The Experts below are selected from a list of 42 Experts worldwide ranked by ideXlab platform

Rakesh K Bhargava - One of the best experts on this subject based on the ideXlab platform.

  • Understanding effects of wet Compression on separated flow behavior in an axial compressor stage using CFD analysis
    Journal of Turbomachinery, 2011
    Co-Authors: Lanxin Sun, Yijin Li, Qun Zheng, Rakesh K Bhargava
    Abstract:

    The effects of wet Compression on the flow field within a compressor stage, particularly in the presence of the separated flow region, are not fully understood. Numerical simulations of 3D compressible separated flows within a wet Compression compressor stage are carried out using a computational fluid dynamics (CFD) program. Numerical computations of flow fields in a compressor cascade with wet Compression assume that a separated region exist in the corner of the rotor blade suction surface and hub surface in the case of dry Compression. Under different operating conditions and with wet Compression, this study presents the changes in the extent of separated region on the flow channel surfaces, Compression efficiency, pressure ratio and Specific Compression Work, etc. Also, effects of factors such as droplet size, droplet temperature, and injected water flow rate on the compressor stage performance and flow field within compressor stage passage have been investigated. The results show that wet Compression could weaken and eliminate the flow separation and then the efficiency and pressure ratio maintain a high level. © 2011 American Society of Mechanical Engineers.

Qun Zheng - One of the best experts on this subject based on the ideXlab platform.

  • Numerical simulation of multistage compressor with wet Compression near rotating stall condition
    Kung Cheng Je Wu Li Hsueh Pao Journal of Engineering Thermophysics, 2013
    Co-Authors: M.-c. Luo, Q.-f. Deng, L.-x. Sun, J.j. Yang, Qun Zheng, Q Wang, Hong Zhang
    Abstract:

    Wet Compression is currently an economical and effective method of improving power and efficiency of gas turbines. By employing software CFX, wet Compression effects on an eight-stage axial subsonic compressor operating near the rotating stall condition is simulated and analyzed through adopting k-ε turbulence model, using the Antoine equation for vapor saturation pressure and choosing CAB model as the secondary aerodynamic breakup model. The simulation results show that wet Compression could improve the flow capacity, increase pressure ratio, reduce the air temperature and Specific Compression Work as the compressor Working near stall condition. The low energy flow region of the 8th rotor passage and the separated region on suction surface of the stator could be abated or even eliminated by inlet fogging and thus moving the compressor away from the stall Working condition.

  • Understanding Effects of Wet Compression on Separated Flow Behavior in an Axial Compressor Stage Using CFD Analysis
    Journal of Turbomachinery-transactions of The Asme, 2011
    Co-Authors: Qun Zheng, Yijin Li, Rakesh Bhargava
    Abstract:

    The effects of wet Compression on the flow field within a compressor stage, particularly in the presence of the separated flow region, are not fully understood. Numerical simulations of 3D compressible separated flows within a wet Compression compressor stage are carried out using a computational fluid dynamics (CFD) program. Numerical computations of flow fields in a compressor cascade with wet Compression assume that a separated region exist in the corner of the rotor blade suction surface and hub surface in the case of dry Compression. Under different operating conditions and with wet Compression, this study presents the changes in the extent of separated region on the flow channel surfaces, Compression efficiency, pressure ratio and Specific Compression Work, etc. Also, effects of factors such as droplet size, droplet temperature, and injected water flow rate on the compressor stage performance and flow field within compressor stage passage have been investigated. The results show that wet Compression could weaken and eliminate the flow separation and then the efficiency and pressure ratio maintain a high level.

  • Understanding effects of wet Compression on separated flow behavior in an axial compressor stage using CFD analysis
    Journal of Turbomachinery, 2011
    Co-Authors: Lanxin Sun, Yijin Li, Qun Zheng, Rakesh K Bhargava
    Abstract:

    The effects of wet Compression on the flow field within a compressor stage, particularly in the presence of the separated flow region, are not fully understood. Numerical simulations of 3D compressible separated flows within a wet Compression compressor stage are carried out using a computational fluid dynamics (CFD) program. Numerical computations of flow fields in a compressor cascade with wet Compression assume that a separated region exist in the corner of the rotor blade suction surface and hub surface in the case of dry Compression. Under different operating conditions and with wet Compression, this study presents the changes in the extent of separated region on the flow channel surfaces, Compression efficiency, pressure ratio and Specific Compression Work, etc. Also, effects of factors such as droplet size, droplet temperature, and injected water flow rate on the compressor stage performance and flow field within compressor stage passage have been investigated. The results show that wet Compression could weaken and eliminate the flow separation and then the efficiency and pressure ratio maintain a high level. © 2011 American Society of Mechanical Engineers.

  • The Effects of Wet Compression on the Separated Flow in a Compressor Stage
    Volume 7: Education; Industrial and Cogeneration; Marine; Oil and Gas Applications, 2008
    Co-Authors: Yijin Li, Qun Zheng, Rakesh Bhargava
    Abstract:

    Effects of wet Compression on the flow field within a compressor stage, particularly in presence of the separated flow region are not fully understood. Numerical simulations of 3D compressible separated flows within a wet Compression compressor stage are carried out using a Computational Fluid Dynamics (CFD) program. Numerical computations of flow fields in a compressor cascade with wet Compression assume that a separated region exist in the corner of the rotor blade suction surface and hub surface in the case of dry Compression. Under different operating conditions and with wet Compression, this study presents the changes in the extent of separated region on the flow channel surfaces, Compression efficiency, pressure ratio and Specific Compression Work etc. Also, effects of factors such as droplet size, droplet temperature, and injected water flow rate on the compressor stage performance and flow field within compressor stage passage have been investigated.Copyright © 2008 by ASME

Lanxin Sun - One of the best experts on this subject based on the ideXlab platform.

  • Understanding effects of wet Compression on separated flow behavior in an axial compressor stage using CFD analysis
    Journal of Turbomachinery, 2011
    Co-Authors: Lanxin Sun, Yijin Li, Qun Zheng, Rakesh K Bhargava
    Abstract:

    The effects of wet Compression on the flow field within a compressor stage, particularly in the presence of the separated flow region, are not fully understood. Numerical simulations of 3D compressible separated flows within a wet Compression compressor stage are carried out using a computational fluid dynamics (CFD) program. Numerical computations of flow fields in a compressor cascade with wet Compression assume that a separated region exist in the corner of the rotor blade suction surface and hub surface in the case of dry Compression. Under different operating conditions and with wet Compression, this study presents the changes in the extent of separated region on the flow channel surfaces, Compression efficiency, pressure ratio and Specific Compression Work, etc. Also, effects of factors such as droplet size, droplet temperature, and injected water flow rate on the compressor stage performance and flow field within compressor stage passage have been investigated. The results show that wet Compression could weaken and eliminate the flow separation and then the efficiency and pressure ratio maintain a high level. © 2011 American Society of Mechanical Engineers.

Yijin Li - One of the best experts on this subject based on the ideXlab platform.

  • Understanding Effects of Wet Compression on Separated Flow Behavior in an Axial Compressor Stage Using CFD Analysis
    Journal of Turbomachinery-transactions of The Asme, 2011
    Co-Authors: Qun Zheng, Yijin Li, Rakesh Bhargava
    Abstract:

    The effects of wet Compression on the flow field within a compressor stage, particularly in the presence of the separated flow region, are not fully understood. Numerical simulations of 3D compressible separated flows within a wet Compression compressor stage are carried out using a computational fluid dynamics (CFD) program. Numerical computations of flow fields in a compressor cascade with wet Compression assume that a separated region exist in the corner of the rotor blade suction surface and hub surface in the case of dry Compression. Under different operating conditions and with wet Compression, this study presents the changes in the extent of separated region on the flow channel surfaces, Compression efficiency, pressure ratio and Specific Compression Work, etc. Also, effects of factors such as droplet size, droplet temperature, and injected water flow rate on the compressor stage performance and flow field within compressor stage passage have been investigated. The results show that wet Compression could weaken and eliminate the flow separation and then the efficiency and pressure ratio maintain a high level.

  • Understanding effects of wet Compression on separated flow behavior in an axial compressor stage using CFD analysis
    Journal of Turbomachinery, 2011
    Co-Authors: Lanxin Sun, Yijin Li, Qun Zheng, Rakesh K Bhargava
    Abstract:

    The effects of wet Compression on the flow field within a compressor stage, particularly in the presence of the separated flow region, are not fully understood. Numerical simulations of 3D compressible separated flows within a wet Compression compressor stage are carried out using a computational fluid dynamics (CFD) program. Numerical computations of flow fields in a compressor cascade with wet Compression assume that a separated region exist in the corner of the rotor blade suction surface and hub surface in the case of dry Compression. Under different operating conditions and with wet Compression, this study presents the changes in the extent of separated region on the flow channel surfaces, Compression efficiency, pressure ratio and Specific Compression Work, etc. Also, effects of factors such as droplet size, droplet temperature, and injected water flow rate on the compressor stage performance and flow field within compressor stage passage have been investigated. The results show that wet Compression could weaken and eliminate the flow separation and then the efficiency and pressure ratio maintain a high level. © 2011 American Society of Mechanical Engineers.

  • The Effects of Wet Compression on the Separated Flow in a Compressor Stage
    Volume 7: Education; Industrial and Cogeneration; Marine; Oil and Gas Applications, 2008
    Co-Authors: Yijin Li, Qun Zheng, Rakesh Bhargava
    Abstract:

    Effects of wet Compression on the flow field within a compressor stage, particularly in presence of the separated flow region are not fully understood. Numerical simulations of 3D compressible separated flows within a wet Compression compressor stage are carried out using a Computational Fluid Dynamics (CFD) program. Numerical computations of flow fields in a compressor cascade with wet Compression assume that a separated region exist in the corner of the rotor blade suction surface and hub surface in the case of dry Compression. Under different operating conditions and with wet Compression, this study presents the changes in the extent of separated region on the flow channel surfaces, Compression efficiency, pressure ratio and Specific Compression Work etc. Also, effects of factors such as droplet size, droplet temperature, and injected water flow rate on the compressor stage performance and flow field within compressor stage passage have been investigated.Copyright © 2008 by ASME

Gustavo Pottker - One of the best experts on this subject based on the ideXlab platform.

  • Potentials for COP increase in vapor Compression systems
    2020
    Co-Authors: Gustavo Pottker
    Abstract:

    This Work presents an experimental and numerical study of three different opportunities for COP increase in vapor Compression systems: Work recovery ejectors, condenser subcooling and increase of relative size of heat exchangers (HXs). Regarding Work recovery ejectors, experimental results showed that the COP of the ejector system increased between 8.2% and 14.8% when compared to a conventional expansion valve system operating with R410A. The two major mechanisms of improvement of the ejector system were quantified separately: COP gains between 1.9% to 8.4% were solely due to the Work recovery, while liquid-feeding the evaporator alone was responsible for 4.9% to 9.0% of COP gain. Overall ejector efficiencies from 12.2% to 19.2% were achieved. A major portion of this dissertation explores the effects of condenser subcooling on the COP of vapor Compressions systems. It is shown that, as condenser subcooling increases, the COP reaches a maximum as a result of a trade-off between increasing refrigerating effect and Specific Compression Work. A thermodynamic analysis pointed out that refrigerants with large ratio of liquid Specific heat to latent heat of vaporization tend to benefit more from condenser subcooling. Numerical results suggested that R1234yf systems would benefit the most from condenser subcooling in comparison to R410A, R134a, and R717. Experimental results obtained with a vehicular air conditioning system revealed COP gains between 6% and 44% for R1234yf and 2% to 21% for R134a due to condenser subcooling. Results also indicated that the larger the air-refrigerant temperature difference in the condenser, the higher the COP maximizing subcooling and the COP gains from condenser subcooling. Additional experiments showed that the presence of an internal heat exchanger reduces the benefits of the condenser subcooling. With a unique set of microchannel condensers, an experimental comparison between subcooling generated in non-designated area (NDA) and designated area (DA) of the condenser showed that both configurations yielded similar values of maximum COP improvement within the operating conditions considered. It was also demonstrated that condensers with a higher air-refrigerant temperature difference would require a larger COP maximizing area ratio allocated for subcooling. Nevertheless, a fixed designated area yielded near maximum COPs within a reasonable range of operating conditions. The effect of refrigerant mal-distribution on the performance of a two-pass parallel-flow microchannel condenser as well as on the overall system COP is numerically investigated. The results showed a COP deterioration of not more than 3% for the worst case of mal-distribution considered. The effect of the size of the heat exchangers (HXs) relative to the cooling capacity on the performance of actual residential air conditioning systems has been experimentally and numerically investigated for R410A and transcritical R744. Experiments were carried out in a limited range of operating conditions but an experimentally…

  • Effect of the condenser subcooling on the performance of vapor Compression systems
    International Journal of Refrigeration-revue Internationale Du Froid, 2015
    Co-Authors: Gustavo Pottker, Predrag Stojan Hrnjak
    Abstract:

    Abstract This paper presents a theoretical study about the effect of condenser subcooling on the performance of vapor-Compression systems. It is shown that, as condenser subcooling increases, the COP reaches a maximum as a result of a trade-off between increasing refrigerating effect and Specific Compression Work. The thermodynamic properties associated with the relative increase in refrigerating effect, i.e. liquid Specific heat and latent heat of vaporization, are dominant to determine the maximum COP improvement with condenser subcooling. Refrigerants with large latent heat of vaporization tend to benefit less from condenser subcooling. For an air conditioning system, results indicate that the R1234yf (+8.4%) would benefit the most from condenser subcooling in comparison to R410A (7.0%), R134a (5.9%) and R717 (2.7%) due to its smaller latent heat of vaporization. On the other hand, the value of COP maximizing subcooling does not seem to be a strong function of thermodynamic properties.

  • Experimental investigation of the effect of condenser subcooling in R134a and R1234yf air-conditioning systems with and without internal heat exchanger
    International Journal of Refrigeration-revue Internationale Du Froid, 2015
    Co-Authors: Gustavo Pottker, Pega Hrnjak
    Abstract:

    Abstract This paper presents an experimental study about the effect of condenser subcooling on the performance of an air conditioning system operating with R134a and R1234yf, under the same operating conditions. For both refrigerants, it has been shown that the COP undergoes a maximum as a consequence of the trade-off between increasing refrigerating effect and increasing Specific Compression Work. At a given operating condition, the system COP increased up to 18% for R1234yf and 9% for R134a. These results confirmed the trends obtained from a previous theoretical analysis, demonstrating that a system operating with R1234yf can benefit more from the condenser subcooling than that with R134a. The experimental results also showed that the presence of an internal heat exchanger significantly reduces the COP increase due to condenser subcooling, since both improvements compete towards reducing the throttling losses. Besides the interference between IHX and condenser subcooling, the use of both simultaneously still yields a more efficient air conditioning system, especially for R1234yf.

  • Effect of Condenser Subcooling of the Performance of Vapor Compression Systems: Experimental and Numerical Investigation
    2012
    Co-Authors: Gustavo Pottker, Predrag Stojan Hrnjak
    Abstract:

    This paper presents a theoretical and experimental analysis of the effect of condenser subcooling on the performance of vapor-Compression systems. It is shown that, as condenser subcooling increases, the COP reaches a maximum as a result of a trade-off between increasing refrigerating effect and Specific Compression Work. The thermodynamic properties associated with the relative increase in refrigerating effect, i.e. liquid Specific heat and latent heat of vaporization, are dominant to determine the maximum COP improvement with condenser subcooling. Refrigerants with large latent heat of vaporization tend to benefit less from condenser subcooling. For a typical AC system, numerical results indicate that the R1234yf would benefit the most from condenser subcooling in comparison to R410A, R134a and R717 due to its smaller latent heat of vaporization. On the other hand, the value of COP maximizing subcooling does not seem to be a strong function of thermodynamic properties. Experimental results comparing R1234yf and R134a confirmed the trends observed during the numerical study. For a given operating condition, the system COP increased up to 18% for R1234yf and only 9% for R134a.