Selection of the design temperature change for energy piles

Abdelaziz, Sherif L.; Ozudogru, Tolga Y.

doi:10.1016/j.applthermaleng.2016.07.067

Cited by 42 publications

(15 citation statements)

References 9 publications

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“…Since the scope of the present work is the evaluation of the effect of the thermal cycles on the pile behaviour, the circulation of the heat-carrier fluid has not been modelled and the temperature variation has been uniformly applied on all the elements of the pile. Past works have shown that the choice of a uniform temperature applied to each pile cross section and along its length does not significantly affect the results [15,16].…”

Section: Finite Element Analysesmentioning

confidence: 98%

Finite element analyses of energy piles using different constitutive models

2020

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Energy piles are foundation elements having the double scope of transferring structural loads from the structure to the ground and of exchanging heat with the surrounding soil. It follows that pile state of stress and settlement are altered by the time-dependent temperature change in both pile and soil. This work is aimed at investigating the effect of thermal cycles on the behaviour of a single energy pile. To this end, fully coupled thermo-hydro-mechanical analyses have been carried out using the Finite Element code ABAQUS. The single pile is installed in a normally consolidated clay behaving according to different constitutive models involving Mohr-Coulomb, Modified Cam Clay and Hypoplastic. The latter is employed with and without the thermal formulation capable of accounting for the thermal collapse of NC clays during heating. A single free-head pile is considered and the results are presented in terms of pile axial force and settlement developed cycle by cycle.

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Section: Finite Element Analysesmentioning

confidence: 98%

Finite element analyses of energy piles using different constitutive models

2020

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“…Classical analytical models include line-source [14] and cylindrical-source [15] solutions, which tend however to make too strong approximations, such as infinitely extended line sources and a constant heat flux inside an infinite and homogeneous medium. These could be extended in several ways though [13,16,17], from analytical g-functions [18] to superposition of thermal response functions (the so-called Hellström approach) [19,20]. Unfortunately, unavoidable approximations (such as constant wall temperatures) still limit the predictive power of these models [11,13].…”

Section: Introductionmentioning

confidence: 99%

Energy Pile Field Simulation in Large Buildings: Validation of Surface Boundary Assumptions

2019

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As the energy efficiency demands for future buildings become increasingly stringent, preliminary assessments of energy consumption are mandatory. These are possible only through numerical simulations, whose reliability crucially depends on boundary conditions. We therefore investigate their role in numerical estimates for the usage of geothermal energy, performing annual simulations of transient heat transfer for a building employing a geothermal heat pump plant and energy piles. Starting from actual measurements, we solve the heat equations in 2D and 3D using COMSOL Multiphysics and IDA-ICE, discovering a negligible impact of the multiregional ground surface boundary conditions. Moreover, we verify that the thermal mass of the soil medium induces a small vertical temperature gradient on the piles surface. We also find a roughly constant temperature on each horizontal cross-section, with nearly identical average values when either integrated over the full plane or evaluated at one single point. Calculating the yearly heating need for an entire building, we then show that the chosen upper boundary condition affects the energy balance dramatically. Using directly the pipes’ outlet temperature induces a 54% overestimation of the heat flux, while the exact ground surface temperature above the piles reduces the error to 0.03%.

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“…Further improvements, including the use of pulsed heat injection strategies [7,31], strategies for the corrections of ambient temperature fluctuations and/or small instrumental errors [7,11,[32][33][34][35][36], comparatives of performance [37], or models of other geothermal structures (energy piles) [38] have also been proposed. The increase of the statistical reliability of the obtained soil and BHE parameters is always the goal, but these methods are not standardized, nor commonly used in TRT practice.…”

Section: Introductionmentioning

confidence: 99%

How Reliable Are Standard Thermal Response Tests? An Assessment Based on Long-Term Thermal Response Tests Under Different Operational Conditions

et al. 2018

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In this contribution, we analyze the results of a number of thermal response test (TRT) experiments performed during several years at the same location at our university campus in Valencia (Spain), a permeable saturated soil area with possible groundwater flow conditions. A combination of different heat injection rates, TRT operation times of up to 32 days, and various methods for parameter estimation of ground thermal properties have been applied to study their influence on the result and accuracy of TRTs. Our main objective has been to experimentally quantify the influence of groundwater flow heat advection using moving infinite and finite line-source theories, as well as to analyze the influence of factors such as test duration, sensor accuracy, and external thermal influences. We have shown that the traditionally used infinite and finite line-source models, as well as the moving line-source models, can accurately represent experimental temperature evolution, but that there are many caveats regarding the significance parameters extracted and its reproducibility and stability. These features can be improved if data from the first test days are disregarded for the analysis, obtaining a much faster convergence to the definitive soil parameter estimates, including the effective Péclet number that represents groundwater flow in our particular case.

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Selection of the design temperature change for energy piles

Cited by 42 publications

References 9 publications

Finite element analyses of energy piles using different constitutive models

Finite element analyses of energy piles using different constitutive models

Energy Pile Field Simulation in Large Buildings: Validation of Surface Boundary Assumptions

How Reliable Are Standard Thermal Response Tests? An Assessment Based on Long-Term Thermal Response Tests Under Different Operational Conditions

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