High Heat Extraction Research Articles

Enhancement of Geothermal Exploitation in Hot Dry Rock Reservoir Through Multilateral Horizontal Well Systems: A Case Study in Qiabuqia Geothermal Field, Gonghe Basin

Horizontal and multilateral well EGSs can potentially achieve the high-heat extraction of HDR. Herein, the performance of a multilateral horizontal well system in geothermal exploitation was investigated based on the geothermal and geological conditions of Qiabuqia geothermal field. The target reservoir is a granitic basement at 2650–3650 m depth, with initial temperatures of 151–190 °C. The simulation results indicate that the initial production temperature and electric power reached 178.4 °C and 2.90 MW and decreased by 8.3% and 17.9% over 20 years of production under the scheme of injecting 60 °C cold water at 50 kg/s, respectively. The reduction in total greenhouse gas (GHG) emissions amounts to 0.15–0.51 Mt relative to a fossil fuel plant. The multilateral horizontal well EGS outperforms conventional double vertical wells in terms of production temperature and electric power generation. The heat production efficiency of the multilateral horizontal well is significantly influenced by well depth and the arrangement of branch wells. Reservoir stimulation can effectively reduce flow impedance and improve the system economy. The multilateral horizontal well system is a promising development scheme for geothermal exploitation in Qiabuqia geothermal field.

Thermal analysis of cooling plate motor jacket and radiator for managing an electric bike energy storage system

The performance of electric bikes has increased with their increased use commercially and it has led to a corresponding increase in the charge and discharge rates for the batteries, and associated battery temperatures. Unfortunately, the cooling mechanisms for these electric bikes have not been able to keep up, with most organizations not implementing any cooling aside from passive ambient air cooling. This has led to a general decrease in battery life and charge capacity for these electric bikes. The proposed research has focused on the development of a novel electric bike cooling system under the practical industrial and environmental framework. It is cheap, effective, and simple to manufacture. Contemporary papers related to the topic have been studied, and the most feasible have been shortlisted to 4 distinct cooling plate designs, 3 Radiator Designs and 5 motor cooling jacket designs, which have been modeled in CAD software and then analyzed through use of CFD software. For the cooling plate design 1 had the lowest cooling capability, design 2 showed a 53.3% increase in total heat transfer from plate to coolant, design 3 showed a 107.52% increase, and design 4 showed a 183.03% increase relative to design 1. For the radiator, design number 2 has been recommended due to optimal cooling and temperature drop of coolant, within the dimensional and space constraints on the electric bike. For the motor cooling jacket, design number 5 was deemed to be the most feasible due to the high heat extraction from motor and good temperature uniformity of contact surface. Their respective advantages and disadvantages are discussed, and the most effective one of them all has been proposed for use. Further potential improvements to its design have also been recommended along with Thermoelectric Generator (TEG) integration for harvesting waste heat to produce energy.

Effects of liquid water injection on flame surface topology and propagation characteristics in spray flames: A direct numerical simulation analysis

The effects of water injection on flame surface topology and local flame propagation characteristics have been analyzed for statistically planar turbulent n-heptane spray flames with an overall (i.e., liquid + gaseous) equivalence ratio of unity using carrier-phase direct numerical simulations. Most fuel droplets have been found to evaporate as they approach the flame even though some droplets can survive until the burnt gas side is reached, whereas water droplets do not significantly evaporate ahead of the flame and the evaporation of water droplets starts to take place in the reaction zone and is completed within the burnt gas. However, the gaseous-phase combustion occurs predominantly in fuel–lean mode although the overall equivalence ratio remains equal to unity. The water injection has been found to suppress the fuel droplet-induced flame wrinkling of the progress variable isosurface under the laminar condition, and this effect is particularly strong for small water droplets. However, turbulence-induced flame wrinkling masks these effects, and thus, water injection does not have any significant impact on flame wrinkling for the turbulent cases considered here. The higher rate of evaporation and the associated high latent heat extraction for smaller water droplets induce stronger cooling effects, which weakens the effects of chemical reaction. This is reflected in the decrease in the mean values of density-weighted displacement speed with decreasing water droplet diameter. The weakening of flame wrinkling as a result of injection of small water droplets is explained through the curvature dependence of the density-weighted displacement speed. The combined influence of cooling induced by the latent heat extraction of water droplets and flame surface flattening leads to a decrease in volume-integrated burning rate with decreasing water droplet diameter in the laminar cases, whereas the cooling effects are primarily responsible for the drop in burning rate with decreasing water droplet diameter in the turbulent cases.

Heat Transfer Analysis for Combustion under Low-Gradient Conditions in a Small-Scale Industrial Energy Systems

The issue of maintaining low-gradient combustion in the conditions of high heat extraction has been investigated numerically in this work. The analyses include the application of a convective boundary condition at the wall (with estimated boiling heat transfer coefficient); analysis of the Internal Recirculation Device’s impact on combustion products and heat transfer under low-gradient conditions; and comparison of both traditional and low-gradient combustion modes. It was shown that the Internal Recirculation Device material and geometry has a significant impact on the nitrogen oxide (NOx) formation mechanism, as NO2 emission becomes predominant and can rise up to several hundreds ppm. What is more, along with decrease in thermal resistance of the IRD, CO emissions also increase rapidly, even achieving over 2000 ppm. Additionally, the convective heat transfer rate decreased by about 25% after switching from traditional to low-gradient combustion, whereas the radiative mechanism increased by ≈40% compared to traditional mode. It should also be mentioned that the low-gradient combustion applied in this work achieved approximately 10% higher efficiency than conventional combustion.

A modified methodology to substitute U-shape well using a single well with fracture network: Design and performance

A modified methodology to substitute U-shape well using a single well with fracture network: Design and performance

Fracture conductivity management to improve heat extraction in enhanced geothermal systems

Fracture conductivity management to improve heat extraction in enhanced geothermal systems

Multifactor analysis of heat extraction performance of coaxial heat exchanger applied to hot dry rock resources exploration: A case study in matouying uplift, Tangshan, China

Multifactor analysis of heat extraction performance of coaxial heat exchanger applied to hot dry rock resources exploration: A case study in matouying uplift, Tangshan, China

Evaluation methods and influence factors of heat extraction performance in hot dry rock reservoir under multi-field coupling

How to improve the heat extraction performance of HDR (hot dry rock) is one of the most concerned problems in HDR extraction. The key is to take a reasonable method to evaluate the heat extraction performance of hot dry rock and find out the main factors influencing the heat extraction performance of hot dry rock. The permeability of HDR reservoir, well type, well spacing, well pattern and injection flow rate of cold water have important influence on heat extraction performance of HDR reservoir. Based on this, a multi-field coupling mathematical model for injection and production of HDR is established and solved by finite element method to analyze the evolutions of seepage field, temperature field and stress field in HDR reservoir. Then, high temperature production time and heat extraction rate were introduced to quantitatively evaluate the heat extraction performance of HDR reservoir under different reservoir permeability, different well type, different well spacing, different well pattern and different injection flow rate. The research results show that different reservoir permeability has little influence on the heat extraction performance of HDR reservoir. Comparing the vertical well production system with the horizontal well production system, horizontal well production system has longer high temperature production time, and vertical well production system has higher heat extraction rate. The greater the well spacing and injection flow rate, the better the heat extraction performance of HDR reservoir. The heat extraction performance of the well pattern is not necessarily better than that of the one-injection and one-production well pattern, the heat extraction performance of the one-injection two-production well pattern and the two-injection one-production well pattern is worse than that of the one-injection one-production well pattern, and the heat extraction performance of the four-injection one-production well pattern and the one-injection four-production well pattern is better than that of the one-injection one-production well pattern. The research results can provide a theoretical basis for the formulation of economic and reasonable HDR development program and working system, and realize efficient utilization of HDR reservoir.

Performance analysis of multi-well EGS system based on unique network structure — Voronoi fractures

Performance analysis of multi-well EGS system based on unique network structure — Voronoi fractures

An optimization of acquiring geothermal energy from a deep geothermal well by downhole coaxial open loop (DCOL)

As one of the methods to extract geothermal energy, downhole coaxial heat exchanger is widely concerned because of its high heat extraction rate and no need of re injection. However, there are few studies on the extraction of open-loop heat from a single deep geothermal shaft, and there is a lack of detailed inlet and outlet transient temperature data. In this study, the downhole coaxial open-loop heat collector is improved, and the slotted liner at the bottom of the well is used to form a free open space to improve the heat exchange. Using the improved experimental device design, the field thermal recovery test was carried out in deep geothermal well of Shengli Oilfield, Dongying, China. According to the field test results, the control equation was established, and the influence of parameters on the thermal recovery rate was studied. It is found that the improved heat output is greater than the reported value of the downhole heat exchanger with the traditional structure. After about eight days, the heat extraction rate reached a gradually stable stage. After 15 days of continuous operation, the heat output is stable at 200 kW, and the water temperature at the water outlet is 34.6 °C.

Evaluation of the heat extraction performance of an abandoned well pattern in multilayer commingled production oil reservoirs

Evaluation of the heat extraction performance of an abandoned well pattern in multilayer commingled production oil reservoirs

Investigations of performance improvements on the evacuated tube solar collector with and without the incorporation of preheater through various engineering approaches

Solar irradiation is a clean form of energy, and absorption cooling systems powered by solar energy allow for significant energy savings. In the future, the demand for renewable energy may be the most effective way to serve clean energy, especially in Iraq, which has an excellent geographical location. In this research work, the performances of solar collector with and without of preheater have been evaluated. When compared to flat plate collectors at temperatures above 80°C, glass evacuated tube solar collectors provide the combined effects of a highly selective surface coating and vacuum insulation of the absorber element, resulting in a high heat extraction efficiency. Firstly, the Evacuated Vacuum Tube Solar Collector (EVTSC) was tested through experimentation. Secondly, Computational Fluid Dynamics (CFD) approach has been involved in this EVTSC system and thereby the conductive, convective and radiation based heat transfers are computed. Additionally, all possible with inclusive preheater cases are computationally investigated, thereafter the comprehensive report is prepared though validated computational procedures. Finally, the maximum efficiency is observed to be 53% without using a preheater and 61.8% with the usage of the preheater. The increase in efficiency using the preheater is found to be 16.6%.

Dynamic simulation and techno-economic optimization of deep coaxial borehole heat exchangers in a building energy system

Deep coaxial borehole heat exchangers (CBHEs) have been considered to enable cost and energy savings in building energy systems. However, achieving improved performance requires optimal design and operation of the CBHE. This work presents a case study for a building energy system in Finland, for which a hydraulic diagram was developed to incorporate a number of deep CBHEs (800 m to 2400 m) with multiple operating modes. To evaluate the techno-economic feasibility with optimized operating strategies, a four-step methodology is introduced, combining steady-state modelling, dynamic simulation and system optimization. The systems with a CBHE were found economically feasible compared to a district heating connection, enabling lower annualized total system cost (18.3–26.3%) and operating costs (49.1–53.5%). With deeper CBHEs, the main cost reductions originated from improved heat pump performance, increased operating flexibility and decreased capacity requirements of process components. However, the benefits partly decreased non-linearly with increased CBHE depth. Economic feasibility displayed the highest sensitivity to the price of electricity, with a relatively smaller impact for deeper CBHEs. Furthermore, maximizing the heat pump performance was found economically more significant than achieving a high borehole heat extraction rate.

Factors controlling the formation of complex fracture networks in naturally fractured geothermal reservoirs

Factors controlling the formation of complex fracture networks in naturally fractured geothermal reservoirs

Thermal strengthening of low‐expansion glasses and thin‐walled glass products by ultra‐fast heat extraction

Abstract Thermal strengthening remains the primary method for enhancing the practical strength of commodity glass products, however, the process is limited in terms of applicable glass thickness and coefficient of thermal expansion. The primary reasons for this limitation are the achievable heat transfer coefficient when using conventional gas cooling, and the occurrence of transient surface tension in the early stages of rapid quenching. We revisit this problem for the case of thin borosilicate glass sheet. Using liquid gallium as the cooling medium, ultra‐fast heat extraction is achieved, with a heat transfer coefficient exceeding 5000 Wm−2 K−1. The low vapor pressure of gallium even at high temperatures enables preheating to a wide range of sheet entrant temperatures. We demonstrate thermal strengthening of low‐expansion borosilicate glass with persistent surface compression of up to 85 MPa, and quenching to a fictive temperature of ~190 K above the glass transition temperature. Glass sheet obtained in this way exhibits notably enhanced surface defect resistance to sharp indentation. In addition to thermal strengthening, the extraordinarily high heat extraction rates achieved by liquid metal immersion enable exploitation of high‐Tf glass properties beyond small and thin sample geometry.

Erythritol impregnated within surface-roughened hydrophilic metal foam for medium-temperature solar-thermal energy harvesting

Erythritol impregnated within surface-roughened hydrophilic metal foam for medium-temperature solar-thermal energy harvesting

Emission Characteristics of Heat Recirculating Porous Burners With High Temperature Energy Extraction

Emission characteristics of heat recirculating porous burners with high temperature heat extraction are studied numerically. Two types of burners are considered: counterflow porous burner (CFB) and reciprocal counterflow porous burner (RCFB). The combustion of methane-air mixtures flowing through the porous media is modeled by solving steady state governing equations to obtain the flame temperature and species profiles. Formation of CO, NO, NO2, and NOx is studied in CFB and RCFB in a range of equivalence ratios from 0.3 to 1.0 and heat extraction temperatures from 300 to 1,300 K. The contribution of various NO formation mechanisms is comparatively analyzed and related to the NO generation predicted by a detailed chemistry mechanism. The effect of high temperature heat extraction on the formation of CO and NOx is analyzed. Numerical predictions indicate a constant monotonic decrease of NOx concentration with increasing temperature of energy extraction. The formation of CO is observed to follow the similar trend. For heat extraction at 1,300 K, simulations predicted 3.6 ppm of NOx and 3.9 ppm of CO for CFB and 4.1 ppm of NOx and 3.5 ppm of CO for RCFB when these burners are operated at an equivalence ratio of 0.7.

Numerical simulation study on the heat extraction performance of multi-well injection enhanced geothermal system

Numerical simulation study on the heat extraction performance of multi-well injection enhanced geothermal system

Study on wellbore fluid flow and heat transfer of a multilateral-well CO2 enhanced geothermal system

Study on wellbore fluid flow and heat transfer of a multilateral-well CO2 enhanced geothermal system

A parametric analysis to evaluate the performance metrics of power generation system involving Trilateral Flash Cycle using three different working fluids for low grade waste heat

With the accelerated growth in population and technology progress in day-to-day life, the traditional fuels demands have increased significantly. Despite the execution of many renewable sources (solar, wind, geothermal, biomass), the modern issues such as high investment and power costs have slowed down their development. In this context, improvisation of the existing power generation ways is required by evolving a highly effective thermal system to extract renewable energy available for low grade waste heat. At present, many of the applicable practices are engrossed on high temperature heat extraction rather than low-grade heat in spite of being expensive. In this work, innovative technology has been recommended by amalgamation of the Trilateral Flash Cycle (TFC) with an expander (reaction turbine) in a binary system to offer improved operation, economical and broader employment of the existing resources. TFC can extract heat more efficiently from hydrothermal means to improve power generation directly and decrease the emissions of greenhouse gas. A theoretical analysis using a computer based model for TFC with simple reaction turbine for three proposed diameters at various rotational speeds and operating fluids is performed. Results of output powers and turbine efficiencies of the recommended system are compared. Also, this design concludes the optimum design factors for the turbine under explicit operational settings and the factors affecting the efficiency and nozzle flow area are discussed for the TFC system.