On the applicability of the moving line source theory to thermal response test under groundwater flow: considerations from real case studies

Angelotti, Adriana; Ly, Franco; Zille, Andrea

doi:10.1186/s40517-018-0098-z

Cited by 16 publications

(13 citation statements)

References 15 publications

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“…Additional parameters for the numerical simulations are listed in Table 1. The discrepancies between simulations and measurements at the beginning are likely the indication of heat transfer within boreholes, which have different thermal properties than the surrounding soil [14]. It is essential to ensure the apparent thermal conductivity adequately represents the value of soil mass.…”

Section: Discussionmentioning

confidence: 99%

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Effect of Groundwater Flow and Thermal Conductivity on the Ground Source Heat Pump Performance at Bangkok and Hanoi: A Numerical Study

Widiatmojo¹,

Uchida²,

Takashima³

2022

Geothermal Energy

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In recent decades, the fast-growing economies of Southeast Asian countries have increased the regional energy demand per capita. The statistic indicates Southeast Asian electricity consumption grows for almost 6% annually, with space cooling becoming the fastest-growing share of electricity use. The ground source heat pump technology could be one of the solutions to improve energy efficiency. However, currently, there are limited data on how a ground source heat pump could perform in such a climate. The thermal response test is widely used to evaluate the apparent thermal conductivity of the soil surrounding the ground heat exchanger. In common practice, the apparent thermal conductivity can be calculated from the test result using an analytical solution of the infinite line source method. The main limitation of this method is the negligence of the physical effect of convective heat transfer due to groundwater flow. While convection and dispersion of heat are two distinctive phenomena, failure to account for both effects separately could lead to an error, especially in high groundwater flow. This chapter discusses the numerical evaluation of thermal response test results in Bangkok, Thailand, and Hanoi, Vietnam. We applied a moving infinite line source analytical model to evaluate the value of thermal conductivity and groundwater flow velocity. While determining the ground thermal properties in a high accuracy is difficult, the moving infinite line source method fulfills the limitation of the infinite line source method. Further, we evaluated the five-year performance of the ground source heat pump system coupled with two vertical ground heat exchangers in Bangkok and Hanoi. The results suggest the importance of groundwater flow to enhance the thermal performance of the system.

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Section: Discussionmentioning

confidence: 99%

“…( 7) calculates the temperature of the soil medium at an arbitrary position adjacent to the line source. The following equation represents heat balance between average fluid temperature and borehole wall temperature [14]:…”

Section: Moving Infinite Line Sourcementioning

confidence: 99%

Effect of Groundwater Flow and Thermal Conductivity on the Ground Source Heat Pump Performance at Bangkok and Hanoi: A Numerical Study

Widiatmojo¹,

Uchida²,

Takashima³

2022

Geothermal Energy

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“…Notar que cuando las dimensiones geométricas de la generación de calor son despreciables (con respecto a las dimensiones geométricas del cuerpo) entonces es razonable considerar al cuerpo como un medio infinito. Los resultados analíticos obtenidos con esta hipótesis han sido validados experimentalmente [30][31][32][33], lo cual demuestra que esta hipótesis puede usarse (bajo las condiciones adecuadas) para modelar correctamente muchos casos relevantes para la ingeniería. Con el propósito de evidenciar la validez de esta hipótesis y resaltar la versatilidad de las técnicas analíticas, los resultados obtenidos en este trabajo (que están basados en la hipótesis de medio infinito) se han comparado con los resultados numéricos obtenidos tomando un cuerpo finito, cuyas dimensiones geométricas son mucho mayores que las dimensiones de la generación de calor (ver Sección IV).…”

Section: Marco Teóricounclassified

Solución Analítica de la Distribución de Temperaturas en un Medio Homogéneo Debido a un Cable Eléctrico con Forma de Onda Rectangular

Diestra-Cruz¹,

Brunet²,

Santos-Sánchez³

et al. 2020

Proceedings of the 18th LACCEI International Multi-Conference for Engineering, Education, and Technology: Engineering, Integrat

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Due to the limited amount of oil reserves, it is essential to ensure the efficient use of available energy, which is closely linked to the optimal design of electrical devices. Because these devices work with electrical energy, they cannot avoid having discrete heat generating sources and their design depends on the precise determination of the temperature field in the body. In this work, the integral method of Green's functions is used to determine the three-dimensional temperature distribution of a homogeneous medium due to a rectangular waveshaped heat generation source. The geometry of the heat generation has been selected in such a way that it has the typical shape of the commercially available flexible electric heaters. The solution obtained is exact and mathematically simple. To demonstrate the versatility of the results, this analytical solution has been compared with the purely numerical solution obtained using a computer package widely used in engineering (COMSOL Multiphysics). The analytical and numerical results coincide well in all the evaluated ranges. Using the equation obtained in this work, a procedure is proposed to determine the effective thermal conductivity of a material from the experimental data of temperature and position. The results of this research offer a simple way to calculate the thermal conductivity of a material and can be applied in the design of thermo-optical devices, flexible electric heaters or thermo-adjustable microfluidic devices.

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“…Several studies investigated analytical models, which consider both conductive and advective heat transport in the subsurface for configuring BHEs [7,16,[24][25][26][27][28][29][30][31][32][33][34][35]. For instance, Claesson et al [27] introduced a groundwater g-function, which is used to reduce the values computed by a g-function for heat conduction.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Steady-State Solution of the Infinite Moving Line Source Model for the Thermal Design of Grouted Borehole Heat Exchangers with Groundwater Advection

2021

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The objective of this study is to assess the suitability of the analytical infinite moving line source (MLS) model in determining the temperature of vertical grouted borehole heat exchangers (BHEs) for steady-state conditions when horizontal groundwater advection is present. Therefore, a numerical model of a grouted borehole is used as a virtual reality for further analysis. As a result of the first analysis, it has been discovered that established analytical methods to determine the borehole thermal resistance as a mean value over the borehole radius can also be applied to BHEs with groundwater advection. Furthermore, the deviation between a finite MLS and the infinite MLS is found to be only less than 5% for BHEs of a depth of 30 m or more, and Péclet numbers greater than 0.05. Finally, the accuracy of the temperature change calculated with the infinite MLS model at the radius of the borehole wall compared to the temperature change at a numerically simulated grouted borehole is addressed. A discrepancy of the g-functions resulting in a poor dimensioning of BHEs by the infinite MLS model is revealed, which is ascribed to the impermeable grouting material of the numerical model. A correction function has been developed and applied to the infinite MLS model for steady-state conditions to overcome this discrepancy and to avoid poor dimensioning of BHEs.

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On the applicability of the moving line source theory to thermal response test under groundwater flow: considerations from real case studies

Cited by 16 publications

References 15 publications

Effect of Groundwater Flow and Thermal Conductivity on the Ground Source Heat Pump Performance at Bangkok and Hanoi: A Numerical Study

Effect of Groundwater Flow and Thermal Conductivity on the Ground Source Heat Pump Performance at Bangkok and Hanoi: A Numerical Study

Solución Analítica de la Distribución de Temperaturas en un Medio Homogéneo Debido a un Cable Eléctrico con Forma de Onda Rectangular

Enhanced Steady-State Solution of the Infinite Moving Line Source Model for the Thermal Design of Grouted Borehole Heat Exchangers with Groundwater Advection

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