Relative constructability and thermal performance of cast-in-place concrete energy pile: Coil-type GHEX (ground heat exchanger)

Park, Sangwoo; Lee, Dongseop; Choi, Hwa-Jung; Jung, Kyoungsik; Choi, Hangseok

doi:10.1016/j.energy.2014.08.012

Cited by 71 publications

(29 citation statements)

References 15 publications

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“…Pile heat exchangers vary in length from 7 to 50 m with a cross section of 0.3 to 1.5 m. The methods of construction include: cast-in-place concrete piles, 0.3-1.5 m in diameter [6] [7][8] [9]; precast concrete piles with side lengths spanning 0.27-0.6 m [10] [11] [12][13]; hollow concrete precast piles [14] and driven steel piles [15] [16].…”

Section: Introductionmentioning

confidence: 99%

Comparing heat flow models for interpretation of precast quadratic pile heat exchanger thermal response tests

Alberdi-Pagola

Poulsen

Loveridge

et al. 2018

Energy

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This paper investigates the applicability of currently available analytical, empirical and numerical heat flow models for interpreting thermal response tests (TRT) of quadratic cross section precast pile heat exchangers. A 3D finite element model (FEM) is utilised for interpreting five TRTs by inverse modelling. The calibrated estimates of soil and concrete thermal conductivity are consistent with independent laboratory measurements. Due to the computational cost of inverting the 3D model, simpler models are utilised in additional calibrations. Interpretations based on semi-empirical pile Gfunctions yield soil thermal conductivity estimates statistically similar to those obtained from the 3D FEM inverse modelling, given minimum testing times of 60 hours. Reliable estimates of pile thermal resistance can only be obtained from type curves computed with 3D FEM models. This study highlights the potential of applying TRTs for sizing quadratic, precast pile heat exchanger foundations.

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Section: Introductionmentioning

confidence: 99%

Comparing heat flow models for interpretation of precast quadratic pile heat exchanger thermal response tests

Alberdi-Pagola

Poulsen

Loveridge

et al. 2018

Energy

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“…However, a massive closed‐loop GHEX unit often needs large construction space that is limited in developed cities with the high density of buildings, such as Tokyo or Seoul. Thus, nowadays a novel type of GHEXs has been installed by adopting existing civil infra‐structures such as an energy textile and an energy pile . In addition, a particular interest in open‐loop GHEXs is also growing.…”

Section: Introductionmentioning

confidence: 99%

Optimum operation of open-loop ground heat exchanger considering subsurface temperature gradient

Choi

Park

Lee

et al. 2015

Int. J. Energy Res.

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This paper proposes an optimum operation method for open-loop ground heat exchangers (GHEX) considering the subsurface temperature gradient. A series of thermal response tests and artificial heating/cooling operations was carried out along with monitoring temperatures in the standing column well. The underground temperature naturally increases with depth, but a switch between the cooling and heating modes can alter the temperature distribution. The effect of the mode change was evaluated by performing logarithmic mean temperature difference (LMTD) and computational fluid dynamics (CFD) analyses for a reduced (or physical) model with the well depth of 150 m. As a result, in the cooling mode, the upstream operation is more efficient than the downstream operation and reduces entering water temperature (EWT) by 2.26°C. On the other hand, in the heating mode, the downstream operation is advantageous over the upstream operation and increases EWT by 3.19°C. According to the results of the LMTD and CFD analysis, the thermal conductivity of the ground formation and the flow direction of water are the most important factors in the open-loop GHEX. Finally, an optimum flow direction with respect to each operation is proposed to enhance its efficiency; thus, a new GHEX system is flexible to a change in the flow direction.

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“…The results of numerical analysis without considering the groundwater effect are shown in [19], where the validity of homogeneous models on short-term thermal response for a large-diameter cast-in-place energy pile was evaluated by comparing analytical solutions with field test results. …”

Section: Effect Of Impermeable Borehole On Ground Thermal Behaviormentioning

confidence: 99%

“…Lamarche [18] discussed limitations of the homogeneous models assuming that the mean fluid temperature is identical to the temperature in the borehole wall. In addition, Park et al [19] evaluated the validity of the homogeneous models for a large-diameter cast-in-place energy pile by comparing the analytical solutions with field measurements of the short-term thermal response.…”

Section: Introductionmentioning

confidence: 99%

Effect of Borehole Material on Analytical Solutions of the Heat Transfer Model of Ground Heat Exchangers Considering Groundwater Flow

Park

Lee

et al. 2016

Energies

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Abstract:Groundwater flow is one of the most important factors for the design of a ground heat exchanger (GHEX) since the thermal environment of the ground around the buried GHEX is significantly affected by heat convection due to the groundwater flow. Several preceding studies have been conducted to develop analytical solutions to the heat transfer model of GHEX with consideration of groundwater flow. One of these solutions is the combined heat transfer model of conduction and convection. However, the developed combined analytical models are inapplicable to all of the configurations of ordinary GHEXs because these solutions assume that the inner part of the borehole is thermally inert or consists of the same material as that of the surrounding ground. In this paper, the applicability of the combined solid cylindrical heat source model, which is the most suitable to energy piles until now, was evaluated by performing a series of numerical analyses. In the numerical analysis, the inner part of the borehole was modeled as two different materials (i.e., permeable ground formation and impermeable fill such as concrete) to evaluate applicability of the analytical solution along with different diameter-length (D/L) ratios of borehole. In a small value of the D/L ratio, the analytical solution to the combined heat transfer model is in good agreement with the result of numerical analysis. On the other hand, when increasing the D/L ratio, the analytical solution significantly overestimates the effect of groundwater flow on the heat transfer of GHEXs because the analytical solution disregards the existence of the impermeable region in the borehole. Consequently, such tendency is more critical in the GHEX with a large D/L ratio such as large-diameter energy piles.

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Relative constructability and thermal performance of cast-in-place concrete energy pile: Coil-type GHEX (ground heat exchanger)

Cited by 71 publications

References 15 publications

Comparing heat flow models for interpretation of precast quadratic pile heat exchanger thermal response tests

Comparing heat flow models for interpretation of precast quadratic pile heat exchanger thermal response tests

Optimum operation of open-loop ground heat exchanger considering subsurface temperature gradient

Effect of Borehole Material on Analytical Solutions of the Heat Transfer Model of Ground Heat Exchangers Considering Groundwater Flow

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