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The Effect of Groundwater Flow on the Thermal Performance of a Novel Borehole Heat Exchanger for Ground Source Heat Pump Systems: Small Scale Experiments and Numerical Simulation

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Title: The Effect of Groundwater Flow on the Thermal Performance of a Novel Borehole Heat Exchanger for Ground Source Heat Pump Systems: Small Scale Experiments and Numerical Simulation
Authors: Serageldin, Ahmed A. Browse this author
Radwan, Ali Browse this author
Sakata, Yoshitaka Browse this author
Katsura, Takao Browse this author →KAKEN DB
Nagano, Katsunori Browse this author →KAKEN DB
Keywords: Ground source heat pump
oval cross-section
groundwater
borehole heat exchanger
CFD
Sandtank
Issue Date: 18-Mar-2020
Publisher: MDPI
Journal Title: Energies
Volume: 13
Issue: 6
Start Page: 1418
Publisher DOI: 10.3390/en13061418
Abstract: New small-scale experiments are carried out to study the effect of groundwater flow on the thermal performance of water ground heat exchangers for ground source heat pump systems. Four heat exchanger configurations are investigated; single U-tube with circular cross-section (SUC), single U-tube with an oval cross-section (SUO), single U-tube with circular cross-section and single spacer with circular cross-section (SUC + SSC) and single U-tube with an oval cross-section and single spacer with circular cross-section (SUO + SSC). The soil temperature distributions along the horizontal and vertical axis are measured and recorded simultaneously with measuring the electrical energy injected into the fluid, and the borehole wall temperature is measured as well; consequently, the borehole thermal resistance (R-b) is calculated. Moreover, two dimensional and steady-state CFD simulations are validated against the experimental measurements at the groundwater velocity of 1000 m/year with an average error of 3%. Under saturated conditions without groundwater flow effect; using a spacer with SUC decreases the R-b by 13% from 0.15 m.K/W to 0.13 m.K/W, also using a spacer with the SUO decreases the R-b by 9% from 0.11 m.K/W to 0.1 m.K/W. In addition, the oval cross-section with spacer SUO + SSC decreases the R-b by 33% compared with SUC. Under the effect of groundwater flow of 1000 m/year; R-b of the SUC, SUO, SUC + SSC and SUO + SSC cases decrease by 15.5%, 12.3%, 6.1% and 4%, respectively, compared with the saturated condition.
Rights: © 2020 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/).
http://creativecommons.org/licenses/by/4.0/
Type: article
URI: http://hdl.handle.net/2115/78401
Appears in Collections:工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

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