Simulation and experimental analysis of optimal buried depth of the vertical U-tube ground heat exchanger for a ground-coupled heat pump system |
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Affiliation: | 1. National Centre for International Research of Low-carbon and Green Buildings, Chongqing University, Chongqing 400045, China;2. Key Laboratory of the Three Gorges Reservoir Region''s Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400045, China;3. Civil Engineering Rover Station, Chongqing University, Shapingba District, Chongqing 400045, China;1. National Centre for International Research of Low-carbon and Green Buildings, Chongqing University, 400045, China;2. Key Laboratory of the Three Gorges Reservoir Region''s Eco-Environment, Ministry of Education, Chongqing University, 400045, China;3. North China Power Engineering Co., Ltd of China Power Engineering Consulting Group, China;1. Key Laboratory of the Three Gorges Reservoir Region''s Eco-Environment, Ministry of Education, Chongqing University, China;2. School of Construction Management and Engineering, University of Reading, Whiteknights, PO Box 219, Reading RG6 6AW, UK;3. School of System Engineering, University of Reading, Whiteknights, PO Box 219, Reading RG6 6AW, UK |
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Abstract: | This paper presents a numerical heat transfer model for vertical U-tube Ground Heat Exchangers (GHE). This model is uniquely able to take into to account different initial soil temperatures and physical properties at different depths. The model has been validated based on an experimental case study and has been used to simulate the thermal performance of GHEs. The simulation results show that for a 100-m vertical GHE, the first 70 m of the vertically buried GHE has a higher heat transfer capability than its last 30-m section. In addition, the validated model is used to investigate the optimal depth of vertical GHEs in five case studies ranging from 60 to 100 m length. Among them, the simulation results demonstrate that the GHE with buried depth of 70 m is able to provide the highest heat exchange rate per unit depth (54.1 and 47.0 W/m under heat rejection/extraction mode). It consequently results in shortest total GHE length of 11,388 m and the minimum cost of 1.82 million Yuan. However, a larger area is needed for boreholes and GHEs installation. Therefore, the optimal buried depth of the vertical U-tube GHEs for the studied case is 70 m on the condition of allocation of an abundant area to set up the boreholes. |
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Keywords: | Ground-coupled heat pump Heat transfer model Heat exchange rate Optimal buried depth |
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