Heat extraction model and characteristics of coaxial deep borehole heat exchanger

Ji, Li; Xu, Wei; Li, Jianfeng; Huang, Shuai; Li, Zhao; Qiao, Biao; Yang, Chun; Sun, Deyu; Guang-qiu, Zhang

doi:10.1016/j.renene.2021.01.036

Cited by 68 publications

(13 citation statements)

References 22 publications

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“…Li et al [126] propose a heat extraction model of a vertical GHE with a coaxial tube, studying the effects on thermal performance due to the soil stratigraphy. The authors model the heat extraction with the outer diameter of the buried pipe and the water flow, and they observe that the COP of the system with the coaxial tube increases by more than half compared with that coupled to a conventional U-tube setup.…”

Section: Temperature Optimizationmentioning

confidence: 99%

Sustainability of Shallow Geothermal Energy for Building Air-Conditioning

2021

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Geothermal heat pumps have a widespread diffusion as they are able to deliver relatively higher energy output than other systems for building air-conditioning. The exploitation of low-enthalpy geothermal energy, however, presents crucial sustainability issues. This review investigates the primary forms of the environmental impact of geothermal heat pumps and the strategies for their mitigation. As life-cycle analyses shows that the highest impacts arise from installation and operation stages, most optimization studies focus on system thermodynamics, aiming at maximizing the energy performance via the optimization in the design of the different components interacting with the ground and serviced building. There are environmental studies of great relevance that investigate how the climate and ground properties affect the system sustainability and map the most suitable location for geothermal exploitation. Based on this review, ground-source heat pumps are a promising technology for the decarbonization of the building sector. However, a sustainable design of such systems is more complex than conventional air-conditioning systems, and it needs a holistic and multi-disciplinary approach to include the broad environmental boundaries to fully understand the environmental consequences of their operation.

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Section: Temperature Optimizationmentioning

confidence: 99%

Sustainability of Shallow Geothermal Energy for Building Air-Conditioning

2021

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“…Theo Renaud conducted a transient simulation of deep double-pipe heat exchangers in Switzerland using CFD and found that by deepening the depth of the well, the heat extraction could be increased [6]. Li et al [7] analyzed the factors affecting the heat extraction characteristics of the middledeep buried tube heat exchanger; the research results showed that increasing the diameter and flow rate of the outer tube is beneficial for improving the heat extraction of the middledeep buried tube heat exchanger. Fang et al [8] found that increasing the thermal resistance of the inner casing of a medium-deep underground heat exchanger can improve its heat transfer capacity.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Heat Transfer Performance of Multi-Borehole Double-Pipe Heat Exchangers in Medium-Shallow Strata

Zhang

Liu

et al. 2022

Energies

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Just as the double-pipe heat exchanger is being utilized in an increasing number of applications, its research content is also deepening. For this paper, based on the air-conditioning cold and heat source project of a building in Handan, Hebei Province, a 300-meter medium-shallow well double-pipe heat exchanger was used for heating and cooling, and a corresponding heat transfer model was established. The changes of parameters such as the inlet and outlet temperature, heat exchange (with and without a temperature gradient), and borehole wall temperature distribution between a single borehole, double boreholes, and four boreholes over one year in medium-shallow wells were simulated and analyzed. By comparing the obtained experimental data and the simulation data, the accuracy of the heat transfer model was verified. This provides a theoretical basis for the further advancement of the project and lays the foundation for an in-depth study of multi-borehole double-pipe heat exchangers.

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“…Beier [21] established a transient heat transfer model and verified it by measured vertical temperature profiles in a borehole and temperatures of previous simulations. Li et al [22] established a model by MATLAB and verified it by an experiment located at the Chang'an District of Xi'an. The radius of influence of rock temperature change during one heat season is about 7 m and the linear meter heat extraction rates is less than 150 W. For the working fluid in DBHEs, Daneshipour [23] added two kinds of nanoparticles to water and carried out the corresponding research.…”

Section: Introductionmentioning

confidence: 99%

Simulations of Heat Supply Performance of a Deep Borehole Heat Exchanger under Different Scheduled Operation Conditions

Zhang

et al. 2022

Processes

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With the changing world energy structure, the development of renewable energy sources is gradually accelerating. Among them, close attention has been given to geothermal energy because of its abundant resources and supply stability. In this article, a deep borehole heat exchanger (DBHE) is coupled with a heat pump system to calculate the heat supply and daily electricity consumption of the system. To make better use of the peaks and valleys in electricity prices, the following three daily operating modes were studied: 24-h operation (Mode 1), 8-h operation plus 16-h non-operation (Mode 2), and two cycles of 4-h operation and 8-h non-operation (Mode 3). Simulation results show that scheduled non-continuous operation can effectively improve the outlet temperature of the heat extraction fluid circulating in the DBHE. The heat extraction rates of Mode 1 is 190.9 kW for mass flowrate of 9 kg/s; in Mode 2 and Mode 3 cases, the rates change to 304.7 kW and 293.0 kW, respectively. The daily operational electricity cost of Mode 1 is the greatest because of 24-h operation; due to scheduled non-continuous operation, the daily operational electricity cost of Mode 3 is only about 66% of that of Mode 2. After an 8-month period without heating, the formation-temperature can be restored within 4 °C of its original state; 90% recovery of the formation-temperature can be achieved by the end of the second month of the non-operation season.

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Heat extraction model and characteristics of coaxial deep borehole heat exchanger

Cited by 68 publications

References 22 publications

Sustainability of Shallow Geothermal Energy for Building Air-Conditioning

Sustainability of Shallow Geothermal Energy for Building Air-Conditioning

Investigation of the Heat Transfer Performance of Multi-Borehole Double-Pipe Heat Exchangers in Medium-Shallow Strata

Simulations of Heat Supply Performance of a Deep Borehole Heat Exchanger under Different Scheduled Operation Conditions

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