Heat Transfer of Helix Energy Pile: Part 2—Novel Truncated Cone Helix Energy Pile

Abstract The energy pile technology has been widely used, and the solid cylindrical heat source (SCS) model is usually adopted to describe the heat transfer process between the energy pile and the surrounding soil. This paper investigates the SCS model with a convective boundary condition (SCS-3 model), and realistic conditions such as transversely isotropic ground and groundwater flow are all included in the model. An analytical solution for the problem is established using Green's function method and the theory of moving heat sources. Solutions for the SCS model with a boundary condition of the first kind (SCS-1 model) and for the line source (LS) model with a convective boundary condition (LS-3 model) are recovered as special cases of the solution in this paper. Computational examples are presented, and comparisons between different models are made. First, the SCS-1 model is compared with the SCS-3 model, showing the error caused by neglecting the surface convective effect. Second, the LS-3 model is compared with the SCS-3 model, showing the error associated with neglecting the size of heat source. The effects of groundwater flow velocity and convective heat transfer coefficient on the temporal and spatial variations of these errors are also investigated.

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Ring coils heat source numerical modeling and thermal interference characteristics analysis of truncated cone helix energy pile

Energy and Buildings ◽

10.1016/j.enbuild.2020.110438 ◽

2020 ◽

Vol 228 ◽

pp. 110438

Author(s):

Fei Gan ◽

Guangqin Huang ◽

Hongyu Zhang ◽

Jun Lu ◽

Chunlong Zhuang ◽

...

Keyword(s):

Numerical Modeling ◽

Heat Source ◽

Energy Pile ◽

Truncated Cone ◽

Characteristics Analysis ◽

Thermal Interference

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Analytical solution and process analysis of energy pile’s heat transfer rate

E3S Web of Conferences ◽

10.1051/e3sconf/202020505026 ◽

2020 ◽

Vol 205 ◽

pp. 05026

Author(s):

Jun Yang ◽

Zhenguo Yan ◽

Zhengwei Zhang ◽

Shu Zeng

Keyword(s):

Heat Transfer ◽

Heat Transfer Rate ◽

Transfer Rate ◽

Heat Transfer Performance ◽

Heat Transfer Process ◽

Transfer Performance ◽

Energy Pile ◽

Energy Piles ◽

The Difference ◽

Surrounding Soil

With the ever-increasing energy demand and implications of climate change, the use of energy piles to absorb shallow geothermal energy to regulate room temperature of buildings is considered the best sustainable energy technology, especially in China, and the use of this technology is becoming increasingly popular. At present, studies generally uses the temperature field to analyze the heat transfer performance of the energy pile, which cannot represent the heat transfer rate distribution intuitively. In this study, we used mathematical models to provide an analytical solution to determine the heat transfer rate distribution between the energy pile and surrounding soil. Analysis of the heat transfer process of concrete piles in clay showed that the difference in thermal properties between the energy pile and the surrounding soil affected the whole heat transfer process, especially in the initial stage. The time required to reach the quasi-steady state mainly depended on the pile’s volume heat capacity, the thermal diffusivity of the pile and the surrounding soil. In engineering practice, to enhance the heat transfer performance of energy piles, the following measures can be taken: reduce the difference in thermal properties between the energy pile and surrounding soil and increase the distance between energy piles to improve the heat transfer conditions.

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