Effects of the Circuit Arrangement on the Thermal Performance of Double U-Tube Ground Heat Exchangers

Aminhossein Jahanbin, Giovanni Semprini, Andrea Natale Impiombato, Cesare Biserni and Eugenia Rossi di Schio
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Aminhossein Jahanbin: Department of Industrial Engineering (DIN), Alma Mater Studiorum—University of Bologna, Viale Risorgimento 2, 40136 Bologna, Italy
Giovanni Semprini: Department of Industrial Engineering (DIN), Alma Mater Studiorum—University of Bologna, Viale Risorgimento 2, 40136 Bologna, Italy
Andrea Natale Impiombato: Department of Industrial Engineering (DIN), Alma Mater Studiorum—University of Bologna, Viale Risorgimento 2, 40136 Bologna, Italy
Cesare Biserni: Department of Industrial Engineering (DIN), Alma Mater Studiorum—University of Bologna, Viale Risorgimento 2, 40136 Bologna, Italy
Eugenia Rossi di Schio: Department of Industrial Engineering (DIN), Alma Mater Studiorum—University of Bologna, Viale Risorgimento 2, 40136 Bologna, Italy

Energies, 2020, vol. 13, issue 12, 1-19

Abstract: Given that the issue of variations in geometrical parameters of the borehole heat exchanger (BHE) revolves around the phenomenon of thermal resistance, a thorough understanding of these parameters is beneficial in enhancing thermal performance of BHEs. The present study seeks to identify relative changes in the thermal performance of double U-tube BHEs triggered by alterations in circuit arrangements, as well as the shank spacing and the borehole length. The thermal performance of double U-tube BHEs with different configurations is comprehensively analyzed through a 3D transient numerical code developed by means of the finite element method. The sensitivity of each circuit configuration in terms of the thermal performance to variations of the borehole length and shank spacing is investigated. The impact of the thermal interference between flowing legs, namely thermal short-circuiting, on parameters affecting the borehole thermal resistance is addressed. Furthermore, the energy exchange characteristics for different circuit configurations are quantified by introducing the thermal effectiveness coefficient. The results indicate that the borehole length is more influential than shank spacing in increasing the discrepancy between thermal performances of different circuit configurations. It is shown that deviation of the averaged-over-the-depth mean fluid temperature from the arithmetic mean of the inlet and outlet temperatures is more critical for lower shank spacings and higher borehole lengths.

Keywords: geothermal energy; ground-source heat pumps; borehole heat exchangers; ground heat exchangers; double U-tube; circuit arrangement; thermal performance; thermal resistance; shank spacing (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: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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