The two-phase ejector refrigeration cycle (TPERC) system with a two-throat nozzle ejector was investigated experimentally, and the entrainment ratio of the ejector and the COP of the system were compared with those of the ejector with Laval nozzle and the TPERC system respectively. The experimental results indicate that the entrainment ratios of the two-throat nozzle ejectors with different geometric size are greater than those of the Laval nozzle ejectors under the working condition of the evaporating/condensing temperatures 1?/45?, the maximum increment of the entrainment ratio is about 18%, and the COP of the TPERC system with two-throat nozzle ejector is greater than that of the TPERC system with Laval nozzle ejector, the maximum increment of the COP is about 12%. Under the condition of the fixed evaporating temperature 1?, the entrainment ratios of both the two-throat nozzle ejector and the Laval nozzle ejector achieve the maximum values as the condensing temperature is about 45?. Under the condition of the fixed condensing temperature 50?, the entrainment ratios of the two types of ejectors achieve the maximum values as the evaporating temperature is about 3?

Guo, Xian Min

Guo, Xin Wei

Li, Tian Long

Ren, Li Qian

English

Purdue E-Pubs

Purdue UniversityPurdue e-PubsInternational Refrigeration and Air ConditioningConference School of Mechanical Engineering2014Experimental Study on Performance of Two-phaseEjector Refrigeration Cycle System with Two-throat NozzleLi Qian RenTianjin University of Commerce, People's Republic of China, renliqian2011@163.comXian Min GuoTianjin University of Commerce, People's Republic of China, xmguo@tjcu.edu.cnXin Wei GuoTianjin University of Commerce, People's Republic of China, 605500616@qq.comTian Long LiTianjin University of Commerce, People's Republic of China, olitianlongo@sina.comFollow this and additional works at: http://docs.lib.purdue.edu/iraccThis document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact epubs@purdue.edu foradditional information.Complete proceedings may be acquired in print and on CD-ROM directly from the Ray W. Herrick Laboratories at https://engineering.purdue.edu/Herrick/Events/orderlit.htmlRen, Li Qian; Guo, Xian Min; Guo, Xin Wei; and Li, Tian Long, "Experimental Study on Performance of Two-phase EjectorRefrigeration Cycle System with Two-throat Nozzle" (2014). International Refrigeration and Air Conditioning Conference. Paper 1472.http://docs.lib.purdue.edu/iracc/1472 2403, Page 115th International Refrigeration and Air Conditioning Conference at Purdue, July 14-17, 2014Experimental Study on Performance of Two-throat Nozzle Ejector and Two-phase EjectorRefrigeration Cycle SystemLiqian REN 1, Xianmin GUO 2*, Xinwei GUO3, Tianlong LI 4Tianjin Key Laboratory of Refrigeration Technology, Tianjin University of Commerce, Tianjin, China1 Phone: +0086 22 26669660, E-mail: renliqian2011@163.com2 Phone/Fax: +0086 22 26686268, E-mail:  xmguo@tjcu.edu.cn3 Phone: +0086 22 26669660, E-mail:  605500616@qq.com4 Phone: +0086 22 26669660, E-mail:  olitianlongo@sina.comABSTRACTThe two-phase ejector refrigeration cycle (TPERC) system with a two-throat nozzle ejector was investigatedexperimentally, and the entrainment ratio of the ejector and the COP of the system were compared with those of theejector with Laval nozzle and its TPERC system respectively. The experimental results indicate that under theworking condition of the evaporating/condensing temperatures 1℃/45 ,℃ the entrainment ratio of the two-throatnozzle ejector with different geometric size is greater than that of the Laval nozzle ejector, the maximum incrementof the entrainment ratio is about 18%, and the COP of the TPERC system with two-throat nozzle ejector is greaterthan that of the TPERC system with Laval nozzle ejector, the maximum increment of the COP is about 12%. Underthe fixed evaporating temperature 1 , the entrainment ratio of the two℃ -throat nozzle ejector and the Laval nozzleejector achieve the maximum as the condensing temperature is 45 . Under the fixed condensing temperature 50℃ ℃,the entrainment ratio of the two types of ejectors achieves the maximum as the evaporating temperature is 3 .℃1. INTRODUCTIONAt present, the expansion work in the refrigeration cycle can be recovered by using two methods. One is to replacethe expansion valve with expander (Xia et al., 2013) and run the fan or compressor with the output power of theexpander. There are many technical problems, such as wet expansion in the impeller and reliability of the expander,to be solved. Another is to use the ejector instead of expansion valve (Sumeru et al., 2012). The refrigerant expands inthe nozzle and the high pressure energy is converted into kinetic energy. The high velocity flow at the outlet of thenozzle entrains the refrigerant steam from the evaporator and the mixture is diffused subsequently. In the ejector thehigh pressure energy of the refrigerant is recovered and the suction pressure of the compressor is increased, so theperformance of the refrigeration cycle is improved.A lot of studies on the performance of the TPERC system and the ejector were reported. Chaiwongsa and Wongwises(2007)  studied  the  effects  of  the  throat  diameter  on  the  performance  of  the  ejector.  Nakagawa et al. (2010)investigated the effect of the mixing length on the ejector system performance experimentally. The results showedthat the mixing length had significant effect on the entrainment ratio, the magnitude and profile of the pressurerecovery. Liu and Groll (2013) established the empirical correlations to estimate the ejector component efficiencies atdifferent ejector geometries and operation conditions. The system simulation model predicted the COP and thecooling capacity within ±8% and ±12% of the measured one, respectively. Wang and Deng (2012) established themathematical model of the ejector with contrivable back pressure in a transcritical CO2 ejector-expansionrefrigeration cycle and analyzed the effects of the ejector back pressure and outlet velocity on the system. Yazdani etal. (2012) provided the capability through pragmatic integration of multiple separately validated sub-models for massand energy transfer between phases, two-phase sonic velocity, and real-fluid properties with an underlyingcommercial CFD simulation through user-defined functions. 2403, Page 215th International Refrigeration and Air Conditioning Conference at Purdue, July 14-17, 2014In all of the published literatures about TPERC system the Laval nozzle ejector were used. In this paper a new typeof two-throat nozzle ejector was introduced, and the performance of the ejector with different geometric size inTPERC system under the variable working conditions were investigated experimentally.2. EXPERIMENTAL SETUPThe diagram of the experimental setup is shown in figure 1. The refrigeration system is consists of the compressor,evaporators, condenser, two-throat nozzle ejector, gas-liquid separator, liquid separator and other accessories. R134ais used as refrigerant. This system can be used for experiments of the TPERC system or the traditional refrigerationcycle system by controlling the state (open or close) of the valves No.1-5 (Pei et al., 2013). The working process ofthe system was detailed in the reference of Pei et al. (2013).All the measuring points of the pressure, temperature and flow rate are marked in figure 1. The precision of theplatinum resistance temperature sensor and the pressure sensor are ±0.1 ℃ and ±0.1 %FS, respectively. The massflow rate of R134a and the flow rate of water are measured by using the mass flow meter (±0.1%R) and the turbineflow meter (±0.5%R), respectively. The power consumption of the compressor is measured in terms of a powertransducer (±0.5%).The cooling water of the condenser is supplied by the water chiller, of witch the temperature isadjusted by the electric heater. The chilled water from the evaporator is heated and the temperature of the chilledwater at the inlet of the evaporator is adjusted by the electric heater. The flow rates of both the cooling water and thechilled water are controlled by adjusting the rotation speed of the water pumps. The refrigeration capacity can becalculated by the water temperature deference between the inlet and outlet of the evaporator and the mass flow rateof the chilled water, also can be got by the enthalpy difference between the refrigerant inlet and outlet of theevaporator and the mass flow rate of the R134a, then the COP can be calculated with the compressor powerconsumption. The entrainment ratio can be determined with the mass flow rate of the main flow and the secondaryflow into the ejector.EjectorCompressorCondenserV1V3V6V2ExpansionValveMain EvaporaterGas-LiquidSeparatorAssistantEvaporatorV7V4LiquidSeperatorV5Cooling WaterCoolingWaterChilled WaterT P T P T PTPPT PT PPMMMTTTTMMTTValveTemperaturePressureMass flow rateTPMV1-7Figure 1: Diagram of experimental setup of TPERC SystemFigure 2 is the schematic diagram of the two-throat nozzle ejector. In the traditional ejector, the difference betweenthe vapor and liquid velocities at the outlet of the Laval nozzle is very large resulting from the great differencebetween vapor and liquid density and large droplet diameter of the liquid refrigerant, witch lead to lowerentrainment ratio of the Laval nozzle ejector [2]. In the two-throat nozzle ejector, the two Laval nozzle is set serially.The gas-liquid refrigerant mixture from the first Laval nozzle flow into the second negative throat nozzle and theliquid refrigerant droplets are broken into smaller one. The refrigerant velocity can achieve sonic at the secondthroat and then supersonic in the expansion section of the second nozzle. It can be expected that the performance ofthe ejector with the two-throat nozzle is improved. 2403, Page 315th International Refrigeration and Air Conditioning Conference at Purdue, July 14-17, 2014Mixing ChamberSuction CamberDiffuserMixed FlowTwo-Throat NozzleNeedleMain FlowSecondary FlowFirst Throat Second ThroatFigure 2: Schematic diagram of two-throat nozzle ejector3. EXPERIMENTAL RESULTS AND ANALYSISIn order to verify the performance and the factors affecting the performance of the two-throat nozzle ejector, a seriesof experiments for the ejectors with different dimensional two-throat nozzles and the Laval nozzles under differentworking conditions were conducted. The experimental prototype of the ejector was designed as a removable nozzle.For all of the experiments the ejector was the same except the nozzle. The cross-sectional throat area of theexperimental nozzles is shown in the table 1. The diffuse angle of the expansion section for all of the nozzles is 3°.Table 1: Cross-sectional throat area of experimental nozzlesPrototype Number No.1 No.2 No.3 No.4 No.5Laval nozzle 2.55 mm2 2.84  mm2 3.14 mm2 3.46 mm2First Throat 2.27 mm2 2.55 mm2 2.84  mm2 3.14 mm2 3.46 mm2Two-ThroatNozzle Second Throat 2.27 mm23.1 Effect of Cross-Sectional Throat Area of NozzleThe COP of the TPERC system and the entrainment ratio of the ejector with different cross-sectional throat area ofthe nozzles under the working condition of the evaporating/condensing temperatures 1 /45℃ ℃ are shown in thefigure 3.2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.61.501.752.002.252.502.753.00 Laval nozzle Two-throat nozzleCross-sectional area ( mm2 )COP0.150.200.250.300.350.400.450.50Entrainment ratioFigure 3: System COP and entrainment ratio of ejector with throat area of nozzle 2403, Page 415th International Refrigeration and Air Conditioning Conference at Purdue, July 14-17, 2014As shown in figure 3, the entrainment ratio of both the two-throat nozzle ejector and the Laval nozzle ejectorincreases with the increase in the cross-sectional throat area, but the entrainment ratio of the two-throat nozzleejector is greater than that of the Laval nozzle ejector, and the maximum increment of the entrainment ratio is about18%.  The  COP  of  the  TPERC  system  with  the  Laval  nozzle  ejector  achieves  the  maximum  value  as  the  cross-sectional throat area is about 2.84mm2. The COP of the TPERC system with two-throat nozzle ejector decreaseswith the increase in the cross-sectional throat area of the nozzle, and is greater than that of the TPERC system withthe Laval nozzle ejector. The maximum increment of the system COP is about 12%. This is because that the use ofthe two-throat nozzle in the ejector improves the entrainment ratio of ejector, as well as the refrigerating capacity ofthe system, and the power consumption of the TPERC system with two-throat nozzle ejector is almost the same tothat of the TPERC system with the Laval nozzle ejector.3.2 Effect of Condensing TemperatureFigure  4  shows  the  variation  of  the  system  COP  and  the  entrainment  ratio  of  the  ejector  in  terms  of  the  nozzleprototype No.5 (Tab. 1) with the condensing temperature under the working condition of evaporating temperature1 .℃35 40 45 50 550.91.21.51.82.12.42.73.03.3COPLaval nozzleTwo-throat nozzleCondensing temperature(oC)0.200.250.300.350.400.450.500.55Entrainment ratioFigure 4: Variation of system COP and entrainment ratio of ejector with condensing temperatureIt can be seen in the figure 4 that the COP of the TPERC system with both the two types of nozzle ejector decreaseswith the increase in the condensing temperature, and the COP of the system with the two-throat nozzle ejector isgreater than that with the Laval nozzle ejector. This is caused by the increase in the power consumption of thecompressor. The variation trend of the entrainment ratio of the ejector with the condensing temperature is differentfrom that of the system COP, the entrainment ratio of both the two-throat nozzle ejector and the Laval nozzle ejectorachieves the maximum value as the condensing temperature is 45℃, and the entrainment ratio of the two-throatnozzle ejector is greater than that of the Laval nozzle ejector. This is because of the increase in the pressuredifference between the inlet and outlet of the nozzle with the increase in the condensing temperature. As thecondensing temperature is less than 45 ,℃ the pressure difference is small, so the shock wave in the ejector is weakand the outlet velocity of the nozzle, as well as the entrainment ratio, increases with the increase in the pressuredifference.  When  condensing  temperature  is  higher  than  45 ,  the  shock  wave  move℃ s into the nozzle, and thepressure difference is higher, the shock wave is stronger, so the entrainment ratio decreases with increase in thecondensing temperature.3.2 Effect of Evaporating TemperatureUnder the working condition of condensing temperature 50 ,℃ the variation of the system COP and the entrainmentratio of the prototype ejector No. 5 (Tab. 1) with evaporating temperature is shown in figure 5. 2403, Page 515th International Refrigeration and Air Conditioning Conference at Purdue, July 14-17, 2014As shown in the figure 5, the entrainment ratio of both the Laval nozzle ejector and the two-throat nozzle ejectorachieves the maximum value as the evaporating temperature is 3℃ under the working condition of condensingtemperature 50℃. The explanation about this trend is similar to the above effect of the condensing temperature. TheCOP of the system with two types of ejectors increases with the increase in the evaporating temperature under thefixed condensing temperature. Both the entrainment ratio and COP of the system with two-throat nozzle ejector ishigher than those of Laval nozzle ejector.-2 -1 0 1 2 3 4 5 6 7 81.21.51.82.12.42.73.0 Two-throat nozzle Laval nozzle?COPEvaporation temperature ( oC )0.240.280.320.360.400.440.48Entrainment ratioFigure 5: Variation of system COP and entrainment ratio of ejector with evaporation temperature4. CONCLUSIONSThe two-phase ejector refrigeration cycle system with a two-throat nozzle ejector was investigated experimentally,and the entrainment ratio of the ejector and the COP of the system were compared with those of the ejector withLaval nozzle and its TPERC system respectively, the conclusions as follow can be obtained:· The experimental results indicate that under the working condition of the evaporating/condensingtemperatures 1 /45 , the entrainment ratio of the two℃ ℃ -throat nozzle ejector with different geometric sizeis greater than that of the Laval nozzle ejector, the maximum increment of the entrainment ratio is about18%. The entrainment ratio of the two types of ejectors increases with the increase in the cross-sectionalthroat area. The COP of the TPERC system with the two-throat nozzle ejector is greater than that of theTPERC system with the Laval nozzle ejector, and the maximum increment of the system COP is about12%.· Under the working condition of the fixed evaporating temperature 1 , the entrainment ratio of the two℃types of ejectors achieves the maximum as the condensing temperature is about 45 , the entrainment ratio℃of the two-throat nozzle ejector increases by 15.2% compared to that of the Laval nozzle ejector.· Under the working condition of the fixed condensing temperature 50 , the entrainment ratio of the two℃ -throat nozzle ejector achieves the maximum as the evaporating temperature is about 3 and increase℃ s by5.1% compared to that of the Laval nozzle ejector.REFERENCESChaiwongsa, P., Wongwises, S., 2007, Effect of Throat Diameters of the Ejector on the Performance of theRefrigeration Cycle Using a Two-phase Ejector as an Expansion Device, Int. J. of Refrigeration, vol. 30: p601-608.Liu, F., Groll, E., A., 2013, Study of Ejector Efficiencies in Refrigeration Cycles, Applied Thermal Engineering, vol.52: p360-370. 2403, Page 615th International Refrigeration and Air Conditioning Conference at Purdue, July 14-17, 2014Nakagawa, M., Marasigan, A., R., Matsukawa, T., et al. 2010, Experimental Investigation on the Effect of MixingLength on the Performance of Two-Phase Ejector for CO2 Refrigeration Cycle with and without HeatExchanger, Int. J. of Refrigeration, vol. 30(1): p1-10.Pei, W., Guo, X., Wang S., et al. 2013, Effects of Geometric Parameter on Performance of Ejector and Two-PhaseEjector Refrigeration System, J. of Refrigeration, vol.34(1):65-68.Sumeru, K., Nasution, H., Ani F., N., 2012, A Review on Two-Phase Ejector as an Expansion Device in VaporCompression Refrigeration Cycle, Renewable and Sustainable Energy Reviews, vol. 16(7):p4927- 4937．Takeuchi, H., Nishijima, H., Ikemoto, T., World’s First High Efficiency Refrigeration Cycle with Two-PhaseEjector: “Ejector Cycle”, 2004, SAE World Congress, Paper 2004-01-0916, Detroit, MI, USA.Wang, F., Deng J., 2012, Critical Back Pressure of Transcritical Carbom Dioxide Refrigeration Cycle with Ejector, J.of Xi’an Jiaotong University, vol. 46(9):66-70.Xia, C., Zhang, W., Bu, G., et al, 2013, Experimental Study on a Sliding Vane Expander in the HFC410ARefrigeration System for Energy Recovery, Applied Thermal Engineering, vol. 59: p 559-567.Yazdani, M., Alahyari, A., A., Radcliff, T., D., Thomas D.Radcliff. 2012, Numerical Modeling of Two-Phase SupersonicEjectors for Work-Recovery Applications, Int. J. of Heat and Mass Transfer, vol.55:5744-5753.ACKNOWLEDGEMENTThe financial support of this work by National Natural Science Foundation of China (No.51176142) is gratefullyacknowledged.

Experimental Study on Performance of Two-phase Ejector Refrigeration Cycle System with Two-throat Nozzle

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Experimental Study on Performance of Two-phase Ejector Refrigeration Cycle System with Two-throat Nozzle

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