The Experts below are selected from a list of 176148 Experts worldwide ranked by ideXlab platform
Gequn Shu - One of the best experts on this subject based on the ideXlab platform.
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a novel composition tunable combined cooling and Power Cycle using co2 based binary zeotropic mixture
Energy Conversion and Management, 2021Co-Authors: Xiaocun Sun, Hua Tian, Xuan Wang, Lingfeng Shi, Yonghao Zhang, Gequn ShuAbstract:Abstract Combined cooling and Power Cycle is a promising integrated system for its multi-function to simultaneously provide cooling and electricity. In order to alleviate temperature mismatch between working fluid and heat source/sink, combined cooling and Power Cycle coupled with zeotropic mixtures is put forward. Generally, a composition-fixed mixture cannot optimally match refrigeration sub-Cycle and Power sub-Cycle meanwhile, as these two sub-Cycles commonly have different performance regulation with various mixture composition. This research creatively proposes a novel composition tunable combined cooling and Power Cycle based on liquid separation condenser to realize different operation composition in two sub-Cycles. CO2 mixture is condensed and separated to two streams with various concentrations through liquid separation condenser, one with high CO2 concentration, the other has low CO2 concentration. According to disparate flowing directions of two streams, two diverse structures are proposed in this study. Results demonstrate that the introduction of composition adjustment can substantially promote the comprehensive performance of the combined Cycle. Taking a refrigeration truck as example, the new devised composition tunable combined Cycle with initial composition of CO2/R32 (0.500/0.500) can recover engine waste heat of the truck to generate Power in Power sub-Cycle with low CO2 concentration (0.494), and provide required cooling capacity (5.43 kW) in refrigeration sub-Cycle with high CO2 concentration (0.634). In addition to neutralizing compression work consumed in refrigeration sub-Cycle, the new proposed system can extra generate 12.2 kW Power, which is 5.18% higher than conventional composition-nonadjustable combined Cycle. Besides, the total heat transfer areas of three systems are similar.
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adaptive flow assignment for co2 transcritical Power Cycle ctpc an engine operational profile based off design study
Energy, 2021Co-Authors: Hua Tian, Lingfeng Shi, Jingyu Wang, Gequn ShuAbstract:Abstract CO2 transcritical Power Cycle (CTPC) is regarded as a promising energy conservation means in engine waste heat recovery. One of the most significant characteristics that should be noted is the considerable variation of waste heat caused by the variable engine operating conditions. Hence, the ability to follow the heat-sources variation should be enhanced to maximize its energy-saving potential. In this paper, an effective and efficient approach is proposed to deal with the different degree of variability of heat sources through a novel CTPC system configuration controlling the internal mass flow rate of the working fluid actively. An adaptive flow assignment strategy is also developed to enhance the ability to follow the heat-sources variation. A comprehensive input-optimization-output framework is constructed consisting of performances analysis under both design and off-design procedures. Results show that the CTPC adaptation to the heat-sources variation can be effectively improved with the proposed system and operational strategy. Promising energy-saving potential is found when the proposed system and strategy with adaptive flow assignment are implemented. The effective operating conditions are expanded from 8 to 22 points based on the engine operational profile, and the net generated Power is increased by 47.5% considering the European stationary Cycle (ESC) 13-mode.
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experimental comparison of dynamic responses of co2 transcritical Power Cycle systems used for engine waste heat recovery
Energy Conversion and Management, 2018Co-Authors: Gequn Shu, Guangdai Huang, Hua Tian, Xuan Wang, Peng Liu, Lingfeng ShiAbstract:Abstract CO2 transcritical Power Cycle (CTPC) is attractive to engine waste heat recovery (WHR) due to its advantages of miniaturization and unique thermophysical properties of its working fluid. Since there is no, if any, literature considering dynamic characteristics of CTPC systems, in current work, a series of dynamic tests has been conducted on a kW-scale CTPC test bench for engine WHR. Effects of mass flow rate and pressure ratio on dynamic responses are mainly focused and compared among four CTPC systems, i.e. a basic CTPC (B-CTPC), a CTPC with a recuperator (R-CTPC), a CTPC with a preheater (P-CTPC) and a CTPC with both a recuperator and a preheater (PR-CTPC). Dynamic characteristics are quantified by time constant and settling time. Results show that the PR-CTPC system has the fastest dynamic responses among these four layouts and the P-CTPC system responds more quickly than the R-CTPC system thanks to the gas–liquid heat exchange. Moreover, for the same layout, larger initial CO2 mass flow rate brings faster responses while initial system pressure ratio has little impacts on system dynamic responses. Also, dynamic characteristics of a basic CTPC system and a basic organic Rankine Cycle (ORC) system are compared. The ORC system adopts R123 as its working fluid. Results indicate the basic CTPC system responds almost four times faster than the basic R123-ORC system.
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multi objective optimization of the carbon dioxide transcritical Power Cycle with various configurations for engine waste heat recovery
Energy Conversion and Management, 2017Co-Authors: Hua Tian, Gequn Shu, Liwen Chang, Lingfeng ShiAbstract:Abstract In this paper, a systematic multi-objective optimization methodology is presented for the carbon dioxide transcritical Power Cycle with various configurations used in engine waste heat recovery to generate more Power efficiently and economically. The parametric optimization is performed for the maximum net Power output and exergy efficiency, as well as the minimum electricity production cost by using the genetic algorithm. The comparison of the optimization results shows the thermodynamic performance can be most enhanced by simultaneously adding the preheater and regenerator based on the basic configuration, and the highest net Power output and exergy efficiency are 25.89 kW and 40.95%, respectively. Meanwhile, the best economic performance corresponding to the lowest electricity production cost of 0.560$/kW·h is achieved with simply applying an additional regenerator. Moreover, a thorough decision making is conducted for a further screening of the obtained optimal solutions. A most preferred Pareto optimal solution or a representative subset of the Pareto optimal solutions is obtained according to additional subjective preferences while a referential optimal solution is also provided on the condition of no additional preference.
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dynamic modeling of co2 transcritical Power Cycle for waste heat recovery of gasoline engines
Energy Procedia, 2017Co-Authors: Gequn Shu, Hua Tian, Lingfeng Shi, Xuan WangAbstract:Abstract Waste heat recovery by means of a CO2 transcritical Power Cycle (CTPC) is capable of dealing with high-temperature heat sources and achieving miniaturization, which has become attractive in thermal management of engines. In current work, a dynamic model of CTPC is presented together with the results of dynamic response and system sensitivity with respect to the external inputs. Results show that pump rotational speed and temperature of exhaust gas and cooling water greatly influence system performance indicated by net Power output and thermal efficiency. While the influence of mass flow rate is less. Moreover, system is more sensitive when input parameters make the system condition severe. This preliminary research will be useful for future system-level design and control studies.
Lingfeng Shi - One of the best experts on this subject based on the ideXlab platform.
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a novel composition tunable combined cooling and Power Cycle using co2 based binary zeotropic mixture
Energy Conversion and Management, 2021Co-Authors: Xiaocun Sun, Hua Tian, Xuan Wang, Lingfeng Shi, Yonghao Zhang, Gequn ShuAbstract:Abstract Combined cooling and Power Cycle is a promising integrated system for its multi-function to simultaneously provide cooling and electricity. In order to alleviate temperature mismatch between working fluid and heat source/sink, combined cooling and Power Cycle coupled with zeotropic mixtures is put forward. Generally, a composition-fixed mixture cannot optimally match refrigeration sub-Cycle and Power sub-Cycle meanwhile, as these two sub-Cycles commonly have different performance regulation with various mixture composition. This research creatively proposes a novel composition tunable combined cooling and Power Cycle based on liquid separation condenser to realize different operation composition in two sub-Cycles. CO2 mixture is condensed and separated to two streams with various concentrations through liquid separation condenser, one with high CO2 concentration, the other has low CO2 concentration. According to disparate flowing directions of two streams, two diverse structures are proposed in this study. Results demonstrate that the introduction of composition adjustment can substantially promote the comprehensive performance of the combined Cycle. Taking a refrigeration truck as example, the new devised composition tunable combined Cycle with initial composition of CO2/R32 (0.500/0.500) can recover engine waste heat of the truck to generate Power in Power sub-Cycle with low CO2 concentration (0.494), and provide required cooling capacity (5.43 kW) in refrigeration sub-Cycle with high CO2 concentration (0.634). In addition to neutralizing compression work consumed in refrigeration sub-Cycle, the new proposed system can extra generate 12.2 kW Power, which is 5.18% higher than conventional composition-nonadjustable combined Cycle. Besides, the total heat transfer areas of three systems are similar.
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adaptive flow assignment for co2 transcritical Power Cycle ctpc an engine operational profile based off design study
Energy, 2021Co-Authors: Hua Tian, Lingfeng Shi, Jingyu Wang, Gequn ShuAbstract:Abstract CO2 transcritical Power Cycle (CTPC) is regarded as a promising energy conservation means in engine waste heat recovery. One of the most significant characteristics that should be noted is the considerable variation of waste heat caused by the variable engine operating conditions. Hence, the ability to follow the heat-sources variation should be enhanced to maximize its energy-saving potential. In this paper, an effective and efficient approach is proposed to deal with the different degree of variability of heat sources through a novel CTPC system configuration controlling the internal mass flow rate of the working fluid actively. An adaptive flow assignment strategy is also developed to enhance the ability to follow the heat-sources variation. A comprehensive input-optimization-output framework is constructed consisting of performances analysis under both design and off-design procedures. Results show that the CTPC adaptation to the heat-sources variation can be effectively improved with the proposed system and operational strategy. Promising energy-saving potential is found when the proposed system and strategy with adaptive flow assignment are implemented. The effective operating conditions are expanded from 8 to 22 points based on the engine operational profile, and the net generated Power is increased by 47.5% considering the European stationary Cycle (ESC) 13-mode.
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experimental comparison of dynamic responses of co2 transcritical Power Cycle systems used for engine waste heat recovery
Energy Conversion and Management, 2018Co-Authors: Gequn Shu, Guangdai Huang, Hua Tian, Xuan Wang, Peng Liu, Lingfeng ShiAbstract:Abstract CO2 transcritical Power Cycle (CTPC) is attractive to engine waste heat recovery (WHR) due to its advantages of miniaturization and unique thermophysical properties of its working fluid. Since there is no, if any, literature considering dynamic characteristics of CTPC systems, in current work, a series of dynamic tests has been conducted on a kW-scale CTPC test bench for engine WHR. Effects of mass flow rate and pressure ratio on dynamic responses are mainly focused and compared among four CTPC systems, i.e. a basic CTPC (B-CTPC), a CTPC with a recuperator (R-CTPC), a CTPC with a preheater (P-CTPC) and a CTPC with both a recuperator and a preheater (PR-CTPC). Dynamic characteristics are quantified by time constant and settling time. Results show that the PR-CTPC system has the fastest dynamic responses among these four layouts and the P-CTPC system responds more quickly than the R-CTPC system thanks to the gas–liquid heat exchange. Moreover, for the same layout, larger initial CO2 mass flow rate brings faster responses while initial system pressure ratio has little impacts on system dynamic responses. Also, dynamic characteristics of a basic CTPC system and a basic organic Rankine Cycle (ORC) system are compared. The ORC system adopts R123 as its working fluid. Results indicate the basic CTPC system responds almost four times faster than the basic R123-ORC system.
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multi objective optimization of the carbon dioxide transcritical Power Cycle with various configurations for engine waste heat recovery
Energy Conversion and Management, 2017Co-Authors: Hua Tian, Gequn Shu, Liwen Chang, Lingfeng ShiAbstract:Abstract In this paper, a systematic multi-objective optimization methodology is presented for the carbon dioxide transcritical Power Cycle with various configurations used in engine waste heat recovery to generate more Power efficiently and economically. The parametric optimization is performed for the maximum net Power output and exergy efficiency, as well as the minimum electricity production cost by using the genetic algorithm. The comparison of the optimization results shows the thermodynamic performance can be most enhanced by simultaneously adding the preheater and regenerator based on the basic configuration, and the highest net Power output and exergy efficiency are 25.89 kW and 40.95%, respectively. Meanwhile, the best economic performance corresponding to the lowest electricity production cost of 0.560$/kW·h is achieved with simply applying an additional regenerator. Moreover, a thorough decision making is conducted for a further screening of the obtained optimal solutions. A most preferred Pareto optimal solution or a representative subset of the Pareto optimal solutions is obtained according to additional subjective preferences while a referential optimal solution is also provided on the condition of no additional preference.
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dynamic modeling of co2 transcritical Power Cycle for waste heat recovery of gasoline engines
Energy Procedia, 2017Co-Authors: Gequn Shu, Hua Tian, Lingfeng Shi, Xuan WangAbstract:Abstract Waste heat recovery by means of a CO2 transcritical Power Cycle (CTPC) is capable of dealing with high-temperature heat sources and achieving miniaturization, which has become attractive in thermal management of engines. In current work, a dynamic model of CTPC is presented together with the results of dynamic response and system sensitivity with respect to the external inputs. Results show that pump rotational speed and temperature of exhaust gas and cooling water greatly influence system performance indicated by net Power output and thermal efficiency. While the influence of mass flow rate is less. Moreover, system is more sensitive when input parameters make the system condition severe. This preliminary research will be useful for future system-level design and control studies.
Hua Tian - One of the best experts on this subject based on the ideXlab platform.
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a novel composition tunable combined cooling and Power Cycle using co2 based binary zeotropic mixture
Energy Conversion and Management, 2021Co-Authors: Xiaocun Sun, Hua Tian, Xuan Wang, Lingfeng Shi, Yonghao Zhang, Gequn ShuAbstract:Abstract Combined cooling and Power Cycle is a promising integrated system for its multi-function to simultaneously provide cooling and electricity. In order to alleviate temperature mismatch between working fluid and heat source/sink, combined cooling and Power Cycle coupled with zeotropic mixtures is put forward. Generally, a composition-fixed mixture cannot optimally match refrigeration sub-Cycle and Power sub-Cycle meanwhile, as these two sub-Cycles commonly have different performance regulation with various mixture composition. This research creatively proposes a novel composition tunable combined cooling and Power Cycle based on liquid separation condenser to realize different operation composition in two sub-Cycles. CO2 mixture is condensed and separated to two streams with various concentrations through liquid separation condenser, one with high CO2 concentration, the other has low CO2 concentration. According to disparate flowing directions of two streams, two diverse structures are proposed in this study. Results demonstrate that the introduction of composition adjustment can substantially promote the comprehensive performance of the combined Cycle. Taking a refrigeration truck as example, the new devised composition tunable combined Cycle with initial composition of CO2/R32 (0.500/0.500) can recover engine waste heat of the truck to generate Power in Power sub-Cycle with low CO2 concentration (0.494), and provide required cooling capacity (5.43 kW) in refrigeration sub-Cycle with high CO2 concentration (0.634). In addition to neutralizing compression work consumed in refrigeration sub-Cycle, the new proposed system can extra generate 12.2 kW Power, which is 5.18% higher than conventional composition-nonadjustable combined Cycle. Besides, the total heat transfer areas of three systems are similar.
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adaptive flow assignment for co2 transcritical Power Cycle ctpc an engine operational profile based off design study
Energy, 2021Co-Authors: Hua Tian, Lingfeng Shi, Jingyu Wang, Gequn ShuAbstract:Abstract CO2 transcritical Power Cycle (CTPC) is regarded as a promising energy conservation means in engine waste heat recovery. One of the most significant characteristics that should be noted is the considerable variation of waste heat caused by the variable engine operating conditions. Hence, the ability to follow the heat-sources variation should be enhanced to maximize its energy-saving potential. In this paper, an effective and efficient approach is proposed to deal with the different degree of variability of heat sources through a novel CTPC system configuration controlling the internal mass flow rate of the working fluid actively. An adaptive flow assignment strategy is also developed to enhance the ability to follow the heat-sources variation. A comprehensive input-optimization-output framework is constructed consisting of performances analysis under both design and off-design procedures. Results show that the CTPC adaptation to the heat-sources variation can be effectively improved with the proposed system and operational strategy. Promising energy-saving potential is found when the proposed system and strategy with adaptive flow assignment are implemented. The effective operating conditions are expanded from 8 to 22 points based on the engine operational profile, and the net generated Power is increased by 47.5% considering the European stationary Cycle (ESC) 13-mode.
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dynamic performance of the transcritical Power Cycle using co2 based binary zeotropic mixtures for truck engine waste heat recovery
Energy, 2020Co-Authors: Rui Wang, Xiaoya Li, Hua Tian, Xuan Wang, Zhiqiang XuAbstract:Abstract CO2 transcritical Power Cycle (CTPC) technology has received substantial interest and attention for use in waste heat recovery, but its high operating pressure and low condensing temperature restrict its wide application. CO2-based binary zeotropic mixtures are considered a promising solution. Therefore, a CTPC system dynamic model with different CO2 mixtures as the working fluids in the context of engine waste heat recovery is examined using Simulink simulation to understand the effects of different mixtures and composition ratios on system performance in various working conditions. A system dynamic model of the system is thoroughly validated against experimental data, and the results are reasonably consistent. Based on these foundations, the dynamic response of the CTPC system with CO2 mixtures of different proportions and components is compared and analysed. The results show that the system responds faster when the proportion of CO2 is greater. The proportion of refrigerant also affects the optimal net Power output and thermal efficiency. The preliminary results presented in this paper will be helpful for future design of CO2 transcritical Power Cycles and the development of control strategies for these systems.
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experimental comparison of dynamic responses of co2 transcritical Power Cycle systems used for engine waste heat recovery
Energy Conversion and Management, 2018Co-Authors: Gequn Shu, Guangdai Huang, Hua Tian, Xuan Wang, Peng Liu, Lingfeng ShiAbstract:Abstract CO2 transcritical Power Cycle (CTPC) is attractive to engine waste heat recovery (WHR) due to its advantages of miniaturization and unique thermophysical properties of its working fluid. Since there is no, if any, literature considering dynamic characteristics of CTPC systems, in current work, a series of dynamic tests has been conducted on a kW-scale CTPC test bench for engine WHR. Effects of mass flow rate and pressure ratio on dynamic responses are mainly focused and compared among four CTPC systems, i.e. a basic CTPC (B-CTPC), a CTPC with a recuperator (R-CTPC), a CTPC with a preheater (P-CTPC) and a CTPC with both a recuperator and a preheater (PR-CTPC). Dynamic characteristics are quantified by time constant and settling time. Results show that the PR-CTPC system has the fastest dynamic responses among these four layouts and the P-CTPC system responds more quickly than the R-CTPC system thanks to the gas–liquid heat exchange. Moreover, for the same layout, larger initial CO2 mass flow rate brings faster responses while initial system pressure ratio has little impacts on system dynamic responses. Also, dynamic characteristics of a basic CTPC system and a basic organic Rankine Cycle (ORC) system are compared. The ORC system adopts R123 as its working fluid. Results indicate the basic CTPC system responds almost four times faster than the basic R123-ORC system.
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preliminary tests on dynamic characteristics of a co2 transcritical Power Cycle using an expansion valve in engine waste heat recovery
Energy, 2017Co-Authors: Xiaoya Li, Guangdai Huang, Hua Tian, Tianyu ChenAbstract:CO2 has been proposed recently as working fluid for Power generation from low grade heat sources due to its good thermodynamic properties and natural feature. CO2 transcritical Power Cycle (CTPC) is suitable for engine waste heat recovery since it has the advantage of miniaturization and better temperature matching. In this research, a constructed test bench of CTPC using an expansion valve was dynamically tested to recover exhaust energy from a heavy-duty diesel engine. CTPC system dynamic responses to mass flow rate and pressure ratio are presented in detail. Based on dynamic characteristics, a steady state detection method is proposed, which will give reference for experiments of waste heat recovery systems and make it more time-saving and economical. Results show that the CTPC system possesses good dynamic characteristics and the average transition time is less than 62 s. System high pressure or expander inlet pressure could be chosen as a representative indicator for steady state detection and experiment guidance. In addition, the test set-up is of high-accuracy and reliable after examining the heat balances over the heat exchangers and error propagation of the measurement uncertainties. CTPC is applicable for engine waste heat recovery although more efficiency improvements are needed.
Yunhan Xiao - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic analysis of a novel dual expansion coal fueled direct fired supercritical carbon dioxide Power Cycle
Applied Energy, 2018Co-Authors: Yongming Zhao, Lifeng Zhao, Bo Wang, Shijie Zhang, Yunhan XiaoAbstract:Abstract The direct-fired supercritical CO2 Power Cycle not only has the potential of reaching high efficiency but also has inherent ability to capture almost all of the combustion derived CO2. A novel direct-fired supercritical CO2 Power Cycle layout is proposed in this paper, using the syngas produced by coal gasification as the fuel. The proposed Cycle layout is specially designed to facilitate heat integration between the Power Cycle, the fuel conversion process and other auxiliary subsystems. Heat from the air compressor intercooler and the low temperature syngas is introduced to the regenerator to correct its imbalanced heat exchange, a typical problem of the supercritical CO2 Power Cycle that is caused by the abrupt physical property variation. Design considerations of the proposed Cycle layout are discussed in detail. The result shows that the net efficiency is 42.1%, with near-zero CO2 emissions. The proposed Cycle layout is then further modified by integrating more heat from the oxygen compressors and the syngas compressor, which reduces the hot end temperature difference of the regenerator to less than 10 °C and increases the net efficiency to 43.7%. Heat integration through novel Cycle layout has been proved essential to guarantee the high efficiency of the supercritical CO2 Power Cycle.
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parametric study of a direct fired supercritical carbon dioxide Power Cycle coupled to coal gasification process
Energy Conversion and Management, 2018Co-Authors: Yongming Zhao, Bo Wang, Yunhan XiaoAbstract:Abstract The direct-fired supercritical carbon dioxide Power Cycle not only has the potential of reaching high efficiency, but also achieves near 100% carbon capture in a more inherent and natural manner. A conceptual flow sheet of the direct-fired supercritical carbon dioxide Power Cycle that is coupled to the coal gasification process is built in this study. A detailed turbine cooling model is added to better assess the performance of the Power plant. To investigate the effect of key Cycle variables on the Cycle performance and determine potential chances for efficiency improvement, a parametric study is conducted in this paper. The result shows that the turbine inlet temperature and turbine outlet pressure have significant effect on the Cycle efficiency while the effect of the turbine inlet pressure is minor. The Cycle efficiency is susceptible to the inlet condition of the carbon dioxide pump, which is the weakness of the supercritical carbon dioxide Power Cycle. The flow sheet and some of the Cycle parameters are modified based on the conclusions drawn from the parametric study. The net efficiency of the Power plant is calculated to be 38.87% (on lower heating value basis) at a turbine inlet temperature of 1200 °C, while capturing most of the carbon dioxide derived from combustion.
Xuan Wang - One of the best experts on this subject based on the ideXlab platform.
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a novel composition tunable combined cooling and Power Cycle using co2 based binary zeotropic mixture
Energy Conversion and Management, 2021Co-Authors: Xiaocun Sun, Hua Tian, Xuan Wang, Lingfeng Shi, Yonghao Zhang, Gequn ShuAbstract:Abstract Combined cooling and Power Cycle is a promising integrated system for its multi-function to simultaneously provide cooling and electricity. In order to alleviate temperature mismatch between working fluid and heat source/sink, combined cooling and Power Cycle coupled with zeotropic mixtures is put forward. Generally, a composition-fixed mixture cannot optimally match refrigeration sub-Cycle and Power sub-Cycle meanwhile, as these two sub-Cycles commonly have different performance regulation with various mixture composition. This research creatively proposes a novel composition tunable combined cooling and Power Cycle based on liquid separation condenser to realize different operation composition in two sub-Cycles. CO2 mixture is condensed and separated to two streams with various concentrations through liquid separation condenser, one with high CO2 concentration, the other has low CO2 concentration. According to disparate flowing directions of two streams, two diverse structures are proposed in this study. Results demonstrate that the introduction of composition adjustment can substantially promote the comprehensive performance of the combined Cycle. Taking a refrigeration truck as example, the new devised composition tunable combined Cycle with initial composition of CO2/R32 (0.500/0.500) can recover engine waste heat of the truck to generate Power in Power sub-Cycle with low CO2 concentration (0.494), and provide required cooling capacity (5.43 kW) in refrigeration sub-Cycle with high CO2 concentration (0.634). In addition to neutralizing compression work consumed in refrigeration sub-Cycle, the new proposed system can extra generate 12.2 kW Power, which is 5.18% higher than conventional composition-nonadjustable combined Cycle. Besides, the total heat transfer areas of three systems are similar.
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dynamic performance of the transcritical Power Cycle using co2 based binary zeotropic mixtures for truck engine waste heat recovery
Energy, 2020Co-Authors: Rui Wang, Xiaoya Li, Hua Tian, Xuan Wang, Zhiqiang XuAbstract:Abstract CO2 transcritical Power Cycle (CTPC) technology has received substantial interest and attention for use in waste heat recovery, but its high operating pressure and low condensing temperature restrict its wide application. CO2-based binary zeotropic mixtures are considered a promising solution. Therefore, a CTPC system dynamic model with different CO2 mixtures as the working fluids in the context of engine waste heat recovery is examined using Simulink simulation to understand the effects of different mixtures and composition ratios on system performance in various working conditions. A system dynamic model of the system is thoroughly validated against experimental data, and the results are reasonably consistent. Based on these foundations, the dynamic response of the CTPC system with CO2 mixtures of different proportions and components is compared and analysed. The results show that the system responds faster when the proportion of CO2 is greater. The proportion of refrigerant also affects the optimal net Power output and thermal efficiency. The preliminary results presented in this paper will be helpful for future design of CO2 transcritical Power Cycles and the development of control strategies for these systems.
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experimental comparison of dynamic responses of co2 transcritical Power Cycle systems used for engine waste heat recovery
Energy Conversion and Management, 2018Co-Authors: Gequn Shu, Guangdai Huang, Hua Tian, Xuan Wang, Peng Liu, Lingfeng ShiAbstract:Abstract CO2 transcritical Power Cycle (CTPC) is attractive to engine waste heat recovery (WHR) due to its advantages of miniaturization and unique thermophysical properties of its working fluid. Since there is no, if any, literature considering dynamic characteristics of CTPC systems, in current work, a series of dynamic tests has been conducted on a kW-scale CTPC test bench for engine WHR. Effects of mass flow rate and pressure ratio on dynamic responses are mainly focused and compared among four CTPC systems, i.e. a basic CTPC (B-CTPC), a CTPC with a recuperator (R-CTPC), a CTPC with a preheater (P-CTPC) and a CTPC with both a recuperator and a preheater (PR-CTPC). Dynamic characteristics are quantified by time constant and settling time. Results show that the PR-CTPC system has the fastest dynamic responses among these four layouts and the P-CTPC system responds more quickly than the R-CTPC system thanks to the gas–liquid heat exchange. Moreover, for the same layout, larger initial CO2 mass flow rate brings faster responses while initial system pressure ratio has little impacts on system dynamic responses. Also, dynamic characteristics of a basic CTPC system and a basic organic Rankine Cycle (ORC) system are compared. The ORC system adopts R123 as its working fluid. Results indicate the basic CTPC system responds almost four times faster than the basic R123-ORC system.
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dynamic modeling of co2 transcritical Power Cycle for waste heat recovery of gasoline engines
Energy Procedia, 2017Co-Authors: Gequn Shu, Hua Tian, Lingfeng Shi, Xuan WangAbstract:Abstract Waste heat recovery by means of a CO2 transcritical Power Cycle (CTPC) is capable of dealing with high-temperature heat sources and achieving miniaturization, which has become attractive in thermal management of engines. In current work, a dynamic model of CTPC is presented together with the results of dynamic response and system sensitivity with respect to the external inputs. Results show that pump rotational speed and temperature of exhaust gas and cooling water greatly influence system performance indicated by net Power output and thermal efficiency. While the influence of mass flow rate is less. Moreover, system is more sensitive when input parameters make the system condition severe. This preliminary research will be useful for future system-level design and control studies.
