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  • 1. Mohammed Raffe Rahamathullah, Karthick Palani, Thiagarajan Aridass, Prabakaran Venkatakrishnan, Sathiamourthy, Sarangapani Palani / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 2, March -April 2013, pp.010-034 A Review On Historical And Present Developments In Ejector Systems Mohammed Raffe Rahamathullah*1, Karthick Palani1, Thiagarajan Aridass1, Prabakaran Venkatakrishnan1, Sathiamourthy2, Sarangapani Palani3. 1 Department of Mechanical Engg. Pondicherry Engineering College, Pondicherry, India 2 Associate Professor, Department of Mechanical Engg. Pondicherry Engineering College, Pondicherry, India3 Assistant Professor, Department of Mechanical Engg. V.R.S.College of Engg. & Technology, Tamilnadu, IndiaAbstractEjectors are simple pieces of equipment. vacuum.Refrigeration is recognized as anNevertheless, many of their possible services are indispensable method of improving human beings’overlooked. They often are used to pump gases living conditions since early twentieth century.and vapours from a system to create a vacuum. Refrigeration systems, in the various applicationsHowever, they can be used for a great number of including food storage and provision of thermalother pumping situations. This paperprovides comfort, have contributed significantly to thereviewon the development in ejectors, industrial and health sectors. Conventional vapourapplications of ejector systems and system compression refrigeration cycles are driven byperformance enhancement. Several topics are electricity with the consumption of fossil fuels.categorized provides useful guidelines However, this results in air pollution and emissionregarding background and operating principles of greenhouse gases, and consequently poses aof ejector including mathematical modelling, threat to the environment. Hence, improvement onnumerical simulation of ejector system, the refrigeration system’s working performancegeometric optimizations. Research works will result in less combustion of primary energy,carried out recently are still limited to and mitigation of the environmental modelling, forthe real industrial Ejector refrigeration systems (ERS) are moreapplications more experimental and large-scale attractive com-pared with traditional vapourwork are needed in order to provide better compression refrigeration systems, with theunderstanding. advantage of simplicity in construction, installation and maintenance. Moreover, in an1. INTRODUCTION ERS, compression can be achieved without Ejectors are co-current flow systems, where consuming mechanical energy directly.simultaneous aspiration and dispersion of the Furthermore, the utilization of low-grade thermalentrained fluid takes place. This causes continuous energy (such as solar energy and industrial wasteformation of fresh interface and generation of large heat) in the system can helps to mitigate theinterfacial area because of the entrained fluid problems related to the environment, particularlybetween the phases. The ejector essentially consists by reduction ofCO2 emission from the combustionof an assemble comprising of nozzle, converging of fossil fuels.section, mixing throat and diffuser. According to the However, due to their relatively lowBernoulli’s principle when the motive fluid is coefficient of performance (COP) [1–3], ERS arepumped through the nozzle of a jet ejector at a high still less dominant in the market place comparedvelocity, a low pressure region is created at just with conventional refrigeration systems.outside the nozzle. A second fluid gets entrained Therefore, in order to promote the use of ERS,into the ejector through this low pressure region. many researchers have been engaged in enhancingThe dispersion of the entrained fluid in the throat of the performance of ejector system and combiningthe ejector with the motive fluid jet emerging from ERS with other refrigeration systems in order tothe nozzle leads to intimate mixing of the two improve the overall system performance. Buildingphases. A diffuser section of the mixing throat on other published review papers [1–3], this paperhelps in pressure recovery. The motive fluid jet aims to update the research progress andperforms two functions one, it develops the suction development in ejector technology in the lastfor the entrainment of the secondary fluid and the decade. This paper will emphasize on the varioussecond; it provides energy for the dispersion of the combination of ejectors and other cycles. Linkagesone phase into the other. This process has been and comparisons between different research caseslargely exploits in vacuum systems in which high are presented, and similar study concepts arespeed fluid stream is used to generate grouped and briefly described as overall summaries. 10 | P a g e
  • 2. Mohammed Raffe Rahamathullah, Karthick Palani, Thiagarajan Aridass, Prabakaran Venkatakrishnan, Sathiamourthy, Sarangapani Palani / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 2, March -April 2013, pp.010-0342. DEVELOPMENTS IN EJECTOR Compared with a similar model designed by SunMODELS and Eames [55] under same operating Ejector refrigeration systems were first temperatures, Yapici’s model showed better COP.invented by Sir Charles Parsons around 1901 for Elakhdar et al. [20] developed a mathematicalremoving air from a steam engine’s condenser. It model in order to specifically design a R134awas later used in the first steam jet refrigeration ejector and predict the performance characteristicssystem by Maurice Leblanc et al. [50] in 1910. over different operating conditions. SimulationSince then, considerable efforts have been results showed that the present model data were inconcentrated on the enhancement and refinement good agreement with experimental data in theof ERS. literature with an average error of 6%. A constant- area 1-D model was recently presented by Khalil2.1 Single Phase Models et al. [30]. Governing equations were developed A one dimensional model described by for the ejector’s three different operating regimes,Keenan et al. [51] in 1950 was the first application supersonic regime, the transition regime and theof continuity, momentum and energy equation in mixed regime. Environmental friendly refrigerantsejector design principle. This model has been used were used as working fluids in the a theoretical basis in ejector design since then. Results were compared with that of experimentalKeenan’s model, however, cannot predict the data available in the literature, and good agreementconstant-capacity characteristic and was later was demonstrated.All the above models are basedmodified by Munday and Bagster [52]. Based on on ideal gas assumption which does not reflect thetheir theory, it is assumed that the primary fluid actual process occurring in the ejector. Rogdakisflows out without mixing with the secondary fluid and Alexis [56] improved the model proposed byimmediately induces a converging duct for the Munday and Bagster [52] by using thesecondary fluid. This duct acts as a converging thermodynamic and transportation properties ofnozzle such that the secondary flow is accelerated real gases. When considering the friction losses, ato a sonic velocity at some place, known as constant coefficient was assumed to simplify theeffective or hypothetical throat. After that both model.fluids mix with a uniform pressure. Eames et al.[44] studied a small-scale steam-jet refrigerator However, the friction losses were closelyand presented a theoretical model that included related to the velocity, and the velocity variedirreversibilities associated with the primary nozzle, considerably along the ejector. Taking this intothe mixing chamber and the diffuser. This model account, Selvaraju and Mani [19] developed awas based on constant-pressure mixing process, model based on Munday and Bagster’s theory forbut without considering the choking of the critical performance analysis of the ejector system.secondary flow. In order to take this in to account, This model applied an expression to describe theHuang et al. [36] presented a one-dimensional friction losses in the constant area section. A 1-Dcritical model (double-chocking) by assuming that model avoiding the ideal gas assumption wasmixing of two streams occurs inside constant area proposed by Grazzini et al. [57]. Heat exchangersection with uniform pressure. The model was irreversibilities were taken into consideration, andexperimentally verified with 11 different ejectors real gas behaviour was simulated. A comparisonusing R141b as the working fluid. In order to between different refrigerants was presented andsimplify the model, more models [53] were R245fa was selected as a working fluid. However,proposed to calculate the performance of ERS. In validation with experimental data in literature wasthese models, the thermo-physical and not available. In order to check the validity of thetransportation properties need to be obtained from ideal gas assumption, Grazzini et al. [58] evolveddata base, which limits their application. another model with the key concept of metastable state. To set the border for metastable region, a Zhu et al. [54] proposed an ejector for a spinodal curve was introduced. The modellingreal time control and optimization of an ejector results were compared with experimental data. Thesystem, which was based on one-dimension author concluded that in order to avoidanalysis. Though the model is simplified, the complexity, the metastable behaviour of steam canexpressions were more complex and some be implemented in a single 1-D model givingparameters needed to be determined stable results.experimentally. In order to give a more accurateprediction of the ejector performance in the mixing 2.2 Two Phase Modelschamber, Yapici and Ersoy [18] derived a local The abovementioned models are based onmodel based on constant-area mixing process. The the assumption that the flow in the ejector is inejector consisted of a primary nozzle, a mixing compressible single phase and recompressionchamber in cylindrical structure and a diffuser. occurs across a normal shock wave. However, 11 | P a g e
  • 3. Mohammed Raffe Rahamathullah, Karthick Palani, Thiagarajan Aridass, Prabakaran Venkatakrishnan, Sathiamourthy, Sarangapani Palani / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 2, March -April 2013, pp.010-034under many real applications, phase change can data and good agreement was found. The selectionoccur and a condensation shock may develop. of correct turbulence model plays an importantThus, some researchers are engaged in ejector role in predicting the mixing process in the ejectorsimulation with two-phase flow. By introducing for CFD studies. Turbulence effects in the ejectordryness of the fluid in the calculation of the have been modelled using the standard k-epsilonspecific volume, enthalpy and entropy, Sherif et al. turbulence model by Scott [61] using CFD. The[59] derived an isentropic homogeneous CFD results were later verified with anexpansion/compression model to account for phase experimental investigation of an ejector withchange due to expansion, compression and mixing. R245fa as a working fluid [62]. Comparisons wereIn this model, the primary fluid was a two-phase made between results from experiments, CFDmixture and the secondary fluid was either a sub- model and a theoretical 1-D model by Ouzzanecooled or saturated liquid having the same and Aidoun [63]. It was concluded that CFDchemical composition as the primary fluid. model provided better agreement (difference ofCizungu et al. [45] derived a two-phase less than 16%) than 1-D model. Aiming atthermodynamic model to calculate the entrainment validation the choice of a turbulence model for theratio. This model can be used both for single-phase computation of supersonic ejectors in refrigerationand two-phase ejector with single component or applications, Bartosiewicz et al. [64] comparedtwo components working fluids. He et al. [60] experimental distribution data with results ofinvestigated the usefulness of a multivariate grey simulation using different turbulence models.prediction model, which incorporated grey However, the choice of air as working fluid andrelational analysis to predict the performance of other test conditions were not very in accordanceERS. The importance of influencing variables was with cooling cycles. Later they extended theirfirst evaluated, and then the variables were ranked work using R142b as refrigerant et al. [65]. Withaccording to the grey relational method. It also consideration of shock-boundary layercompared the performance of the combined grey interactions, this ejector model contributed to themodel with that of conventional one-dimension understanding of the local structure of the flow andtheory model as well as experimental data. The demonstrated the crucial role of the secondarysimulation results showed that the grey system nozzle for the mixing rate performance.theory can be used to analyze the ERS. Pianthong et al. [5] employed the CFD with realizable k-epsilon turbulence model to2.3 CFD models predict the flow phenomena and performance in Despite the remarkable progress, made in steam ejectors with application in refrigerationthermodynamic modelling, these models were system. The result indicated that CFD can predictunable to reproduce the flow physics locally along ejector performance very well and reveal the effectthe ejector. It is the understanding of local of operating conditions on the effective area thatinteractions between shock waves and boundary was directly related to its performance. In order tolayers, their influence on mixing and re- consider the sensitivity of the turbulence modelcompression rate that will produce a more reliable over several conditions, Hemidi et al. [66] carriedand accurate design, in terms of geometry, out CFD analysis of a supersonic air ejector withrefrigerant type and operation conditions. single and two phase operation. Entrainment ratioComputational Fluid Dynamics (CFD) modelling based on K-epsilon model and k-o-sst model werecan provide more accurate simulations of the compared with experimental data. The resultsejector in accordance with experiment results. demonstrated that even with the same predictionEarly CFD studies can be traced back to late level, both models could provide very different1990s. However, they failed to overcome some of local flow structures.the fundamental problems, especially regarding thesimulation of shock-mixing layer interaction and 2.4 Non Steady Flow Modelsejector operation under different working Since the mid-1990s, some researchersconditions. Compressibility or turbulence was have focused on the theory and implementation ofhardly taken into consideration. Even when non-steady or pressure-exchange ejector.turbulence was considered, only k-epsilon based Compared with conventional steady ejectors, non-models were used. No experimental validations or steady ejectors allow energy transfer between twojustification, except for CPUcost were carried out. directly interacting fluids but maintaining themRecently, Rusly et al. [32] stimulated the flow separable. By utilizing the reversible work ofthrough an R141b ejector by using the real gas pressure forces acting at fluid interfaces betweenmodel in the commercial code, FLUENT. The primary flow and secondary flow, non-steadyeffects of ejector geometries on system ejectors have the potential of much greaterperformance were investigated numerically. momentum transfer efficiency. The CFD results were validated with experimental Recently, Hong et al. [67] presented a novel 12 | P a g e
  • 4. Mohammed Raffe Rahamathullah, Karthick Palani, Thiagarajan Aridass, Prabakaran Venkatakrishnan, Sathiamourthy, Sarangapani Palani / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 2, March -April 2013, pp.010-034thermal driven rotor-vane/pressure-exchange ERS. However, due to mechanical difficulties, theUnlike other pressure-exchange ejectors which had experimental work was halted, only numericalcanted primary nozzles on their rotors, the rotor of simulation was presented. Gould et al. [29] carriedthis ejector had vanes directly on it and a primary out theoretical analysis of a steam pressurenozzle separated from it. Computational study and exchange (PE) ejector in automotive airexperimental work were included in order to conditioning (AC) system. Waste heat from theoptimize the ejector geometry. However, the engine of vehicle was utilized as the main heatconcentrations were only placed on the overall source. Comparisons were made between ashape of rotor vane, without considering Mach conventional R134a AC system and the steam PEnumber of incoming flow, the geometry in the ejector AC system at idling and 50 mphinteraction zone and the diffuser geometry. conditions. The results showed that the steam PEAbabneh et al. [68] studied the effects of the ejector system consumed at least 68% less energysecondary fluid temperature on the energy transfer than R134a AC system. And COP of PE ejectorin a non-steady ejector with a radial-flow diffuser. AC system was 2.5–5.5 times that of R134a ACThe flow field was analyzed at Mach numbers 2.5 system at both conditions. However, theand 3.0, with a range of temperatures from À 10 theoretical data were not verified with1C to 55 1C. The results revealed that the actual experimental results.Table 1 lists the referencesenergy transfer to the secondary fluid, which with different model types and their key simulationincluded the effects of irreversibilities, decreased results.with the increase in ambient temperature. Table 1 – Working conditions and Simulation Results for Selected Models3.DEVELOPMENTS IN EJECTOR between primary nozzle and constant area section.GEOMETRIC OPTIMIZATION It is known that flow emerges from the primary In order to make the ejector system more nozzle and maintains its definition as primary fluideconomically attractive, a number of researches for some distance. The secondary fluid is entrainedhave been investigated the optimization of the into the region between the primary fluid and theejector geometry on system performance. ejector wall. If an ejector of fixed primary pressure, secondary pressure and nozzle geometry3.1 Area Ratio is considered, increasing the mixing section area An important non-dimensional factor will result in a greater flow area for the secondaryaffecting ejector performance is the area ratio A stream. The entrainment ratio will therefore 13 | P a g e
  • 5. Mohammed Raffe Rahamathullah, Karthick Palani, Thiagarajan Aridass, Prabakaran Venkatakrishnan, Sathiamourthy, Sarangapani Palani / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 2, March -April 2013, pp.010-034increase but since the compression work available conditions. In order to overcome this problem, afrom the primary flow is unchanged, the ejector is new feature a spindle was implemented and testedunable to compress to higher discharge pressures. numerically and experimentally by Ma et al. [6]In this case, according to Varga et al. [42] and Varga et al. [69]. By changing the spindleincreasing A increases entrainment ratio and position, the area ratio A can be changed. As thedecreases the critical back (condenser) pressure spindle tip travels forward, the primary nozzleand therefore an optimal value should exist, throat area decreases, and consequently Adepending on operating conditions. Yapici et al. increases. CFD simulation was carried out by[15] studied the performance of R123, using six Varga et al. [70] to analyze the effect area ratio onconfigurations of ejector over a range of the ejector the ejector performance. The authors indicated thatarea ratio from 6.5 to 11.5. It was concluded that ejectors with area ratios varying from 13.5 to 26.4the optimum area ratio increased approximately could achieve entrainment ratios from 0.18 to 0.38.linearly with generator temperature in the ranges They also pointed out that by changing the spindleof 83–103 1C. Instead of using water-cooled position, an optimal A can be achieved with acondenser, Jia et al. [21] presented an experimental single ejector.investigation on air-cooled ERS using R134a with Experimental investigation of this spindle system2 kW cooling capacity. Replaceable nozzles with was carried out by Ma et al. [6] using water asvarying ejector area ratios from 2.74 to 5.37 were refrigerant. The results showed that when spindleused, and the best system performance was shown position was 8 mm inwards the mixing chamber,for area ratio from 3.69 to 4.76. an optimum entrainment ratio of 0.38 could be Cizungu et al. [45] modelled a two-phase achieved, which were less than the maximumejector with ammonia as working fluid, and found value of Varga’s CFD modelling [70] at almostout a quasi linear dependence between A and the same designed working conditions. The group [69]driving pressure ratio (pressure ratio of boiler to later summarized and compared the experimentalcondenser). This result was suitable for the rough results with CFD data. It was concluded that CFDdraft of sizing and operational behaviour of the and experimental primary flow rates agreed well,refrigerator. Area ratio, however, can be identified with an average relative error of 7.7%. Table 2as a single optimum that would bring the ejector to shows the various studies on the ejector’s areaoperate at critical mode for a given condenser ratio with different working conditions.temperature. Obviously, this would requiredifferent ejectors for different operatingTable 2 Results on the Ejector’s Area Ratio with Different Working Conditions3.2 Nozzle Exit Position (NXP) exit into the mixing chamberreduced COP andThe nozzle exit position (NXP) inwards or cooling capacity. Recently, Eames et al. [48]foundoutwards the mixing chamber is known to affect a clear optimum of the entrainment ratio (40%both the entrainment and pressure lift ratio increases) at5 mm from the entrance of theperformance of ejectors. In the experimental entrainment chamber. In this casethe ejector tailstudies [7,10,16] and CFD simulations [32, 64, 71– was designed by the constant momentum74], it was demonstrated that moving the nozzle ratechange (CMRC) method and R245fa was used 14 | P a g e
  • 6. Mohammed Raffe Rahamathullah, Karthick Palani, Thiagarajan Aridass, Prabakaran Venkatakrishnan, Sathiamourthy, Sarangapani Palani / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 2, March -April 2013, pp.010-034as working fluid.Similar conclusions can be found effects of various nozzle outlet diameters D nt (Dntfrom numerical investigationscarried out by Varga 2 mm, 2.5 mm and 3 mm) of a motive nozzle onet al. [70] and Zhu et al. [75]. CFD the system performance. The Nozzle with outletmodellingresults from Varga et al. [70] indicated diameter of 2 mm was found to yield the highestthat an optimum entrainment ratio of 0.33 can be COP.achieved when NXP was 60 mmdownstream. Zhuet al. [75] reported that the optimum NXPwas not 3.4 Constant Area Section Length and Diffuseronly proportional to the mixing section throat Geometrydiameter,but also increased as the primary flow Constant area section length is commonlypressure rises. The authorsalso pointed out that the believed to have no influence on the entrainmentejector performance was very sensitiveto the ratio [26, 40]. However, Pianthong et al. [5]converging angle y of the mixing section. When reported that the critical back pressure increasedNXP waswithin its optimum range, the optimum y with Lm and thus allowed to operate the ejector inwas in the range of1.45–4.21. A relative larger y double chocking mode in a wider range ofwas required to maximize ejectorperformance operating conditions. As seen from Fig. 1, awhen the primary flow pressure raised. In contrast, thermodynamic shock wave can cause a suddenCFD analyses of Rusly et al. [32] and Pianthonget fall in Mach number as the flow changes fromal. [5] showed that NXP only had a small influence supersonic (Ma>1) to subsonic (Ma<1). Thisonentrainment ratio. In the first case, a 20% process results in a fall in total pressure and thisvariation in NXP wasconsidered in an ejector effect reduces the maximum pressure lift ratio,using R141b as working fluid. Comparedto the which a conventional ejector refrigerator canbase model, moving the nozzle towards the achieve. With the aim to overcome this shortfall,constant areasection caused l to decrease, while Eames et al. [77] developed the constant rate ofmoving it in the otherdirection l remained momentum change (CRMC) method to produce apractically unchanged. The authors claimedthat the diffuser geometry that removes theoptimum NXP of 1.5 diameters of the constant thermodynamics shock process within the diffuserareasection produced better performance. at the design-point operating conditions.Pianthong et al. [5] varied NXP in the range from Theoretical results described in this paper15 to 10 mm from the mixing chamberinlet. The indicated significant improvements in bothentrainment ratio increased slightly as NXP was entrainment ratio and pressure lift ratio, abovemovedfurther from the inlet section.Optimum those achievable from ejector designed usingprimary nozzle position or converging angle conventional methods. Experimental data werecannot bepredefined to meet all operating presented by Worall et al. [78] that supported theconditions. When the operatingconditions are theoretical findings.different from the design point, the NXP shouldbeadjusted accordingly to maximize the ejector 4. DEVELOPMENTS IN EJECTORperformance. An ejectorwith movable primary PERFORMANCE IMPROVEMENTnozzle can provide a flexible NXP when The ability of making use of renewabletheconditions are out of the design point. This was energy and theadvantages of simplicity infirst presented byAphornratana and Eames [76]. construction, installation and maintenance make Recently Yapici et al. [13] carried outan ERS more cost-effectively competitiveexperimental investigation on an ejector comparedwith other refrigeration system. Therefrigerator with movableprimary nozzle. The system performance for ERS,however, is relativelyauthor concluded that the optimum primary nozzle low. Hence, the engineers and researchersareexit should be 5 mm from the mixing chamber making efforts to improve system efficiency forinlet.Due to the varying nature of the operation ERS. Pastdecade has seen many researchconditions as wellas the different ejector innovations of enhancing systemperformance,geometries, no general agreement can beachieved including reduction of the mechanical pumpamong various researches. workin ERS, utilization of the special refrigerants, and utilization andstorage of available renewable3.3 Primary Nozzle Diameter energy. Many research groupshave widely carried The relationship between primary nozzle out theoretical calculations, computer simulationsdiameter and the boiler temperature was reported and experimental works in these Cizungu et al. [45]. Using ammonia as workingfluid, the author stated that the optimum primary 4.1 EJECTOR REFRIGERATION SYSTEMnozzle diameter decreased with increase in the WITHOUT PUMPboiler temperature. Similar results were obtained The pump, with the function to conveyby Sun [16] with an ejector driven by the working liquid condensate inthe condenser back to thefluid R123. Chaiwongsa et al. [10] analyzed the generator, is the only moving part inthe ERS. This 15 | P a g e
  • 7. Mohammed Raffe Rahamathullah, Karthick Palani, Thiagarajan Aridass, Prabakaran Venkatakrishnan, Sathiamourthy, Sarangapani Palani / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 2, March -April 2013, pp.010-034equipment, however, not only requires refrigerant hydrostatic pressure, theverticaladditionalmechanical energy, but also needs more arrangement of the heat exchangers enablesmaintenance than otherparts. Hence, many pressuredifferences between the exchangers to beresearchers have tried to utilize other methods to equalized. The lowestpressure in the refrigeratoreliminate those shortcomings. installation was obtained in theevaporator. It caused the inflow of liquid to the highest4.1.1 Gravitational Ejector installation level. The highest pressure was Kasperski et al. [79] presented a obtained in a steam generator, which forces thegravitational ERS (as shown inFig. 1) in a lowest liquid level.The limitation of this systemsimulation model. Unlike the pump version lies in its requirement of greatheight differencesejectorrefrigerator, the heat exchangers are placed and the length of pipe work, whichat different levels.Thus, with the help of the increasesfriction and heat losses. Fig. 1 Schematic Diagram of a Gravitational Ejector Refrigerator [79]Fig. 2 Schematic Diagram of Liquid Refrigerant Levels in Gravitational (a) and Roto-Gravitational (b) Ejector Refrigerators [80]Therefore, the conception of the gravitational A schematic view of a solar-powered bi-ERSrefrigerator (Fig. 2a) was later developed into a designed by Shenet al. [81] is shown in Fig. 3. Inrotatingrefrigerator (Fig. 2b) by Kasperski et this system, an ejector (injector)replaces theal.[80]. With lager accelerations of rotary motion, mechanical pump to promote pressure of thethis roto-gravitational refrigerator significantly liquidcondensate and conveys the condensate backdecreased the size of the gravitational to the generator.Ideally, the system will lead torefrigerator.However, the author only proposed a zero electricity consumption.The authors studiedmathematical model, no experimental results were the performance of this system withdifferentpresented. refrigerants using numerical modelling. The resultshowed that the overall COP of the system4.1.2 Bi-Ejector Refrigeration System was mainly affectedby the gas–gas ejector 16 | P a g e
  • 8. Mohammed Raffe Rahamathullah, Karthick Palani, Thiagarajan Aridass, Prabakaran Venkatakrishnan, Sathiamourthy, Sarangapani Palani / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 2, March -April 2013, pp.010-034entrainment ratio in the refrigeration (injector) entrainment ratio ofR718 was relativelyloop.Compared with other refrigerants, under the high.same operatingconditions, the gas–liquid ejector Fig. 3 Schematic Diagram of Solar-Powered Bi-ERS [81]However, the best overall system COPachieved evacuation chamber. The vapourgenerator was awas 0.26 using R717 as the refrigerant.In the heat exchanger like a conventional boilerproceeding work, Wang and Shen [82] took forpressurizing and to generating vapour. Theconsiderations of the effect of injector structures evacuation chamberwas composed of a coolingon the system performance. The real fluid’s jacket and a liquid holding tank. Thecooling jacketthermal properties were considered in thenew provided a cooling effect to depressurizeinjector thermodynamic model. The authors thegenerator in order to intake the liquid fromconcluded thatwith increasing generator condenser. Detailedsystem description can betemperature, the entrainment ratio ofthe injector referred to Huang and Wang [83, 84].This systemand the thermal efficiency of the solar collector makes use of the pressure change in thewerereduced, whilst the entrainment ratio of the generatorto create backflow of liquid condensate.ejector and COP ofbi-ER sub-system were However, the system iscomposed of too manyimproved. The overall COP of the systemreached elements, which will lead toan optimum value of 0.132. unavoidableconsumption of available thermal energy.4.1.3 Ejector Refrigeration System withThermal Pumping Effect 4.1.4 Heat Pipe and Ejector Cooling SystemAn ERS that utilizes a multi-function generator Integration of the heat pipe with an ejector will(MFG) to eliminate the mechanical pump was result in a compact and high performance system,presented by Huang and Wang[83,84]. The MFG which does not require additional pump work. Thisserves as both a pump and a vapour generator. system can also utilize solar energy or hybridTherewere two generators in the ECS/MFG. Each sources and so reduces the demand for electricitygenerator consisted ofa vapour generator and an and thus fossil fuel consumption. Fig. 4 Schematic Diagram of Heat Pipe / Ejector Refrigeration System [85] 17 | P a g e
  • 9. Mohammed Raffe Rahamathullah, Karthick Palani, Thiagarajan Aridass, Prabakaran Venkatakrishnan, Sathiamourthy, Sarangapani Palani / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 2, March -April 2013, pp.010-034The basic cycle of the heat pipe/ERS is shown in that the COP of this system increased from 9.3% toFig. 4. The system consists of a heat pipe, ejector, 12.1% when generator temperature was in arrangeevaporator and expansion valve. The low potential of 80–160 1C, the condensing temperature was inheat is added to the system in the generator section. arrange of 35–45 1C and the evaporatingThen the working fluid evaporates and flows temperature was fixed at10 1C.through the primary nozzle of the ejector.Therefore it expands and contributes to thedecrease of the pressure in the evaporator. Thus,the refrigeration cycle can be completed. In thecondenser, some of the working fluid was returnedto the generator by the wick action, while theremainder was expanded through the expansionvalve to the evaporator. Unlike other vapourcompression refrigeration system, which ispowered by mains electricity generated by largeplants, the heat pipe/ERS does not require anyelectricity input. With the aim of finding theoptimum operating conditions for a heat pipe/ERS,Ziapour et al. [85] carried out an energy and exergyanalysis based on the first and second laws ofthermo- dynamics. The simulation results were Fig. 5 Schematic diagram of an Ejectorcompared with available experimental data from Refrigeration System with Additional Jet Pumpliterature for steam ejector refrigerator. [25]4.2.EJECTOR REFRIGERATION SYSTEMWITH MULTI-COMPONENTSAlthough the single stage ERS is simple, it isdifficult to keep the system running at optimumconditions due to the variation of workingconditions. Ambient temperatures above designconditions or lower generator temperature oftenlead to operational difficulties. Attempts have beenmade to solve this problem by using multi-components ejectors.4.2.1Ejector Refrigeration System with anAdditional Jet PumpYu et al. [25] proposed an ERS with an additionalliquid–vapour jet pump, as shown in Fig. 5. Thisadditional jet pump is applied to entrain the mixingvapour from the ejector, which acts as secondaryflow for jet pump. In this case, the backpressure of Fig.6. Schematic Diagram of a Refrigerationthe ejector can be reduced by the jet-pump, and System with Additional Jet Pump [86]then the entrainment ratio and COP of the systemcould be increased. Simulation results showed that, 4.2.2 Multi-Stage Ejector Refrigeration Systemcompared with conventional ERS at same working An example of the multi-stage ejector refrigerationconditions, the COP of NERS was increased by system arrangement is shown in Fig. 7. Several57.1% and 45.9%, with R152a and R134a, ejectors are placed in parallel before the condenser.respectively as refrigerants. The group [86] later One ejector operates at a time and the operation ofpresented another system with similar each ejector is determined by the condenserconfiguration (as shown in Fig. 6). In this system, pressure. Ejector 1 operates when the condenserthe auxiliary jet pump was designed to accomplish pressure is below Pc1ejector2 operates at athe effects of both entrainment and regeneration. condenser pressure between Pc1 and Pc2; andDifferent from conventional ERS, the exhaust of ejector 3 operates at a condenser pressure betweenthe ejector in this system was divided into two Pc2 and Pc3. This arrangement was proposed byparts. One part was discharged at the normal Sokolov and Hershgal [87]. However practicalcondenser pressure, another part was discharged at work was not available.a higher pressure than the condenser pressure, andthus this part with higher temperature was rejectedas heat for regeneration. Compared with theconventional system, the simulation results showed 18 | P a g e
  • 10. Mohammed Raffe Rahamathullah, Karthick Palani, Thiagarajan Aridass, Prabakaran Venkatakrishnan, Sathiamourthy, Sarangapani Palani / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 2, March -April 2013, pp.010-034 hybrid circulatory system, where the evaporators of the cooling chamber and freezing chamber are in parallel.Fig. 7 Schematic Diagram of Multi-Stage ERS[87]4.2.3 Multi-Evaporator Compression SystemMulti-evaporator compression systems (MECS) aregenerally used in transport refrigerationapplications. Kairouani et al. [27] studied a multi-evaporator refrigeration system utilizing ejector forvapour pre-compression. As shown in Fig. 8, theejectors are positioned at the outlets of evaporators,which can increase the suction pressure. In thediffuser, the kinetic energy of the mixture isconverted into pressure energy. The specific workof the compressor is reduced and then the COP ofthe system is improved. A comparison of thesystem performances with environment friendlyrefrigerants (R290, R600a, R717, R134a, R152a,and R141b) is made. R141b proved to give themost advantageous COP among all working fluids. Fig. 9Schematic Diagram of (a) Two-Evaporator Refrigeration Cycle in Series Hybrid System, (b) Two-Evaporator Refrigeration Cycle in Parallel Hybrid System, (c) Two-Evaporator Refrigeration Cycle in Parallel and Crossed- Regenerative Hybrid Systems [88] The pressure at the connector of the three ejectorsFig. 8 Schematic Diagram of a Multi- and the power consumption were measured, andEvaporators Compression System [27] the performances of the three different connectionLiu et al. [88] presented three different forms for compressor-jet mixing of theconfigurations for two- evaporator refrigeration refrigeration cycle were compared. Results showedcycle. As shown in Fig. 13 the working principles that for the compression–injection crossed-of series (Fig. 9a) and parallel (Fig. 9b) systems regenerative hybrid refrigeration cycle system, losscan be easily recognized from the schematic views. of heat in the throttle processing was decreasedThe combined circulatory cross-regenerative effectively by an ejector. Energy consumptions ofthermal system (Fig. 9c) is an improvement of the the first two prototypes were 0.775kWh/day and 0.748 kWh/day, which were higher than the 19 | P a g e
  • 11. Mohammed Raffe Rahamathullah, Karthick Palani, Thiagarajan Aridass, Prabakaran Venkatakrishnan, Sathiamourthy, Sarangapani Palani / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 2, March -April 2013, pp.010-034traditional prototype. The power consumption can (TERS) with R134a as working fluid. Thebe reduced to 0.655kWh/day for the third one, schematic diagram is shown in Fig. 11. The studywhich was 7.75% lower than the traditional calculation model for the ejector is the constant-prototype.Autocascade refrigeration system can use pressure mixing model. The generatingonly one compressor to obtain lower refrigerating temperatureranged from 60 to 100°C with atemperature between -40°c to -180°c. In order to pressure range of 6–10 MPa.The numericalreduce the throttling loss generated by throttling results indicated that COP of TERS weredevices, an ejector is introduced to the system to between0.35 and 0.75, almost double that ofrecover the kinetic energy in the expansion process. conventional ERS, withgenerator temperature atYu et al. [28] applied an ejector in autocascade 80°C, evaporator temperature in therange of 10–refrigerator with refrigerant mixture of R23/R134a. 15°C and the condensing temperature in the rangeAs shown in Fig. 10, the ejector is set between the of30–40°C. The authors conclude that the higherevaporative, condenser and the evaporator. working pressurein the TERS resulted in a moreThermo- dynamic analysis showed that the system compact system. However, no experimentalemployed with an ejector had merits in decreasing verification is available.the pressure ratio of the compressor as well asincreasing COP. With condenser outlet temperature Fig. 11 Schematic Diagram of the Transcriticalof 40°c, evaporator inlet temperature of -40.3°c and Ejector Refrigeration System [89]the mass fraction of R23 were0.15; the COP wasimproved by 19.1% over the conventionalautocascade refrigeration cycle. Similarly, a number of studies [90–93] have concentrated on TERSwith CO2 as refrigerant. Li and Groll [90] investigated theoretically theperformance of transcritical CO2 refrigeration cycle with ejector-expansion device (as shown in Fig. 12). This system incorporated avapour backflow valve to relax the constraints between the entrainment ratio of the ejector and the qualityFig. 10 Schematic Diagram of Autocascade of the ejector outlet stream.The effect of differentRefrigeration Cycle with an Ejector [28] operating conditions on the relative performance of the ejector expansion transcritical CO2 cycle was alsoinvestigated using assumed values for the4.3 Transcritical Ejector Refrigeration Systems entrainment ratio andpressure drop in the Different from other ERS whose receiving section of the ejector. Therefrigerants are working in their subcritical cycle, resultsdemonstrated that the ejector expansionthe refrigerant of transcritical ERS (TERS) cycle improved the COP bymore than 16%operates in transcritical process. Characteristic for compared to the basic cycle for typical airthe process is heat rejection in the supercritical conditioning applications.region, introducing a gliding temperature instead ofcondensation at constant temperature. Comparedwith an ERS, the TERS has a higher potential inmaking use of the low-grade thermal energy withgradient temperature due to a better matching to thetemperature glide of the refrigerant. Yu et al. [89]carried out a theoretical study of a transcritical ERS 20 | P a g e
  • 12. Mohammed Raffe Rahamathullah, Karthick Palani, Thiagarajan Aridass, Prabakaran Venkatakrishnan, Sathiamourthy, Sarangapani Palani / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 2, March -April 2013, pp.010-034 conventional ejector-expansion TRCC.Fig. 12 Schematic Diagram of the New EjectorExpansion Refrigeration Cycle [90] Fig. 14 Schematic Diagram of Transcritical Carbon Dioxide Cycle with Ejector [94] 4.4 SOLAR-DRIVEN EJECTOR REFRIGERATION SYSTEM Because of the ability of harnessing solar energy, the solar-driven ERS is less energy demanding and more environmentalfriendly in comparison with conventional vapour compressionrefrigeration system. However, due to the intermittent feature ofsolar energy, the unstable heat gains from solar sources inherently affect the operation of solar-driven ERS. Thus, thermalstorage system integrated with solar- driven ERS is becoming ahot research topic.Fig. 13 Schematic Diagram of the EjectorExpansion System [91] 4.4.1 Conventional Solar-Driven EjectorDeng et al. [91] presented a theoretical analysis of Refrigeration Systema transcritical CO2 ejector expansion refrigeration Conventional solar-driven ERS has beencycle (shown in Fig. 13),which uses an ejector as widely studied duringpast decade. Heat from thethe main expansion device instead of anexpansion solar collector is carried by theintermediatevalve. The results indicated that the ejector medium and transferred to the refrigerant byentrainment ratio significantly influence the theheat exchanger. The heat transfer mediumsrefrigeration effect with anoptimum ratio giving should have theboiling point higher than thethe ideal system performance. It was foundthat for possible temperature in the system,low viscositythe working conditions described in their paper, and good heat transfer properties. Water withtheejector improved the maximum COP to 18.6% acorrosion inhibitor additive and transforming oilcompared tothe internal heat exchanger system are recommended for operating temperatureand 22% compared to theconventional below and above 100°C,respectively. However,system.Yari and Sirousazar [94] investigated a since water will freeze below 0°C, Vargaet transcritical CO 2refrigeration cycle (TRCC) [43] found that the system working at very lowwith an ejector, internal heat exchangerand evaporatortemperature was not suitable for usingintercooler (shown in Fig. 14). This cycle utilized water as refrigerant.Theoretical analysis of athe internalheat exchanger and intercooler to solar-driven ERS in the Mediterraneanwas carriedenhance its performancesignificantly. It was out by Varga et al. [43]. Based on a simplified 1-found that, the new ejector expansion Dmodel, the authors studied both the refrigerationTRCCimproved the maximum COP and second and solarcollector cycles for a 5 kW coolinglaw efficiency up to 26%compared to 21 | P a g e
  • 13. Mohammed Raffe Rahamathullah, Karthick Palani, Thiagarajan Aridass, Prabakaran Venkatakrishnan, Sathiamourthy, Sarangapani Palani / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 2, March -April 2013, pp.010-034capacity. The results indicatedthat, in order toachieve acceptable COP, generatortemperatureshould not fall below 90°C and solarcollector output temperature of about 100°Cwould be required. For highercondensertemperatures (>35°C) and lowerevaporator temperature(<10°C), the solarcollector area required for 5 kW cooling loadwaslarger than 50 m2.R134a was proposed as arefrigerant for a solar-driven ejectorsystem byAlexis and Karayiannis et al. [22]. It was foundthat COPof ejector cooling system varied from0.035 to 0.199 for generatortemperatures rangingfrom 82 to 92°C, condenser temperaturesrangingfrom 32 to 40°C and evaporator temperatures Fig. 15 Schematic Diagram of Solar-Assistedrangingfrom-10 to 0°C.Ersoy et al. [17] Ejector Refrigerator with Cold Storage [97]conducted a numerical investigation ontheperformance of a solar-driven ejector coolingsystem using R114under Turkish climaticconditions. When generator, condenser,andevaporator temperatures were taken at 85°C, 30°Cand 12°C,respectively, the maximum overall COPand the cooling capacityobtained were as 0.197and 178.26 W/m2.4.2.2 Solar-Driven Ejector RefrigerationSystem with ThermalStorage SystemDuring some adverse weather conditions, thecooling capacityprovided by available solarenergy cannot be essentially matchedwith thecooling demand. Taken this into consideration,energystorage technology was applied in solar-driven ERS. Two kinds ofthermal storage areconsidered: hot storage-high temperatureenergyfrom the solar collectors, and cold storage-low Fig. 16 Schematic Diagram of Ejectortemperature energy from the evaporator.Guo and Refrigeration System with Thermal Ice StorageShen [95] numerically investigated a solar-driven [100]airconditioning system with hot storage for office In order to provide better compliancebuildings. Withgenerator temperature of 85°C, with varying ambientconditions, a variableevaporator temperature of 8°Cand condenser geometry ejector with cold storagetemperature varying with ambient temperature,the wasinvestigated by Dennis et al. [98]. The annualaverage COP and the average solar fraction of the cooling simulationsystem were0.48 and 0.82, respectively. It was results concluded that a variable geometry ejectorconcluded that the systemcould save was able toincrease yield by 8–13% compared toapproximately 75% of the electricity used for a fixed geometry ejector.The modelling furtherconventional air conditioning under Shanghai’s showed that the solar collector area mayclimatic conditions.In contrast, Pridasawas and bedecreased if a cold storage was used.Worall etLundqvist [39] reported that thesize of the hot al. [99] and Eames et al. [100]carried anstorage tank did not improve significantly experimental investigation of a novel ejectortheperformance of the system. Hence, cold refrigeration cycle withthermal ice storage systemstorage, with the help ofPhase changing materials, (as shown in Fig. 16). Ice was formedin thecold water or ice storage, was recommended by evaporator vessel under normal operation andBejan et al. [96]. Moreover, using computer acted as acoolth storage medium. The lowsimulations, Diaconu et al. [97] analyzed a solar- evaporator temperature resultedin a relatively lowassisted ejector coolingsystem with cold storage COP of 0.162 during experiments. The(as shown in Fig. 15) over one year inAlgeria. authorsargued that such system powered by solarCompared to that without cold storage, the annual energy would help tostore the coolth to level outenergyremoval of the system with cold storage the off-peak conditions.achieved higher values. 22 | P a g e
  • 14. Mohammed Raffe Rahamathullah, Karthick Palani, Thiagarajan Aridass, Prabakaran Venkatakrishnan, Sathiamourthy, Sarangapani Palani / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 2, March -April 2013, pp.010-0345. APPLICATION OF EJECTORREFRIGERATION SYSTEM COMBINEDWITH OTHER SYSTEMS5.1 Combined Ejector-Absorption RefrigerationSystem Absorption system can also make use oflow-grade heat sources, such as solar energy, wasteor exhaust heat. However, because of its complexconfiguration and low COP, it is less competitivethan the conventional vapour compression system.Applying ejector to the conventional absorptionsystems is one of the remarkable alternatives. Theappropriate installation configuration can help toimprove the system performance almost similar tomulti-effect absorption cycle machine. Moreover,due to the simplicity of the combined ejector-absorption refrigeration machine, its capitalinvestment cost is comparatively low com- pared toother conventional high performance absorptioncycle systems. Fig. 18 Schematic Diagram of the CombinedRecently, Sozen et al. [46] proposed a solar-driven Power and Ejector-Absorption Refrigerationejector- absorption system (shown in Fig. 17) Cycle [47]operated with aqua- ammonia under the climatic Wang et al. [47] presented a combined power andcondition of Turkey. Ejector was located at the ejector- absorption refrigeration cycle with aqua-absorber inlet, which helped the pressure recovery ammonia as working fluids. This system (shown infrom the evaporator. According to results obtained Fig. 18) combined the Rankine cycle with ejector-in this study, using the ejector, the COP was absorption refrigeration cycle, and could produceimproved by about 20%. For 8–9 months (March– both power output and refrigeration outputOctober) of the year, the collector surface area of simultaneously. This combined cycle introduces an4m2 was sufficient for different applications of ejector between the rectifier and the condenser, andrefrigeration all over Turkey. provides a performance improvement without greatly increasing the complexity of the system. The comparisons of the parametric results between a similar combined system without ejector [101] and this system showed that refrigeration output increased from 149 kW to 250 kW at evaporator temperature of -8°C and generator temperature of 87°C.In order to make sufficient use of high-grade heat with a simple structure refrigeration system, Hong et al. [102] proposed a novel ejector- absorption combined refrigeration cycle (shown in Fig. 19).Fig. 17 Schematic Diagram of a Novel Ejector-Absorption Combined Refrigeration Cycle [46] 23 | P a g e
  • 15. Mohammed Raffe Rahamathullah, Karthick Palani, Thiagarajan Aridass, Prabakaran Venkatakrishnan, Sathiamourthy, Sarangapani Palani / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 2, March -April 2013, pp.010-034 21): ejector sub-system to provide refrigeration during the day and an adsorption sub-system which refrigerates at night-time. Detailed system description can be found in [104].Fig. 19 Schematic Diagram of a Novel Ejector-Absorption Combined Refrigeration Cycle [102](Ab, Absorber; Con, Condenser; Evap, Fig. 20 Schematic Diagram of a Novel Ejector-Evaporator; Gh, High-Pressure Generator; Gl, Absorption Combined Refrigeration Cycle [46]Low-Pressure Generator; P, Pump; Shx, Heat It was demonstrated that the COP of theExchanger; V, Valve). ejection sub-system improved when theWhen the temperature of the heat source is high temperature of the adsorbent increased or when theenough, the cycle would work as a double-effect pressure decreased. A COP of 0.4 was achievedcycle. Two generators were used in the cycle, so with 9°C evaporating temperature, 40°Cthat the pressure of the high-pressure generator and condensing temperature, 120°C regeneratingthat of the low-pressure generator could be temperature and 200°C desorbing temperature. Itoptimized to get maximum COP at any given was further concluded that by increasing theworking condition. The simulation results showed temperature or reducing the pressure within thethat system COP was 30% higher than that of the adsorbent bed, the COPs of the ejection sub-systemconventional single-effect absorption refrigeration could be improved slightly.cycle. However, no experimental validation was 5.2 Ejector Refrigeration System withavailable. Theoretical and experimental study of Compressor or Vapour Compression Systemsolar-ejector absorption refrigeration system Since the system performance of ERS is(shown in Fig. 20) was conducted by Abdulateef et determined by ejector entrainment ratio andal. [103]. The effects of the operating conditions on operating conditions, one way to enhance thethe COP and the cooling capacity of the system performance is to increase the secondary flowwere investigated. A mathematical model was pressure. In1990, Sokolov and Hearshgal [105],developed for design and performance evaluation introduced new configurations of efficient uses ofof the ERS. A wide range of compression, the mechanical power in order to enhance theexpansion and entrainment ratios, especially those secondary pressure without disturbing theused in industrial applications were covered in the refrigeration temperature, which are: (1) themathematical model. With the aim of overcoming booster assisted ejector cycle and (2) the hybridthe intermittency of adsorption refrigeration, Li et vapour compression-jet cycle. Their simulatedal. [104] presented a novel combined cycle solar- results showed that the compression enhancedpowered adsorption–ejection refrigeration system ejector could significantly improve systemusing Zeolite 13X-water as the pair. The cycle performance.consisted of two sub- systems (as shown in Fig. 24 | P a g e
  • 16. Mohammed Raffe Rahamathullah, Karthick Palani, Thiagarajan Aridass, Prabakaran Venkatakrishnan, Sathiamourthy, Sarangapani Palani / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 2, March -April 2013, pp.010-034Fig. 21 Schematic Diagram of a Solar-Powered Adsorption–Ejection Refrigeration System [104](a) System Layout, (b) Ejector Refrigeration System During Daytime and (c) Adsorption RefrigerationSystem At Night (A, Absorber; B, Auxiliary Heater; C, Condenser; E, Evaporator; G, Generator; J,Ejector; K, Expansion Valve; P1, Pump; P2, Heat Pipe; X, Heat Exchangers; V, Valves)Fig.22 Schematic Diagram of a Solar-Powered ERS [106]Recently, Sokolov et al. [106] improved their cycles interact. Heat absorbed in the evaporator issystem by using a booster and intercooler in a boosted up to the intercooler pressure andsolar-powered ERS (as shown in Fig. 22). The temperature bythe compression cycle. Thesystem consisted of a conventional compression elevated suction pressure from theintercooler toandejector sub-cycles with an intercooler as an the ejector results in a higher mass flow rateinterface betweenthem. The intercooler is a heat withwhich the ejector operates. The ejector sub-and mass exchanger throughwhich the two sub- cycle further raisesthe heat from the evaporator to 25 | P a g e
  • 17. Mohammed Raffe Rahamathullah, Karthick Palani, Thiagarajan Aridass, Prabakaran Venkatakrishnan, Sathiamourthy, Sarangapani Palani / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 2, March -April 2013, pp.010-034the condenser’s pressure andtemperature. The thatCOP increased by 5.5% with R152a and 8.8%system operated at 4°C evaporator with R22 comparedwith the basic system.temperatureand 50°C condenser temperature, with However, no experimental results wereavailablecooling capacity of3.5 kW. The overall system to validate these.COP could reach up to 0.5. The grouplater revisedtheir work [107] by substituting the refrigerantofR114 with R142b. The results indicated thatR142b providedhigher efficiency than the oneoperating with R114. Fig. 24 Schematic Diagram of Hybrid CO2 Ejector and Vapour Compression System [108] Worall et al. [93,108] proposed a similar hybrid CO2 ejectorand vapour compression system as shown in Fig. 24. The ejectorrefrigeration system was proposed toFig. 23 Schematic Diagram of a Refrigeration extract heat from theexhaust of an independentSystem with the Integrated Ejector [38] diesel engine and sub-cool the CO2vapour compression system. The modelling resultsA similar system configurations was presented by showed that atan evaporator temperature of -Hernandezet al. [23] with R134a and R142b as 15°C, an ambient temperature of35°C and aworking fluids. The theoretical analysis generator temperature of 120°C, COP coulddemonstrated that the optimum COP of 0.48 beincreased from 1.0 to 2.27 as sub-coolingcouldbe achieved at condenser temperature of increased from 0 to 20°C. At the same time, the30°C and generatortemperature of 85°C, with compressor work could be reduced by 24% atR134a as working fluid. The authorsfurther 20°C sub-cooling. The group [109] later carriedindicated that when higher condenser temperature outpreliminary experimental investigations on thewasimposed, the system with R142b would ejector cycle.perform better.Vidal et al. [24] implemented acomputer simulation on a solarassisted combined 5.3 Combined Power and Ejector Refrigerationejector-compression system. Themechanicalcompression cycle and the thermal System Recently, many combined power anddriven ejector cycle wereperformed with two refrigeration cycles havebeen proposed to makedifferent refrigerants, R134a and better use of low grade heat sources.Zhang andR141brespectively. The final optimum results Lior [110] discussed the combined power andshowed that an intercooler temperature of 19°C refrigeration cycles with both parallel and series-resulting in a solar fraction of thesystem of 82% connected configurations. The cycle has largeand a COP of the combined ejector cycle of refrigeration capacity. However, itoperated at0.89.A 10.5 kW cooling capacity was achieved temperatures about 450 1C, which iswith the flat platecollector area of 105 m2. Zhu et incompatiblewith low temperature heat sourcesal. [38] proposed a hybrid vapour compression such as solar thermal andwaste heat.Wang et al.refrigeration system which combined with an [111] proposed a combined power andejector cooling cycle (as shown in Fig. 23). The refrigeration cycle as shown in Fig. 25, whichejector cooling cycle was driven bywaste heat combined the Rankine cyclewith the ERS byfrom the condenser in the vapour adding an extraction turbine betweencompressionrefrigeration cycle. The additional heatrecovery vapour generator (HRVG) andcooling capacity from theejector cycle in directly ejector. This combinedcycle could produce bothinput to the evaporator of the vapourcompression power output and refrigerationrefrigeration cycle. Simulation results showed 26 | P a g e
  • 18. Mohammed Raffe Rahamathullah, Karthick Palani, Thiagarajan Aridass, Prabakaran Venkatakrishnan, Sathiamourthy, Sarangapani Palani / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 2, March -April 2013, pp.010-034outputsimultaneously. The HRVG is a device in The parametric analysis results concluded that thewhich high pressure andtemperature vapour is amounts of exergy destruction in the HRVG,generated by absorbing heat from sourcessuch as ejector and turbine accounted for a largesolar thermal, geothermal and waste heat. percentage. The author suggested several methods to improve system efficiency including increasing the area of heat transfer and the coefficient of heat transfer in the HRVG, optimization design parameters in the ejector and turbine. Similarly, Alexis et al. [112] studied a combined power and ejector cooling cycle (Fig. 26) in which extracted steam from the turbine in Rankine power cycle was used to heat the working fluid in an independent steam ejector refrigeration cycle.Fig. 25 Schematic Diagram of Combined Powerand ERS [111]Fig. 26Schematic View of Combined Refrigeration and Electrical Power Cogeneration System [112] (B, Boiler; T, Turbine; G, Generator; Cr, Main Condenser; Pr1, Condensate Pump; Dfh, Deaerating Feed Water Heater, Pr2; Feed Water Pump; Ge, Heat Generator; Ej, Ejector; Ce, Condenser; E, Evaporator;Pe, Pump; Ev, Expansion Valve). noted that whilethe generator temperatureRankine cycle and steam ejector refrigeration increased the fluid inlet pressure of the ejectorcycle produced electrical powerand refrigeration increased.capacity, respectively. Computer modellingresults Exergy analysis of combined power and ejectorshowed that when the ratio between electrical refrigeration cycle presented by Wang [101]powerand heat transfer rate was varied between showed that the largest exergy destruction0.1 and 0.4, the ratiobetween electrical power and occurred in the heat recovery vapor generatorrefrigeration capacity was variedbetween 0.23 and (HRVG) followed by the ejector and turbine. In0.92.A combined power and ERS with R245fa as order to recover some of the thermal energy fromworking fluid waspresented by Zheng et al. [113]. the turbine exhaust, Khaliq [35] combined a Libr-Simulation results showed that athermal H2O absorption system with power and ejectorefficiency of 34.1%, an effective efficiency of refrigeration system using R141b as refrigerant.18.7% and anexergy efficiency of 56.8% could be The results of first and second law investigationobtained at a generatortemperature of 122 1C, a showed that the proposed congeneration cyclecondensing temperature of 25 1C andan yielded better thermal and exergy efficienciesevaporating temperature of 7 1C. It was also than the cycle without absorption system. 27 | P a g e
  • 19. Mohammed Raffe Rahamathullah, Karthick Palani, Thiagarajan Aridass, Prabakaran Venkatakrishnan, Sathiamourthy, Sarangapani Palani / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 2, March -April 2013, pp.010-034However, no experimental results were available.Godefroy et al. [114] designed a small CHP-ejector trigeneration system which combined heatand power (CHP) to drive an ejector coolingcycle. In the system (shown in Fig. 27) consistedof a CHP unit and an ejector cooling cycle. Theejector cooling cycle was driven by heat from theCHP unit supplied through a flat-plate heatexchanger to bring the refrigerant to its vapourstate. The design had been tested and validated bya model based on the real fluid properties. Theresults showed that this system offered an overallefficiency around 50% and would have an almostneutral effect on overall emissions. Fig. 28Schematic Diagram of Ground Coupled Steam Ejector Heat Pump System [115] Simulation results were validated with experimentaldata from the literature. The authors concluded that the system had the smallest mean total annual cost value and maximum overall COP in temperature climates in comparison withFig. 27Schematic Diagram of a CHP-Ejector cold andtropical climates.System [114]5.4 Ground Coupled Steam Ejector Heat ConclusionsPump Studies in ejector systems that have been carried out over the past decade involved systemGround coupled heat pump (GCHP) is being used modeling, design fundamentals, refrigerantsfor heatingand cooling residential and commercial selection and system optimization. The researchbuildings by exchangingheat with the ground as and development was broad based and productive,the thermal source or sink. However theinitial concentrating on performance enhancementinvestment is higher than that for the air source methodology and feasibility of combining ERSheatpumps due to the costs of ground loop pipes, with other systems. This paper presents not only awells, channels andcirculation pumps. Ejector basic background and principles for ejector design,systems, with its advantage of longoperating but also the recent improvement in ejectorlifetime, high reliability, low maintenance cost, refrigeration technologies.are onealternative to reduce the initial cost of The following conclusions can be drawnGCHP. Sanaye et al. [115] investigated a GCHP from the reviewed works that have been carried out(shown in Fig. 28) which included two in ejector refrigeration system: (1) Attempts havemainsections of closed vertical ground heat been made on the investigations of properexchanger and steamejector heat pump. Thermal mathematical models that may help to optimizeand economic simulation and optimization of the design parameters. Taking into consideration ofsystem, optimum design of ejector main cross friction losses and irreversibilites, some researcherssection and investigation of the effects of weather, have carried out computer simulations on thesoil type, and system capacity on system improvement of constant-area model and constant-performance were carried out in this research. pressure model. A number of researchers have concentrated on the studies of two-phase flow and specific characteristics of working fluids. CFD has been identified as a suitable tool for the turbulence models of the mixing process which can better simulate and optimize the geometry of ejector. Although these simulated results were claimed to become more accurate than others, very few of 28 | P a g e
  • 20. Mohammed Raffe Rahamathullah, Karthick Palani, Thiagarajan Aridass, Prabakaran Venkatakrishnan, Sathiamourthy, Sarangapani Palani / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 2, March -April 2013, pp.010-034them were experimentally verified and approved. Processing: Process Intensification’ 2002;(2) Different configurations of ejectors with 41:551–61.various geometric features were proposed and [5] Pianthong K, Seehanam W, Behnia M,tested numerically and experimentally. Area ratio Sriveerakul T, Aphornratana S.and nozzle exit position were the most widely ‘Investigation and Improvement of Ejectorinvestigated parameters. It can be concluded that Refrigeration System Usingthe optimal area ratio and NXP have varied for the Computational Fluid Dynamicsdifferent operating conditions. A spindle, which Technique’ Energy Conversion andcan adjust primary nozzle position, could be Management 2007; 48:2556–64.implemented to provide both flexible area ratio and [6] Ma X, Zhang W, Omer SA, Riffat SB.NXP. (3) Since the ejector refrigeration systems Experimental investigation of a novelsuffer from relatively low COP, a number of steam ejector refrigerator suitable for solarstudies have focused on system performance energy applications. Applied Thermalenhancement. Operation of ERS without a pump Engineering 2010; 30:1320-5.has been declared to considerably reduce the [7] Chunnanond K, Aphornratana S.mechanical energy consumption. In contrast, ERS ‘AnExperimental Investigation of a Steamwith an additional pump could help to increase the Ejector Refrigerator: The Analysis of theentrainment ratio and COP. In order to cope with Pressure Profile along the Ejector’.variations of working conditions, multi- Applied Thermal Engineering 2004;components ERS are parametrically studied. On the 24:311–22.other hand, transcritical ERS is proposed, which [8] Selvaraju A, Mani A. Experimentalprovides higher potential in utilizing low-grade investigation on R134a vapour ejectorheat. The remarkable COP improvements from refrigeration system. International Journalcombined ejector and other types of refrigeration of Refrigeration 2006; 29: 1160– (vapor compression, absorption system, [9] Sankarlal T, Mani A. Experimentaletc.) are reported by many research groups. Investigations on Ejector RefrigerationHowever, most of those studied are limited to System with Ammonia. Renewablenumerical analysis, with few experimental results Energy 2007; 32:1403–13.available. [10] Chaiwongsa P, Wong wises S. With the concept of energy conservation Experimental study on R-134aand environment protection, the utilization of low refrigeration system using a two-phasegrade energy, especially solar energy with ERS has ejector as an expansion device. Appliedbeen widely studied during past decade. The major Thermal Engineering 2008; 28:467–77.technical problem of solar-driven ejector [11] Chen SL, Yen JY, Huang MC. Anrefrigeration system is that the system is strongly Experimental Investigation of Ejectorreliant on ambient conditions, like the solar Performance Based upon Differentradiation, air temperature, cooling water Refrigerants. ASHRAE Transaction 1998;temperature, wind speed and other transient factors. 104(part 2):153–60.Thus the combination of energy storage in the [12] Aidoun Z, Ouzzane M. The Effect ofsolar-driven ERS remains to be the research topic Operating Conditions on the Performancein this field of technology. of a Supersonic Ejector For Refrigeration. International Journal of RefrigerationReferences 2004; 27:974–84. [1] Riffat SB, Jiang L, Gan G. Recent [13] YapIcI R. Experimental Investigation of Development in Ejector Technology: A Performance of Vapor Ejector Review. International Journal of Ambient Refrigeration System using Refrigerant Energy1995; 26:13–26. R123’, Energy Conversion and [2] Chunnanond K, Aphornratana S. Ejectors: Management 2008; 49:953–61 Applications in Refrigeration Technology. [14] Cizungu K, Mani A, Groll M. Renewable and Sustainable Energy Performance comparison of vapour jet Reviews 2004; 8:129–55. refrigeration system with environment [3] Abdulateef JM, Sopian K, Alghoul MA, friendly working fluids. Applied Thermal Sulaiman MY. ‘Review on Solar-Driven Engineering 2001; 21:585–98. Ejector Refrigeration Technologies. [15] YapIcI R, Ersoy HK, Aktoprakoglu A, Renewable and Sustainable Energy HalkacI HS, Yigit O. Experimental Reviews 2009; 13:1338–49. determination of the optimum [4] El-Dessouky H, Ettouney H, Alatiqi I, Al- performance of ejector refrigeration Nuwaibit G. ‘Evaluation of Steam Jet system depending on ejector area ratio. Ejectors’ Chemical Engineering and 29 | P a g e
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