Experimental and analytical study of the overall heat transfer coefficient of water flowing through a single fracture in a granite core

Bai, Bing; He, Yanlin; Li, Xiaochun; Li, Jun; Huang, Xiaoxue; Zhu, Jun

doi:10.1016/j.applthermaleng.2017.01.020

Cited by 90 publications

(36 citation statements)

References 13 publications

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“…The heat transfer coefficient is a key parameter for heat transfer model when considering the local thermal non‐equilibrium between the fluid and the fracture surface. Studying heat transfer coefficient can help to optimize the numerical model of heat extraction and predict the HER . Therefore, theoretical analysis and experiments had been conducted to investigate the heat transfer coefficient .…”

Section: Introductionmentioning

confidence: 99%

Effects of injection parameters on heat extraction performance of supercritical CO₂ in enhanced geothermal systems

Liu

et al. 2019

Energy Science & Engineering

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Supercritical CO 2 (SCCO 2 ) is considered as a promising alternative heat extraction fluid in the enhanced geothermal system (EGS) which can reduce atmospheric CO 2 emissions and water waste. However, the heat extraction performance of SCCO 2 is greatly affected by its thermophysical properties, which are high sensitivity to temperature/pressure. In this study, by considering the impacts of temperature and pressure on thermophysical properties of SCCO 2 , a thermo-hydro-mechanical coupling numerical model was established to investigate the effects of the initial reservoir temperature as well as the SCCO 2 injection pressure and temperature on heat extraction. The variations of reservoir permeability and mass productivity as well as the net heat extraction rate (HER) were simulated by implementing the model into COMSOL Multiphysics, which showed a good consistency compared with the hightemperature/pressure triaxial seepage experiments. Simulation results indicate that there are three distinct stages in mass productivity including the slow decline stage, the rapid increase stage, and the stabilization stage. Increasing the initial reservoir temperature or the injection temperature will reduce the net HER to varying degrees.Appropriate increase of the injection pressure and injection temperature can extend Stage 2 duration which can subsequently enhance the mass productivity and the net HER. Meanwhile, the higher injection pressure or the lower injection temperature will inhibit heat compensation within rock masses and accelerate the reservoir heat depletion. This study provides guidance for optimizing the injection parameters of CO 2 -EGS and aims to enhance the net HER while ensuring a reasonable reservoir production life. K E Y W O R D S enhanced geothermal system, heat extraction experiment, high temperature/pressure, numerical simulation, supercritical CO 2 How to cite this article: Li P, Wu Y, Liu J-F, et al. Effects of injection parameters on heat extraction performance of supercritical CO 2 in enhanced geothermal systems. Energy Sci Eng. 2019;7:3076-3094. https ://doi.

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Section: Introductionmentioning

confidence: 99%

Effects of injection parameters on heat extraction performance of supercritical CO₂ in enhanced geothermal systems

Liu

et al. 2019

Energy Science & Engineering

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“…By integrating Equation (19) and introducing the effective stress, the hydraulic aperture of the fracture can be expressed as follows Assume that the parallel fracture surfaces have dissimilar morphology to account for the effect of the surface roughness on flow behavior through the fracture system. Based on the Cubic law, the equivalent permeability of the rough fracture can be obtained as follows where f is the roughness factor of the fracture.…”

Section: Governing Equation For Stress Equilibriummentioning

confidence: 99%

“…[17][18][19] At present, numerical simulation is still the most efficient method to analyze the THM coupling problem. Some small-scale experiments have been carried out to reveal the multiphysical-interaction mechanisms during heat extraction.…”

Section: Introductionmentioning

confidence: 99%

“…Some small-scale experiments have been carried out to reveal the multiphysical-interaction mechanisms during heat extraction. [17][18][19] At present, numerical simulation is still the most efficient method to analyze the THM coupling problem. Based on the thermal-hydraulic (TH) coupling theory, the effects of different fracture morphology, 20,21 circulating fluids, 21,22 and conceptual models or well layouts [23][24][25] on heat extraction performance were investigated, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Investigation on heat extraction characteristics in randomly fractured geothermal reservoirs considering thermo‐poroelastic effects

Han

Cheng

Gao

et al. 2019

Energy Science & Engineering

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A fully coupled thermal‐hydraulic‐mechanical (THM) model was developed to investigate the underlying response mechanisms during heat extraction in fractured geothermal reservoirs. The random fracture network in the stimulated zone was reproduced based on the fractal theory. The coupled model accounts for the dominant physical phenomena including (a) fluid flow, heat transport, and solid deformation in porous media and fractures; (b) local thermal nonequilibrium (LTNE) between rock matrix and flowing fluid; and (c) temperature‐dependent fluid thermodynamic properties and stress‐dependent pore and fracture permeability. The proposed model was validated by several analytic solutions. Sequentially, the evolution of pore pressure, equivalent temperature, effective stress, and reservoir permeability was analyzed. The sensitivity of the heat extraction performance to fracture network morphology was discussed. Results show that interconnected large‐scale fractures dominate mass and heat transport. Widely distributed small‐scale fractures contribute to the cooling of the heat rock mass along many flow paths in parallel. The change in effective stress associated with fully coupled thermo‐poroelastic effects may induce fracture shear dilation and pore expansion, resulting in an enhancement of the overall reservoir permeability. There is a significant temperature difference between the solid phase and the fluid phase in fractures, but not in porous media. It is more reasonable to use the LTNE theory to analyze the heat extraction of fractured geothermal reservoirs. The fracture network morphology has a profound effect on heat extraction efficiency and injectivity. Undeveloped fracture networks will result in a higher injection pressure, earlier thermal breakthrough, and shorter lifetime, but higher heat extraction ratio. Properly increasing the fracture density can delay the thermal breakthrough time, prolong the service life, and improve the injectivity. Fully connected fracture networks may result in thermal short‐circuiting and earlier thermal breakthrough. Generating a complex and scattered fracture network but without preferential channels is conducive to extracting more heat from geothermal reservoirs.

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“…A single fracture is the basic unit of the fracture network model. Considerable amount of research has been undertaken on the fluid-heat coupling heat transfer in the surrounding rock with a single fracture [12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Analysis of Heat Transfer Characteristics of Fractured Surrounding Rock in Deep Underground Spaces

Chen

Chu

Han

et al. 2019

Mathematical Problems in Engineering

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The study of fluid-heat coupling in deep fractured surrounding rock is the basis of design, safety, and extraction of geothermal energy of deep underground spaces. The heat transfer and fractured media seepage theories were employed to establish a three-dimensional unsteady model for fluid-heat coupling heat transfer in fractured surrounding rock. Using COMSOL multiphysics simulation software, the temperature field of the fractured surrounding rock was determined. Furthermore, the influences of ventilation time, Darcy’s velocity, fracture aperture, and thermal conductivity coefficient of the surrounding rock on the fractured surrounding rock temperature field distribution were investigated. The results of the numerical simulation show that the ventilation time and fracture have a major impact on the temperature field distribution of the fractured surrounding rock. As ventilation time is 200 days, an average water temperature in centerline of the fracture decreases 9.4 K as Darcy’s velocity increased from 3e-4m/s to 2e-3m/s. As ventilation time is 200 days, an average water temperature in centerline of the fracture decreases 5.3 K as fracture aperture increased from 3 mm to 9 mm. A set of experimental devices for fluid-heat coupling heat transfer in surrounding rock with a single fracture was designed and built to validate the numerical simulation results. Numerical simulation results are, in general, in agreement with the experimental results.

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Experimental and analytical study of the overall heat transfer coefficient of water flowing through a single fracture in a granite core

Cited by 90 publications

References 13 publications

Effects of injection parameters on heat extraction performance of supercritical CO₂ in enhanced geothermal systems

Effects of injection parameters on heat extraction performance of supercritical CO₂ in enhanced geothermal systems

Investigation on heat extraction characteristics in randomly fractured geothermal reservoirs considering thermo‐poroelastic effects

Analysis of Heat Transfer Characteristics of Fractured Surrounding Rock in Deep Underground Spaces

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Experimental and analytical study of the overall heat transfer coefficient of water flowing through a single fracture in a granite core

Cited by 90 publications

References 13 publications

Effects of injection parameters on heat extraction performance of supercritical CO2 in enhanced geothermal systems

Effects of injection parameters on heat extraction performance of supercritical CO2 in enhanced geothermal systems

Investigation on heat extraction characteristics in randomly fractured geothermal reservoirs considering thermo‐poroelastic effects

Analysis of Heat Transfer Characteristics of Fractured Surrounding Rock in Deep Underground Spaces

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Effects of injection parameters on heat extraction performance of supercritical CO₂ in enhanced geothermal systems

Effects of injection parameters on heat extraction performance of supercritical CO₂ in enhanced geothermal systems