The Experts below are selected from a list of 333 Experts worldwide ranked by ideXlab platform
Souvik Bhattacharyya - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic analysis and optimization of a novel two Stage transcritical n2o cycle
International Journal of Refrigeration-revue Internationale Du Froid, 2011Co-Authors: Neeraj Agrawal, Jahar Sarkar, Souvik BhattacharyyaAbstract:Thermodynamic (energy and exergy) analyses and optimization studies of two-Stage transcritical N2O and CO2 cycles, incorporating compressor intercooling, are presented based on cycle simulation employing simultaneous optimization of intercooler Pressure and gas cooler Pressure. Further, performance comparisons with the basic single-Stage cycles are also presented. The N2O cycle exhibits higher cooling COP, lower optimum gas cooler Pressure and discharge temperature and higher second law efficiency as compared to an equivalent CO2 cycle. However, two-Stage compression with intercooling yields lesser COP improvement for N2O compared to CO2. Based on the cycle simulations, correlations of optimum gas cooler Pressure and inter-Stage Pressure in terms of gas cooler exit temperature and evaporator temperature are obtained. This is expected to be of help as a guideline in optimal design and operation of such systems.
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studies on a two Stage transcritical carbon dioxide heat pump cycle with flash intercooling
Applied Thermal Engineering, 2007Co-Authors: Neeraj Agrawal, Souvik BhattacharyyaAbstract:Abstract Simulation studies on a two-Stage flash intercooling transcritical carbon dioxide heat pump cycle are presented. Sub-critical and super-critical thermodynamic and transport properties of carbon dioxide are calculated employing an exclusive precision property code based on recently published correlations. Results exhibit that flash intercooling technique is not economical with CO2 refrigerant unlike NH3 as the refrigerant. COP is considerably lower than that of the single cycle for a given gas cooler and evaporator temperature. There is no optimum inter-Stage Pressure as well. However, a marginal increase in COP occurs as inter-Stage Pressure decreases from the classical estimate of geometric mean of gas cooler and evaporator Pressure. It is observed that incorporation of desuperheating of vapour in the intercooler almost doubles the mass flow rate in the second Stage which can be attributed to the large flashing that occurs in the intercooler; this increase depends on the discharge temperature from the first Stage and mass flow rate of refrigerant flow in the evaporator. Compressor isentropic efficiency shows marginal influence on system performance.
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Optimization of two-Stage transcritical carbon dioxide heat pump cycles
International Journal of Thermal Sciences, 2007Co-Authors: Neeraj Agrawal, Souvik Bhattacharyya, Jahar SarkarAbstract:Optimization studies of two-Stage transcritical carbon dioxide heat pump cycles, incorporating options such as flash gas bypass, flash intercooling and compressor intercooling, are presented based on cycle simulation. Sub-critical and super-critical thermodynamic and transport properties of carbon dioxide coded and then integrated with the simulation code for further analyses. Results exhibit improvement in performance by adopting optimal operating conditions. The optimum interStage Pressure, thus obtained, deviate from the classical estimate of geometric mean of gas cooler and evaporator Pressure. It is observed that the flash gas bypass system yields the best performance among the three two Stage cycles analyzed. Internal heat exchanger effectiveness and compressor isentropic efficiency shows marginal influence on the system performance. Internal heat exchanger effectiveness shows marginal influence on the system performance while compressor isentropic efficiency shows an about 10% variation in COP. However, optimum gas cooler Pressure and optimum intermediate Pressure are only marginally affected. Based on the cycle simulations, correlations of optimum gas cooler Pressure and inter-Stage Pressure in terms of gas cooler temperature and evaporator temperature are obtained. This would be useful as a guideline in design of such systems.
Neeraj Agrawal - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic analysis and optimization of a novel two Stage transcritical n2o cycle
International Journal of Refrigeration-revue Internationale Du Froid, 2011Co-Authors: Neeraj Agrawal, Jahar Sarkar, Souvik BhattacharyyaAbstract:Thermodynamic (energy and exergy) analyses and optimization studies of two-Stage transcritical N2O and CO2 cycles, incorporating compressor intercooling, are presented based on cycle simulation employing simultaneous optimization of intercooler Pressure and gas cooler Pressure. Further, performance comparisons with the basic single-Stage cycles are also presented. The N2O cycle exhibits higher cooling COP, lower optimum gas cooler Pressure and discharge temperature and higher second law efficiency as compared to an equivalent CO2 cycle. However, two-Stage compression with intercooling yields lesser COP improvement for N2O compared to CO2. Based on the cycle simulations, correlations of optimum gas cooler Pressure and inter-Stage Pressure in terms of gas cooler exit temperature and evaporator temperature are obtained. This is expected to be of help as a guideline in optimal design and operation of such systems.
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studies on a two Stage transcritical carbon dioxide heat pump cycle with flash intercooling
Applied Thermal Engineering, 2007Co-Authors: Neeraj Agrawal, Souvik BhattacharyyaAbstract:Abstract Simulation studies on a two-Stage flash intercooling transcritical carbon dioxide heat pump cycle are presented. Sub-critical and super-critical thermodynamic and transport properties of carbon dioxide are calculated employing an exclusive precision property code based on recently published correlations. Results exhibit that flash intercooling technique is not economical with CO2 refrigerant unlike NH3 as the refrigerant. COP is considerably lower than that of the single cycle for a given gas cooler and evaporator temperature. There is no optimum inter-Stage Pressure as well. However, a marginal increase in COP occurs as inter-Stage Pressure decreases from the classical estimate of geometric mean of gas cooler and evaporator Pressure. It is observed that incorporation of desuperheating of vapour in the intercooler almost doubles the mass flow rate in the second Stage which can be attributed to the large flashing that occurs in the intercooler; this increase depends on the discharge temperature from the first Stage and mass flow rate of refrigerant flow in the evaporator. Compressor isentropic efficiency shows marginal influence on system performance.
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Optimization of two-Stage transcritical carbon dioxide heat pump cycles
International Journal of Thermal Sciences, 2007Co-Authors: Neeraj Agrawal, Souvik Bhattacharyya, Jahar SarkarAbstract:Optimization studies of two-Stage transcritical carbon dioxide heat pump cycles, incorporating options such as flash gas bypass, flash intercooling and compressor intercooling, are presented based on cycle simulation. Sub-critical and super-critical thermodynamic and transport properties of carbon dioxide coded and then integrated with the simulation code for further analyses. Results exhibit improvement in performance by adopting optimal operating conditions. The optimum interStage Pressure, thus obtained, deviate from the classical estimate of geometric mean of gas cooler and evaporator Pressure. It is observed that the flash gas bypass system yields the best performance among the three two Stage cycles analyzed. Internal heat exchanger effectiveness and compressor isentropic efficiency shows marginal influence on the system performance. Internal heat exchanger effectiveness shows marginal influence on the system performance while compressor isentropic efficiency shows an about 10% variation in COP. However, optimum gas cooler Pressure and optimum intermediate Pressure are only marginally affected. Based on the cycle simulations, correlations of optimum gas cooler Pressure and inter-Stage Pressure in terms of gas cooler temperature and evaporator temperature are obtained. This would be useful as a guideline in design of such systems.
Jahar Sarkar - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic analysis and optimization of a novel two Stage transcritical n2o cycle
International Journal of Refrigeration-revue Internationale Du Froid, 2011Co-Authors: Neeraj Agrawal, Jahar Sarkar, Souvik BhattacharyyaAbstract:Thermodynamic (energy and exergy) analyses and optimization studies of two-Stage transcritical N2O and CO2 cycles, incorporating compressor intercooling, are presented based on cycle simulation employing simultaneous optimization of intercooler Pressure and gas cooler Pressure. Further, performance comparisons with the basic single-Stage cycles are also presented. The N2O cycle exhibits higher cooling COP, lower optimum gas cooler Pressure and discharge temperature and higher second law efficiency as compared to an equivalent CO2 cycle. However, two-Stage compression with intercooling yields lesser COP improvement for N2O compared to CO2. Based on the cycle simulations, correlations of optimum gas cooler Pressure and inter-Stage Pressure in terms of gas cooler exit temperature and evaporator temperature are obtained. This is expected to be of help as a guideline in optimal design and operation of such systems.
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Optimization of two-Stage transcritical carbon dioxide heat pump cycles
International Journal of Thermal Sciences, 2007Co-Authors: Neeraj Agrawal, Souvik Bhattacharyya, Jahar SarkarAbstract:Optimization studies of two-Stage transcritical carbon dioxide heat pump cycles, incorporating options such as flash gas bypass, flash intercooling and compressor intercooling, are presented based on cycle simulation. Sub-critical and super-critical thermodynamic and transport properties of carbon dioxide coded and then integrated with the simulation code for further analyses. Results exhibit improvement in performance by adopting optimal operating conditions. The optimum interStage Pressure, thus obtained, deviate from the classical estimate of geometric mean of gas cooler and evaporator Pressure. It is observed that the flash gas bypass system yields the best performance among the three two Stage cycles analyzed. Internal heat exchanger effectiveness and compressor isentropic efficiency shows marginal influence on the system performance. Internal heat exchanger effectiveness shows marginal influence on the system performance while compressor isentropic efficiency shows an about 10% variation in COP. However, optimum gas cooler Pressure and optimum intermediate Pressure are only marginally affected. Based on the cycle simulations, correlations of optimum gas cooler Pressure and inter-Stage Pressure in terms of gas cooler temperature and evaporator temperature are obtained. This would be useful as a guideline in design of such systems.
Vasko N. Šarevski - One of the best experts on this subject based on the ideXlab platform.
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Preliminary study of a novel R718 refrigeration cycle with single Stage centrifugal compressor and two-phase ejector
International Journal of Refrigeration-revue Internationale Du Froid, 2014Co-Authors: Milan N. Šarevski, Vasko N. ŠarevskiAbstract:Abstract The paper describes the investigations of a novel R718 refrigeration cycle with single Stage centrifugal compressor and two-phase ejector as a second Stage compression device. The limitations of the R718 centrifugal Stage Pressure ratio, connected with small molecular mass of the water and high isentropic exponent, result on high impeller peripheral speed, high Mach number and high discharge temperature. Reynolds number is low and dimensions of the compressor Stage are large. The complex thermal and flow phenomena inside two-phase ejector flow field are investigated and performance characteristics are estimated. Although efficiency of the concept of compression with hydraulic pump and two-phase ejectors is lower, the integration of two-phase ejectors in the R718 centrifugal unit results in low cost high capacity refrigeration system with high energy efficiency, competitive with traditional refrigeration systems by environmental, technical and economical reasons.
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Characteristics of water vapor turbocompressors applied in refrigeration and heat pump systems
International Journal of Refrigeration-revue Internationale Du Froid, 2012Co-Authors: Milan N. Šarevski, Vasko N. ŠarevskiAbstract:Abstract Interdependence between centrifugal Stage Pressure ratio, peripheral Mach number and impeller peripheral speed, as well the influence of the refrigerating capacity on the dimensions of the centrifugal compressor are determined to obtain the range of reasonable usage of R718 refrigerating/heat pump systems. The deep vacuum operating conditions, the low specific volumetric cooling capacity of the R718 and the small molecular mass of the water are the peculiarities which determined the main parameters of the centrifugal compressor and the range of rational application of the R718 refrigerating/heat pump systems. The high peripheral impeller speed, high Mach number and high Pressure ratio cause separated jet-wake flow and transonic flow phenomena in the compressor flow field. Estimation of the flow characteristics and of the performance characteristics of the water vapor centrifugal compressors is presented, using results of CFD simulations and experimental investigations for high Pressure ratio centrifugal compressors.
Fu-qiang Chen - One of the best experts on this subject based on the ideXlab platform.
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turbulent compressible flow analysis on multi Stage high Pressure reducing valve
Flow Measurement and Instrumentation, 2018Co-Authors: Fu-qiang Chen, Jin-yuan Qian, Min Rui Chen, Ming Zhang, Li Long ChenAbstract:Abstract Pressure reducing valve plays an important role in thermodynamic systems. Under extreme operating conditions, greater demands are requested on Pressure reducing systems. In this paper, a novel multi-Stage high Pressure reducing valve (MSHPRV) is proposed, which can achieve multi-Stage Pressure reducing processes, improve the flow characteristics and deal with complex conditions. Here, the effects of different structural parameters on turbulent compressible flow inside MSHPRV are numerically investigated to achieve low valve noise and energy consumption. Mach number is taken as the parameter to reflect the fluid compressibility. Higher Mach number can cause serious aerodynamic noise and large amount of energy consumption. Based on this, transmission loss of MSHPRV is also studied to achieve better noise control performances. Meanwhile, larger turbulent dissipation rate means larger degree of energy consumption, so it is with the exergy loss. Thus, numerical models with different valve openings, perforated plate diameters, chamfer radii of perforated plates, Pressure ratios and Stages of perforated plates are established, and the effects of these structural parameters on the compressible turbulent flow and energy consumption of MSHPRV are investigated. Results show that different structural parameters have significant impacts on compressible turbulent flow and energy consumption performance in MSHPRV. The best noise control and least energy consumption of MSHPRV is achieved with such parameters as Pressure ratio 7, perforated plate diameter 4 mm and 4 Stage plates. This work can benefit the further research work on energy saving and multi-Stage design of Pressure reducing devices.
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thermo mechanical stress and fatigue damage analysis on multi Stage high Pressure reducing valve
Annals of Nuclear Energy, 2017Co-Authors: Fu-qiang Chen, Jin-yuan Qian, Ming Zhang, Li Long ChenAbstract:Abstract A multi-Stage high Pressure reducing valve (MSHPRV) is proposed. It can achieve a multi-Stage Pressure reducing way. Valve failure mainly occurs under high Pressure and high temperature conditions, thus it is necessary to investigate the strength of MSHPRV under those complex conditions. In this paper, the mathematical model of MSHPRV is established and Computational Fluid Dynamics (CFD) method is employed to simulate its flow fields and thermo-mechanical stress. Next, the stress of MSHPRV under different opening time and the fatigue damage of MSHPRV under different valve openings are studied. Finally, two changes are provided on geometry of MSHPRV and the geometrical factors are optimized. The results show that, the radial direction from inner wall to outer wall is the main heat transfer direction for valve body. At opening time 50 s, the working condition of MSHPRV is dangerous condition. Meanwhile, the maximum value of thermal stress is 487 MPa, which is located at the upper end face of valve chamber region B3. There is a lag effect of stress distribution with respect to temperature distribution. The combined stress of valve body is composed of thermal stress and mechanical stress, in which thermal stress holds the dominant position. Moreover, with the increasing of valve opening, the fatigue damage of valve body increases correspondingly. It can be concluded that MSHPRV can cope with complex conditions like high Pressure and high temperature. In the optimization design of MSHPRV, it can be found that the best strength of MSHPRV is achieved with such geometrical factors as angle 15, diameter 4 mm and 2 Stage plates. Besides, radian design as the improved structure is recommended. This work can benefit the further research work on the regulation performance and safe operation of high Pressure reducing valve.
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numerical analysis of flow and temperature characteristics in a high multi Stage Pressure reducing valve for hydrogen refueling station
International Journal of Hydrogen Energy, 2016Co-Authors: Fu-qiang Chen, Jin-yuan Qian, Li Long Chen, Ming Zhang, F. WangAbstract:Hydrogen refueling station is one of the most important parts for the hydrogen energy utilization. In this paper, a novel high multi-Stage Pressure reducing valve (HMSPRV) is proposed, which can be used for hydrogen stable decompression in hydrogen refueling station. In HMSPRV, the inner and outer porous shrouded valve core is used to replace piston valve core to achieve the first-Stage throttling, and the porous orifice plate is chosen as the second-Stage throttling component. Meanwhile, in order to verify the applicability of HMSPRV, the flow characteristics of two fluids are studied. Firstly, the choked flow, flow and temperature characteristics of superheated steam under different valve openings are carried out. Secondly, the flow characteristic of hydrogen is also conducted to validate the application of HMSPRV in hydrogen refueling station. The results show that, for superheated steam flow, with the increasing of valve openings, the maximum gradient of fluid Pressure moves from the fitting surface where inner and outer porous shrouded to the orifice plate. The regulation of its amount is decreasing first and then increasing. With the increasing of valve openings, the maximum velocity, turbulent dissipation rate and Pressure loss are all increasing gradually, while the temperature does not change significantly. For hydrogen flow, both the Pressure changing process and velocity changing process are similar to superheated steam. It can be concluded that HMSPRV has good flow and temperature characteristics in complex conditions, and it does not prone to choked flow. Throttling effect of the multi-Stage Pressure reducing way is obvious. This work can benefit the further research work on hydrogen stable decompression in hydrogen refueling station.
