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An average fluid temperature to estimate borehole thermal resistance of ground heat exchanger
- Du, Ciyuan, Chen, Youming
- Renewable energy 2011 v.36 no.6 pp. 1880-1885
- heat exchangers, heat tolerance, models, renewable energy sources, temperature
- Analysis of borehole thermal resistance is important for the standard sizing of ground heat exchanger (GHE). In this paper, a p-linear dimensionless average fluid temperature is proposed to estimate borehole thermal resistance. A p-linear dimensionless fluid temperature and p-linear dimensionless average fluid temperature are introduced, and the p-linear dimensionless fluid temperature is compared with theoretical dimensionless fluid temperature calculated by quasi-three-dimensional model for both single and double U-tubes. Results show that the p-linear dimensionless temperatures with parameters p→0 and p=−1/2 are respectively in good agreement with the theoretical dimensionless fluid temperatures of single and double U-tubes. Therefore, the dimensionless logarithmic mean temperature for p→0 and the dimensionless geometric mean temperature for p=−1/2 should respectively be adopted to reasonably estimate the thermal resistance of single and double U-tube boreholes.