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Flox Chillarón Gonzalo - One of the best experts on this subject based on the ideXlab platform.

  • Caracterización numérica de un eyector de geometría variable equipado en ciclos de refrigeración accionados por fuentes térmicas de baja temperatura
    'Universitat Politecnica de Valencia', 2020
    Co-Authors: Flox Chillarón Gonzalo
    Abstract:

    [ES] El presente proyecto tiene como objetivo caracterizar la envolvente de operación de un eyector de geometría variable mediante técnicas de mecánica de fluidos computacional. El eyector opera con el fluido refrigerante R1234yf y está ideado para ser implementado en un ciclo de refrigeración accionado por fuentes de calor de baja temperatura. Se pretende modificar activamente la geometría del eyector para hacer frente a cambios en las condiciones de condensación, íntimamente ligadas con los cambios en la temperatura ambiente, así como en las condiciones en el generador, directamente relacionadas con la disponibilidad de calor en la fuente térmica.[EN] In the present project the opeRation envelope of a variable geometry ejector is calculated using computational fluid mechanics techniques. In addition, the differences between the Entrainment Ratio provided by a variable geometry ejector and a fixed geometry ejector are studied. The Entrainment Ratio is selected as a study variable, since the overall performance of the cycle is proportional to this parameter. The ejector operates with R1234yf as the refrigerant fluid and is geometrically optimised to integrate it into a refrigeRation cycle driven by low temperature heat sources. The geometry of the ejector is actively modified by a needle to adapt to changes in condensing conditions, closely linked to changes in ambient temperature, as well as to changes in conditions in the generator, directly related to the availability of heat in the heat source.Flox Chillarón, G. (2020). Caracterización numérica de un eyector de geometría variable equipado en ciclos de refrigeración accionados por fuentes térmicas de baja temperatura. http://hdl.handle.net/10251/151251TFG

  • Caracterización numérica de un eyector de geometría variable equipado en ciclos de refrigeración accionados por fuentes térmicas de baja temperatura
    'Universitat Politecnica de Valencia', 2020
    Co-Authors: Flox Chillarón Gonzalo
    Abstract:

    [ES] El presente proyecto tiene como objetivo caracterizar la envolvente de operación de un eyector de geometría variable mediante técnicas de mecánica de fluidos computacional. El eyector opera con el fluido refrigerante R1234yf y está ideado para ser implementado en un ciclo de refrigeración accionado por fuentes de calor de baja temperatura. Se pretende modificar activamente la geometría del eyector para hacer frente a cambios en las condiciones de condensación, íntimamente ligadas con los cambios en la temperatura ambiente, así como en las condiciones en el generador, directamente relacionadas con la disponibilidad de calor en la fuente térmica.[EN] In the present project the opeRation envelope of a variable geometry ejector is calculated using computational fluid mechanics techniques. In addition, the differences between the Entrainment Ratio provided by a variable geometry ejector and a fixed geometry ejector are studied. The Entrainment Ratio is selected as a study variable, since the overall performance of the cycle is proportional to this parameter. The ejector operates with R1234yf as the refrigerant fluid and is geometrically optimised to integrate it into a refrigeRation cycle driven by low temperature heat sources. The geometry of the ejector is actively modified by a needle to adapt to changes in condensing conditions, closely linked to changes in ambient temperature, as well as to changes in conditions in the generator, directly related to the availability of heat in the heat source.Flox Chillarón, G. (2020). Caracterización numérica de un eyector de geometría variable equipado en ciclos de refrigeración accionados por fuentes térmicas de baja temperatura. Universitat Politècnica de València. http://hdl.handle.net/10251/151251TFG

Peixue Jiang - One of the best experts on this subject based on the ideXlab platform.

  • comprehensive experimental study on a transcritical co2 ejector expansion refrigeRation system
    Energy Conversion and Management, 2017
    Co-Authors: Yinhai Zhu, Fuzhen Zhang, Peixue Jiang
    Abstract:

    Abstract A comprehensive experimental study on the ejector and cooling performances of a transcritical CO 2 ejector-expansion system is presented. The ejector performance of the Entrainment Ratio, pressure lift Ratio, and efficiency were investigated under various primary flow pressure, secondary flow pressure, and back pressure conditions. A new coefficient of mass balance, β , was introduced based on the liquid mass balance in and/or out of the vapor–liquid separator, which was able to estimate the deviation between current operating state and a steady state. The experiment results show that the coefficient of performance (COP) Ratio of the ejector-expansion refrigeRation system to the basic system decreases from 18.9% to −11% with the coefficient of mass balance increasing from −0.1 to 0.1. Both the Entrainment Ratio and COP decrease with an increase in the coefficient of mass balance.

  • particular characteristics of transcritical co2 refrigeRation cycle with an ejector
    Applied Thermal Engineering, 2007
    Co-Authors: Jianqiang Deng, Peixue Jiang
    Abstract:

    Abstract The present study describes a theoretical analysis of a transcritical CO2 ejector expansion refrigeRation cycle (EERC) which uses an ejector as the main expansion device instead of an expansion valve. The system performance is strongly coupled to the ejector Entrainment Ratio which must produce the proper CO2 quality at the ejector exit. If the exit quality is not correct, either the liquid will enter the compressor or the evaporator will be filled with vapor. Thus, the ejector Entrainment Ratio significantly influences the refrigeRation effect with an optimum Ratio giving the ideal system performance. For the working conditions studied in this paper, the ejector expansion system maximum cooling COP is up to 18.6% better than the internal heat exchanger cycle (IHEC) cooling COP and 22.0% better than the conventional vapor compression refrigeRation cycle (VCRC) cooling COP. At the conditions for the maximum cooling COP, the ejector expansion cycle refrigeRation output is 8.2% better than the internal heat exchanger cycle refrigeRation output and 11.5% better than the conventional cycle refrigeRation output. An exergy analysis showed that the ejector expansion cycle greatly reduces the throttling losses. The analysis was also used to study the variations of the ejector expansion cycle cooling COP for various heat rejection pressures, refrigerant temperatures at the gas cooler exit, nozzle efficiencies and diffuser efficiencies.

Jianqiang Deng - One of the best experts on this subject based on the ideXlab platform.

  • performance analysis of a novel adiabatic compressed air energy system with ejectors enhanced charging process
    Energy, 2020
    Co-Authors: Shenghui Zhou, Yang He, Haisheng Chen, Yujie Xu, Jianqiang Deng
    Abstract:

    Abstract In an adiabatic compressed air energy storage system (A-CAES) with isochoric air storage tank, the throttle valve downstream the compressor results in large irreversible loss. In this paper, a novel A-CAES with ejectors in the charging process (ECA-CAES) is proposed to reduce throttling loss and enhance system performance. A thermodynamics model and an exergy calculation model of an ECA-CAES are established. By simulation, the influences of Entrainment Ratio, heat transfer temperature difference at cooling/heating exchangers and initial storage pressure on system performance are investigated. The simulation results show that a smaller Entrainment Ratio, a lower initial storage pressure or a smaller heat transfer temperature difference could more obviously improve the system performance. Compared with A-CAES system, the maximum roundtrip efficiency improvement of the proposed system is up to 2.34%, the maximum charge time, energy consumption of compressors and Ratio of exergy destruction improvement in charging process are up to 3.63%, 3.64%, 3.85%, respectively. The exergy analysis depicts that the introduction of ejectors decreases the exergy destruction of the CAES, especially the irreversible loss in throttling valve and compressors. Hence, the proposed system is verified to be an effective way to improve the efficiency of compressed air energy storage system.

  • Experimental study on the primary flow expansion characteristics in transcritical CO2 two-phase ejectors with different primary nozzle diverging angles
    Energy, 2019
    Co-Authors: Jianqiang Deng
    Abstract:

    Abstract This paper presented an experimental study to explore the primary flow expansion characteristics in the transcritical CO2 two-phase ejectors for various primary nozzle diverging angles (NDAs) and secondary flow pressure. The phase change of the primary flow was visualized, and the effect of the primary flow expansion state on the Entrainment Ratio was evaluated. The results disclosed that the primary flow changed from the under-expanded state to the over-expanded state with increasing the NDA, and the primary flow expansion state was insensitive to the secondary flow pressure. The visualization images showed that the phase change position moved towards the nozzle exit visibly when the NDA was 0.0°, and the effect of secondary flow pressure on the phase change position was insignificant. Besides, the results revealed that the over-expanded state of primary flow had a negative effect on the Entrainment Ratio, and the Entrainment Ratio obtained the maximum when the NDA was 2.0°. The present work is indispensable to realize a comprehensive understanding of the primary flow expansion mechanism inside the transcritical CO2 ejector, and the insights gained from this study may be of assistance to optimize the ejector structure and improve the ejector performance.

  • experimental investigation on a transcritical co2 ejector expansion refrigeRation system with two stage evapoRation
    Applied Thermal Engineering, 2017
    Co-Authors: Lixing Zheng, Jianqiang Deng
    Abstract:

    Abstract Adding a two-stage evaporator in the transcritical CO 2 ejector expansion refrigeRation system can not only regulate the quality equilibrium of system refrigerant but also improve the system performance. This paper presents an experimental study on the transcritical CO 2 ejector expansion refrigeRation system with two-stage evapoRation under variable operating conditions. Some key performance indicators such as gas cooler pressure, mass flow rate, Entrainment Ratio and pressure lift Ratio of ejector, cooling capacity and COP of system were evaluated through varying the volumetric flow rate of the second evaporator chilled water V te,wa , area Ratio of ejector A t / A mix , compressor speed N and expansion valve opening EV . The present results indicated that the second evaporator played a significant role in improving the system performance, and such improvement was more evident for smaller Entrainment Ratio. Greater gas cooler pressure, pressure lift Ratio of ejector and cooling capacity of system could be obtained by increasing the volumetric flow rate V te,wa, and compressor speed. The small area Ratio of ejector was conducive to high gas cooler pressure, great Entrainment Ratio of ejector as well as large cooling capacity and COP of system. This study provides an approach for the improvement of ejector expansion refrigeRation system.

  • particular characteristics of transcritical co2 refrigeRation cycle with an ejector
    Applied Thermal Engineering, 2007
    Co-Authors: Jianqiang Deng, Peixue Jiang
    Abstract:

    Abstract The present study describes a theoretical analysis of a transcritical CO2 ejector expansion refrigeRation cycle (EERC) which uses an ejector as the main expansion device instead of an expansion valve. The system performance is strongly coupled to the ejector Entrainment Ratio which must produce the proper CO2 quality at the ejector exit. If the exit quality is not correct, either the liquid will enter the compressor or the evaporator will be filled with vapor. Thus, the ejector Entrainment Ratio significantly influences the refrigeRation effect with an optimum Ratio giving the ideal system performance. For the working conditions studied in this paper, the ejector expansion system maximum cooling COP is up to 18.6% better than the internal heat exchanger cycle (IHEC) cooling COP and 22.0% better than the conventional vapor compression refrigeRation cycle (VCRC) cooling COP. At the conditions for the maximum cooling COP, the ejector expansion cycle refrigeRation output is 8.2% better than the internal heat exchanger cycle refrigeRation output and 11.5% better than the conventional cycle refrigeRation output. An exergy analysis showed that the ejector expansion cycle greatly reduces the throttling losses. The analysis was also used to study the variations of the ejector expansion cycle cooling COP for various heat rejection pressures, refrigerant temperatures at the gas cooler exit, nozzle efficiencies and diffuser efficiencies.

A. Mani - One of the best experts on this subject based on the ideXlab platform.

  • experimental investigations on ejector refrigeRation system with ammonia
    Renewable Energy, 2007
    Co-Authors: T. Sankarlal, A. Mani
    Abstract:

    A vapor ejector refrigeRation system has been designed and developed to operate with ammonia. In this paper, performance of ejector refrigeRation system has been experimentally studied with three different area Ratio ejectors by varying opeRational parameters namely generator, condenser and evaporator temperatures. Effect of non-dimensional parameters like compression Ratio, expansion Ratio and area Ratio on the system performance is studied. Entrainment Ratio and coefficient of performance of the system increase with increase in ejector area Ratio and expansion Ratio and they increase with decrease in compression Ratio.

  • Experimental studies on an ammonia ejector refrigeRation system
    International Communications in Heat and Mass Transfer, 2006
    Co-Authors: T. Sankarlal, A. Mani
    Abstract:

    An ejector refrigeRation system has been designed and developed to operate with a simulated (electric) heat source, which can be realized in practical applications by renewable energy sources like solar energy, geothermal energy, etc., or waste heat. In this paper, an experimental study on an ejector refrigeRation system working with ammonia is presented. The influence of the generator, condenser, and evaporator temperatures on the ejector refrigeRation system performance is presented. The Entrainment Ratio and COP of the system increase with increasing generator and evaporator temperatures and decrease with increasing condenser temperature.

  • Analysis of an ejector with environment friendly refrigerants
    Applied Thermal Engineering, 2004
    Co-Authors: A. Selvaraju, A. Mani
    Abstract:

    When an ejector is operated at choking-mode, it gives a better performance with higher Entrainment Ratio. To obtain this better performance at different operating conditions, area Ratio of the ejector is varied. A computer code based on existing one-dimensional ejector theory is written to analyze performance of the ejector. The code includes effects of friction at the constant-area mixing chamber and change in specific heat of the working fluid besides internal irreversibility of the ejector. The simulated performance is compared with the available experimental data from the literature for validation. The effects of operating parameters on critical ejector area Ratio and critical Entrainment Ratio are studied. Comparison of performance of ejector with environment friendly refrigerants, R134a, R152a, R290, R600a and R717 is made.

  • performance comparison of vapour jet refrigeRation system with environment friendly working fluids
    Applied Thermal Engineering, 2001
    Co-Authors: K Cizungu, A. Mani, Manfred Groll
    Abstract:

    A computer simulation of a vapour jet refrigeRation system is carried out using a one-dimensional model based on mass, momentum and energy balances. The simulated performance of the system is in good agreement with the available experimental performance from the literature. A comparison of system performance is carried out for the same ejector geometry using the environmentally friendly working fluids R123, R134a, R152a and R717 (ammonia). The results suggest that, for different boiler temperatures, the Entrainment Ratio and the system efficiency (COP) depend mainly on the ejector geometry and the compression Ratio.

Saffa B. Riffat - One of the best experts on this subject based on the ideXlab platform.

  • experimental and numerical analysis of a variable area Ratio steam ejector
    International Journal of Refrigeration-revue Internationale Du Froid, 2011
    Co-Authors: Szabolcs Varga, Armando C Oliveira, Siddig Omer, Wei Zhang, Saffa B. Riffat
    Abstract:

    Abstract In the present paper, experimental and CFD results for a 5 kW capacity steam ejector with variable primary nozzle geometry are presented and compared. The variable geometry was achieved by applying a movable spindle at the primary nozzle inlet. Operating conditions were considered in a range that would be suitable for an air-conditioning application, with thermal energy supplied by vacuum tube solar collectors. The CFD model was based on the axi-symmetric representation of the experimental ejector, using water as working fluid. The experimental Entrainment Ratio varied in the range of 0.1–0.5 depending on operating conditions and spindle tip position. It was found that the primary flow rate can be successfully adjusted by the spindle. CFD and experimental primary flow rates agreed well, with an average relative error of 7.7%. CFD predicted the secondary flow rate and Entrainment Ratio with good accuracy only in 70% of the cases.

  • comparison of cfd and experimental performance results of a variable area Ratio steam ejector
    International Journal of Low-carbon Technologies, 2011
    Co-Authors: Szabolcs Varga, Armando C Oliveira, Siddig Omer, Wei Zhang, Saffa B. Riffat
    Abstract:

    The advantages of numerical modelling compared with experimental studies (e.g. reduced cost, easy control of the variables, high yield etc.) are well known. Theoretical studies where experimental validation is also presented provide an important added value to numerical investigations. In the present paper, experimental and computational fluid dynamics (CFD) results for a 5-kW-rated capacity steam ejector, with a variable primary nozzle geometry, are presented and compared. The variable geometry was achieved by applying a movable spindle at the primary nozzle inlet. Relatively low operating temperatures and pressures were considered, so that the cooling system could be operated with thermal energy supplied by solar collectors (solar air-conditioning). The CFD model was based on the axi-symmetric representation of the experimental ejector, using water as a working fluid. The experimental Entrainment Ratio varied in the range of 0.1--0.5, depending on operating conditions and spindle tip position. It was found that the primary flow rate can be successfully adjusted by the spindle. CFD and experimental primary flow rates agreed well, with an average relative error of 8%. CFD predicted the secondary flow rate and Entrainment Ratio with good accuracy only in 70% of the cases. Copyright The Author 2010. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com, Oxford University Press.