A numerical study on heat transfer performances of horizontal ground heat exchangers in ground-source heat pumps

• Published in: PloS one Vol. 16; no. 5; p. e0250583
• Main Authors: Zou, Hang, Pei, Peng, Wang, Chen, Hao, Dingyi
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 19-05-2021; Public Library of Science (PLoS)
• Subjects: Abbreviations; Additives; Air Content; Coefficient of friction; Computational fluid dynamics; Convection; Copper; Density; Diameters; Energy; Engineering and Technology; Fluid flow; Fluids; Foams; Geothermal energy; Groundwater; Heat conductivity; Heat exchange; Heat exchangers; Heat pumps; Heat storage; Heat transfer; Heat transfer coefficients; Latent heat; Mathematical models; Metal foams; Moisture content; Numerical models; Numerical simulations; Permeability; Permeability coefficient; Phase change materials; Physical Sciences; Porosity; Porous media; Pressure; Research and Analysis Methods; Simulation; Soil porosity; Soil water; Soil water potential; Soils; Specific heat; Storage capacity; Temperature; Thermal conductivity; Thermal properties; Three dimensional models; Velocity; Viscosity; Water content; Water potential; China
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0250583

Horizontal ground heat exchangers (HGHEs) have advantages such as convenient construction and low cost; however, their application and popularization are restricted owing to traditional linear HGHEs occupying large space and presenting low total heat transfer capacity. Spiral-coil and slinky-coil HGHEs have been proposed, but currently a comprehensive comparison and evaluation for these types of HGHEs are still needed. In this study, a three-dimensional heat transfer model of the three types of HGHEs for ground source heat pumps (GSHPs) was established. Based on the simulation results, the long-term heat transfer performances were investigated, including the temperature field of surrounding energy-storage soils, outlet working fluid temperature, coefficient of performance (COP) of units, and surplus temperature of the energy-storage soils. A new concept named heat transfer capacity per heat-affected area was proposed in this paper. It is found that the spiral-coil HGHEs have the best performances in terms of working-fluid outlet temperature, unit COP, total heat transfer capacity, heat transfer rate heat-affected area. The linear HGHEs shows the best performances in terms of mitigating heat imbalance risk and heat transfer rate per length. The results provide a reliable basis for selection of HGHE types in engineering practice and improvement guide in the future.