Full-Time-Scale Fluid-to-Ground Thermal Response of a Borefield with Uniform Fluid Temperature

Claudia Naldi and Enzo Zanchini
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Claudia Naldi: Department of Industrial Engineering, Alma Mater Studiorum University of Bologna, Viale Risorgimento 2, 40136 Bologna, Italy
Enzo Zanchini: Department of Industrial Engineering, Alma Mater Studiorum University of Bologna, Viale Risorgimento 2, 40136 Bologna, Italy

Energies, 2019, vol. 12, issue 19, 1-18

Abstract: The most accurate method for the design and the simulation of a borehole heat exchanger (BHE) field is employing the fluid-to-ground thermal response of the field, namely the mean-fluid-temperature rise produced by a time-constant thermal power supplied to the fluid. Usually, a short-term and a long-term model are applied, with results matched at a selected time instant. In this paper we propose a method to determine the full-time-scale thermal response of a BHE field that employs one numerical model and yields accurate results with a reasonable computation time. Each BHE is modeled as a one-material cylinder with the same radius as the BHE, surrounded by the ground and containing a heat-generating cylindrical surface whose temperature represents that of the fluid. The condition of uniform fluid temperature and time-constant total power supplied to the fluid, necessary for the long-term accuracy, is obtained iteratively, by imposing at the generating surface uniform time-dependent temperatures that converge to the desired condition. A 2 × 2 square BHE field is employed as an example. The method is recommended to obtain the thermal response of a BHE field with uniform fluid temperature, with high accuracy both in the short and in the long term.

Keywords: ground-coupled heat pumps; borehole heat exchangers; fluid-to-ground thermal response; full-time-scale; isothermal fluid; numerical method (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (7)

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