scholarly journals Numerical Simulation on Heat Recovery Efficiency of Different Working Fluids in High-Temperature Rock Mass

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Xu Dong ◽  
Haozhe Geng ◽  
Guan Hao ◽  
Pan Li ◽  
Yi Teng ◽  
...  
Keyword(s):  
Rock Mass ◽  
High Temperature ◽  
Heat Recovery ◽  
Injection Pressure ◽  
Recovery Process ◽  
Thermal Recovery ◽  
Heat Extraction ◽  
Recovery Efficiency ◽  
Working Fluids ◽  
Hot Dry Rock

It is of great significance for the sustainable development of global energy to develop hot dry rock (HDR) geothermal resources by using enhanced geothermal system (EGS) technology. Different working fluids in EGS have different heat recovery efficiencies. Therefore, this paper takes water and CO2 as the heat-carrying media and establishes a thermal hydraulic mechanical coupling model to simulate the heat recovery process in high-temperature rock mass. By considering the different confining pressures, rock temperature, and injection pressure, the advantages of H2O-EGS and CO2-EGS are obtained. The results show that with the increase of confining pressure, the heat recovery efficiency of water is significantly higher than that of CO2, but at higher reservoir temperature, CO2 has more advantages as a heat-carrying medium. The net heat extraction rate will increase with the increase of injection pressure, which indicates that the mass flow rate plays a leading role in the heat recovery process and increases the injection pressure of fluid which is more conducive to the thermal recovery of EGS. This study will provide a technical guidance for thermal energy exploitation of hot dry rock under different geological conditions.

scholarly journals Performance Comparison of Advanced Transcritical Power Cycles with High-Temperature Working Fluids for the Engine Waste Heat Recovery

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5886
Author(s):  
Xinxing Lin ◽  
Chonghui Chen ◽  
Aofang Yu ◽  
Likun Yin ◽  
Wen Su
Keyword(s):  
High Temperature ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Performance Comparison ◽  
Design System ◽  
Working Fluids ◽  
Power Cycles ◽  
System Parameters ◽  
Pressure Cycle

To efficiently recover the waste heat of mobile engine, two advanced transcritical power cycles, namely split cycle and dual pressure cycle, are employed, based on the recuperative cycle. Performances of the two cycles are analyzed and compared through the development of thermodynamic models. Under given gas conditions, seven high-temperature working fluids, namely propane, butane, isobutane, pentane, isopentane, neopentane, and cyclopentane, are selected for the two cycles. At the design system parameters, the highest work 48.71 kW, is obtained by the split cycle with butane. For most of fluids, the split cycle has a higher work than the dual pressure cycle. Furthermore, with the increase of turbine inlet pressure, net work of the split cycle goes up firstly and then decreases, while the work of dual pressure cycle increases slowly. For the split cycle, there exists a split ratio to get the maximum network. However, for the dual pressure cycle, the larger the evaporation temperature, the higher the net work. On this basis, system parameters are optimized by genetic algorithm to maximize net work. The results indicate that the highest work 49.96 kW of split cycle is obtained by pentane. For the considered fluids, except cyclopentane, split cycle always has a higher work than dual pressure cycle. Due to the higher net work and fewer system components, split cycle is recommended for the engine waste heat recovery.

scholarly journals On the Conceptual Design of Novel Supercritical CO2 Power Cycles for Waste Heat Recovery

Energies ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 370 ◽  
Author(s):  
Giovanni Manente ◽  
Mário Costa
Keyword(s):  
High Temperature ◽  
Heat Source ◽  
Thermal Efficiency ◽  
Supercritical Co2 ◽  
Heat Recovery ◽  
Waste Heat ◽  
Heat Extraction ◽  
Heat Sources ◽  
Partial Heating ◽  
Single Flow

The supercritical CO2 power cycle (s-CO2) is receiving much interest in the utilization of waste heat sources in the medium-to-high temperature range. The low compression work and highly regenerative layout result in high thermal efficiencies, even at moderate turbine inlet temperatures. The capability of heat extraction from the waste heat source is, however, limited because the heat input takes place over a limited temperature range close to the maximum cycle temperature. Accordingly, novel s-CO2 layouts have been recently proposed, aimed at increasing the heat extraction from the heat source while preserving as much as possible the inherently high thermal efficiency. Among these, the most promising ones feature dual expansion, dual recuperation, and partial heating. This work concentrates on the conceptual design of these novel s-CO2 layouts using a systematic approach based on the superimposition of elementary thermodynamic cycles. The overall structure of the single flow split with dual expansion (also called cascade), partial heating, and dual recuperated cycles is decomposed into elementary Brayton cycles to identify the building blocks for the achievement of a high performance in the utilization of waste heat sources. A thermodynamic optimization is set up to compare the performance of the three novel layouts for utilization of high temperature waste heat at 600 °C. The results show that the single flow split with a dual expansion cycle provides 3% and 15% more power compared to the partial heating and dual recuperated cycles, respectively, and 40% more power compared to the traditional single recuperated cycle used as the baseline. The separate evaluation of thermal efficiency and heat recovery effectiveness shows the main reasons behind the achievement of the highest performance, which are peculiar to each novel layout.

Water Shutoff and Profile Control with the Combination of Single Fluid and Double Fluids

2014 ◽  
Vol 962-965 ◽  
pp. 741-745
Author(s):  
Hao Wang
Keyword(s):  
High Temperature ◽  
Temperature Profile ◽  
Field Tests ◽  
Economic Benefits ◽  
Thermal Recovery ◽  
Working Fluids ◽  
Water Shutoff ◽  
Profile Control ◽  
Utilization Ratio ◽  
Chemical Water

Both the single fluid and double-fluid method for water shutoff and profile control have their limitations. If the two kinds of working fluids are used in combination for water shutoff and profile control, each of them exhibits its own plugging capability while they can form plugging materials when they contact and react with each other. This method can be used as a plugging system in the formations, eliminating the low utilization ratio and huge waste of the single or double-fluid chemicals. It can enhance the plugging capability and improve the water shutoff and profile control results. The single and double fluid (SAD) system has been proved satisfactory in the field tests of conventional chemical water shutoff and profile control, high temperature chemical water shutoff and high temperature profile control and channeling-plugging in thermal recovery wells. The economic benefits are remarkable from the field tests of 14 wells.

Alkanes as working fluids for high-temperature exhaust heat recovery of diesel engine using organic Rankine cycle

2014 ◽  
Vol 119 ◽  
pp. 204-217 ◽  
Author(s):  
Gequn Shu ◽  
Xiaoning Li ◽  
Hua Tian ◽  
Xingyu Liang ◽  
Haiqiao Wei ◽  
...  
Keyword(s):  
High Temperature ◽  
Diesel Engine ◽  
Heat Recovery ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluids ◽  
Exhaust Heat ◽  
Exhaust Heat Recovery

scholarly journals Study On Optimization Mechanism of Thermal Recovery Efficiency Under Different Geothermal Well Layout Conditions

2021 ◽  
Author(s):  
Jun-yi Gao
Keyword(s):  
Temperature Field ◽  
Rock Mass ◽  
Water Temperature ◽  
Working Condition ◽  
Thermal Recovery ◽  
Recovery Efficiency ◽  
Production Well ◽  
Injection Wells ◽  
Production Wells ◽  
Geothermal Wells

Abstract Efficient exploitation of geothermal energy is a hot issue concerned by scientific and engineering circles. The layout of different injection wells and production wells directly affects the temperature field of production wells and rock mass. In order to study the thermal recovery efficiency under different geothermal well layout conditions, based on the conceptual model of two injection wells and two production wells, a 3DEC program is used to calculate and analyze the influence of the different water inlet and water inlet of two injection wells and two production wells on the temperature field of rock mass, geothermal wells and the water temperature of production wells outlet. The results show that: (1) After the model injection wells are switched with the production wells, the temperature gradients of rock mass, production wells and injection wells are almost the same in numerical value and opposite in direction. (2) Production wells are set on the left side and injection wells are set on the right side of the model, and the injection wells and production wells are set at intervals; The temperature field of rock mass on both sides of the edge forms a central symmetry; The temperature gradient of rock mass from the middle to the edge is smaller and smaller, which indicates that the heat transfer speed of rock mass from the middle to the edge is slower and slower. Because the thermal superposition of adjacent injection wells and production wells through the rock mass between them is dominant, the water temperature at the outlet of production wells is the highest; In the interval water injection well and production well, the heat convection between water flow and rock is dominant, which makes the water temperature of production well outlet drops. (3) According to the water temperature at the outlet of production well, the optimal order of the model is working condition 3 > working condition 1 = working condition 2 > working condition 4, and the time to reach a steady state is the shortest in working condition 3 and the longest in working condition 4. The research results can provide important theoretical and practical reference for optimizing the layout of geothermal wells in efficient geothermal exploitation.

scholarly journals Carbon Dioxide Mixtures as Working Fluid for High-Temperature Heat Recovery: A Thermodynamic Comparison with Transcritical Organic Rankine Cycles

Energies ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 4014 ◽  
Author(s):  
Abubakr Ayub ◽  
Costante M. Invernizzi ◽  
Gioele Di Marcoberardino ◽  
Paolo Iora ◽  
Giampaolo Manzolini
Keyword(s):  
Carbon Dioxide ◽  
Thermal Stability ◽  
High Temperature ◽  
Supercritical Co2 ◽  
Heat Recovery ◽  
Waste Heat ◽  
Working Fluid ◽  
Maximum Pressure ◽  
Total Efficiency ◽  
Working Fluids

This study aims to provide a thermodynamic comparison between supercritical CO2 cycles and ORC cycles utilizing flue gases as waste heat source. Moreover, the possibility of using CO2 mixtures as working fluids in transcritical cycles to enhance the performance of the thermodynamic cycle is explored. ORCs operating with pure working fluids show higher cyclic thermal and total efficiencies compared to supercritical CO2 cycles; thus, they represent a better option for high-temperature waste heat recovery provided that the thermal stability at a higher temperature has been assessed. Based on the improved global thermodynamic performance and good thermal stability of R134a, CO2-R134a is investigated as an illustrative, promising working fluid mixture for transcritical power cycles. The results show that a total efficiency of 0.1476 is obtained for the CO2-R134a mixture (0.3 mole fraction of R134a) at a maximum cycle pressure of 200 bars, which is 15.86% higher than the supercritical carbon dioxide cycle efficiency of 0.1274, obtained at the comparatively high maximum pressure of 300 bars. Steam cycles, owing to their larger number of required turbine stages and lower power output, did not prove to be a suitable option in this application.

scholarly journals Mechanical Properties of Spruce Wood Extracted from GLT Beams Loaded by Fire

2021 ◽  
Vol 13 (10) ◽  
pp. 5494
Author(s):  
Lucie Kucíková ◽  
Michal Šejnoha ◽  
Tomáš Janda ◽  
Jan Sýkora ◽  
Pavel Padevět ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Cross Section ◽  
Negative Impact ◽  
Tensile Tests ◽  
Thermal Recovery ◽  
Bending Test ◽  
Small Scale ◽  
Spruce Wood ◽  
The Impact

Heating wood to high temperature changes either temporarily or permanently its physical properties. This issue is addressed in the present contribution by examining the effect of high temperature on residual mechanical properties of spruce wood, grounding on the results of full-scale fire tests performed on GLT beams. Given these tests, a computational model was developed to provide through-thickness temperature profiles allowing for the estimation of a charring depth on the one hand and on the other hand assigning a particular temperature to each specimen used subsequently in small-scale tensile tests. The measured Young’s moduli and tensile strengths were accompanied by the results from three-point bending test carried out on two groups of beams exposed to fire of a variable duration and differing in the width of the cross-section, b=100 mm (Group 1) and b=160 mm (Group 2). As expected, increasing the fire duration and reducing the initial beam cross-section reduces the residual bending strength. A negative impact of high temperature on residual strength has also been observed from simple tensile tests, although limited to a very narrow layer adjacent to the charring front not even exceeding a typically adopted value of the zero-strength layer d0=7 mm. On the contrary, the impact on stiffness is relatively mild supporting the thermal recovery property of wood.

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