A Boundary Element Method for Circulating Thermal Resistance of U-Tube Underground Heat Exchanger

Abstract:

The boundary element method was introduced to calculate the thermal resistance between pipe outside surface and the borehole inner surface of vertical U-shaped pipe underground heat exchanger. The effects of U-tube diameter, borehole diameter and tube spacing on the thermal resistance were also discussed. The results showed that it took only 10 min to complete a simulation of an underground heat pump running continually for 1000 h, which took least 3 h to complete the same cycle through finite volume method. When the thermal conductivity λ of the backfill material was 1.8 W/m²·K, the thermal resistance of the U-shaped pipe decreased with the increase in the tube spacing, it decreased with the increase in the U-tube diameter, however, it increased when the borehole diameter increased.

• Periodical: Advanced Materials Research (Volumes 953-954)
• Pages: 705-709
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.953-954.705
• Online since: June 2014
• Authors: Yi Liu*, Yang Shi, Ya Ning Zhang
• Keywords: Boundary Element Method (BEM), Soil Source Heat Pump System, Thermal Resistance, Underground Heat Exchanger

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