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Wang Yongqing - One of the best experts on this subject based on the ideXlab platform.
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thermal performance analysis of single effect Evaporation mechanical vapor compression seawater desalination system
Chemical Engineering(China), 2012Co-Authors: Wang YongqingAbstract:As the only thermal desalination process is run by mechanical energy,the mechanical vapor compression distillation system has advantages of higher quality of production water,higher energy efficiency,and lower thermal pollution to the environment.A thermal performance analysis of a single-effect Evaporation mechanical vapor compression(SEE-MVC) seawater desalination system was presented.The mathematic model was built,and a parametric analysis was performed.The results show that lower compression ratio,higher isentropic efficiency of compressor and lower Evaporation Temperature of seawater lead to lower power consumption and higher recovery rate of water production.The suitable range of Evaporation Temperature is 55-70 ℃,and that of compression ratio is 1.2-1.3.Taking the minimum specific work consumption as objective function,the main parameters of several cases were given for reference.
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exergy analysis of a single effect Evaporation mechanical vapor compression seawater desalination system
Journal of Jimei University, 2012Co-Authors: Wang YongqingAbstract:An exergy analysis of a single-effect Evaporation mechanical vapor compression(SEE-MVC) seawater desalination system was given in this paper.A mathematic model of SEE-MVC was built,The calculation results from energetic balance and exergetic balance were compared.The exegetic performance of SEE-MVC,including the influence of the compression ratio,the isentropic efficiency of compressor and the Evaporation Temperature of seawater,was analyzed.The ways to improve the performance improvement of SEE-MVC were discussed.
Gang Zhao - One of the best experts on this subject based on the ideXlab platform.
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Thermodynamic analysis of a novel transcritical-subcritical parallel organic Rankine cycle system for engine waste heat recovery
Energy Conversion and Management, 2019Co-Authors: Liang-hui Zhi, Long-xiang Chen, Gang ZhaoAbstract:Abstract In this study, a novel transcritical-subcritical parallel organic Rankine cycle system is proposed to recover the engine exhaust gas and coolant waste heat. Firstly, the proposed system is compared with the dual-loop organic Rankine cycle and parallel organic Rankine cycle systems. According to the results, the proposed system shows more net power output, higher thermal and exergy efficiency, and lower heat transfer requirement. Then the thermodynamic analysis including energy and exergy analysis are carried out, and the effects of design parameters including high-pressure turbine inlet Temperature and pressure, low-pressure Evaporation Temperature on the performance of proposed system based on R601a are investigated. The results indicate that for a given high-pressure turbine inlet Temperature, the net power output of system firstly increases and then decreases as high-pressure turbine inlet pressure increases and reaches to the maximum at turbine inlet Temperature and pressure of 520 K and 8 MPa, and the net power output also shows a trend of firstly increasing and then decreasing with low-pressure Evaporation Temperature and reaches to the maximum at 330 K. Furthermore, five low global warming potential fluids are selected as working fluids of proposed system, and the results demonstrate that the R1233zd is the best candidate working fluid for proposed system. The maximum net power output of proposed system based on R1233zd reaches to 119.72 kW at the turbine inlet Temperature and pressure of 530 K and 10 MPa, low-pressure Evaporation Temperature of 330 K, which achieves net power output increment of 12.02% for the engine system. Finally, an exergy destruction analysis demonstrates that the heat transfer processes have less exergy destruction for proposed system based on R1233zd compared with other working fluids.
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parametric analysis and optimization of transcritical subcritical dual loop organic rankine cycle using zeotropic mixtures for engine waste heat recovery
Energy Conversion and Management, 2019Co-Authors: Liang-hui Zhi, Long-xiang Chen, Gang ZhaoAbstract:Abstract Dual-loop organic Rankine cycle is a great potential technology to recover engine waste heat for energy saving. Transcritical cycle can improve exergy efficiency of heat transfer process in the evaporator, and zeotropic mixtures furtherly can improve thermal match with heat source and sink. Thus, a transcritical-subcritical dual-loop organic Rankine cycle system using zeotropic mixtures is adopted for engine waste heat recovery, and system without and with regenerator is considered. The whole system is assumed in the steady state, R600a/R601a and R134a/R245fa mixtures are used as working fluid of transcritical and subcritical cycle, respectively. Parametric analysis and optimization about turbine inlet Temperature and pressure of high-Temperature loop, Evaporation Temperature of low-Temperature loop are carried out. According to the results, the designed parameters have great effect on performance of system, and for the system without and with regenerator, the optimal turbine inlet Temperature, pressure and Evaporation Temperature are 260 °C, 11 MPa, 85 °C and 250 °C, 10 MPa, 85 °C respectively. Moreover, the effects of components of mixtures on the performance of system are analyzed. The results demonstrate that system with zeotropic mixtures can significantly improve the performance of system. The system without regenerator using R600a/R601a (0.2/0.8) and R134a/R245fa (0.4/0.6) shows the maximum power output of 97.49 kW which is higher 5.48–20.00% than pure fluids, and system with regenerator using R600a/R601a (0.3/0.7) and R134a/R245fa (0.4/0.6) achieves the maximum power output of 97.95 kW, increment of 6.52–19.78% compared with using pure fluids. And the power output of engine can be improved by 9.79% and 9.83% for the system without and with regenerator, respectively. Furthermore, the exergy destruction analysis demonstrates that zeotropic mixtures can reduce heat transfer exergy destruction and total exergy destruction of system.
Paul Feron - One of the best experts on this subject based on the ideXlab platform.
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condensation re Evaporation and associated heat transfer in membrane Evaporation and sweeping gas membrane distillation
Journal of Membrane Science, 2015Co-Authors: Shuaifei Zhao, Leigh Wardhaugh, Jianhua Zhang, Paul FeronAbstract:Abstract Vapor transport through membranes is very important in many industrial processes such as membrane distillation (MD), membrane condensation and flue gas dehydration. In this study, we explore the condensation, re-Evaporation and associated heat transfer in membrane Evaporation and sweeping gas membrane distillation (SGMD) at low gas flow rates. It is found that both condensation and re-Evaporation are closely related to the membrane properties. Condensation is more severe for the membrane with lower mass transfer resistance. The condensation layer takes place between the separation layer and the bulk gas in the module. The re-Evaporation rate is determined by the total surface area of the droplets, the gas stripping velocity and the gas Temperature. The overall mass transfer coefficient increases significantly with the increases of the gas flow rate, while the liquid flow rate has limited effect on the overall mass transfer coefficient. The overall mass transfer coefficient decreases with the increase in the Evaporation Temperature. The traditional way to quantify Temperature polarization effect may not be applicable for SGMD at low gas flow rates because of vapor condensation. The increase in the gas flow rate or Evaporation Temperature can effectively improve Evaporation efficiency (EE) in SGMD, while the liquid flow rate has limited effect on EE.
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Membrane Evaporation of amine solution for energy saving in post-combustion carbon capture: Performance evaluation
Journal of Membrane Science, 2015Co-Authors: Shuaifei Zhao, Leigh Wardhaugh, Chencheng Cao, Paul FeronAbstract:Abstract In this study, we propose a membrane Evaporation system for energy penalty reduction in post-combustion carbon capture (PCC) and carry out membrane Evaporation of amine solutions. The effects of some key factors (i.e. Evaporation Temperature, gas and liquid flow rates and solvent concentration) on mass and heat transfer are systematically investigated. It is found that both Evaporation Temperature and gas flow rates have significant influences on vapor and heat transfer, while liquid flow rates have limited effect on mass and heat transfer in membrane Evaporation. The vapor and recovered heat fluxes increase exponentially with the rise in Evaporation Temperature, and increase linearly with the rise in gas flow rates. The increase in Evaporation Temperature and gas flow rates also significantly improves the Evaporation efficiency and heat recovery. Mass and heat transfer rates decrease as the concentration of the solvent increases because of the reduced vapor pressure of the liquid at higher concentration. It is estimated that the recovered heat flux can be up to 32 MJ m−2 h−1 and heat recovery can be over 40% when the gas/liquid flow rate ratio is 150. Therefore, the proposed membrane Evaporation system has great potential to save considerable energy in large-scale PCC pilot plant operation.
Liang-hui Zhi - One of the best experts on this subject based on the ideXlab platform.
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Thermodynamic analysis of a novel transcritical-subcritical parallel organic Rankine cycle system for engine waste heat recovery
Energy Conversion and Management, 2019Co-Authors: Liang-hui Zhi, Long-xiang Chen, Gang ZhaoAbstract:Abstract In this study, a novel transcritical-subcritical parallel organic Rankine cycle system is proposed to recover the engine exhaust gas and coolant waste heat. Firstly, the proposed system is compared with the dual-loop organic Rankine cycle and parallel organic Rankine cycle systems. According to the results, the proposed system shows more net power output, higher thermal and exergy efficiency, and lower heat transfer requirement. Then the thermodynamic analysis including energy and exergy analysis are carried out, and the effects of design parameters including high-pressure turbine inlet Temperature and pressure, low-pressure Evaporation Temperature on the performance of proposed system based on R601a are investigated. The results indicate that for a given high-pressure turbine inlet Temperature, the net power output of system firstly increases and then decreases as high-pressure turbine inlet pressure increases and reaches to the maximum at turbine inlet Temperature and pressure of 520 K and 8 MPa, and the net power output also shows a trend of firstly increasing and then decreasing with low-pressure Evaporation Temperature and reaches to the maximum at 330 K. Furthermore, five low global warming potential fluids are selected as working fluids of proposed system, and the results demonstrate that the R1233zd is the best candidate working fluid for proposed system. The maximum net power output of proposed system based on R1233zd reaches to 119.72 kW at the turbine inlet Temperature and pressure of 530 K and 10 MPa, low-pressure Evaporation Temperature of 330 K, which achieves net power output increment of 12.02% for the engine system. Finally, an exergy destruction analysis demonstrates that the heat transfer processes have less exergy destruction for proposed system based on R1233zd compared with other working fluids.
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parametric analysis and optimization of transcritical subcritical dual loop organic rankine cycle using zeotropic mixtures for engine waste heat recovery
Energy Conversion and Management, 2019Co-Authors: Liang-hui Zhi, Long-xiang Chen, Gang ZhaoAbstract:Abstract Dual-loop organic Rankine cycle is a great potential technology to recover engine waste heat for energy saving. Transcritical cycle can improve exergy efficiency of heat transfer process in the evaporator, and zeotropic mixtures furtherly can improve thermal match with heat source and sink. Thus, a transcritical-subcritical dual-loop organic Rankine cycle system using zeotropic mixtures is adopted for engine waste heat recovery, and system without and with regenerator is considered. The whole system is assumed in the steady state, R600a/R601a and R134a/R245fa mixtures are used as working fluid of transcritical and subcritical cycle, respectively. Parametric analysis and optimization about turbine inlet Temperature and pressure of high-Temperature loop, Evaporation Temperature of low-Temperature loop are carried out. According to the results, the designed parameters have great effect on performance of system, and for the system without and with regenerator, the optimal turbine inlet Temperature, pressure and Evaporation Temperature are 260 °C, 11 MPa, 85 °C and 250 °C, 10 MPa, 85 °C respectively. Moreover, the effects of components of mixtures on the performance of system are analyzed. The results demonstrate that system with zeotropic mixtures can significantly improve the performance of system. The system without regenerator using R600a/R601a (0.2/0.8) and R134a/R245fa (0.4/0.6) shows the maximum power output of 97.49 kW which is higher 5.48–20.00% than pure fluids, and system with regenerator using R600a/R601a (0.3/0.7) and R134a/R245fa (0.4/0.6) achieves the maximum power output of 97.95 kW, increment of 6.52–19.78% compared with using pure fluids. And the power output of engine can be improved by 9.79% and 9.83% for the system without and with regenerator, respectively. Furthermore, the exergy destruction analysis demonstrates that zeotropic mixtures can reduce heat transfer exergy destruction and total exergy destruction of system.
Zhili Sun - One of the best experts on this subject based on the ideXlab platform.
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energetic performance of transcritical co2 refrigeration cycles with mechanical subcooling using zeotropic mixture as refrigerant
Energy, 2018Co-Authors: Baomin Dai, Shengchun Liu, Zhili Sun, Mengjie Song, Qianru YangAbstract:Abstract Transcritical CO2 refrigeration cycle integrated with mechanical subcooling (MS) cycle operating with zeotropic mixture is proposed in this study, based on the concept of Lorenz cycle. An energetic model is developed and analyses are conducted in detail. A maximum overall coefficient of performance (COP) is achieved at the optimum discharge pressure and optimum subcooling degree. The maximum overall COP, optimum subcooling degree and discharge pressure are closely related to the Temperature glide of the mixtures. The energy efficiency of the transcritical CO2 refrigeration cycle can be efficiently improved, and the high pressure can be reduced when mixtures with proper Temperature glide are used as MS cycle refrigerant. Compared with pure R32, the overall COP is enhanced by 4.91%, and the discharge pressure decreases by 0.11 MPa at Evaporation Temperature of −5 °C and ambient Temperature of 35 °C when R32/R1234ze(Z) (55/45) is employed as MS refrigerant. The mixtures with proper Temperature glide are recommended. The thermal performance of the overall cycle can be enhanced more significantly for hot and warm climate regions, or relative low Evaporation Temperature applications, though a high subcooling degree is required to meet the optimum operation condition.
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thermodynamic performance analysis of co2 transcritical refrigeration cycle assisted with mechanical subcooling
Energy Procedia, 2017Co-Authors: Baomin Dai, Shengchun Liu, Zhili SunAbstract:Abstract The thermal performance of CO 2 transcrtical refrigeration cycle can be improved by cooling the CO 2 fluid exiting the gas cooler with an assisted vapor compression refrigeration cycle (auxiliary cycle). Thus, a thermodynamic analysis is performed to study the operation characteristics of the subcooling CO 2 transcritical refrigeration cycle. The results indicate that a maximum COP is achieved at the corresponding optimum discharge pressure and the optimum subcooling Temperature. The improvement in COP is more significant in the case of higher ambient Temperature and lower Evaporation Temperature, and the discharge pressure and Temperature can be obviously reduced. The auxiliary cycle refrigerant is screened and R717 performs with the highest COP. The CO 2 transcritical assisted with mechanical subcooling is recommended for the cases with higher ambient Temperature and lower Evaporation Temperature.
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thermodynamic performance evaluation of transcritical carbon dioxide refrigeration cycle integrated with thermoelectric subcooler and expander
Energy, 2017Co-Authors: Baomin Dai, Shengchun Liu, Kai Zhu, Zhili SunAbstract:New configurations of transcritical CO2 refrigeration cycle combined with a thermoelectric (TE) subcooler and an expander (TES+EXPHM and TES+EXPML) are proposed. The expander can operate between the high-pressure to the vessel pressure, or from vessel pressure to Evaporation pressure. A power system is utilized to balance and supply power to thermoelectric subcooler and compressor. Thermodynamic performance optimizations and analyses are presented. Comparisons are carried out with the BASE, EXPHM, EXPML, and TES cycles. The results show that the coefficient of performance (COP) improvement is more notable when the expander is installed between the liquid receiver and the evaporator. Maximum COP is obtained for the new cycles with a simultaneous optimization of discharge pressure and subcooling Temperature. The new proposed TES+EXPML cycle shows an excellent and steady performance than other cycles. It operates not only with the highest COP, but also the lowest discharge pressure. Under the working conditions of high gas cooler outlet Temperature or low Evaporation Temperature, the merits of COP improvement and discharge pressure reduction are more prominent. The new cycle is more suitable for the hot regions where the CO2 can not be sufficiently subcooled or the refrigerated space operates at low Evaporation Temperature.