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Prof. Zhongjun Hu
College of Construction Engineering, Jilin University, Changchun, 130026, China

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Research Keywords & Expertise

0 fracture behavior
0 Enhanced geothermal systems
0 mass and heat transfer
0 hot dry rock
0 Concrete bridge

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Journal article
Published: 20 June 2021 in Geothermics
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Seepage characteristics and heat transfer efficiency in rough fracture are indispensable to evaluate thermal reservoir lifetime and production performance. This study presents the seepage experiment, experiment and simulation on convective heat transfer in rough fracture for two artificial specimens. The repeatable artificial specimens are prepared by cement mortar. The roughness on the fracture surface is manufactured based on JRC profiles and 3D printing technology. The effects of fracture surface property (including proppant) and specimen temperature on seepage characteristics under confining pressure of 30 MPa are obtained. The convective heat transfer performance is evaluated considering roughness, multiple flow rates and specimen temperatures. Moreover, the effects of roughness on temperature distribution, local heat transfer and flow velocity in two specimens are analyzed and discussed. The main results indicate that the proppant and higher specimen temperature can improve hydraulic aperture and be conducive to seepage in rough fracture. The higher specimen temperature can strengthen thermal convection and conduction. The higher flow rate can extract more heat to develop thermal breakthrough. Furthermore, the anisotropy of roughness can affect heat transfer efficiency by reducing effective heat transfer area. The bulge and groove on rough fracture can interfere with temperature distribution and local heat transfer by controlling retention time of fluid.

ACS Style

Yibin Huang; Yanjun Zhang; Xuefeng Gao; YueQiang Ma; Zhongjun Hu. Experimental and numerical investigation of seepage and heat transfer in rough single fracture for thermal reservoir. Geothermics 2021, 95, 102163 .

AMA Style

Yibin Huang, Yanjun Zhang, Xuefeng Gao, YueQiang Ma, Zhongjun Hu. Experimental and numerical investigation of seepage and heat transfer in rough single fracture for thermal reservoir. Geothermics. 2021; 95 ():102163.

Chicago/Turabian Style

Yibin Huang; Yanjun Zhang; Xuefeng Gao; YueQiang Ma; Zhongjun Hu. 2021. "Experimental and numerical investigation of seepage and heat transfer in rough single fracture for thermal reservoir." Geothermics 95, no. : 102163.

Journal article
Published: 27 April 2021 in Applied Sciences
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The test results on the performance of carbon fiber-reinforced polymer (CFRP)-confined reinforced concrete (RC) columns under axial compression load are presented in this study. Twelve slender CFRP-confined circular RC columns with a diameter of 200 mm were divided into two groups. Six specimens with different slenderness ratios of 12, 20, 32, 40, 48, and 56 were contained in each group. The experimental results demonstrated the circumferential CFRP wrap was effective in enhancing the ultimate axial load of slender CFRP-confined circular RC columns compared with unwrapped RC columns. The experimental investigation also showed that the slenderness of the specimens had important influences on the axial compressive behavior, and the axial bearing capacity of slender CFRP-confined circular RC columns decreased as the slenderness ratio increased. In order to predict the load-carrying capacities of slender CFRP-confined circular RC columns, a formula was proposed and the prediction agreed with the experiments. The slenderness of slender CFRP-confined circular RC columns was recommended to be less than 26.5 in practical engineering.

ACS Style

Zhongjun Hu; QuanHeng Li; Hongfeng Yan; Yuchuan Wen. Experimental Study on Slender CFRP-Confined Circular RC Columns under Axial Compression. Applied Sciences 2021, 11, 3968 .

AMA Style

Zhongjun Hu, QuanHeng Li, Hongfeng Yan, Yuchuan Wen. Experimental Study on Slender CFRP-Confined Circular RC Columns under Axial Compression. Applied Sciences. 2021; 11 (9):3968.

Chicago/Turabian Style

Zhongjun Hu; QuanHeng Li; Hongfeng Yan; Yuchuan Wen. 2021. "Experimental Study on Slender CFRP-Confined Circular RC Columns under Axial Compression." Applied Sciences 11, no. 9: 3968.

Research article
Published: 16 March 2021 in Advances in Materials Science and Engineering
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This study investigates the suitability of the circularization technique for strengthening square concrete-filled square steel tube (CFSST) short columns. A total of 16 specimens were tested under axial compression. The main parameters under investigation were concrete strength, the thickness of arc cement mortar layer components (CAM), and the layers of carbon fiber-reinforced polymer (CFRP) sheets. Test results indicated that the failure mode of CFRP-confined circularized CFSST (C-C-CFSST) columns was similar to that of CFRP-confined concrete columns. The CFRP-confined circularized strengthening method can increase confinement efficacy and reduce the stress concentration at the corners of CFSST columns. Three existing CFRP-confined concrete stress-strain models were evaluated using the test results. The predictions of the Lam and Teng stress-strain model agree well with the test data.

ACS Style

Yuchuan Wen; Zhongjun Hu; Anningjing Li; QuanHeng Li; Xuepeng Li; Yan Xu. Experimental Study on CFRP-Confined Circularized Concrete-Filled Square Steel Tube Short Columns. Advances in Materials Science and Engineering 2021, 2021, 1 -13.

AMA Style

Yuchuan Wen, Zhongjun Hu, Anningjing Li, QuanHeng Li, Xuepeng Li, Yan Xu. Experimental Study on CFRP-Confined Circularized Concrete-Filled Square Steel Tube Short Columns. Advances in Materials Science and Engineering. 2021; 2021 ():1-13.

Chicago/Turabian Style

Yuchuan Wen; Zhongjun Hu; Anningjing Li; QuanHeng Li; Xuepeng Li; Yan Xu. 2021. "Experimental Study on CFRP-Confined Circularized Concrete-Filled Square Steel Tube Short Columns." Advances in Materials Science and Engineering 2021, no. : 1-13.

Journal article
Published: 14 January 2021 in Applied Sciences
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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.

ACS Style

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 Style

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 (2):751.

Chicago/Turabian Style

Xuefeng 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.

Journal article
Published: 05 February 2020 in Renewable Energy
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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.

ACS Style

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 Style

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.

Chicago/Turabian Style

YueQiang 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.

Journal article
Published: 04 June 2019 in Energies
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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.

ACS Style

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 Style

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 (11):2138.

Chicago/Turabian Style

Zhihong 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.

Journal article
Published: 20 July 2018 in Energies
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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.

ACS Style

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 Style

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 (7):1896.

Chicago/Turabian Style

Yanjun 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.