The Experts below are selected from a list of 624 Experts worldwide ranked by ideXlab platform
Li Zhao - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic performance comparison of organic rankine cycle between Zeotropic Mixtures and pure fluids under open heat source
Energy Conversion and Management, 2018Co-Authors: Yunho Hwang, Li Zhao, Shuai Deng, Dongpeng ZhaoAbstract:Abstract Zeotropic Mixtures have been widely investigated for the development of Organic Rankine Cycle (ORC) as an alternative option for pure fluids. However, few Zeotropic Mixtures have been applied to the ORC in practical engineering. Therefore, a nature question is that whether Zeotropic Mixture has better thermodynamic performance of ORC than pure fluid. In this contribution, a comprehensive performance comparison between Zeotropic Mixtures and pure fluids is conducted via cycle simulation for the basic ORC and recuperative ORC driven by open heat source. In the simulation, a certain range of mass flow rate of cooling water is considered as the condition of heat sink, and Mixtures R600a/R601a, R600a/R227ea are employed. Performances of these Mixtures are optimized and compared with those of their constituents from the points of first and second laws. It can be concluded that Zeotropic Mixture may have lower cycle performance than pure fluid. For the optimal Mixture R600a/R601a (0.1/0.9, mass fraction) with the highest net power of basic ORC, the cycle efficiency 8.18% is lower than that of R601a 8.24%. Although Zeotropic Mixture generally has lower temperature differences in the evaporator and condenser, the exergy losses of these heat exchangers are not certain to be reduced. In the basic ORC, the exergy efficiency 34.61% of optimal R600a/R227ea (0.2/0.8, mass fraction) is lower than that of R227ea 35.68%. Furthermore, the introduction of internal heat exchanger (IHE) can enhance the output work and cycle efficiency. The exergy loss in the evaporator and condenser can be reduced by IHE. The Mixture with a larger temperature glide can generally recover more heat in the IHE.
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how to approach carnot cycle via Zeotropic working fluid research methodology and case study
Energy, 2018Co-Authors: Shuai Deng, Ying Zhang, Li ZhaoAbstract:Abstract A great amount of researches on thermodynamic cycles have been active in recent years, such as ORC (organic Rankine cycle), Kalina cycle, et al. However, the ultimate aim of such researches, which could even be traced back to more than one century ago, has not changed with a tireless pursuing to Carnot cycle. In exiting researches, the working fluid, as a medium for energy conversion, is commonly considered to play an important role in the thermodynamic cycle: (1) relative to ideal cycle, most of actual power cycles in the engineering field cannot operate without working fluid; (2) energy efficiency, considering the analysis of second-law efficiency, of actual cycle has a significant decrease due to the introduction of working fluid. Thus, working fluid is a hot spot in the research of thermodynamic cycle in recent years. Zeotropic Mixture, which commonly consists of two or more pure working fluids, has flexibility in thermos-physical properties with a possible potential to enhance the cycle performance. The effects of thermos-physical properties of Zeotropic Mixture should be considered when determining the cycle structure and the design of components. This paper presents a novel construction method of thermodynamic cycle based on the Zeotropic Mixture. By adding the thermodynamic coordinate of working fluid, a 3D cycle diagram based on the traditional temperature and entropy cycle diagram is applied for performance analysis of cycle. According the proposed construction method, a baseline cycle, composed by ORC sub-system and compositions regulating sub-system, is put forward and available compositions regulating techniques for such cycle are discussed as well. Finally, a representative case is described briefly and the features are summarized. This work provides a new methodology view to guide researchers in energy-efficient design of thermodynamic cycles.
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2d numerical study on flow boiling of Zeotropic Mixture isobutane pentane in internal countercurrent flow system
Applied Thermal Engineering, 2017Co-Authors: Jianyuan Zhang, Junjiang Bao, Shuai Deng, Jue Wen, Li ZhaoAbstract:Abstract Based on effective diffusion model and volume of fluid (VOF) model, the evaporation process of Zeotropic Mixture isobutane/pentane in an inclined straight flow channel is investigated. The physical properties of Mixture and the source terms in the continuity, momentum, energy and species conservation equations are coded through User Defined Functions (UDF). The simulation results show that the evaporation rate first increases and then decreases from the entrance of vapor to the exit. The interaction of shearing force is relatively stronger at the top and bottom walls than that of near the interface. The velocity boundary layer is similar to the temperature boundary layer. The evaporation rate of pentane is higher than that of isobutane in the unit of kg/s because of its higher molecular weight. In addition, according to available experimental data, another physical model is built to validate the effective diffusion model. The mean absolute percentage error (MAPE) of heat transfer coefficient for all the four cases is 6.9%. This statistical indicator shows that the effective diffusion model proposed by Banerjee can reasonably describe the flow boiling of Zeotropic Mixture isobutane/pentane.
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Zeotropic Mixture and Organic Ranking Cycle
Lecture Notes in Energy, 2016Co-Authors: Li ZhaoAbstract:The Intergovernmental Panel on Climate Change (IPCC) reported in 2014 that scientists were more than 95 % certain that most of global warming is caused by increasing concentrations of greenhouse gases [1]. Since the Second Industrial Revolution, steam Rankine cycle driven by fossil fuel has become the dominant method of power supply, and the accelerated consumption of fossil fuel has increased the amount of greenhouse gases in the atmosphere, leading to increased radiative forcing from CO2, methane and nitrous oxide.
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experimental research on the influence of system parameters on the composition shift for Zeotropic Mixture isobutane pentane in a system occurring phase change
Energy Conversion and Management, 2016Co-Authors: Li ZhaoAbstract:Abstract Zeotropic Mixture can improve the performance of the thermodynamic cycle ascribed to the better temperature match during the heat transfer process with the characteristics of temperature glide during evaporation and condensing processes. Another characteristic of Zeotropic Mixture is composition shift. Composition shift means that the circulating composition and charge composition is different and is mainly caused by the two-phase hold-up and different solubility in lubricating oil. The existence of composition shift will affect the design and operation of thermodynamic system. The previous study gave little information about the influence of system parameters on the composition shift in a system occurring phase change. This paper mainly discuss the influence of system parameters on the composition shift for Zeotropic Mixture in a system occurring phase change as well as the validation of the linear relationship between the circulating composition and the charge composition and the inverse proportion relationship between the circulating composition and the charge mass found based on our previous theory study (Zhao and Bao, 2014). With isobutane and pentane as the research object, the impact of the key system parameters (hot water temperature, mass flow rate of hot water, feed pump frequency, cold water temperature and evaporator length) on composition shift are experimentally carried out. The results show that when the hot water temperature, mass flow rate of hot water and evaporator length increase and cold water temperature decreases, circulating composition will increase. For feed pump frequency, when the outlet of evaporator is in two phase region, and circulating composition will decreased with the increase of feed pump frequency; while the outlet of evaporator is in a state of overheating, circulating composition will increase as the feed pump frequency rises. The linear relationship between the circulating composition and the charge composition and the inverse proportion relationship between the circulating composition and the charge mass are verified by the experiment.
Gang Yan - One of the best experts on this subject based on the ideXlab platform.
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theoretical study on a modified heat pump cycle with Zeotropic Mixture r32 r290 for district heating in cold region
Applied Thermal Engineering, 2019Co-Authors: Chaochao Fan, Gang YanAbstract:Abstract This paper proposes an ejector enhanced internal auto-cascade heat pump cycle (EIHP) with Zeotropic Mixture R32/R290 for district heating in cold region. The internal auto-cascade and ejector techniques are applied for enhancing the system performance. Performances of the EIHP are investigated by using a developed thermodynamic model. The simulation results indicate that as the evaporator outlet temperature ranges −25 °C to 5 °C, EIHP yields 19–9% higher COP and 37–12% higher volumetric heating capacity over the conventional heat pump cycle (CHP) at a fixed condenser outlet temperature of 60 °C. Moreover, to evaluate the system performance in detail, the other critical parameters are investigated including condenser outlet temperature, refrigerant mass fraction of R32, ejector performance and so on. Generally, the EIHP system can obtain a significant performance enhancement for district heating applications.
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thermodynamic analysis of a modified solar assisted ejector compression heat pump cycle with Zeotropic Mixture r290 r600a
Applied Thermal Engineering, 2019Co-Authors: Chaochao Fan, Gang YanAbstract:Abstract This paper proposes a modified solar assisted ejector-compression heat pump cycle with Zeotropic Mixture R290/R600a (MHP) for water heater applications, which could efficiently utilize both the air source energy and solar energy. Depending on the solar radiation intensity, MHP contains two operation modes, i.e., Mode-A/-B for high/low solar radiation intensity conditions, respectively. In MHP, the use of Zeotropic Mixture ensures a better matching characteristic between the temperature variations of the refrigerant and water in the condenser due to its temperature glide feature. The simulation results show that compared with the conventional heat pump cycle (CHP), as the condenser inlet saturated temperature ranges 45–80 °C, MHP-A yields 28–33% higher COP and 22–47% higher volumetric heating capacity at a fixed evaporator outlet temperature of 10 °C. And increasing the solar radiation intensity is beneficial to the performance improvement of MHP-A. Additionally, in order to display the cycle characteristic, the effects of other critical parameters are studied in detail, including the evaporator outlet temperature, Mixture composition, heat source capacity ratio, etc.
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performance analysis of a modified Zeotropic Mixture r290 r600 refrigeration cycle with internal subcooler for freezer applications
Applied Thermal Engineering, 2016Co-Authors: Qi Chen, Gang YanAbstract:Abstract This study presents a modified vapor compression refrigeration cycle (MVRC) using Zeotropic Mixture R290/R600 for freezers. In the MVRC, an internal subcooler with additional bypass tube is introduced to enhance the overall system performance. Energetic and exergetic analysis methods are introduced to theoretically evaluate the system operating performance, and compared with the performance of the traditional vapor compression refrigeration cycle (TVRC). The results show that the MVRC yields higher refrigeration coefficient of performance (COP), volumetric cooling capacity and exergy efficiency than the TVRC. Under the given condition, the COP, volumetric cooling capacity and exergy efficiency of MVRC could be improved by up to an average of 8.9%, 12.4% and 10.4%. Moreover, COP and exergy efficiency of MVRC increases with the rising bypass coefficient of the refrigerant. The performance characteristics of the proposed novel cycle demonstrate the potential advantages for application in freezer systems.
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thermodynamic analysis on a modified ejector expansion refrigeration cycle with Zeotropic Mixture r290 r600a for freezers
Energy, 2016Co-Authors: Gang Yan, Tao BaiAbstract:This study presents a modified ejector expansion cycle with Zeotropic Mixtures (R290/R600a) for freezers, in which an ejector and a phase-separator are employed to enhance the cycle performance. Energetic and exergetic methods are used to theoretically investigate the system operating characteristics. In addition, comparative research among the modified cycle, conventional ejector expansion cycle and basic throttling cycle is carried out. The results demonstrate that the modified cycle exhibits higher refrigeration COP (coefficient of performance), volumetric refrigeration capacity and system exergy efficiency than conventional ejector expansion cycle and basic throttling cycle. Under the given operation conditions, the system performance improvements of the modified cycle in terms of the COP, refrigeration capacity and system exergy efficiency over the basic throttling cycle could reach about 56.0%, 4.5% and 77.7%, respectively. The performance characteristics of the proposed cycle show its potential practical advantages in freezer applications.
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solar assisted auto cascade heat pump cycle with Zeotropic Mixture r32 r290 for small water heaters
Renewable Energy, 2015Co-Authors: Gang YanAbstract:Abstract In this study, a novel solar-assisted auto-cascade heat pump cycle (SAHPC) operating with the Zeotropic Mixture of R32/R290 for small water heaters is proposed. In the SAHPC system, a cascade heat exchanger (CHEX) associated with a phase separator is used to achieve auto cascade cycle and enhance the overall system performance. The performances of the SAHPC are evaluated by using the developed mathematical model, and then compared with the conventional air-sourced heat pump cycle (CAHPC). Simulation results show the SAHPC has 4.23–9.85% and 4.37–9.68% improvements in COP and volumetric heating capacity compared with those of the CAHPC, respectively, under the same operating conditions. However, the improvement of performance of this novel cycle largely depends on the absorbing heat ratio and the Zeotropic composition. It is expected that this new cycle will be beneficial to developing dual-source coupled heat pump applications.
Jian Liu - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic analysis of a novel dual temperature air source heat pump combined ejector with Zeotropic Mixture r1270 r600a
Energy Conversion and Management, 2020Co-Authors: Jian Liu, Zhang LinAbstract:Abstract This study presents a novel dual-temperature air-source heat pump system with an ejector using Zeotropic Mixture R1270/R600a. The system provides a high-temperature heat source (around 60 °C hot water) and low-temperature heat source (around 35 °C hot water) respectively. The system improves its performance via the application of an ejector. The mathematical model based on the energetic method is established to analyze and compare the performance between the novel dual-temperature air-source heat pump system (DTHP-II and DTHP-III) and the conventional dual-temperature air-source heat pump system (DTHP-I), including the heating coefficient of performance (COPh), the heating capacity per volumes (qv) and the second law efficiency (ηII). The results show that the DTHP-II and DTHP-III systems significantly outperform the DTHP-I system under various operation conditions due to the application of ejector. Compared with the DTHP-I, the COPh, qv and η = 2 \ * ROMAN II of DTHP-II are improved by 20.2%, 19.5% and 18.2%. Again, compared with the DTHP-II, the COPh, qv and ηII of DTHP-III are improved by 36.5%, 37.2% and 38.5% respectively. The heat source temperature affects heat pump system performance significantly. And the DTHP-II and DTHP-III save more energy under the demand for a higher temperature source. Mass fraction of R600a in the Zeotropic Mixture (z) and the high low-temperature heat source load ratio (LR) show a noticeable effect on the system performance, which should be given attention when designing the DTHP system.
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experimental study of a novel double temperature chiller based on r32 r236fa
Energy Conversion and Management, 2016Co-Authors: Jian Liu, Xiaohui She, Xiaosong Zhang, Liang Man, Wei ZhouAbstract:Abstract A novel double-temperature chiller with Zeotropic Mixture R32/R236fa is proposed in this paper, and chilled water with two different temperatures is produced, such as low temperature water ( T L , out = 7 °C) and high temperature water ( T H , out = 16 °C). An experimental setup is established to test the performance of the chiller. Effects of mass fraction of R32 in Mixture R32/R236fa ( M (R32)), T L , out , T H , out and the heat transfer media flow rate on the performance of the chiller are studied. When T H , out is 18 °C, T L , out is 8 °C and M (R32) is 0.6, COP and refrigerating capacity are 4.11 and 4.42 kW, respectively. COP and refrigerating capacity increase as M (R32) increases. Exhausting pressure of the chiller increases with the increase of M (R32). As M (R32) is 0.6, exhausting pressure is about 1.95 MPa. Compression ratio decreases with the increase of M (R32). When M (R32) increases from 0.3 to 0.6, the compression ratio decreases from 3.0 to 2.9.
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performance analysis of a novel double temperature chilling water unit using large temperature glide Zeotropic Mixture
Procedia Engineering, 2015Co-Authors: Jian Liu, Xiaosong ZhangAbstract:Abstract Accordingly to the properties of Zeotropic Mixture R32:R236fa, a novel double-temperature chilling water unit was proposal in this paper, this unit can produce two different temperature of chilled water (such as low temperature is 7 °C, high temperature is 16 °C). An experimental system is established to test the performance of the unit. The paper studied the effects of mass component concentrations of the Zeotropic Mixture and high - low temperature evaporator's source temperature on the performance of the unit. The results show that, when the inlet water temperature of the condenser is 32 °C, outlet water temperature of the evaporator is 7 °C and 16 °C. The coefficient of performance (COP) of the unit can reach 4.14 when the mass component concentration of R32 is 60% and the COP of the unit increase with the increase of mass component concentration of R32 and the chilled water temperature.
Yongzhen Wang - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic optimization of rankine cycle using co2 based binary Zeotropic Mixture for ocean thermal energy conversion
Applied Thermal Engineering, 2020Co-Authors: Chengyu Li, Yongzhen WangAbstract:Abstract This work provides an exploration on improving the performance of a closed ocean thermal energy conversion (OTEC) system. In order to approach the Lorenz cycle and obtain better thermal matching, a Rankine cycle using CO2-based binary Zeotropic Mixtures is considered. Six organic working fluids, including R134a, R152a, R161, R1234yf, R1234ze(E) and R32, are selected to be additives for binary Mixtures, in addition, various concentrations of CO2 are investigated in order to obtain varying temperature glide. Besides, pure working fluids, including NH3 and CO2, are also comparatively investigated with the Mixtures. The specific net power output and thermal efficiency are used to evaluate OTEC thermodynamic performance, and the ratio of net power output to total heat transfer area is adopted for a preliminary economic analysis. Different effects on cycle performance are analyzed. Finally, an overall optimization to maximize the system thermal efficiency and specific work are carried out, respectively. The simulation is based on a designed Matlab program. The results indicate that CO2-based binary Zeotropic Mixtures could improve thermodynamic coupling of cycle and external seawater, achieving a deeper heat utilization of warm/cold seawater than that of pure working fluid. The performance of Rankine cycle is affected by the Mixture composition, and composition at which Mixture has evaporating temperature glide of 7-8 °C is recommended. The binary Mixtures produce larger specific power output than pure working fluids, and CO2/R32 (0.76/0.24 wt%) produces the maximum value of 0.696 kJ/kg, nearly 38% higher than that of pure NH3. Although the Mixtures are inferior to NH3 according to preliminary economic analysis. The thermodynamic findings still prove that Rankine cycle with CO2-based binary Mixture is a promising alternative for OTEC system.
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thermodynamic optimization of rankine cycle using co2 based binary Zeotropic Mixture for ocean thermal energy conversion
Applied Thermal Engineering, 2020Co-Authors: Lisheng Pan, Yongzhen WangAbstract:Abstract This work provides an exploration on improving the performance of a closed ocean thermal energy conversion (OTEC) system. In order to approach the Lorenz cycle and obtain better thermal matching, a Rankine cycle using CO2-based binary Zeotropic Mixtures is considered. Six organic working fluids, including R134a, R152a, R161, R1234yf, R1234ze(E) and R32, are selected to be additives for binary Mixtures, in addition, various concentrations of CO2 are investigated in order to obtain varying temperature glide. Besides, pure working fluids, including NH3 and CO2, are also comparatively investigated with the Mixtures. The specific net power output and thermal efficiency are used to evaluate OTEC thermodynamic performance, and the ratio of net power output to total heat transfer area is adopted for a preliminary economic analysis. Different effects on cycle performance are analyzed. Finally, an overall optimization to maximize the system thermal efficiency and specific work are carried out, respectively. The simulation is based on a designed Matlab program. The results indicate that CO2-based binary Zeotropic Mixtures could improve thermodynamic coupling of cycle and external seawater, achieving a deeper heat utilization of warm/cold seawater than that of pure working fluid. The performance of Rankine cycle is affected by the Mixture composition, and composition at which Mixture has evaporating temperature glide of 7-8 °C is recommended. The binary Mixtures produce larger specific power output than pure working fluids, and CO2/R32 (0.76/0.24 wt%) produces the maximum value of 0.696 kJ/kg, nearly 38% higher than that of pure NH3. Although the Mixtures are inferior to NH3 according to preliminary economic analysis. The thermodynamic findings still prove that Rankine cycle with CO2-based binary Mixture is a promising alternative for OTEC system.
Xiaosong Zhang - One of the best experts on this subject based on the ideXlab platform.
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experimental and theoretical study on a novel double evaporating temperature chiller applied in thics using r32 r236fa
International Journal of Refrigeration-revue Internationale Du Froid, 2017Co-Authors: Jia Liu, Li Cong, Xiaohui She, Xiaosong Zhang, E A LindemaAbstract:Abstract A novel chiller with double evaporating temperatures is proposed in this paper, which can be applied in temperature and humidity independent control system (THICS). A Zeotropic Mixture R32/R236fa is selected as the refrigerant, and chilled water with two different temperatures is produced. The experimental coefficient of performance ( COP exp ), theoretical coefficient of performance ( COP th ), and second law efficiency ( η ) of the chiller are studied. The performance of the chiller is studied by varying the mass fraction of R32 in the R32/R236fa ( W (R32)), chilled water temperature, and the flow rates of the heat transfer media (chilled water and cooling water). The results show that the high temperature chilled water ( T H,out ) can be at 15–18 °C, and the low temperature chilled water ( T L,out ) can be at 6–8 °C. When T H,out is 17 °C and T L,out is 7 °C, the maximum COP th and COP exp are 4.73 and 3.97, respectively. Second law efficiency, η , increases to 31% as W (R32) increases from 0.3 to 0.6.
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experimental study of a novel double temperature chiller based on r32 r236fa
Energy Conversion and Management, 2016Co-Authors: Jian Liu, Xiaohui She, Xiaosong Zhang, Liang Man, Wei ZhouAbstract:Abstract A novel double-temperature chiller with Zeotropic Mixture R32/R236fa is proposed in this paper, and chilled water with two different temperatures is produced, such as low temperature water ( T L , out = 7 °C) and high temperature water ( T H , out = 16 °C). An experimental setup is established to test the performance of the chiller. Effects of mass fraction of R32 in Mixture R32/R236fa ( M (R32)), T L , out , T H , out and the heat transfer media flow rate on the performance of the chiller are studied. When T H , out is 18 °C, T L , out is 8 °C and M (R32) is 0.6, COP and refrigerating capacity are 4.11 and 4.42 kW, respectively. COP and refrigerating capacity increase as M (R32) increases. Exhausting pressure of the chiller increases with the increase of M (R32). As M (R32) is 0.6, exhausting pressure is about 1.95 MPa. Compression ratio decreases with the increase of M (R32). When M (R32) increases from 0.3 to 0.6, the compression ratio decreases from 3.0 to 2.9.
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performance analysis of a novel double temperature chilling water unit using large temperature glide Zeotropic Mixture
Procedia Engineering, 2015Co-Authors: Jian Liu, Xiaosong ZhangAbstract:Abstract Accordingly to the properties of Zeotropic Mixture R32:R236fa, a novel double-temperature chilling water unit was proposal in this paper, this unit can produce two different temperature of chilled water (such as low temperature is 7 °C, high temperature is 16 °C). An experimental system is established to test the performance of the unit. The paper studied the effects of mass component concentrations of the Zeotropic Mixture and high - low temperature evaporator's source temperature on the performance of the unit. The results show that, when the inlet water temperature of the condenser is 32 °C, outlet water temperature of the evaporator is 7 °C and 16 °C. The coefficient of performance (COP) of the unit can reach 4.14 when the mass component concentration of R32 is 60% and the COP of the unit increase with the increase of mass component concentration of R32 and the chilled water temperature.
