of GSHP. 12,[21][22][23][24][25][26] Lei and Zhu 21 selected different PCMs for use as grouting and showed that the number of boreholes may be decreased for a fixed energy demand. Spitler and Bernier 22 also mentioned in an article published in 2011 of the need for investigating the potential inclusion of phase change materials inside the borehole of a GSHP.…”