A modified multi-ground-layer model for borehole ground heat exchangers with an inhomogeneous groundwater flow

Lee, C.K.; Lam, H.N.

doi:10.1016/j.energy.2012.09.056

Cited by 83 publications

(15 citation statements)

References 14 publications

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“…Codes developed for use with borehole heat exchangers, eg [15,16] are equally applicable to pile applications. In addition, numerical methods may be used to couple the thermal and mechanical aspects of the pile behaviour [17].…”

Section: Existing Design Approachesmentioning

confidence: 99%

Temperature response functions (G-functions) for single pile heat exchangers

Loveridge

Powrie

2013

Energy

108

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Foundation piles used as heat exchangers as part of a ground energy system have the potential to reduce energy use and carbon dioxide emissions from new buildings. However, current design approaches for pile heat exchangers are based on methods developed for boreholes which have a different geometry, with a much larger aspect (length to diameter) ratio. Current methods also neglect the transient behaviour of the pile concrete, instead assuming a steady state resistance for design purposes. As piles have a much larger volume of concrete than boreholes, this neglects the significant potential for heat storage within the pile. To overcome these shortcomings this paper presents new pile temperature response functions (G-functions) which are designed to reflect typical geometries of pile heat exchangers and include the transient response of the pile concrete. Owing to the larger number of pile sizes and pipe configurations which are possible with pile heat exchangers it is not feasible to developed a single unified G-function and instead upper and lower bound solutions are provided for different aspects ratios. (172 words)

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Section: Existing Design Approachesmentioning

confidence: 99%

Temperature response functions (G-functions) for single pile heat exchangers

Loveridge

Powrie

2013

Energy

108

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“…While numerical methods present another effective alternative with an acceptable accuracy to full-scale experimental tests. Computational fluid dynamics (CFD) approach can study the impacts of the diversity of factors on the performance of BHX with various configurations and arrangements [27][28][29][30][31][32][33][34][35][36]. For example, Jahangir MH et al [37] utilized the classical finite element method to study the thermal and moisture behavior of the heat exchanger during the heat transfer process of several U-shape straight pipes.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

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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 (Rb) 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 Rb by 13% from 0.15 m·K/W to 0.13 m·K/W, also using a spacer with the SUO decreases the Rb 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 Rb by 33% compared with SUC. Under the effect of groundwater flow of 1000 m/year; Rb 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.

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“…However, most existing models either regard the heat transfer between BHEs and their surrounding ground as a pure heat conduction process or assume the ground to be a fully saturated homogeneous porous. Few reported models consider the effect of layered ground conditions on the heat transfer of BHEs, especially when BHEs are partially located below the groundwater table where groundwater seepage is occurring [18,19]. In such cases, the combined effect of unsaturated soil properties above the groundwater table and groundwater flow below should be considered.…”

Section: Introductionmentioning

confidence: 99%