A new analytical heat transfer model for deep borehole heat exchangers with coaxial tubes

Pan, Aiqiang; Lu, Lin; Cui, Ping; Jia, Linrui

doi:10.1016/j.ijheatmasstransfer.2019.07.041

Cited by 86 publications

(19 citation statements)

References 18 publications

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“…As mentioned, the geothermal gradient is significant, so the models for BHE do not apply to DBHE. Analytical heat transfer models for coaxial DBHE were presented by Pan et al [32] and Luo et al [33]. These models had simplified heat transfer, so further improvement in analytical modeling of heat transfer in DBHE was made by Luo et al [34] with their model based on a segmented finite cylindersource model.…”

Section: Literature Reviewmentioning

confidence: 99%

“…Increasing the outer pipe diameter would increase the heat transfer area and improve the thermal performance of DBHE, but financial aspects of drilling at high depth should be considered [30,77,154]. Regarding the material of the outer pipe, the authors suggested that is better to apply a thermally enhanced grout material than to use a high conductivity outer pipe [77,154] because outer pipe conductivity does not have much influence on performance since the thermal resistance of the ground plays a dominant role [32,77,118]. Different types of deep coaxial GHE are compared by Wang et al [116].…”

Section: Pipe Arrangement and Materialsmentioning

confidence: 99%

“…When increasing depth, the authors suggested that the economical side of the system has to be considered [123,153]. Some authors [32,33,151] concluded that better performance in heat extraction mode is achieved when circulating fluid flows down through the outer pipe and flows back upward through the inner pipe, despite the borehole depth. Inlet temperature does not have much effect on the performance of DBHE [30], but a larger temperature difference between soil and circulating fluid increases heat transfer [29].…”

Section: Pipe Arrangement and Materialsmentioning

confidence: 99%

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Application and Design Aspects of Ground Heat Exchangers

et al. 2021

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With the constant increase in energy demand, using renewable energy has become a priority. Geothermal energy is a widely available, constant source of renewable energy that has shown great potential as an alternative source of energy in achieving global energy sustainability and environment protection. When exploiting geothermal energy, whether is for heating or cooling buildings or generating electricity, a ground heat exchanger (GHE) is the most important component, whose performance can be easily improved by following the latest design aspects. This article focuses on the application of different types of GHEs with attention directed to deep vertical borehole heat exchangers and direct expansion systems, which were not dealt with in detail in recent reviews. The article gives a review of the most recent advances in design aspects of GHE, namely pipe arrangement, materials, and working fluids. The influence of the main design parameters on the performance of horizontal, vertical, and shallow GHEs is discussed together with commonly used performance indicators for the evaluation of GHE. A survey of the available literature shows that thermal performance is mostly a point of interest, while hydraulic and/or economic performance is often not addressed, potentially resulting in non-optimal GHE design.

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Section: Literature Reviewmentioning

confidence: 99%

Section: Pipe Arrangement and Materialsmentioning

confidence: 99%

Section: Pipe Arrangement and Materialsmentioning

confidence: 99%

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Application and Design Aspects of Ground Heat Exchangers

et al. 2021

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“…To further investigate the heat extraction performance of the DBHE heating system, considerable research about the DBHE system has been conducted in the last few years. With analytical (Luo et al, 2019;Pan et al, 2019) and numerical approaches (Kong et al, 2017;Fang et al, 2018;Song et al, 2018), researchers developed several simulation tools to investigate and quantify the performance of the DBHE and the response of surrounding soil/ rock. Some commercial software, such as FLUENT and COMSOL (Hu et al, 2020), are also applied to simulate the heat transfer process of the DBHE system.…”

Section: Introductionmentioning

confidence: 99%

Long-term Performance Evaluation and Economic Analysis for Deep Borehole Heat Exchanger Heating System in Weihe Basin

et al. 2022

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To reduce carbon emission and achieve carbon neutrality, deep geothermal energy has been widely extracted for building heating purpose. In recent years, deep borehole heat exchanger (DBHE) heating system has gained more attention, especially in densely populated urban areas in Weihe Basin, northern China. The long-term performance and the economic feasibility are essential for the system application. In this work, the DBHE model implemented in OpenGeoSys software is verified against an analytical solution and a comprehensive economic analysis approach is further proposed. Then the short-term thermal performance tests are conducted to obtain the tentative heat extraction capacity for long-term simulation. The long-term simulations are further performed with the heat pump unit under the adjusted tentative heat extraction rate imposed on the DBHE. Finally, a comprehensive economic analysis is applied to the DBHE heating system over 15 heating seasons. Results show that the minimum coefficient of performance value of the heat pump is 4.74 over the operation of 15 heating seasons. With the increase of depth for the DBHE, the total electricity consumption of heat pumps and circulation pumps has a prominent promotion. With the comprehensive approach of economic analysis, the depth of 2,600 m has the lowest levelized cost of total heating amount, which is the best system design for the application in Weihe Basin. The present results are specific to the conditions in Weihe Basin, but the proposed economic analysis approach is generic.

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“…The BHE has different types including U-shaped, double U-shaped, W-shaped, spiral-shaped, and coaxial [9][10][11]. Focus on the coaxial deep borehole heat exchanger, numerous researches have been conducted recently.…”

Section: Introductionmentioning

confidence: 99%

Performance analysis of a residential heating system using borehole heat exchanger coupled with solar assisted PV/T heat pump

et al. 2020

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Borehole heat exchanger (BHE) is a promising method for extracting heat from the deep geothermal energy which has been widely used for residential heating in high latitude areas. The solar assisted photovoltaic/thermal (PV/T) heat pump could convert solar energy into useful heat efficiently, and could be further used to heat water from the BHE to a higher temperature level. In this paper, a residential heating system using BHE coupled with solar assisted PV/T heat pump is therefore proposed with further performance analysis. The simulation results show that a larger mass flow rate could increase the BHE's heat extract capacity but also increase the flow resistance and pump power under nominal conditions. The circulating water would not extract heat from rock-soil if the inlet temperature exceeds 48.5 ℃ when mass flow rate is 12 kg/s. Furthermore, the maximum water temperature from this hybrid system could reach 40.8 ℃ while the solar fraction is 67.5% when the area of PV/T module is 1000 m 2 , solar irradiation is 600 W/m 2 and depth of the BHE is 2500 m. In the meantime, the heating COP of this hybrid system could reach 7.4 and the system could operate independently without power input from electrical grid.

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A new analytical heat transfer model for deep borehole heat exchangers with coaxial tubes

Cited by 86 publications

References 18 publications

Application and Design Aspects of Ground Heat Exchangers

Application and Design Aspects of Ground Heat Exchangers

Long-term Performance Evaluation and Economic Analysis for Deep Borehole Heat Exchanger Heating System in Weihe Basin

Performance analysis of a residential heating system using borehole heat exchanger coupled with solar assisted PV/T heat pump

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