Open AccessA numerical study on heat transfer performances of horizontal ground heat exchangers in ground-source heat pumps
Author(s) -
Hui Zou,
Peng Pei,
Chen Wang,
Dingyi Hao
Publication year - 2021
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0250583
Subject(s) - ntu method , heat transfer , heat pump , heat capacity rate , heat transfer coefficient , micro heat exchanger , plate heat exchanger , plate fin heat exchanger , heat exchanger , heat spreader , coefficient of performance , mechanics , mechanical engineering , environmental science , materials science , thermodynamics , engineering , physics
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.