Behavior of Heat‐Exchanger Piles from Physical Modeling

Tang, Anh Minh; Pereira, Jean‐Michel; Hassen, Ghazi; Yavari, Neda

doi:10.1002/9781118761809.ch4

Cited by 5 publications

(4 citation statements)

References 25 publications

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“…The most common approaches employed to investigate the thermal deformation of energy piles, the thermal‐induced down drag and axial stresses and the interaction between the pile and the soil are as follows: (i) physical modelling and (ii) numerical simulations. The former category includes in situ real scale testing , model piles at the laboratory scale and centrifuge experiments . All of them have been fundamental to understand the physical mechanisms of energy piles.…”

Section: State Of Knowledgementioning

confidence: 99%

Numerical analysis of the geotechnical behaviour of energy piles

Donna

Laloui

2014

Num Anal Meth Geomechanics

108

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Summary Energy geostructures are rapidly gaining acceptance around the world; they represent a renewable and clean source of energy that can be used for the heating and cooling of buildings and for de‐icing of infrastructures. This technology couples the structural role of geostructures with the energy supply, using the principle of shallow geothermal energy. The geothermal energy exploitation represents an additional thermal loading, seasonally cyclic, which is imposed on the soil and the structure itself. Because the primary role of the piles is the stability of the superstructure, this aspect needs to be ensured even in the presence of the additional thermal load. The goal of this paper is to numerically investigate the behaviour of energy pile foundations during heating–cooling cycles. For this purpose, the finite element method is used to simulate both a single and a group of energy piles. The piles are subjected to a constant mechanical load and a seasonally cyclic thermal load over several years, imposed in terms of injected–extracted thermal power. The soil and the pile–soil interface behaviours are reproduced using a thermoelastic‐thermoplastic constitutive model. The thermal‐induced stresses inside the piles and the additional displacements of the foundations are discussed. The group model is used to investigate the interactions between the piles during thermo‐mechanical loading. The presented results are specific to the studied cases but lead to the conclusion that both the thermal‐induced displacements and stresses, despite being acceptable under normal working conditions, deserve to be taken into account in the geotechnical design of energy piles. Copyright © 2014 John Wiley & Sons, Ltd.

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Section: State Of Knowledgementioning

confidence: 99%

Numerical analysis of the geotechnical behaviour of energy piles

Donna

Laloui

2014

Num Anal Meth Geomechanics

108

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“…">Introduction1 Over the past decades, the depletion of fossil energy along with the demand to reduce carbon footprint in the 2 energy sector has promoted the development of renewable energy techniques including solar, wind, geothermal energy, 3 bioenergy, hydropower, etc. The renewable energy revolution has spread worldwide, which accounted for 19% of the 4 global energy generation in 2012 and quickly increased to 23% in 2013 [1]. In the United States, the cumulative 5 installation of renewable electricity capacity has doubled since 2000.…”

mentioning

confidence: 99%

“…In the United States, the cumulative 5 installation of renewable electricity capacity has doubled since 2000. Particularly, the United States led the world in 6 energy production from geothermal and biomass in 2013 [1]. There has been adoption of geothermal heat pump (GHP) 7 systems at a fast pace.…”

mentioning

confidence: 99%

Sensitivity analysis of a vertical geothermal heat pump system

Han

2016

Applied Energy

120

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This paper conducts sensitivity analyses on factors affecting the performance of vertical geothermal heat pump system, aiming to formulate design and operation strategies to improve its performance. It firstly describes the development of a 3D coupled Finite Element Model (FEM), which is utilized to simulate the steady state and transient behaviors of geothermal heat exchanger (GHE). The model holistically couples the heat exchange processes between pipe fluid flow, grouting backfill material, and adjacent ground associated with GHE. The model is firstly validated by comparison with the experimental data from an in-service GHE. Base on the calibrated model, a series of sensitivity analyses are conducted on the influence of geological, design, and operational factors intermittent operation mode of GHE achieves higher such as the initial ground temperature profile, GHE pipe installation depth, circulation fluid flow velocity, inlet temperature, subsurface water flow velocity, and material thermal properties. It also assess the behaviors of GHE under continuous operation versus intermittent operation modes. The results show that both design parameter (i.e., GHE pipe installation depth) and operational parameters (i.e, circulation fluid flow velocity) have major influence on the GHE performance. For a certain design length of GHE, the GHE performance improves with higher circulation fluid flow velocity until beyond a critical velocity. For GHE working in the heating mode, the heat extraction by GHE increases with decreasing fluid temperature at the inlet. In the geological factor aspect, the thermal conductivity of the ground material plays a very important role on the GHE performance operating in the continuous operation mode, while its specific heat capacity exerts no appreciable influence. However, for intermittent operation mode, both thermal conductivity and specific heat capacity of the ground, particularly the grouting materials, affect the ground thermal energy extraction. The results also showed that the presence of subsurface ground water flow improves the heat exchange of GHE. Operation wise, the GHE achieves higher performance and Coefficient of Performance (COP) under intermittent operation mode than under continuous operation mode. These observations point to ways to improve the performance of GHE from both design and operation aspects. Introduction1 Over the past decades, the depletion of fossil energy along with the demand to reduce carbon footprint in the 2 energy sector has promoted the development of renewable energy techniques including solar, wind, geothermal energy, 3 bioenergy, hydropower, etc. The renewable energy revolution has spread worldwide, which accounted for 19% of the 4 global energy generation in 2012 and quickly increased to 23% in 2013 [1]. In the United States, the cumulative 5 installation of renewable electricity capacity has doubled since 2000. Particularly, the United States led the world in 6 energy production from geothermal and biomass in 2013 [1]. There has been adoption o...

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“…Various studies on the behavior of energy piles and their thermo-mechanical response have been conducted in-situ (Laloui et al, 2003;Bourne-Webb et al, 2009;Akrouch et al, 2014;Murphy and McCartney, 2015) and in the laboratory (Stewart and McCartney, 2013;Tang et al, 2013). All these studies have focused on pile behaviour.…”

Section: Introductionmentioning

confidence: 99%

Impact of Temperature Variations on the Hydro-Mechanical Parameters of a Sensitive Soil

et al. 2016

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The incorporation of heat exchangers in geostructures produces a cyclic variation of the temperature in the adjacent soil. Therefore, there are important questions about the effect of temperature variations on hydro-mechanical soil parameters. In this study, mini-pressuremeter tests were conducted in laboratory on a homogeneous material submitted to different thermal loading (1 to 40 °C). The tested material, an illitic soil, is compacted in a thermo-regulated container with 0.6 m diameter and 0.8 m height, at optimal water content (31.3 %) and 90% of maximum dry density (1.29 Mg/m 3). Only six tests are performed in each container to prevent edge effects and the influence between the tests. The impact of temperature variation on creep pressure (pf), limit pressure (pl) and pressuremeter modulus (Ep) were determined. A decrease in creep pressure and limit pressure with increasing temperature was observed, while the variation of pressuremeter modulus was less pronounced. The first cycle induced more important parameter variations than the subsequent cycles.

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Behavior of Heat‐Exchanger Piles from Physical Modeling

Cited by 5 publications

References 25 publications

Numerical analysis of the geotechnical behaviour of energy piles

Numerical analysis of the geotechnical behaviour of energy piles

Sensitivity analysis of a vertical geothermal heat pump system

Impact of Temperature Variations on the Hydro-Mechanical Parameters of a Sensitive Soil

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