Simulation study on the thermal performance of vertical U-tube heat exchangers for ground source heat pump system

Abstract The Vertical U-tube ground source heat exchanger (GSHE) is a significant component of the ground source heat pump (GSHP) system. This paper investigates the effect of Reynolds number, tube diameter and tube-connection configurations on the thermal and pressure performance of vertical U-tube GSHEs numerically. The simulation study was verified by ground thermal response experimental test. Meanwhile, the dimensionless evaluation criterion and the integrated evaluation criterion were adopted to analyze the thermal and pressure performance of GSHEs. The results show that the integrated evaluation factor was 5.11, 11.55, and 13.25 for Re = 100, Re = 1000, Re = 1600, respectively. The integrated evaluation factor was 11.48, 11.55 and 12.14 for different tube external diameters of DN25, DN32 and DN40. Therefore, better integrated performance can be obtained by increasing Reynolds number and U-tube diameter under laminar flow condition. Furthermore, parallel U-tubes GSHEs can ensure higher heat flux and lower pressure drop.

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