The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Saffa Riffat - One of the best experts on this subject based on the ideXlab platform.
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Solar Ejector Cooling Technologies
Advanced Energy Efficiency Technologies for Solar Heating Cooling and Power Generation, 2019Co-Authors: Xiaoli Ma, Wei Zhang, Fenglei Li, Saffa RiffatAbstract:Using low-grade thermal energy instead of electricity to operate a refrigeration System can have important environmental benefits, especially when it is powered by a renewable energy source. Ejector refrigeration is one of the most promising technologies because of its relative simplicity and low capital cost when compared to an absorption refrigerator. An Ejector heat pump is a heat-operated cycle capable of utilizing solar energy, waste energy, natural gas or hybrid sources (e.g. solar/gas). An Ejector System basically consists of a generator, evaporator, condenser, Ejector, expansion valve, and a pump. The Ejector System has very few moving parts and so is simple in design. In addition, it has the potential of long life and, unlike vapour-compression Systems, produces no noise or vibration. The System could be manufactured at relatively low cost, since inexpensive construction materials may be used. Although they have a relatively low coefficient of performance compared to air-conditioning Systems using mechanical compressors, the Ejector cooling technologies have attracted extensive attentions with ever-increasing awareness and pressures for protecting the environment and have achieved significant improvement in coefficient of performance as compared to other Systems. The continuous developments in solar collector technology open the way to the effective utilization of solar energy to power the Ejector Systems and utilization of environmental friendly refrigerants is also the major concern. This chapter introduces the principle of the Ejector, basic Ejector cycle, solar-driven Ejector System and its operating. The refrigerants, solar collectors, and PCM heat storage for solar Ejector System applications are also introduced. A complete solar Ejector air-conditioning System used in a building is presented in this chapter.
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recent developments in Ejector refrigeration technologies
Renewable & Sustainable Energy Reviews, 2013Co-Authors: Xiangjie Chen, Siddig Omer, Mark Worall, Saffa RiffatAbstract:This paper aims at providing a literature review on the recent development in Ejectors, applications of Ejector refrigeration Systems and System performance enhancement. The paper presents useful guidelines regarding background and operating principles of Ejector. A number of studies are reported and categorized in several topics including, refrigerant selections, mathematical modelling and numerical simulation of Ejector System, geometric optimizations, operating conditions optimizations and combinations with other refrigeration Systems. Most of the works that have been carried out recently are still limited to computer modelling, more experimental and large-scale work are needed in order to provide better understanding for the real industrial application.
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Recent development in Ejector technology—a review
International journal of ambient energy, 2005Co-Authors: Saffa Riffat, Liben JiangAbstract:SYNOPSIS This paper presents a review of the main studies carried out on Ejectors and their applications during the period of 1995 to the present. The performance of Ejectors has been carefully considered theoretically and by experiment. It is necessary to avoid damage to the environment when using the natural working fluids. The use of water, halocarbon compounds and working pairs such as LiBr-H2O are reviewed. Applications of heat sources, e.g., solar energy, and low-grade energy have been studied. This includes the use of combined Systems, including a solar-powered Ejector refrigeration System, an absorption Ejector hybrid refrigeration System, an adsorption-Ejector System, and an Ejector/mechanical compressor System.
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Experimental and CFD modelling of an Ejector System for vehicle air conditioning
Journal of The Institute of Energy, 1999Co-Authors: Saffa Riffat, P. EverittAbstract:This paper describes the design of a steam jet Ejector and its validation. The Ejector formed part of an experimental Ejector cycle designed to be installed in a small motor vehicle to provide air-conditioning. The coolant and/or exhaust heat from the engine could be used to drive the Ejector cycle. The design of the Ejector was derived from guidelines published in the ESDU series. The Ejector System was then manufactured and tested on a laboratory controlled test rig that simulated conditions present in a small motor vehicle. Computational fluid dynamics (CFD) analysis was performed on the Ejector to determine its expected performance. The results obtained through CFD analysis were compared with the practical test data for a range of operating conditions. Comparisons were made using the mass flow ratio of the Ejector. The coefficient of performance (COP R ) of the System is presented for all operating conditions tested.
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Steam jet Ejector System for vehicle air conditioning
International journal of ambient energy, 1999Co-Authors: P. Everitt, Saffa RiffatAbstract:SYNOPSIS This paper describes the design of a steam jet Ejector. The Ejector forms the major component in an Ejector cycle, which could be installed in vehicles to provide air-conditioning. The cycle could be driven by waste heat provided by the exhaust from the engine and/or cooling water supply. The design of the Ejector was derived from 1-D analysis, as well as from guidelines published in the ESDU series. The Ejector was then manufactured and tested in a laboratory controlled test rig that simulated conditions present in a small motor vehicle. The Ejector analysis was then compared with the practical test data under design conditions as well as off design conditions. Comparisons were made using the mass flow ratio of the Ejector. The coefficient of performance (COPR) of the System is also presented for all operating conditions tested.
Bjorn Palm - One of the best experts on this subject based on the ideXlab platform.
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a review on versatile Ejector applications in refrigeration Systems
Renewable & Sustainable Energy Reviews, 2015Co-Authors: Jianyong Chen, Hans Havtun, Sad Jarall, Bjorn PalmAbstract:This paper presents a useful knowledge of Ejector working principles and the versatility and diversity of its applications in refrigeration technologies. Various Ejector refrigeration Systems are described with the associated studies, and categorized as conventional Ejector refrigeration System, advanced Ejector refrigeration Systems, combined refrigeration Systems and Ejector enhanced vapor compression Systems. This paper also presents the important elements that affect the optimum performance of the Ejector System, and the results of studies that have generally confirmed their energy saving, great potential for large refrigerating temperature scales and performance enhancement.
Takanori Matsukawa - One of the best experts on this subject based on the ideXlab platform.
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experimental analysis on the effect of internal heat exchanger in transcritical co2 refrigeration cycle with two phase Ejector
International Journal of Refrigeration-revue Internationale Du Froid, 2011Co-Authors: Masafumi Nakagawa, Ariel R Marasigan, Takanori MatsukawaAbstract:The performance of CO2 Ejector refrigeration System needs further improvement to make CO2 more viable than traditional harmful refrigerants. In this research, the effect of internal heat exchanger (IHX) in the performance of Ejector refrigeration System was analyzed experimentally and compared with conventional expansion refrigeration System. Experiments were performed at different operating pressure and temperature for the cases of without IHX, 30 cm IHX and 60 cm IHX. The results showed that IHX significantly increased the coefficient of performance (COP) of Ejector System. At the conditions used in this research, the Ejector System with 60 cm IHX provided the maximum COP improvement of up to 27% compared to similar conventional System. The motive nozzle’s inlet condition had significant effect on the performance of Ejector System. The results also confirmed the presence of considerable amount of liquid refrigerant at separator’s gas outlet of Ejector System which was deemed possible in our previous research.
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experimental investigation on the effect of mixing length on the performance of two phase Ejector for co2 refrigeration cycle with and without heat exchanger
International Journal of Refrigeration-revue Internationale Du Froid, 2011Co-Authors: Masafumi Nakagawa, Ariel R Marasigan, Takanori Matsukawa, A KurashinaAbstract:Abstract In Ejector System using the promising natural refrigerant CO 2 , the mixing of high-speed two-phase primary flow and suction vapor is crucial in designing an efficient Ejector. In this study, the effect of mixing length on Ejector System performance was analyzed experimentally. The mixing lengths used were 5 mm, 15 mm, and 25 mm, with constant rectangular cross-section. The experiments were performed for both Ejector and conventional expansion Systems with and without internal heat exchanger (IHX) at different operating conditions. Based on the experimental results, mixing length had significant effect on entrainment ratio and on magnitude and profile of pressure recovery. The 5 mm and 15 mm types yielded the lowest and highest Ejector efficiency and COP in all of the conditions used in this research, respectively. The use of IHX had net positive effect on System performance which verified the results of our previous study. A COP improvement of up to 26% over conventional System was obtained but improper sizing of mixing length lowered the COP by as much as 10%.
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EXPERIMENTAL ANALYSIS OF TWO-PHASE Ejector System WITH VARYING MIXING CROSS-SECTIONAL AREA USING NATURAL REFRIGERANT CO2
International Journal of Air-Conditioning and Refrigeration, 2010Co-Authors: Masafumi Nakagawa, Ariel R Marasigan, Takanori MatsukawaAbstract:The use of two-phase Ejector in improving the performance of transcritical CO2 refrigeration System needs further experimental verification particularly the effects of its geometrical design. In this study, experimental data were gathered for Ejectors with different mixing cross-sectional areas at different operating temperature and pressure. The results have shown that a smaller mixing area yields higher efficiency due to its higher pressure recovery and entrainment ratio, but its advantages are limited to lower Ejector inlet pressure Pc. A larger mixing area is required for higher cooling capacity which can be achieved at higher Ejector inlet pressure or lower Ejector inlet temperature but excessive increase in this area considerably decreases the efficiency of the System. In this study, the Ejector with the largest mixing area was the most inefficient and reduced the COP up to 10% compared to most efficient type. It demonstrates the significant effect of Ejector's geometrical features, particularly the mixing cross-sectional area and its related geometrical ratio, in the performance of CO2 Ejector System. The effect of motive nozzle inlet condition on pressure recovery profile has been more evident for Ejector with smaller mixing area while the evaporator temperature has the least effect in the performance of the System. In the conditions used in this study, using Ejector yielded a COP improvement of up to 35% compared to the conventional System.
Charles A. Garris - One of the best experts on this subject based on the ideXlab platform.
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Characteristics of Flow Around Cone-Vane Configurations for a Novel Crypto-Steady Pressure Exchange Ejector System
ASME 2009 3rd International Conference on Energy Sustainability Volume 1, 2009Co-Authors: Kartik V Bulusu, Charles A. GarrisAbstract:A novel Ejector based on the concept of supersonic crypto-steady pressure exchange rather than the more energy dissipative turbulent entrainment phenomenon is being developed. Crypto-steady flow is one in which, the flow is steady in a certain moving frame of reference, but is non-steady relative to the laboratory. The process of pressure exchange occurs where flows exchange mechanical energy through work of mutually exerted pressure forces at their interfaces. Such an Ejector would have higher efficiency and environmental benefits. It has been envisioned that crypto-steady pressure-exchange can be obtained by the use of a free spinning rotor (cone-vane configuration) having canted jets of primary fluid. The resolution of the flow structure with emphasis on shock and expansion waves and mixing between primary and secondary fluids is being considered under certain rotor configurations. A single component Laser Doppler Velocimeter (LDV) System has been employed in studying the interaction between the supersonic primary jet, and the entrained subsonic secondary jet under nonrotating rotor conditions. The data reduction of measurements is being performed using a simple signal conditioning and data analysis algorithm executed in real time with a digital oscilloscope and in parallel, with a more advanced frequency tracking flow processor. Crypto-steady pressure-exchange has the potential of providing society with a highly efficient means of compressing a low energy fluid through direct contact with a relatively high energy fluid. An experimental framework for investigating the process of pressure exchange is reported and a hypothesis for pseudoblade formation is also established.
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Non-Steady Pressure-Exchange Ejector
Volume 1: Fora Parts A and B, 2002Co-Authors: Khaled Alhussan, Woo Jong Hong, Charles A. GarrisAbstract:This paper will examine development of practical pressure-exchange Ejector to useful level of performance, using our knowledge of aerodynamic design of a compressible fluid. A novel supersonic rotor-vane/pressure-exchange Ejector System has been investigated both experimentally and numerically.Copyright © 2002 by ASME
Masafumi Nakagawa - One of the best experts on this subject based on the ideXlab platform.
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experimental analysis on the effect of internal heat exchanger in transcritical co2 refrigeration cycle with two phase Ejector
International Journal of Refrigeration-revue Internationale Du Froid, 2011Co-Authors: Masafumi Nakagawa, Ariel R Marasigan, Takanori MatsukawaAbstract:The performance of CO2 Ejector refrigeration System needs further improvement to make CO2 more viable than traditional harmful refrigerants. In this research, the effect of internal heat exchanger (IHX) in the performance of Ejector refrigeration System was analyzed experimentally and compared with conventional expansion refrigeration System. Experiments were performed at different operating pressure and temperature for the cases of without IHX, 30 cm IHX and 60 cm IHX. The results showed that IHX significantly increased the coefficient of performance (COP) of Ejector System. At the conditions used in this research, the Ejector System with 60 cm IHX provided the maximum COP improvement of up to 27% compared to similar conventional System. The motive nozzle’s inlet condition had significant effect on the performance of Ejector System. The results also confirmed the presence of considerable amount of liquid refrigerant at separator’s gas outlet of Ejector System which was deemed possible in our previous research.
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experimental investigation on the effect of mixing length on the performance of two phase Ejector for co2 refrigeration cycle with and without heat exchanger
International Journal of Refrigeration-revue Internationale Du Froid, 2011Co-Authors: Masafumi Nakagawa, Ariel R Marasigan, Takanori Matsukawa, A KurashinaAbstract:Abstract In Ejector System using the promising natural refrigerant CO 2 , the mixing of high-speed two-phase primary flow and suction vapor is crucial in designing an efficient Ejector. In this study, the effect of mixing length on Ejector System performance was analyzed experimentally. The mixing lengths used were 5 mm, 15 mm, and 25 mm, with constant rectangular cross-section. The experiments were performed for both Ejector and conventional expansion Systems with and without internal heat exchanger (IHX) at different operating conditions. Based on the experimental results, mixing length had significant effect on entrainment ratio and on magnitude and profile of pressure recovery. The 5 mm and 15 mm types yielded the lowest and highest Ejector efficiency and COP in all of the conditions used in this research, respectively. The use of IHX had net positive effect on System performance which verified the results of our previous study. A COP improvement of up to 26% over conventional System was obtained but improper sizing of mixing length lowered the COP by as much as 10%.
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EXPERIMENTAL ANALYSIS OF TWO-PHASE Ejector System WITH VARYING MIXING CROSS-SECTIONAL AREA USING NATURAL REFRIGERANT CO2
International Journal of Air-Conditioning and Refrigeration, 2010Co-Authors: Masafumi Nakagawa, Ariel R Marasigan, Takanori MatsukawaAbstract:The use of two-phase Ejector in improving the performance of transcritical CO2 refrigeration System needs further experimental verification particularly the effects of its geometrical design. In this study, experimental data were gathered for Ejectors with different mixing cross-sectional areas at different operating temperature and pressure. The results have shown that a smaller mixing area yields higher efficiency due to its higher pressure recovery and entrainment ratio, but its advantages are limited to lower Ejector inlet pressure Pc. A larger mixing area is required for higher cooling capacity which can be achieved at higher Ejector inlet pressure or lower Ejector inlet temperature but excessive increase in this area considerably decreases the efficiency of the System. In this study, the Ejector with the largest mixing area was the most inefficient and reduced the COP up to 10% compared to most efficient type. It demonstrates the significant effect of Ejector's geometrical features, particularly the mixing cross-sectional area and its related geometrical ratio, in the performance of CO2 Ejector System. The effect of motive nozzle inlet condition on pressure recovery profile has been more evident for Ejector with smaller mixing area while the evaporator temperature has the least effect in the performance of the System. In the conditions used in this study, using Ejector yielded a COP improvement of up to 35% compared to the conventional System.