Transient forced convection from an infinite cylindrical heat source in a saturated Darcian porous medium

Conti, Paolo; Testi, Daniele; Grassi, Walter

doi:10.1016/j.ijheatmasstransfer.2017.10.012

Cited by 11 publications

(4 citation statements)

References 25 publications

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“…• The presence of groundwater flow means that convection has a greater influence than conduction, while the groundwater level influences the moisture content of the ground, thus affecting its conductivity. Several criteria have been proposed for considering this [21,30,36]. • The ground is generally stratified such that the BHE exchanges heat with layers with different thermal conductivities.…”

Section: Thermal Response Test: Methodological Description and Theore...mentioning

confidence: 99%

“…Furthermore, in the case of significant flow, convection has a greater influence than conduction. Several criteria have been proposed in the literature to find out the influence of convective heat transfer on the evaluation of thermal conductivity (see, for instance, Conti et al [30]). Another problem is that the ground is generally stratified such that the BHE exchanges heat with layers with different conductivities; this invalidates the assumption of constant linear heat flux, which is typical of conventional TRT.…”

Section: Measuring Soil Thermal Properties With Experimental Analysismentioning

confidence: 99%

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Clearing a Path for Ground Heat Exchange Systems: A Review on Thermal Response Test (TRT) Methods and a Geotechnical Routine Test for Estimating Soil Thermal Properties

Franco

Conti

2020

Energies

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The performance of ground heat exchanger systems depends on the knowledge of the thermal parameters of the ground, such as thermal conductivity, capacity, and diffusivity. The knowledge of these parameters often requires quite accurate experimental analysis, known as a thermal response test (TRT). In this paper, after a general analysis of the various available types of TRT and a study of the theoretical basics of the method, we explore the perspective of the definition of a simplified routine method of analysis based on the combination of a particular version of TRT and the routine geotechnical tests for the characterization of soil stratigraphy and the ground characteristics. Geotechnical analyses are indeed mandatory before the construction of new buildings, even if limited to 30 m below the ground level or foundation base when piles are needed. The idea of developing TRT in connection with geotechnical test activity has the objective of promoting the widespread use of in situ experimental analysis and reducing TRT costs and time. The considerations presented in the present paper lead to reconsidering a particular variety of the TRT, in particular, the versions known as thermal response test while drilling (TRTWD) and TRT using heating cables (HC-TRT).

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Section: Thermal Response Test: Methodological Description and Theore...mentioning

confidence: 99%

Section: Measuring Soil Thermal Properties With Experimental Analysismentioning

confidence: 99%

Clearing a Path for Ground Heat Exchange Systems: A Review on Thermal Response Test (TRT) Methods and a Geotechnical Routine Test for Estimating Soil Thermal Properties

Franco

Conti

2020

Energies

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“…In saturated coarse gravel, the Peclet number usually has a value greater than 500, which means that there is a dominant convective heat transfer; while for fine saturated sand, the value is around 1. Silts and clays give values lower than 0.01, which suggests a completely conductive heat transfer [26][27][28].…”

Section: Experimental Site Setupmentioning

confidence: 99%

Applying Petroleum the Pressure Buildup Well Test Procedure on Thermal Response Test—A Novel Method for Analyzing Temperature Recovery Period

2018

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Abstract:The theory of Thermal Response Testing (TRT) is a well-known part of the sizing process of the geothermal exchange system. Multiple parameters influence the accuracy of effective ground thermal conductivity measurement; like testing time, variable power, climate interferences, groundwater effect, etc. To improve the accuracy of the TRT, we introduced a procedure to additionally analyze falloff temperature decline after the power test. The method is based on a premise of analogy between TRT and petroleum well testing, since the origin of both procedures lies in the diffusivity equation with solutions for heat conduction or pressure analysis during radial flow. Applying pressure build-up test interpretation techniques to borehole heat exchanger testing, greater accuracy could be achieved since ground conductivity could be obtained from this period. Analysis was conducted on a coaxial exchanger with five different power steps, and with both direct and reverse flow regimes. Each test was set with 96 h of classical TRT, followed by 96 h of temperature decline, making for almost 2000 h of cumulative borehole testing. Results showed that the ground conductivity value could vary by as much as 25%, depending on test time, seasonal period and power fluctuations, while the thermal conductivity obtained from the falloff period provided more stable values, with only a 10% value variation.

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“…Conti et al . 11 presented the numerical solution of the problem of an infinite cylindrical heat source embedded into a saturated porous medium. However, the above models are usually used to study heat transfer in saturated soil.…”

Section: Introductionmentioning

confidence: 99%

A Simulation Model for Coupled Heat Transfer and Moisture Transport under the Action of Heat Source in Unsaturated Soils

Jin

Guo

Deng³

et al. 2018

Sci Rep

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Ground source heat pump (GSHP) system has been installed as the air-conditioning system worldwide due to it has the characteristics of high efficiency, easy access and environmental protection. Since ground heat exchanger (GHE) plays a key role in the performance of GSHPs, many models of GHE have been proposed to simulate temperature distribution around the borehole. However, most of these models depict only the heat conduction process between buried pipes and surrounding soil based on the line source model or cylindrical source model. And these models do not consider water transfer under the action of heat source, which can cause some prediction errors. The objective of this study is to provide a numerical model to simulate the spatiotemporal distribution of temperature and moisture caused by a GHE with constant temperature in unsaturated soils. The numerical model is developed by establishing two tridiagonal matrices and adopting Thomas algorithm to achieve the programming. The experiment is operated at the Taiyuan University of Technology and the comparisons between modeled and experimental data prove the high accuracy of this model. The model shows significant engineering values in designs and operations of GSHP.

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Transient forced convection from an infinite cylindrical heat source in a saturated Darcian porous medium

Cited by 11 publications

References 25 publications

Clearing a Path for Ground Heat Exchange Systems: A Review on Thermal Response Test (TRT) Methods and a Geotechnical Routine Test for Estimating Soil Thermal Properties

Clearing a Path for Ground Heat Exchange Systems: A Review on Thermal Response Test (TRT) Methods and a Geotechnical Routine Test for Estimating Soil Thermal Properties

Applying Petroleum the Pressure Buildup Well Test Procedure on Thermal Response Test—A Novel Method for Analyzing Temperature Recovery Period

A Simulation Model for Coupled Heat Transfer and Moisture Transport under the Action of Heat Source in Unsaturated Soils

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