Engineering and Technological Sciences
Abstract
Energy piles, which serve both load-bearing and heat exchange functions, hold significant value in ground source heat pump applications. However, under stratified ground conditions, the heat transfer mechanism of pile-soil heat exchange is relatively complex. Most existing analytical methods are based on constant heat source models, and this simplified assumption cannot effectively reflect the impact of dynamic thermal power variations on the thermal response of energy piles. Therefore, improving the accuracy of such dynamic responses has become a key issue in current research.
To address this, a dynamic response calculation model for U-tube buried pipe energy pile-soil heat exchange under non-constant heat source conditions in stratified ground is proposed, based on finite-layer heat conduction theory and step heat flux theory. This model takes the inlet temperature of the U-tube as the input condition and, combined with a segmented superposition method accounting for temperature influence effects, equates the pile-soil heat exchange process to a time-varying heat source, thereby establishing a non-constant heat flux model.
According to the principle of energy conservation, the temperature distribution along the U-tube and the variable heat source intensity distribution at different time steps are solved. Furthermore, using the variable heat source intensity along the U-tube as the input condition and combining it with the finite-layer heat conduction calculation method for stratified ground, the time-varying characteristics of the ground temperature field are solved, effectively simulating the response process of energy pile-soil heat exchange under dynamic thermal power variations.
The research results show that the proposed model not only avoids the high computational time associated with complex numerical calculations but also achieves high computational efficiency, accurately characterizing the temperature response variations of energy piles under non-constant heat flux conditions. This model provides a reliable theoretical basis and an efficient computational tool for engineering design, system optimization, and operational analysis.
Full Text
Dynamic Response Analysis Method for Heat Conduction of U-shaped Buried Pipe Energy Pile in Layered Foundation under Unsteady Heat Source Conditions
Gang Jiang¹, Chenfeng Zong¹,²,³, Ziyi Wang¹, Qinhu Wang³, Haofan Yang¹
¹ School of Transportation Engineering, Nanjing Tech University, Nanjing 211816, China
² School of Civil Engineering, Nantong Institute of Technology, Nantong 226002, China
³ China Construction Installation Group Co., Ltd.
Abstract
Energy piles serve dual functions of load-bearing and heat exchange, holding significant value in ground source heat pump applications. However, under stratified ground conditions, the heat transfer mechanism of pile-soil heat exchange is relatively complex. Most existing analytical methods are based on constant heat source models, and this simplified assumption cannot effectively reflect the impact of dynamic thermal power variations on the thermal response of energy piles. Therefore, improving the accuracy of such dynamic responses has become a key issue in current research.
To address this, a dynamic response calculation model for U-tube buried pipe energy pile-soil heat exchange under non-constant heat source conditions in stratified ground is proposed, based on finite-layer heat conduction theory and step heat flux theory. This model takes the inlet temperature of the U-tube buried pipe as the input condition and, combined with a segmented superposition method for temperature influence effects, equates the pile-soil heat exchange process to a time-varying heat source, thereby establishing a non-constant heat flux model.
Based on the principle of energy conservation, the temperature distribution along the U-tube and the variable heat source intensity distribution at different time steps are solved. Furthermore, using the variable heat source intensity along the U-tube as the input condition and combining it with the finite-layer heat conduction calculation method for stratified ground, the time-varying characteristics of the ground temperature field are solved, effectively simulating the response process of energy pile-soil heat exchange under dynamic thermal power variations.
The research results show that the proposed model not only avoids the high time consumption associated with complex numerical calculations but also has high computational efficiency, accurately characterizing the temperature response variations of energy piles under non-constant heat flux conditions. This model provides a reliable theoretical basis and an efficient computational tool for engineering design, system optimization, and operational analysis.
Keywords: energy pile; non-constant heat source; layered foundation; U-shaped buried pipe; dynamic thermal response;
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This version posted 2025-09-02.