Numerical simulation of vertical ground heat exchangers: Intermittent operation in unsaturated soil conditions |
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Authors: | Jung Chan Choi Seung Rae Lee Dae Soo Lee |
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Institution: | 1. Dept. of Civil and Environmental Engineering, KAIST, Daejeon 305-701, Republic of Korea;2. Korea Electric Power Research Institute, Daejeon 305-308, Republic of Korea |
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Abstract: | The effect of varying the thermal properties of inhomogeneous unsaturated soil on the intermittent operation of a vertical ground heat exchanger (GHE) was simulated by a conjugate heat transfer simulation using a transient conductive heat transfer model. A three-phase soil model was used to introduce soil properties that vary with depth. The performance during the first few hours was significantly different from that of an analytical infinite line source model that assumes steady-state borehole conditions, although relatively good agreement was obtained thereafter. Unsaturated soil conditions afforded a 40% lower mean heat exchange rate than saturated conditions. This demonstrates the importance of considering unsaturated conditions in the design and performance evaluation of GHEs. |
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Keywords: | Ground source heat pump Ground heat exchanger Numerical simulation Unsaturated soil Intermittent operation |
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