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The Eastern Helan Mountain can be the largest concentrated and contiguous producing areas for the wine grape in China. Specifically, the wine grape planting area reached 388.7 square kilometers in Ningxia by the end of 2022, accounting for nearly 1/3 of the nation, and the comprehensive output value exceeded 30 billion Yuan. However, the extremely low temperatures (down to -30.0℃) in winter in the eastern part of the Helan Mountains can lead to the occurrence of overwintering frost damage, which greatly limits the sustainable development of Ningxia's grape industry. In this study, a gravity heat pipe system was designed using shallow groundwater geothermal energy for the soil warming in the root zone of grapes. Numerical simulation was also carried out to analyze the influence range and distribution of the gravity heat pipe temperature field under different spacing. A series of field experiments were used to verify the working performance of the gravity heat pipe and the warming characteristics of the soil. The results show that the soil temperature field was evenly spread around the gravity heat pipe. The temperature field around the heat pipe was divided into four regions, according to the temperature level: the temperature range was 5.0-8.50℃ high-temperature affected region â… , the temperature range was 0-5.0℃ medium-temperature affected region â…¡, the temperature range was -2.57-0 ℃ low-temperature affected region â…¢, and the temperature field was not affected region â…£. The highest temperature (8.50 ℃) appeared in the temperature field area â…  condensation section pipe wall, whereas, the lowest temperature (-2.57 ℃) was in the temperature field unaffected area â…£. In addition, the diameter of the medium temperature affected area of the heat pipe in the soil was 30.8 cm horizontally and 32.8 cm vertically, where the grape roots were not affected by frost. There were evenly distributed temperature fields around the heat pipes partially overlapped and the temperature fields under the conditions of 10 cm burial depth and 15 cm spacing between adjacent heat pipes. The soil temperature increased by 7.0 ℃ on average in the experimental group during the test period, compared with the control group, indicating the outstanding increase in temperature. The maximum temperature difference was 3.5 ℃ between the evaporation and condensation sections during the normal operation of the gravity heat pipe. The maximum temperature differences were 1.0 and 0.2 ℃ within the evaporation section, and within the adiabatic section, respectively, indicating the excellent isothermal distribution. The average start-up and operating temperature difference of the heat pipe were 5.4 and 2.9 ℃, respectively. The clean and renewable shallow geothermal energy was taken as a source of heating energy in the root zone of grapes, which was in line with the current green development concept. The finding can provide the theoretical basis and technical support to treat the frost damage in the root zone of grapes. In addition, a way was proposed to realize the development and utilization of shallow geothermal energy using gravity heat pipes. The Eastern Helan Mountain can be the largest concentrated and contiguous producing areas for the wine grape in China. Specifically, the wine grape planting area reached 388.7 square kilometers in Ningxia by the end of 2022, accounting for nearly 1/3 of the nation, and the comprehensive output value exceeded 30 billion Yuan. However, the extremely low temperatures (down to -30.0℃) in winter in the eastern part of the Helan Mountains can lead to the occurrence of overwintering frost damage, which greatly limits the sustainable development of Ningxia's grape industry. In this study, a gravity heat pipe system was designed using shallow groundwater geothermal energy for the soil warming in the root zone of grapes. Numerical simulation was also carried out to analyze the influence range and distribution of the gravity heat pipe temperature field under different spacing. A series of field experiments were used to verify the working performance of the gravity heat pipe and the warming characteristics of the soil. The results show that the soil temperature field was evenly spread around the gravity heat pipe. The temperature field around the heat pipe was divided into four regions, according to the temperature level: the temperature range was 5.0-8.50℃ high-temperature affected region Ⅰ, the temperature range was 0-5.0℃ medium-temperature affected region Ⅱ, the temperature range was -2.57-0 ℃ low-temperature affected region Ⅲ, and the temperature field was not affected region Ⅳ. The highest temperature (8.50 ℃) appeared in the temperature field area Ⅰ condensation section pipe wall, whereas, the lowest temperature (-2.57 ℃) was in the temperature field unaffected area Ⅳ. In addition, the diameter of the medium temperature affected area of the heat pipe in the soil was 30.8 cm horizontally and 32.8 cm vertically, where the grape roots were not affected by frost. There were evenly distributed temperature fields around the heat pipes partially overlapped and the temperature fields under the conditions of 10 cm burial depth and 15 cm spacing between adjacent heat pipes. The soil temperature increased by 7.0 ℃ on average in the experimental group during the test period, compared with the control group, indicating the outstanding increase in temperature. The maximum temperature difference was 3.5 ℃ between the evaporation and condensation sections during the normal operation of the gravity heat pipe. The maximum temperature differences were 1.0 and 0.2 ℃ within the evaporation section, and within the adiabatic section, respectively, indicating the excellent isothermal distribution. The average start-up and operating temperature difference of the heat pipe were 5.4 and 2.9 ℃, respectively. The clean and renewable shallow geothermal energy was taken as a source of heating energy in the root zone of grapes, which was in line with the current green development concept. The finding can provide the theoretical basis and technical support to treat the frost damage in the root zone of grapes. In addition, a way was proposed to realize the development and utilization of shallow geothermal energy using gravity heat pipes. [ABSTRACT FROM AUTHOR]

Exploiting heat from abandoned mine water using heat pumps is attracting increasing attention worldwide. China has a large number of abandoned coal mines, but there are few applications of geothermal heat recovery from mine water. Here, we report a new case from Shandong, North China. Based on actual geological and underground space structures, numerical analysis is performed to study the flow and heat transfer in the complex connection network among roadways. For given temperature differences on the source side, the underground heat transfer is greatly influenced by flow rates in roadways. Under the acceptable performances and long-term stability of heat pumps, the maximum heat transfer capacity of roadways reaches 697.3 kW at the flow rate of 100 m3/h, with the power per unit length of 151.3 W/m, indicating a promising heat recovery potential. When switching between the extraction and injection well, both fluid directions and the distribution of flow rates in roadways change obviously, thereby affecting the underground heat transfer. Besides dominant flow paths, there exist weak flow paths, which can be identified by numerical analysis, and necessary blocking can be applied to optimize the flow and heat transfer. Excessively long horizontal straight roadways for heat exchange should be avoided. [ABSTRACT FROM AUTHOR]

• A three-dimensional unsteady state mathematical model of the multi-field coupling of backfill body, tube and fracture was established. • A test bench was designed and built to verify the three-dimensional coupling model. • The effects of a single fracture position, aperture and fractured depth on the heat extraction performance of a full-size BFHEs unit in the fully dry or fully saturated conditions were investigated. • The combined effects of multiple fractures on the performance of a BFHES unit were discussed. Thermal hazards in deep mines can be mined synergistically with the deposit as associated geothermal energy resources. Backfill heat exchangers (BFHEs) as a combination of mine backfilling and ground heat exchanger technology are one of the effective methods to realize ore deposit-geothermal energy synergy mining. However, in the complex environment of deep mines, BFHEs will inevitably suffer from fracture damage during long-term heat storage/release cycle operation, which will affect their working performance. To address this problem, this paper established a scaled-down experimental setup for fractured BFHEs units, and used the experimental data to verify the accuracy of the established three-dimensional transient heat transfer mathematical model of the BFHEs unit. Numerical simulation methods were used to investigate the effects of the position, aperture and fractured depth of a single fracture on the heat extraction performance of the BFHEs unit under fully dry or fully saturated working conditions. Significant differences were found in the effect of different fracture positions on the heat extraction capacity of the BFHEs unit. The extraction of geothermal heat by the BFHEs unit was favored when it was in the middle of two tubes, while the opposite was true for other positions. The effect of fracture on the heat extraction capacity of the BFHEs unit increased linearly with fracture aperture. The effect of the fractured depth was relatively greater in the 1/2–3/4 H b range. The presence of groundwater significantly reduced the effect of the fracture. The effect of the fracture on the heat extraction capacity of the BFHEs unit was reduced by more than 80 % by changing the operating conditions from fully dry to fully saturated condition. The overall effect of a fracture on the heat extraction capacity of the BFHEs unit was not significant, with a 5 mm wide fracture having an effect of no more than 2.5 %, even under the fully dry condition. However, there was a combined effect of multiple fractures, and for a deposit size of 900 × 7 × 80 m, ten 2 mm apertures fractures would results in a maximum reduction of geothermal extraction from BFHEs by 8527 GJ in 10 years, which was equivalent to the heat load of a 13,753 m2 building for one winter in the cold climate of China. [ABSTRACT FROM AUTHOR]

In consumer fireworks, various functions of chemicals create an energetic reaction with a type of colored light, smoke, heat, and the sound to achieve the pyrotechnic effects. Fireworks mixtures may be highly sensitive to external disturbances such as ignition sources, temperature changes, shocks, friction, and static electricity. Approximately 95% of fireworks are imported from China by ocean shipment, taking 4 days to a week to Taiwan. The prediction and assessment for the nth-order reaction, and thermokinetic parameters from thermal safety model for fireworks and pyrotechnic compositions were investigated. This study showed which reaction intensity of the propellant as water was added. It can be seen from the results that water will affect the thermal hazard of propellant. Moreover, the novel findings indicated that the water increased the thermal hazard of the propellant and consequently increased the risk for launching a degradation. Based on the heat transfer theoretical models, the time to maximum rate and time to conversion limit were extrapolated for consideration and discussion. [ABSTRACT FROM AUTHOR]

To match for the different temperature of the geothermal resource and strengthen the flexibility of organic Rankine cycle, a variable capacity power generation superstructure based on flash and organic Rankine cycle for geothermal energy was proposed. A combined flash-binary experimental prototype is newly established to investigate thermodynamic performance both on system and equipment in this paper. Pressured hot water is adopted as the extensive worldwide existed hydrothermal geothermal resource, eliminating the influence of the used heat transfer oil on evaporating process. The experimental results show that there is an optimal mass-flow rate of R245fa under the condition of different heat source temperature. Flash and binary power subsystem dominate the flash-binary power system, respectively, when the heat source temperature is 120 °C and 130 °C. The isotropic efficiency of modified compressor just between 0.2 and 0.25. The power output of per ton geofluid are 0.78 kWh/t and 1.31 kWh/t, respectively, when the heat source temperature are 120 °C and 130 °. These results will predict the operation data of flash-binary power plant driven by the low-medium temperature geothermal water for construction in western of China. [ABSTRACT FROM AUTHOR]

High-temperature geothermal systems in China, such as those found in Tenchong and Tibet, are common. A similar system without obvious manifestations found in the Tashkorgan basin in the western Xinjiang Autonomous Region, however, was not expected. The results from borehole measurements and predictions with geothermometers, such as quartz, Na-K and Na-K-Mg, indicate that the reservoir temperature is approximately 250–260 °C. Geothermal water is high in Total Dissolved Solids (>2.5 g/L) and SiO 2 content (>273 mg/L), and the water type is Cl·SO 4 -Na, likely resulting from water-rock interactions in the granodiorite reservoirs. Based on isotope analysis, it appears to be recharged by local precipitation and river water. Evidence from the relationships between major ions and the Cl and molar Na/Cl ratio suggests mixing between deep geothermal water and shallow cold groundwater during the upwelling process. Mixing ratios calculated by the relationship between Cl and SiO 2 show that the proportion from cold end-members are 96–99% and 40–90% for riparian zone springs and geothermal water from boreholes, respectively. Active regional tectonic and Neo-tectonic movements in the Pamir syntax as well as radioactive elements in the granodiorite reservoir of the Himalayan stage provide basis for the high heat flow background (150–350 mW/m 2 ). NNW trending fault systems intersecting with overlying NE faults provide circulation conduits with high permeability for geothermal water. [ABSTRACT FROM AUTHOR]

Groundwater flow in deep sedimentary basins results from complex evolution processes on geological timescales. Groundwater flow systems conceptualized according to topography and/or groundwater table configuration generally assume a near-equilibrium state with the modern landscape. However, the time to reach such a steady state, and more generally the timescales of groundwater flow system evolution are key considerations for large sedimentary basins. This is true in the North China Basin (NCB), which has been studied for many years due to its importance as a groundwater supply. Despite many years of study, there remain contradictions between the generally accepted conceptual model of regional flow, and environmental tracer data. We seek to reconcile these contractions by conducting simulations of groundwater flow, age and heat transport in a three dimensional model, using an alternative conceptual model, based on geological, thermal, isotope and historical data. We infer flow patterns under modern hydraulic conditions using this new model and present the theoretical maximum groundwater ages under such a flow regime. The model results show that in contrast to previously accepted conceptualizations, most groundwater is discharged in the vicinity of the break-in-slope of topography at the boundary between the piedmont and central plain. Groundwater discharge to the ocean is in contrast small, and in general there are low rates of active flow in the eastern parts of the basin below the central and coastal plain. This conceptualization is more compatible with geochemical and geothermal data than the previous model. Simulated maximum groundwater ages of ∼1 Myrs below the central and coastal plain indicate that residual groundwater may be retained in the deep parts of the basin since being recharged during the last glacial period or earlier. The groundwater flow system has therefore probably not reached a new equilibrium state with modern-day hydraulic conditions. The previous hypothesis that regional groundwater flow from the piedmont groundwater recharge zone predominantly discharges at the coastline may therefore be false. A more reliable alternative might be to conceptualize deep groundwater below the coastal plains a hydrodynamically stagnant zone, responding gradually to landscape and hydrological change on geologic timescales. This study brings a new and original understanding of the groundwater flow system in an important regional basin, in the context of its geometry and evolution over geological timescales. There are important implications for the sustainability of the ongoing high rates of groundwater extraction in the NCB. [ABSTRACT FROM AUTHOR]

The hybrid ground-coupled heat pump (HGCHP) systems with supplemental heat rejecter/supplier can effectively solve heat imbalance problems in the subsurface, and consequently improve the operation performance of the geothermal systems. For example, solar energy and/or industrial waste heat may be used as stable heat sources for underground heat storage in northern China with higher heating load, and cooling towers are installed to release heat into the air in southern China, where more cooling demand is needed. This paper reviews and discusses different HGCHP systems, which have been applied in China. And based on the heat transfer model of vertical borehole heat exchangers (BHE) for HGCHP systems, physical and mathematical models of multistage series circuits are developed to illustrate the heat transfer process of the underground thermal storage. A set of parameters, such as borehole spacing, heat recharging rate fractions and thermal properties of soils, which affect the thermal performance of the ground heat exchangers are analyzed, and the optimal solutions are discussed for engineering application. [ABSTRACT FROM AUTHOR]

The study of thermal conductivity anisotropy is of great importance for more accurate heat flow calculations, geodynamic studies, development and utilization of hot dry rock, and simulation of heat transfer in geological reservoirs of nuclear waste, and so on. To study the thermal conductivity anisotropy of rocks, 1158 cores from 60 boreholes in East China were tested for thermal conductivity, including thermal conductivity values parallel to (λ∥) and perpendicular to (λ⊥) structural planes of basalt, mudstones, gneisses, sandstones, carbonates, evaporites, and metamorphic rocks. The thermal conductivity anisotropy is not obvious for sand, clay, and evaporate, and the average anisotropic factors of 1.19 ± 0.22, 1.18 ± 0.17, and 1.18 ± 0.17 for tuff/breccia, granitoid and contact metamorphic rocks, respectively, indicate that these three rocks have strong anisotropy characteristics. Finally, the effect of thermal conductivity anisotropy on heat flow is studied and discussed in detail, showing that the results of thermal conductivity tests have a significant effect on the calculation of heat flow and thermal structure, and the data show that a deviation of about 10% in thermal conductivity causes a deviation of about 11% in heat flow, which may lead to a misperception of deep thermal structure studies. The regular and anisotropic characteristics of thermal conductivity of various rocks in Eastern China obtained in this paper can provide parameter support for projects such as heat flow calculations, thermal structure studies, and geothermal resource development and utilization. [ABSTRACT FROM AUTHOR]

Abstract: Thermal infrared (TIR) remote sensing is an important technique in the exploration of geothermal resources. In this study, a geothermal survey is conducted in Tengchong area of Yunnan province in China using TIR data from Landsat-7 Enhanced Thematic Mapper Plus (ETM+) sensor. Based on radiometric calibration, atmospheric correction and emissivity calculation, a simple but efficient single channel algorithm with acceptable precision is applied to retrieve the land surface temperature (LST) of study area. The LST anomalous areas with temperature about 4–10K higher than background area are discovered. Four geothermal areas are identified with the discussion of geothermal mechanism and the further analysis of regional geologic structure. The research reveals that the distribution of geothermal areas is consistent with the fault development in study area. Magmatism contributes abundant thermal source to study area and the faults provide thermal channels for heat transfer from interior earth to land surface and facilitate the present of geothermal anomalies. Finally, we conclude that TIR remote sensing is a cost-effective technique to detect LST anomalies. Combining TIR remote sensing with geological analysis and the understanding of geothermal mechanism is an accurate and efficient approach to geothermal area detection. [Copyright &y& Elsevier]

Brackish water poses a health hazard worldwide, but especially to rural residents in China. In this study, a direct contact hollow fiber membrane distillation system was established based on a filter-pretreated hot spring resource in the Jiaodong area of China. The effects of the operating temperature, flow rate, and composition of brackish water on the properties of membrane distillation were investigated. A multistage system model was established using the Aspen plus platform and the economic cost of the system was analyzed. The results showed that the permeate flux could reach 12.599 kg/m2·h. The effect of the MgSO 4 content of the brackish water on the flux decreased above 20 g/L. Electron microscopy and elemental analysis showed that carbonate crystallization occurred mainly in the scaling part. The simulation results showed that the inlet temperature of the feed side had major effects on the increase in the flux and gain output ratio. A parallel layout was more effective and the regenerator improved the gain output ratio (GOR), with a 30% maximum increase for the system. The unit water production cost decreased to $18.2/m3 as the subsystem number increased to 10. These findings may help to improve the performance and economic benefits of this special type of distillation system. • Geothermal direct contact membrane distillation system for purifying brackish water • Scale removal method proposed for the membrane distillation system • Heat and mass transfer models established for the system • Methods for improving the flux, gain output ratio, and economic benefits [ABSTRACT FROM AUTHOR]

Excessive water production from hydraulically fractured unconventional reservoirs is historically considered as burdensome liability in terms of costly treatment and disposal. However, this paper demonstrated produced water as a valuable asset, which is capable of producing geothermal energy, and it can actually help offset the operation costs for unconventional oil and gas producers. Harnessing geothermal energy of produced water for power generation from unconventional horizontal wells features significant advantages over traditional geothermal wells, especially in reducing capital expenditure and operational risks. This paper proposed a novel design of downhole power generation in horizontal wells by integration of thermoelectric technology with hydrocarbon production. In the design, we retrofit the horizontal wellbore to circulate cold water inside the tubing so that a cold temperature interface can be created. The produced fluids flow through the annulus of the tubing and casing to maintain hot temperature on the side of tubing. By attaching thermoelectric generators (TEG) on the outer surface of tubing, this retrofit will make it possible to capture subsurface in-situ geothermal energy of the produced fluid and directly transfer heat to electricity inside the horizontal wellbore. Furthermore, we also built the mathematical model to account for the heat conduction and convention in the wellbore and surrounding formation, which could accurately simulate the temperature distribution and power generation under variable operational conditions. Based on the model, we identified the key parameters with significant impact on power generation and established the well section criteria for best power generation performance. To discover the potential of power generation in horizontal wells, we conducted a case study in Daqing Oilfield in northeast China and compared the power generation performance with vertical well with same TVD and same power generation device installation. The results of case study indicated that horizontal well displayed exceeding power generation performance over vertical wells. In practice, this paper could contribute to enrich geothermal development methods and provide the guidelines for oil and gas producer to evaluate their horizontal assets and identify the opportunity to capitalize on geothermal power generation from horizontal wells. [ABSTRACT FROM AUTHOR]