SIMULATION AND ANALYSIS OF HEAT TRANSFER CHARACTERISTICS OF COAXIAL DEEP BOREHOLE HEAT EXCHANGERS BASED ON DYNAMIC HEATING LOAD CONSTRAINTS

Shi Zhigang; Li Zhigang; Zhang Lin; Xia Shiwei; Liu Wanqing; Gao Jianing

doi:10.19912/j.0254-0096.tynxb.2025-0164

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Acta Energiae Solaris Sinica ›› 2026, Vol. 47 ›› Issue (6) : 544-551. DOI: 10.19912/j.0254-0096.tynxb.2025-0164

SIMULATION AND ANALYSIS OF HEAT TRANSFER CHARACTERISTICS OF COAXIAL DEEP BOREHOLE HEAT EXCHANGERS BASED ON DYNAMIC HEATING LOAD CONSTRAINTS

Shi Zhigang, Li Zhigang, Zhang Lin, Xia Shiwei, Liu Wanqing, Gao Jianing

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Abstract

A numerical model based on the finite difference method is developed for deep borehole heat exchangers used in medium-deep ground source heat pump systems, and the heat transfer characteristics under dynamic thermal load conditions are analyzed. Using this model along with actual meteorological data from Qingdao and validation via field experiments, the effect of fluid velocity, geothermal gradient, and geological parameters on the thermal performance of the deep borehole heat exchanger are investigated. The results indicate that while the inlet and outlet temperatures of the exchanger fluctuate in response to dynamic thermal loads, the outlet temperature exhibits greater stability. Although increasing fluid velocity enhances heat extraction, it also leads to higher heat loss caused by reverse heat transfer in shallow rock and soil layers. Higher geothermal gradients significantly improve heat extraction performance, and heat exchange efficiency is found to be greater in deeper regions compared to shallow zones.

Key words

geothermal energy / geothermal heat pumps / heat exchangers / numerical simulation / dynamic thermal load / heat flux per unit depth

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Shi Zhigang, Li Zhigang, Zhang Lin, Xia Shiwei, Liu Wanqing, Gao Jianing. SIMULATION AND ANALYSIS OF HEAT TRANSFER CHARACTERISTICS OF COAXIAL DEEP BOREHOLE HEAT EXCHANGERS BASED ON DYNAMIC HEATING LOAD CONSTRAINTS[J]. Acta Energiae Solaris Sinica. 2026, 47(6): 544-551 https://doi.org/10.19912/j.0254-0096.tynxb.2025-0164

References

[1] 李锦堂, 李骥, 张广秋, 等. 中深层地埋管热泵系统供暖源侧参数设计方法[J]. 太阳能学报, 2024, 45(9): 1-13.
LI J T, LI J, ZHANG G Q, et al.Optimum design method of source side parameter for deep borehole geothermal heat pump heating system[J]. Acta energiae solaris sinica, 2024, 45(9): 1-13.
[2] LUND J W, TOTH A N.Direct utilization of geothermal energy 2020 worldwide review[J]. Geothermics, 2021, 90: 101915.
[3] 赵鹏, 张东海, 李晓昭, 等. 基于p阶线性模型的地埋管换热器流体温度分布研究[J]. 太阳能学报, 2024, 45(6): 51-59.
ZHAO P, ZHANG D H, LI X Z, et al.Study on fluid temperature distribution of buried tube heat exchanger based on p-order liner model[J]. Acta energiae solaris sinica, 2024, 45(6): 51-59.
[4] WELSCH B, RÜHAAK W, SCHULTE D O, et al. Characteristics of medium deep borehole thermal energy storage[J]. International journal of energy research, 2016, 40(13): 1855-1868.
[5] HOLMBERG H, ACUÑA J, NÆSS E, et al. Thermal evaluation of coaxial deep borehole heat exchangers[J]. Renewable energy, 2016, 97: 65-76.
[6] SAADI M S, GOMRI R.Investigation of dynamic heat transfer process through coaxial heat exchangers in the ground[J]. International journal of hydrogen energy, 2017, 42(28): 18014-18027.
[7] LIU J, WANG F H, GAO Y, et al.Influencing factors analysis and operation optimization for the long-term performance of medium-deep borehole heat exchanger coupled ground source heat pump system[J]. Energy and buildings, 2020, 226: 110385.
[8] 刘福强, 施志钢, 蔡超, 等. 中深层深井换热器实验测试及传热特性模拟研究[J]. 可再生能源, 2023, 41(7): 891-898.
LIU F Q, SHI Z G, CAI C, et al.The experimental test and the simulation study of the heat transfer characteristics of the deep well heat exchanger[J]. Renewable energy resources, 2023, 41(7): 891-898.
[9] 李思奇, 赵军, 李扬, 等. 闭式中深层井下换热数值模拟与内管分段绝热影响研究[J]. 太阳能学报, 2020, 41(11): 369-374.
LI S Q, ZHAO J, LI Y, et al.Numerical simulation of closed loop medium-deep downhole heat exchange: a focus on influence of segmented insulation on central pipe[J]. Acta energiae solaris sinica, 2020, 41(11): 369-374.
[10] BROWN C S, KOLO I, BANKS D, et al.Comparison of the thermal and hydraulic performance of single U-tube, double U-tube and coaxial medium-to-deep borehole heat exchangers[J]. Geothermics, 2024, 117: 102888.
[11] DENG J W, WEI Q P, HE S, et al.Simulation analysis on the heat performance of deep borehole heat exchangers in medium-depth geothermal heat pump systems[J]. Energies, 2020, 13(3): 754.
[12] NORDBECK J, BEYER C, BAUER S.Experimental and numerical analysis of a cement based thermal energy storage system with a helical heat exchanger[J]. Applied thermal engineering, 2021, 185: 116339.