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Understanding the flow and heat transfer in fractured geothermal reservoir is critical for the development of enhanced geothermal system (EGS) in the future. Under the framework of discrete fracture network, a thermal-hydraulic coupled model is proposed to evaluate the heat extraction performance of multilateral wells in fractured reservoirs. Five cases with varying numbers of branch wells considering well orientation are compared. In addition, we analyze the heat extraction performance response of multilateral wells in fractured reservoirs to the operating parameters. Results demonstrate the minimal effect of the increasing number of branch wells on the production temperature, while impacts on the well pressure are much greater. The injection pressure is observed to decrease significantly as the number of branch wells increases, resulting in a reduced reservoir flow resistance and increased net thermal energy by reducing pump energy consumption. For the same case, increasing the number of intersections between wells and fractures reduces the production temperature and injection pressure. Parameter sensitivity analysis reveals heat production to increases with the mass flow rate, well length and well spacing, and decreases with increasing fracture permeability. This study is expected to provide a view for the application of multilateral wells in fractured geothermal reservoirs.
Xuefeng Gao; Yanjun Zhang; Yibin Huang; Yongjie Ma; Yi Zhao; Qiangbin Liu. Study on heat extraction considering the number and orientation of multilateral wells in a complex fractured geothermal reservoir. Renewable Energy 2021, 177, 833 -852.
AMA StyleXuefeng Gao, Yanjun Zhang, Yibin Huang, Yongjie Ma, Yi Zhao, Qiangbin Liu. Study on heat extraction considering the number and orientation of multilateral wells in a complex fractured geothermal reservoir. Renewable Energy. 2021; 177 ():833-852.
Chicago/Turabian StyleXuefeng Gao; Yanjun Zhang; Yibin Huang; Yongjie Ma; Yi Zhao; Qiangbin Liu. 2021. "Study on heat extraction considering the number and orientation of multilateral wells in a complex fractured geothermal reservoir." Renewable Energy 177, no. : 833-852.
Geothermal energy has been widely proposed as a potential renewable energy to replace traditional fossil fuel energy. Hot dry rock (HDR) reservoir which contains abundant geothermal energy widely distributes in China. The Gonghe Basin in Northwest China is chosen to develop the Chinese first HDR field operation project. HDR is a low-permeability, high temperature and hard granite without fluid. Developing HDR requires water cyclically flowing between injection and production wells to extract heat energy. Hydraulic fracturing, as a key reservoir stimulation technology, can create the path of fluid cyclically flowing. However, few studies have investigated hydraulic induced artificial fractures in HDR geothermal formations. This paper investigated HDR geothermal reservoir stimulation characteristics and fracture patterns during hydraulic fracturing. Reservoir stimulation was conducted with a true triaxial hydraulic fracturing apparatus which could establish a real HDR formation environment in the laboratory. The factors affecting breakdown pressure and fracture creation were investigated via experiments and numerical simulations. This study could be used to evaluate and design reservoir stimulation in field HDR geothermal operation.
Yuxiang Cheng; Yanjun Zhang; Ziwang Yu; Zhongjun Hu. Investigation on Reservoir Stimulation Characteristics in Hot Dry Rock Geothermal Formations of China During Hydraulic Fracturing. Rock Mechanics and Rock Engineering 2021, 1 -29.
AMA StyleYuxiang Cheng, Yanjun Zhang, Ziwang Yu, Zhongjun Hu. Investigation on Reservoir Stimulation Characteristics in Hot Dry Rock Geothermal Formations of China During Hydraulic Fracturing. Rock Mechanics and Rock Engineering. 2021; ():1-29.
Chicago/Turabian StyleYuxiang Cheng; Yanjun Zhang; Ziwang Yu; Zhongjun Hu. 2021. "Investigation on Reservoir Stimulation Characteristics in Hot Dry Rock Geothermal Formations of China During Hydraulic Fracturing." Rock Mechanics and Rock Engineering , no. : 1-29.
As fluid passes through the fracture of an enhanced geothermal system, the flow direction exhibits distinct angular relationships with the geometric profile of the rough fracture. This will inevitably affect the heat transfer characteristics in the fracture. Therefore, we established a hydro-thermal coupling model to study the influence of the fluid flow direction on the heat transfer characteristics of granite single fractures and the accuracy of the numerical model was verified by experiments. Results demonstrate a strong correlation between the distribution of the local heat transfer coefficient and the fracture morphology. A change in the flow direction is likely to alter the transfer coefficient value and does not affect the distribution characteristics along the flow path. Increasing injection flow rate has an enhanced effect. Although the heat transfer capacity in the fractured increases with the flow rate, a sharp decline in the heat extraction rate and the total heat transfer coefficient is also observed. Furthermore, the model with the smooth fracture surface in the flow direction exhibits a higher heat transfer capacity compared to that of the fracture model with varying roughness. This is attributed to the presence of fluid deflection and dominant channels.
Xuefeng Gao; Yanjun Zhang; Zhongjun Hu; Yibin Huang. Numerical Investigation on the Influence of Surface Flow Direction on the Heat Transfer Characteristics in a Granite Single Fracture. Applied Sciences 2021, 11, 751 .
AMA StyleXuefeng Gao, Yanjun Zhang, Zhongjun Hu, Yibin Huang. Numerical Investigation on the Influence of Surface Flow Direction on the Heat Transfer Characteristics in a Granite Single Fracture. Applied Sciences. 2021; 11 (2):751.
Chicago/Turabian StyleXuefeng Gao; Yanjun Zhang; Zhongjun Hu; Yibin Huang. 2021. "Numerical Investigation on the Influence of Surface Flow Direction on the Heat Transfer Characteristics in a Granite Single Fracture." Applied Sciences 11, no. 2: 751.
In order to reduce the harm of induced earthquakes in the process of geothermal energy development, it is necessary to analyze and evaluate the induced earthquake risk of a geothermal site in advance. Based on the tectonic evolution and seismogenic history around the Qiabuqia geothermal field, the focal mechanism of the earthquake was determined, and then the magnitude and direction of in-situ stress were inversed with the survey data. At the depth of more than 5 km, the maximum principal stress is distributed along NE 37°, and the maximum principal stress reaches 82 MPa at the depth of 3500 m. The induced earthquakes are evaluated by using artificial neural network (ANN) combined with in-situ stress, focal mechanism, and tectonic conditions. The predicted earthquake maximum magnitude is close to magnitude 3.
Kun Shan; Yanjun Zhang; Yanhao Zheng; Liangzhen Li; Hao Deng. Risk Assessment of Fracturing Induced Earthquake in the Qiabuqia Geothermal Field, China. Energies 2020, 13, 5977 .
AMA StyleKun Shan, Yanjun Zhang, Yanhao Zheng, Liangzhen Li, Hao Deng. Risk Assessment of Fracturing Induced Earthquake in the Qiabuqia Geothermal Field, China. Energies. 2020; 13 (22):5977.
Chicago/Turabian StyleKun Shan; Yanjun Zhang; Yanhao Zheng; Liangzhen Li; Hao Deng. 2020. "Risk Assessment of Fracturing Induced Earthquake in the Qiabuqia Geothermal Field, China." Energies 13, no. 22: 5977.
In geothermal development, induced earthquakes can be problematic side effects. To research the effect of fault distribution on induced earthquakes by hydraulic fracturing, a series of hydraulic fracturing tests were carried out on granite samples. We compared the performance of intact rock and prefabricated fault rock in the process of hydraulic fracturing, and an acoustic emission (AE) system was used to monitor acoustic emission events in the fracturing process. The test results revealed that fracture pressure increases with the increase of injection rate, and the acoustic emission cumulative energy of the prefabricated fault rock sample was higher than that of the intact rock sample. Also, in the process of fracturing, shear fracture accounted for more than 70% of all fractures for the prefabricated fault rock sample. However, for the intact rock sample, shear fracture only accounted for about 50% of all fractures. Our results support the conclusion that the existence of prefabricated faults could lead to an increase in shear fractures and fracture energy.
Kun Shan; Yanjun Zhang; Yanhao Zheng; Yuxiang Cheng; Yunxing Yang. Effect of fault distribution on hydraulic fracturing: Insights from the laboratory. Renewable Energy 2020, 163, 1817 -1830.
AMA StyleKun Shan, Yanjun Zhang, Yanhao Zheng, Yuxiang Cheng, Yunxing Yang. Effect of fault distribution on hydraulic fracturing: Insights from the laboratory. Renewable Energy. 2020; 163 ():1817-1830.
Chicago/Turabian StyleKun Shan; Yanjun Zhang; Yanhao Zheng; Yuxiang Cheng; Yunxing Yang. 2020. "Effect of fault distribution on hydraulic fracturing: Insights from the laboratory." Renewable Energy 163, no. : 1817-1830.
Geothermal energy has been widely proposed as a potential renewable energy to replace traditional fossil fuel energy. Hot dry rock (HDR) reservoirs were the main geothermal energy resources and usually consist of low‐permeability hard granite without fluid. Developing HDR requires water cyclically flowing between injection and production wells to extract heat energy. Hydraulic fracturing, as a key reservoir stimulation technology, can create the path of fluid cyclically flowing. However, few studies have investigated hydraulic induced artificial fractures in HDR geothermal formations. This paper investigated HDR geothermal reservoir stimulation characteristics and fracture patterns under different injection flow rates. Numerical simulations were conducted to model the laboratory tests. Results showed they were in good agreement, and this indicated the possibility of numerical simulation to predict hydraulic fracturing behavior under different injection flow rates. With the increase of injection flow rate, the fracture initiation pressures and breakdown pressures increased, and the propagation times and postfracturing pressures decreased. The fracture geometries were observed and analyzed, mean injection power was proposed, and results showed that it could be used to roughly estimate the fracture total lengths. Moreover, the fracture permeabilities based on the pressure data were calculated. These results can provide some reasonable advice for implementing reservoir stimulations on application to field‐scale HDR operation.
Yuxiang Cheng; Yanjun Zhang; Ziwang Yu; Zhongjun Hu; YueQiang Ma; Yunxing Yang. Experimental and numerical studies on hydraulic fracturing characteristics with different injection flow rates in granite geothermal reservoir. Energy Science & Engineering 2020, 9, 142 -168.
AMA StyleYuxiang Cheng, Yanjun Zhang, Ziwang Yu, Zhongjun Hu, YueQiang Ma, Yunxing Yang. Experimental and numerical studies on hydraulic fracturing characteristics with different injection flow rates in granite geothermal reservoir. Energy Science & Engineering. 2020; 9 (1):142-168.
Chicago/Turabian StyleYuxiang Cheng; Yanjun Zhang; Ziwang Yu; Zhongjun Hu; YueQiang Ma; Yunxing Yang. 2020. "Experimental and numerical studies on hydraulic fracturing characteristics with different injection flow rates in granite geothermal reservoir." Energy Science & Engineering 9, no. 1: 142-168.
Geothermal energy has been widely proposed as a potential renewable energy to replace traditional fossil fuel energy. Deep buried geothermal reservoirs are usually called Hot Dry Rock (HDR) or Enhanced Geothermal Systems (EGS). Hot dry rock (HDR) reservoirs are the main geothermal energy resources, and usually consist of low-permeability hard granite without fluid. Developing HDR requires water cyclically flowing between injection and production wells to extract heat energy. Hydraulic fracturing, as a key reservoir stimulation technology, can create the path of fluid cyclically flowing. Although hydraulic fracturing in HDR formations has attracted more and more attention these years, large-size HDR formation environment is difficult to establish in laboratory and large granite samples are difficult to crack because of their high toughness and strength, the reservoir stimulation characteristics in this hard granite have not been thoroughly addressed by the researchers and the hydraulic induced fracture morphology has yet remained unnoticed. To advance this technology development, a true triaxial hydraulic fracturing apparatus with high temperature heated system has been developed by Jilin University to simulate the real HDR environment, and this paper investigated HDR geothermal reservoir stimulation characteristics in large-size granite under different injection flow rates, temperatures and confining stresses conditions. The granite samples were collected form Gonghe Basin where the Chinese first EGS field operation will be built. Results showed that these laboratorial conditions affected hydraulic fracturing characteristics, breakdown pressures increased with the increase of injection flow rate and confining stresses, decreased with the increase of temperatures. Numerical simulations were conducted to model the laboratory tests. These results can provide some reasonable advice for implementing reservoir stimulations on the application of field-scale HDR operation.
Yuxiang Cheng; Yanjun Zhang; Ziwang Yu; Zhongjun Hu; Yunxing Yang. An investigation on hydraulic fracturing characteristics in granite geothermal reservoir. Engineering Fracture Mechanics 2020, 237, 107252 .
AMA StyleYuxiang Cheng, Yanjun Zhang, Ziwang Yu, Zhongjun Hu, Yunxing Yang. An investigation on hydraulic fracturing characteristics in granite geothermal reservoir. Engineering Fracture Mechanics. 2020; 237 ():107252.
Chicago/Turabian StyleYuxiang Cheng; Yanjun Zhang; Ziwang Yu; Zhongjun Hu; Yunxing Yang. 2020. "An investigation on hydraulic fracturing characteristics in granite geothermal reservoir." Engineering Fracture Mechanics 237, no. : 107252.
As an attractive renewable energy source, deep geothermal energy is increasingly explored. Granite is a typical geothermal reservoir rock type with low permeability, and hydraulic fracturing is a promising reservoir stimulation method which could obviously enhance the reservoir permeability. Previous hydraulic fracturing studies were mostly conducted on artificial samples and small cylindrical granites. The fracturing pressures of artificial samples and small real rock sample were much lower than that of field operation, and it was difficult to observe morphological changes in small rocks. Hence, this paper presents a hydraulic fracturing experimental study on large-scale granite with a sample size of 300 × 300 × 300 mm under high temperatures. Besides, injection flow rate is an important parameter for on-site hydraulic fracturing; previous studies usually only focused on breakdown pressure, and there is a lack of comprehensive analysis about fracturing pressure curves and fracturing characteristics caused by different injection flow rates. This study aims to investigate the influence of injection flow rate on different pressure curve characteristic parameters which are initiation pressure, propagation time, breakdown pressure, postfracturing pressure, fracture geometry, and fracture permeability. The mean injection power was proposed to roughly estimate the fracture total lengths. These results could provide some guidance for field-scale reservoir stimulation and heat extraction efficiency improvement.
Yuxiang Cheng; Yanjun Zhang. Hydraulic Fracturing Experiment Investigation for the Application of Geothermal Energy Extraction. ACS Omega 2020, 5, 8667 -8686.
AMA StyleYuxiang Cheng, Yanjun Zhang. Hydraulic Fracturing Experiment Investigation for the Application of Geothermal Energy Extraction. ACS Omega. 2020; 5 (15):8667-8686.
Chicago/Turabian StyleYuxiang Cheng; Yanjun Zhang. 2020. "Hydraulic Fracturing Experiment Investigation for the Application of Geothermal Energy Extraction." ACS Omega 5, no. 15: 8667-8686.
Hydraulic fracturing has been widely used in recent years as a key technology to improve energy mining efficiency in petroleum and geothermal industries. Laboratory hydraulic fracturing experiments recently were completed in six large-scale 300 × 300 × 300 mm rock specimens to better understand this complex process of hydraulic fracturing. When injection flow rate increases from 5 to 30 mL/min. The fracture initiation pressures and breakdown pressures increase, the propagation times and post-fracturing pressures decrease. The fracture geometries are observed and analyzed, mean injection power is proposed and results show that it could be used to roughly estimate the fracture total lengths. Moreover, the fracture permeabilities based on the pressure data are calculated and linearly ascend with the increase of injection flow rates. These results can provide some reasonable advice for implementing hydraulic fracturing reservoir simulations and improving energy production efficiency on application to field-scale operation.
Yuxiang Cheng; Yanjun Zhang. Experimental Study of Fracture Propagation: The Application in Energy Mining. Energies 2020, 13, 1411 .
AMA StyleYuxiang Cheng, Yanjun Zhang. Experimental Study of Fracture Propagation: The Application in Energy Mining. Energies. 2020; 13 (6):1411.
Chicago/Turabian StyleYuxiang Cheng; Yanjun Zhang. 2020. "Experimental Study of Fracture Propagation: The Application in Energy Mining." Energies 13, no. 6: 1411.
Understanding the water flow and heat transfer process in rock fractures is crucial for the development and utilization of geothermal reservoirs. This study develops a numerical model of a granite reservoir with two intersecting fractures to evaluate the heat production performance. Then, the evolution of the distribution of the rock and fluid temperatures is investigated. In addition, the effect of the injection temperature, heat transfer coefficient and injection flow velocity on the heat transfer characteristics are analyzed. Additionally, in order to study heat transfer performance with different fracture distributions, four cases of intersecting fractures with different angles are designed. The results indicate that, at different locations along the direction of seepage, the water temperature changes with time follow different rules. The results also show that, when the distribution of fractures is more uniform in the reservoir, the heat extraction rate of flowing water from the surrounding reservoir is faster. These results provided theoretical basis for geothermal system location selection, optimal selection of the reservoir stimulation scheme and reservoir thermal output prediction.
YueQiang Ma; Yanjun Zhang; Zhongjun Hu; Ziwang Yu; Ling Zhou; Yibin Huang. Numerical investigation of heat transfer performance of water flowing through a reservoir with two intersecting fractures. Renewable Energy 2020, 153, 93 -107.
AMA StyleYueQiang Ma, Yanjun Zhang, Zhongjun Hu, Ziwang Yu, Ling Zhou, Yibin Huang. Numerical investigation of heat transfer performance of water flowing through a reservoir with two intersecting fractures. Renewable Energy. 2020; 153 ():93-107.
Chicago/Turabian StyleYueQiang Ma; Yanjun Zhang; Zhongjun Hu; Ziwang Yu; Ling Zhou; Yibin Huang. 2020. "Numerical investigation of heat transfer performance of water flowing through a reservoir with two intersecting fractures." Renewable Energy 153, no. : 93-107.
Yitong Basin is located in subfrigid zone, and it has a good prospect to use geothermal clean heating. The evaluation of economic efficiency for heating with enhanced geothermal system (EGS) is indispensable. A simplified single‐fracture hydrothermal coupling model with laboratory test is developed in the EGS project to calculate temperature and pressure based on Yitong Basin data. The effects of four factors (K, q, D, and T) on heat production and reservoir characteristics are discussed. The parameters and results of H‐T coupling were applied to economic analysis for heating with EGS from private and social perspectives considering costs and revenues. The results indicate that the combination of laboratory tests (rock physical properties) makes the numerical simulation results more suitable for the study area. The production temperature and heating power will decrease with continuous injection of cold water, and the injection pressure and flow impedance will increase due to the increase in μ/ρ. Four factors (K, q, D, and T) will affect difficulty of fluid injection and reservoir thermal breakthrough, and the high injection rate q may trigger secondary fracturing of reservoir. Heating with EGS in single‐fracture model was uneconomical due to expensive drilling costs. However, heating with EGS can be considered from social perspective based on environment, which can provide advice for decision‐making of the government and business.
Yibin Huang; Yanjun Zhang; Zhongjun Hu; Honglei Lei; Chen Wang; Jingchen Ma. Economic analysis of heating for an enhanced geothermal system based on a simplified model in Yitong Basin, China. Energy Science & Engineering 2019, 7, 2658 -2674.
AMA StyleYibin Huang, Yanjun Zhang, Zhongjun Hu, Honglei Lei, Chen Wang, Jingchen Ma. Economic analysis of heating for an enhanced geothermal system based on a simplified model in Yitong Basin, China. Energy Science & Engineering. 2019; 7 (6):2658-2674.
Chicago/Turabian StyleYibin Huang; Yanjun Zhang; Zhongjun Hu; Honglei Lei; Chen Wang; Jingchen Ma. 2019. "Economic analysis of heating for an enhanced geothermal system based on a simplified model in Yitong Basin, China." Energy Science & Engineering 7, no. 6: 2658-2674.
Understanding the sensitivity to different reservoir parameters can help optimize the use of a designated reservoir. Four key parameters, namely, fracture permeability, well spacing, injection temperature, and injection rate, are considered in this study. The effects of various factors on the thermal performance of the 4300-4700 m granodiorite reservoir in the Zhacang geothermal field in Guide Basin, Qinghai Province, China is analyzed via numerical simulation and artificial neural network (ANN). The ANN models are designed to develop an effective system in less time. The training and test data of the ANN models are the results of numerical simulation. The prediction accuracy is measured by the coefficient of determination and the root mean squared error. Results demonstrate that the use of ANN for predicting the production temperature has high prediction accuracy. Finally, the effects of various factors on the total heat extraction are further analyzed. The results show that the injection rate exerts the largest influence on total heat extraction, followed by the injection temperature and well spacing, and fracture permeability is the least relevant. Increasing the injection flow rate, lowering the injection temperature, increasing the distance between the injection and the production well, and reducing the fracture permeability can improve heat production within certain ranges. In this study, the combination of an injection temperature of 30°C, injection flow rate of 60 kg/s, fracture permeability of 1 × 10−12 and well spacing of 600 m was chosen as the best scheme for the heat production.The accumulative total energy produced in 30 years period is 4.08 × 1016 J based on the simulation results, which can save 1.7 × 109 kg of the coal.
Ling Zhou; Yanjun Zhang; Zhongjun Hu; Ziwang Yu; Yinfei Luo; Yude Lei; Honglei Lei; Zhihong Lei; YueQiang Ma. Analysis of influencing factors of the production performance of an enhanced geothermal system (EGS) with numerical simulation and artificial neural network (ANN). Energy and Buildings 2019, 200, 31 -46.
AMA StyleLing Zhou, Yanjun Zhang, Zhongjun Hu, Ziwang Yu, Yinfei Luo, Yude Lei, Honglei Lei, Zhihong Lei, YueQiang Ma. Analysis of influencing factors of the production performance of an enhanced geothermal system (EGS) with numerical simulation and artificial neural network (ANN). Energy and Buildings. 2019; 200 ():31-46.
Chicago/Turabian StyleLing Zhou; Yanjun Zhang; Zhongjun Hu; Ziwang Yu; Yinfei Luo; Yude Lei; Honglei Lei; Zhihong Lei; YueQiang Ma. 2019. "Analysis of influencing factors of the production performance of an enhanced geothermal system (EGS) with numerical simulation and artificial neural network (ANN)." Energy and Buildings 200, no. : 31-46.
Currently, water fracturing under deep geothermal conditions remains poorly understood because the reservoir rocks are usually high-strength crystalline rocks characterized by high temperatures. The aim of this study is to investigate the effects of rock properties, injection rates, and temperatures on hydraulic fracturing behavior and the induced crack characteristics through experimental investigations. A series of hydraulic fracturing experiments was conducted on two Indosinian granite types to investigate the differences in hydraulic fracturing behavior caused by rock properties. Among others, six samples were tested under a room-temperature condition at different injection rates from 1 to 30 mL/min to clarify the effect of the injection rate and three samples were tested under a high-temperature condition (150 °C) to simulate specific geothermal environments. The results indicated that granites with different rock properties have different injection rate thresholds. When the injection rate is below the threshold, the injection pressure finally reached a constant value without fracturing. For rocks with the same properties, the temperature effect can lead to a high injection rate threshold due to the occurrence of thermally-induced cracks. The number of acoustic emission events recorded during the room-temperature experiments increased linearly with increasing injection rate, while high-temperature tests increased sharply. The investigation results imply that a complex hydraulically-induced crack network is expected to be achieved in geothermal reservoirs by a high injection rate or high temperature differences (between injected fluid and rock). Additionally, the characteristics of the hydraulically-induced cracks were investigated by cutting through the sample blocks and measuring the residual pressure. The results indicated that the induced crack aperture can maintain a fluid conductivity of 0.1–0.8 mm/s at a closure pressure of 12 MPa.
Zhihong Lei; Yanjun Zhang; Zhongjun Hu; Liangzhen Li; Senqi Zhang; Lei Fu; GaoFan Yue. Application of Water Fracturing in Geothermal Energy Mining: Insights from Experimental Investigations. Energies 2019, 12, 2138 .
AMA StyleZhihong Lei, Yanjun Zhang, Zhongjun Hu, Liangzhen Li, Senqi Zhang, Lei Fu, GaoFan Yue. Application of Water Fracturing in Geothermal Energy Mining: Insights from Experimental Investigations. Energies. 2019; 12 (11):2138.
Chicago/Turabian StyleZhihong Lei; Yanjun Zhang; Zhongjun Hu; Liangzhen Li; Senqi Zhang; Lei Fu; GaoFan Yue. 2019. "Application of Water Fracturing in Geothermal Energy Mining: Insights from Experimental Investigations." Energies 12, no. 11: 2138.
Ground source heat pumps (GSHPs) have been widely applied worldwide in recent years because of their high efficiency and environmental friendliness. An accurate estimation of the thermal conductivity of rock and soil layers is important in the design of GSHP systems. The distributed thermal response test (DTRT) method incorporates the standard test with a pair of fiber optic-distributed temperature sensors in the U-tube to accurately calculate the layered thermal conductivity of the rock/soil. In this work, in situ layered thermal conductivity was initially obtained by DTRT for four boreholes in the study region. A series of laboratory tests was also conducted on the rock samples obtained from drilling. Then, an artificial neural network (ANN) model was developed to predict the layered thermal conductivity on the basis of the DTRT results. The primary modeling factors were water content, density, and porosity. The results showed that the ANN models can predict the layered thermal conductivity with an absolute error of less than 0.1 W/(m·K). Finally, the trained ANN models were used to predict the layered thermal conductivity for another study region, in which only the effective thermal conductivity was measured with the thermal response test (TRT). To verify the accuracy of the prediction, the product of pipe depth and layered thermal conductivity was suggested to represent heat transfer capacity. The results showed that the discrepancies between the TRT and ANN models were 5.43% and 6.37% for two boreholes, respectively. The results prove that the proposed method can be used to determine layered thermal conductivity.
Yanjun Zhang; Ling Zhou; Zhongjun Hu; Ziwang Yu; Shuren Hao; Zhihong Lei; Yangyang Xie. Prediction of Layered Thermal Conductivity Using Artificial Neural Network in Order to Have Better Design of Ground Source Heat Pump System. Energies 2018, 11, 1896 .
AMA StyleYanjun Zhang, Ling Zhou, Zhongjun Hu, Ziwang Yu, Shuren Hao, Zhihong Lei, Yangyang Xie. Prediction of Layered Thermal Conductivity Using Artificial Neural Network in Order to Have Better Design of Ground Source Heat Pump System. Energies. 2018; 11 (7):1896.
Chicago/Turabian StyleYanjun Zhang; Ling Zhou; Zhongjun Hu; Ziwang Yu; Shuren Hao; Zhihong Lei; Yangyang Xie. 2018. "Prediction of Layered Thermal Conductivity Using Artificial Neural Network in Order to Have Better Design of Ground Source Heat Pump System." Energies 11, no. 7: 1896.