Biomass supercritical water gasification is clean and renewable, which can convert biomass into hydrogen rich gas. Previous studies indicated that external recycle of liquid residual could improve gas yield and gasifi...
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Biomass supercritical water gasification is clean and renewable, which can convert biomass into hydrogen rich gas. Previous studies indicated that external recycle of liquid residual could improve gas yield and gasification efficiency. However, the influence mechanism of external recycle on energy and exergy efficiency is complicated and theoretical model for system optimization is insufficient. Thermodynamic model of external recycle of liquid residual was built in this paper. Exergy efficiency of the main components and exergy loss distribution were specified and the result showed that exergy loss of reactor and preheater accounted for 26.06% and 35.88% of the total exergy loss, which were the main exergy loss sources. Effective ways to reduce exergy loss of components with large exergy loss and to improve energy and exergy efficiency of the system were proposed. Moreover, life cycle assessment of biomass gasification process was carried out. The results indicated that the increase of gasification temperature, pressure and external recycle flow rate of liquid residual and decrease of biomass concentration could improve energy and exergy efficiency of the system. Energy and exergy efficiency reached 63.67% and 48.29% respectively at the condition of gasification temperature of 560 degrees C, pressure of 25 MPa, recycle flow ratio of 32.43%, biomass concentration of 2.78%. Besides, the increase of gasification temperature and decrease of biomass slurry concentration and pressure could decrease GWP. (C) 2019 Elsevier Ltd. All rights reserved.
CO2 emission to the atmosphere is the most prominent cause of climate change and a major risk to environmental health. Although several techniques are very promising to reduce the CO2 emission from central emission po...
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CO2 emission to the atmosphere is the most prominent cause of climate change and a major risk to environmental health. Although several techniques are very promising to reduce the CO2 emission from central emission points, the CO2 absorption by amines remains the most mature and reliable technology. Yet, there is more potential to improve absorption performance by choosing suitable solvents. Thus, the present research is intended to explore a better solvent combination for CO2 absorption by adopting the amine absorption process using molecular dynamic simulation. The study is designed to compare the intermolecular interactions of N-C and N-H bond between single 2EAE, DMAE (or 2DMAE), and blended solvent, i.e., 2EAE/PZ, 2DMAE/PZ with carbon dioxide and water and then to catch the effect of piperazine on these amines. The molecular dynamic simulations were performed by using the Material Studio application. The solvent concentration, 30 wt% under the condition of 313 K temperature at 0.1 MPa pressure, was taken for solvent systems. The results were interpreted by the Radial Distribution Function analysis. It was found that the blend of secondary and tertiary amines with piperazine 2EAE/PZ, DMAE/PZ reflect higher intermolecular interaction with CO2 as compared to single DMAE & 2EAE. This finding shows that piperazine acts as a promoter on 2EAE and 2DMAE when interacting with CO2.
experimental design, to simulation methodology, to approaches for uncertainty quantification for material and transport properties of fluids under nanoconfinement [10]. Such work is critical for advancing fundamental ...
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experimental design, to simulation methodology, to approaches for uncertainty quantification for material and transport properties of fluids under nanoconfinement [10]. Such work is critical for advancing fundamental physics and chemistry; from an engineering perspective, this work can also promote the development of novel energy-related technologies, with applications ranging from energy storage (e.g., supercapacitors [11,12]), to energy harvesting (e.g., solar evaporation [13,14] or electricity generation via reverse electrodialysis [15,16]), to enhanced oil and gas recovery [17], to membrane-based separation processes [18]. A schematic illustration of energy applications of NCFs is presented in Figure 1. In this Research Topic, we aim to present frontier research in experimental, computational, and theoretical approaches to thermodynamics; mass, momentum, and energy transport; flow physics; and phase behavior of NCFs, especially in energy-related applications. It also aims to discuss and identify research challenges in the field, worthy of the community's broader attention. Main topics of interest in this Research Topic include 1) Reviews on recent developments in the field of NCFs; 2) Novel experimental and theoretical investigations of NCFs; 3) Novel computational studies of NCFs; and 4) NCFs in energy-related applications. The bilayer pore in their work exhibits 3.7 times higher selectivity of CO 2 /CH 4 as compared to the single-layer graphene nanopore of the same *** summary, this Research Topic highlights the promising prospects of nanoconfined fluids in energy applications, showcases several areas of exciting current research, and also highlights several open questions in this field. We sincerely hope that more researchers will invest effort in the study of nanoconfined fluids, from basic theory to application, and especially in the context of energy applications.
Spindles in precision boring machines usually operate without internal cooling, and thermal error in such spindles is nonnegligible and can severely affect the end-processing quality of the machines. This study aims t...
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Spindles in precision boring machines usually operate without internal cooling, and thermal error in such spindles is nonnegligible and can severely affect the end-processing quality of the machines. This study aims to investigate the effects that external cooling exerts on the thermal behavior of such spindles. A helical tube cooler is taken for external cooling. An analytical thermal resistance model for the grease-coated cooler-housing joint surface, which considers the pressured cambered-flat contact pair and rough metal surface-grease contact, is presented and validated, and a numerical thermal-fluid-solid coupling model for the cooler-spindle system is then established. An evaluation method is put forward to obtain the stability of the thermal error, which determines the boring processing accuracy and thermal equilibrium time, from experimental data. Then, the external cooling was optimally designed based on the simulation results from the numerical model. Experiments show that the designed cooler reduced the thermal equilibrium time by 47.13% and the maximum thermal error by 81.7%, and the proposed model can accurately predict the cooling effect on the spindle thermal behavior. This study not only provides a thermal error control method for the spindle but is expected to advance the theoretical basis of cooling design for complex electromechanical systems.
Submerged steam jet condensation is widely used in many industries. However, this process may cause damage to equipment due to pressure oscillation, especially at low steam mass flux. The dynamic process of steam bubb...
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Submerged steam jet condensation is widely used in many industries. However, this process may cause damage to equipment due to pressure oscillation, especially at low steam mass flux. The dynamic process of steam bubble and different pressure oscillation types were investigated in this numerical study. Five typical stages were observed, which were bubble growth stage, bubble slow necking stage, bubble rapid necking stage, bubble detachment stage and secondary bubble oscillation stage. Two pressure oscillation types were found by the synchronization analysis of bubble pattern and pressure field. The mechanisms of condensation oscillation of unstable steam jet were revealed. As for the first type, two pressure peaks existed in the fluctuation process of secondary bubble volume. The higher pressure peak was generated when secondary bubble was oscillated to its minimum volume, and the other was generated when secondary bubble was collapsed. As for the second type, only one pressure peak existed and secondary bubble was quickly contracted without volume fluctuation. Pressure peak was generated when secondary bubble was quickly contracted to its minimum volume. Moreover, analyses of flow field pressure at different locations were carried out. Results indicated that the pressure fluctuation was mainly induced by the condensation oscillation of secondary bubble for both types. The trends of pressure at different locations were the same as that of secondary bubble internal pressure. (C) 2019 Elsevier Ltd. All rights reserved.
With the advantages of environmental protection, energy saving and sustainability, the technology of energy harvesting and conversion coupled with atmospheric water gathering has gradually attracted the attention of r...
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With the advantages of environmental protection, energy saving and sustainability, the technology of energy harvesting and conversion coupled with atmospheric water gathering has gradually attracted the attention of researchers under the threat of global water and energy issues. This review paper briefly described the basic working principles of energy harvesting and conversion coupled with atmospheric water gathering technology at first and then comprehensively summarized the representative materials and corresponding devices recently developed for the generation of different kinds of energies (such as electricity and chemical energy, especially hydrogen energy) by energy harvesting and conversion coupled with atmospheric water gathering technology. Electricial energy was generated based on four effects (thermoelectric, electrokinetic, triboelectric and hydrovoltaic effects) and two processes (electrochemical and photoelectric chemical processes), while hydrogen was produced based on photoelectrochemistry, photocatalysis and photovoltaic electrolysis. Based on the above analysis, it was found that the great progress, including new mechanisms and new technical paths, has been achieved on energy harvesting and conversion coupled with atmospheric water gathering technology in the last few years, but there are still many challenges to overcome and directions to explore for further development. At last, this review paper discussed some potential strategies for promoting the output efficiency and performance of energy harvesting and conversion devices. Optimizing the materials and components used in energy harvesting and conversion devices and adding energy storage modules to achieve all-weather energy supply will push this technology into a wider range of applications and better solve the global water and energy crises.
Supercritical water gasification (SCWG) technology shows a promising future due to its high efficiency and low emissions. Influenced by special water properties variation near the pseudocritical point, well-establishe...
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Supercritical water gasification (SCWG) technology shows a promising future due to its high efficiency and low emissions. Influenced by special water properties variation near the pseudocritical point, well-established heat transfer correlations are ill-suited for SCWG reactor design. To solve the problems caused by heat transfer, particle-resolved simulations were conducted to study the heat transfer characteristics of supercritical water (SCW) flow around a spherical particle, which served as a basic reacting unit. Through varying the temperature difference between the inflow and particle surface, heat transfer characteristics with different water properties variation tendencies were studied. Detailed analyses of the velocity and temperature boundary layers, and flow field around the particle were also presented to gain greater understanding. Furthermore, heat transfer characteristics under different pressures were studied. Based on the simulated results, a new correlation applicable for SCW flow around a sphere for the Reynolds number range 10-200 was obtained.
ObjectiveTo investigate the clinical efficacy of plasma exchange (PE) with or without prednisone and hydroxychloroquine (HCQ) for the treatment of systemic lupus erythematosus (SLE) during *** clinical characteristics...
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ObjectiveTo investigate the clinical efficacy of plasma exchange (PE) with or without prednisone and hydroxychloroquine (HCQ) for the treatment of systemic lupus erythematosus (SLE) during *** clinical characteristics of 14 pregnant women with SLE admitted to our hospital were retrospectively analyzed, including 7 only treated with prednisone and HCQ (non-PE group) as well as 7 combined PE (PE group). The delivery situations of 14 patients were recorded. Data like erythrocyte sedimentation rate (ESR), urine protein, platelet count, and SLEDAI scores were compared between two groups before treatment and 3, 6, and 12 months after *** patients in the non-PE group ended in miscarriage while all patients in the PE group were delivered successfully. Eleven successfully delivered fetuses in the two groups were healthy, and the Apgar scores were over 8. The ESR of the PE group was significantly lower than that of the non-PE group at 6 and 12 months after delivery, while there was no statistical difference in ESR between the two groups before treatment and 3 months after delivery. The ESR and urine protein were significantly higher in the non-PE group at months 3, 6, and 12 postpartum. There was a significant decrease in disease activity postpartum in the PE group compared to predelivery disease activity. The change in platelet counts between the two groups significantly increased over time in the PE group, while SLEDAI scores *** combination of PE and oral prednisone and HCQ is possibly a more effective treatment than oral prednisone and HCQ alone for patients with active SLE during pregnancy. This treatment option reduces pregnancy loss and promotes the patients' postpartum condition to a certain extent. In this study, we recruit 14 SLE patients to analyze the clinical efficacy of prednisone and HCQ alone or in combination with PE for the treatment of SLE during pregnancy. The data showed that PE in the combination of
For the design verification and licensing of newly pressurized water reactors (PWRs), many integral test facilities were conducted. From the above integral test facilities, the obtained experimental results were adopt...
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For the design verification and licensing of newly pressurized water reactors (PWRs), many integral test facilities were conducted. From the above integral test facilities, the obtained experimental results were adopted in the assessment and development of safety analysis codes. In this study, scaling analysis and design parameters of integral test facilities were summarized from the perspective of scaling method, basic scaling choice, equipment design, test matrix and application. The scaling method is the guideline for establishing scaling ratios of integral test facilities and different scaling methods were proposed. With the basic scaling choices of system pressure, geometrical parameters, working medium and equipment material, the design parameters of equipment were discussed. The test matrix and application of different integral test facilities were compared. This work is expected to sum up experience and provide guidance for the design and application of newly integral test facilities. (c) 2021 Elsevier Ltd. All rights reserved.
Ultra-supercritical double-reheat technology, as one of the most advanced coal-fired power generation technology, is an important direction for emission reduction and energy saving in the world. In this study, the num...
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Ultra-supercritical double-reheat technology, as one of the most advanced coal-fired power generation technology, is an important direction for emission reduction and energy saving in the world. In this study, the numerical calculation was executed in a 660-MW ultra-supercritical double-reheat tower-type boiler under deep-air-staging conditions. The refined HCN oxidation model was adopted to substitute the default model implemented by the user-defined functions to calculate the NOx emission. The influences of the boiler load, over-fire air (OFA) ratio, and excess air coefficient on temperature, species, and heat flux distributions were investigated. Results show that the decrement of the boiler load from boiler maximum continuous rating to 50% turbine heat acceptance gives rise to an increase of NOx emission. The heat flux distributions along with the furnace width direction present bell shaped. When the OFA ratio rises from 17% to 43%, NOx emission descends from 357.7 to 179.3 mg m(-3) at the furnace outlet, and the heat flux distributions become more uniform along with the furnace width direction with lower peaks. Temperatures, species, and heat flux distributions are similar under the three different excess air coefficients. The NOx emission is the lowest when the excess air coefficient is 1.15. The results could provide a reference for combustion characteristics optimization and hydrodynamic calculation of ultra-supercritical double-reheat tower-type boiler.
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