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Słowa kluczowe CO2 Ejector Transcritical cycle
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Abstrakt

The geometry and operating parameters have an important influence on the performance of ejectors. The improvement of the refrigeration cycle performance and the design of the ejectors for the compression energy recovery requires a detailed analysis of the internal ejector working characteristics and geometry. To this aim, an experimental investigation of an ejector refrigeration system is conducted to determine the effect of the most important ejector dimensions on ejector working characteristics and system performance. Different dimensions of ejector components are tested. The influence of the ejector’s geometrical parameters on the system performance was analysed. The experiments with respect to the variation of ejector geometry such as the motive nozzle throat diameter, the mixing chamber diameter and the distance between the motive nozzle and diffuser were carried out. There exist optimum design parameters in each test. The experimental results show that the performance (entrainment ratio and a compression ratio of the ejector) increases significantly with the position between the primary nozzle and the mixing chamber. A maximum entrainment ratio of 57.3% and a compression ratio of 1.26 were recorded for the different parameters studied. The results obtained are consistent with experimental results found in the literature.
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Bibliografia

[1] Elbel S., Hrnjak P.: Experimental validation of a prototype ejector designed to reduce throttling losses encountered in transcritical R744 system operation. Int. J. Refrig. 31(2008), 3, 411–422.
[2] Liu J.P., Chen J.P., Chen Z.J.: Thermodynamic analysis on transcritical R744 vapor compression/ejection hybrid refrigeration cycle. In: Prelim. Proc. 5th IIR Gustav Lorentzen Conf. on Natural Working Fluids, Guangzhou 2002, 184–188.
[3] Jeong J., Saito K., Kawai S., Yoshikawa C., Hattori K.: Efficiency enhancement of vapor compression refrigerator using natural working fluids with two-phase flow ejector. In: Proc. 6th IIR-Gustav Lorentzen Conf. on Natural Working Fluids at Glasgow 2004, CD-ROM.
[4] Jian-qiang Deng, Pei-xue Jiang, Tao Lu, Wei Lu: Particular characteristics of transcritical CO2 refrigeration cycle with an ejector. Appl. Therm. Eng. 27(2007), 381–388.
[5] Da Qing Li, Groll E.A.: Transcritical CO2 refrigeration cycle with ejectorexpansion device. Int. J. Refrig. 28(2005), 5, 766–773.
[6] Ksayer E.B., Clodic D.: Enhancement of CO2 refrigeration cycle using an ejector: 1D analysis. In: Proc. Int. Refrigeration and Air Conditioning Conf., Purdue 2026, Purdue Univ. R058.2006.
[7] Bartosiewicz Y., Aidoun Z., Mercadier Y.: Numerical assessment of ejector operation for refrigeration applications based on CFD. Appl. Therm. Eng. 26(2006), 5-6, 604–612.
[8] Petrenko V.O., Huang B.J., Ierin V.O.: Design-theoretical study of cascade CO2 sub-critical mechanical compression/butane ejector cooling cycle. Int. J. Refrig. 34(2011), 7, 1649–1656.
[9] Martel S.: Étude numérique d’un écoulement diphasique critique dans un convergent- divergent. PhD thesis, Université de Sherbrooke, Sherbrooke 2013 (in French).
[10] Marynowski T.: Étude expérimentale et numérique d’écoulements supersoniques en éjecteur avec et sans condensation. PhD thesis, Université de Sherbrooke, Sherbrooke 2007 (in French).
[11] Scott D., Aidoun Z., Ouzzane M.: An experimental investigation of an ejector for validating numerical simulations. Int. J. Refrig. 34(2011), 7, 1717–1723.
[12] Chen H., Zhu J., Ge J., Lu W., Zheng L.: A cylindrical mixing chamber ejector analysis model to predict the optimal nozzle exit position. Energy 208(2020), 118302.
[13] Mondal S., De D.: Performance assessment of a low-grade heat driven dual ejector vapor compression refrigeration cycle. Appl. Therm. Eng. 179(2020), 115782.
[14] Ringstad K.E., Allouche Y., Gullo P., Banasiak K., Hafner A.: A detailed review on CO2 two-phase ejector flow modeling. Thermal Sci. Eng. Progress 20(2020), 100647.
[15] Yu B., Yang J., Wang D., Shi J., Chen J.: An updated review of recent advances on modified technologies in transcritical CO2 refrigeration cycle. Energy 189(2019), 116147.
[16] Chen W., Liu M., Chong D., Yan J., Little A.B., Bartosiewicz Y.A.: 1D model to predict ejector performance at critical and sub-critical operational regimes. Int. J. Refrig. 36(2013), 6, 1750–1761.
[17] Banasiak K., Hafner A., Andresen T.: Experimental and numerical investigation of the influence of the two-phase ejector geometry on the performance of the R744 heat pump. Int. J. Refrig. 35(2012), 6, 1617–1625.
[18] Domanski P.A.: Theoretical Evaluation of the Vapor Compression Cycle With a Liquid-Line/Suction-Line Heat Exchanger, Economizer, and Ejector. National Institute of Standards and Technology, NISTIR-5606, 1995.
[19] Elbel S.W., Hrnjak P.S.: Effect of internal heat exchanger on performance of transcritical CO2 systems with ejector. In: Proc. 10th Int. Refrigeration and Air Conditioning Conf. Purdue 2004, R166, West Lafayette 2004.
[20] Kornhauser A.A.: The use of an ejector as a refrigerant expander. In: Proc. USNC/IIR-Purdue Refrigeration Conf., Purdue Univ.,West Lafayette 1990, 10–19.
[21] Lawrence N., Elbel S.: Experimental and analytical investigation of automotive ejector air-conditioning cycles using low-pressure refrigerants. In: Proc. Int. Refrigeration and Air Conditioning Conf., Purdue, July 16-19, 2012, 1169, 1–10.
[22] Liu F., Li Y., Groll E.A.: Performance enhancement of CO2 air conditioner with a controllable ejector. Int. J. Refrig. 35(2012), 6, 1604–1616.
[23] Domanski P.A.: Minimizing throttling losses in the refrigeration cycle. In: Proc. 19th Int. Congress of Refrigeration, Hague 1995, 766–773.
[24] Varga S., Oliveira A., Diaconu B.: Influence of geometrical factors on steam ejector performance – A numerical assessment. Int. J. Refrig. 32(2009), 7, 1694– 1701.
[25] Sarkar J.: Optimization of ejector-expansion transcritical CO2 heat pump cycle. Energy 33(2008), 9, 1399–1406.
[26] Elbel S.: Historical and present developments of ejector refrigeration systems with emphasis on transcritical carbon dioxide air-conditioning applications. Int. J. Refrig. 34(2011), 7, 1545–1561.
[27] Lee J.S., Kim M.S., Kim M.S.: Experimental study on the improvement of CO2 air conditioning system performance using an ejector. Int. J. Refrig. 34(2011), 7, 1614–1625.
[28] Lucas C., Koehler J.: Experimental investigation of the COP improvement of a refrigeration cycle by use of an ejector. Int. J. Refrig. 35(2012), 6, 1595–1603.
[29] Nakagawa M., Marasigan A.R., Matsukawa T., Kurashina A.: Experimental investigation on the effect of mixing length on the performance of two-phase ejector for CO2 refrigerationcycle with and without heat exchanger. Int. J. Refrig. 34(2011), 7, 1604–1613.
[30] Nakagawa M., Marasigan A.R., Matsukawa T.: Experimental analysis on the effect of internal heat exchanger in transcritical CO2 refrigeration cycle with twophase ejector. Int. J. Refrig. 34(2011), 7, 1577–1586.
[31] Nakagawa M., Marasigan A.R., Matsukawa T.: Experimental analysis of two phase ejector system with varying mixing cross-sectional area using natural refrigerant CO2. Int. J. Air-Cond. Refrig. 18(2010), 4, 297–307.
[32] Liu F., Groll E.A., Li D.: Investigation on performance of variable geometry ejectors for CO2 refrigeration cycles. Energy 45(2012), 1, 829–839.
[33] Liu F., Groll E.A.: Analysis of a two-phase flow ejector for transcritical CO2 cycle. Int. Refrig. Air Cond. Conf., Purdue, July 14–17, 2008, 924.
[34] Liu F., Groll E.A.: Study of ejector efficiencies in refrigeration cycles. Appl. Therm. Eng. 52(2013), 2, 360–370.
[35] Lawrence N., Elbel S.: Experimental investigation on the effect of evaporator design and application of work recovery on the performance of two-phase ejector liquid recirculation cycles with R410A. Appl. Therm. Eng. 100(2016), 398–411.
[36] Van Nguyen V., Varga S., Soares J., Dvorak V., Oliveira A.C.: Applying a variable geometry ejector in a solar ejector refrigeration system. Int. J. Refrig. 113(2020), 187–195.
[37] Pereira P.R., Varga S., Soares J., Oliveira A.C., Lopes A.M., de Almeida F.G., Carneiro J.F.: Experimental results with a variable geometry ejector using R600a as working fluid. Int. J. Refrig. 46(2014), 77–85.
[38] Liu F., Groll E.: A preliminary study of the performance enhancement of a dualmode heat pump using an ejector. In: Proc. 25th IIR Int. Cong. of Refrigeration, ICR2015, Yokohama, Aug. 16-22, 2015, 16–22.
[39] Eames I.W., Wu S., Worall M., Aphornratana S.: An experimental investigation of steam ejectors for application in jet-pump refrigerators powered by low-grade heat. P. I. Mech. Eng. A-J Pow. A 213(1999), 5, 351–361. [40] Lee J.S., Kim M. Se, Kim M. Soo: Experimental study on the improvement of CO2 air conditioning system performance using an ejector. Int. J. Refrig. 34(2011), 7, 1614–1625.
[41] Bouzrara A.: Etude expérimentale des éjecteurs- application à la récupération de l’énergie de détente des machines frigorifiques au CO2. PhD thesis, INSA Lyon (CETHIL)-ENI Tunis 2018 (in French).
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Autorzy i Afiliacje

Philippe Haberschill
1
Ezzeddine Nehdi
2
Lakdar Kairouani
2
Mouna Abouda Elakhdar
2

  1. University of Lyon, CNRS, INSA-Lyon, CETHIL UMR5008, F-69621, Villeurbanne, France
  2. Research Lab Energetic and Environment, National Engineering School of Tunis, Tunis El Manar University, Tunisia

Abstrakt

This paper presents a mathematical model of a vapour vacuum system, which is a crucial component of steam power plants of critical importance for energy efficiency. This system consists of three stages, with each stage containing a steam ejector and a gas phase separator in the form of an interstage heat exchanger. The primary purpose of this system is to remove inert gases and maintain the appropriate level of vacuum in the power plant condenser. The presented mathematical model can be used to analyse the operation of the vacuum system in a steady state. Preliminary pressure calculations in various components of the vacuum system show the influence of additional measurement orifice resistance on the vacuum drop in the condenser, which can reduce the efficiency of the entire energy system. It is worth noting that the presented model can be used as a tool for analysing elements of the vacuum system in energy systems.
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Autorzy i Afiliacje

Robert Matysko
1

  1. Institute of Fluid-Flow Machinery, Polish Academy of Sciences, Fiszera 14, Gdańsk 80-231, Poland

Abstrakt

The two-stage ejector mixing-diffuser section in this study was computed using the Redlich-Kwong equation of state. The ejector was designed based on the constant rate of kinetic energy change (CRKEC) approach. The water vapor mixing diffuser profile and flow properties were calculated using a one-dimensional gas dynamic model. For the numerical investigation, the estimated geometrical profile based on the input design and operating conditions was utilized. ANSYS-Fluent 14.0 was em-ployed for the numerical study. The analysis was conducted under both on-design and off-design scenarios using the standard k-ε turbulence model. The impact of operating factors on flow behavior and entrainment ratios was investigated at off-design conditions. The findings demonstrated that the operational total pressures of the primary, secondary, and exit flows are a function of the two-stage ejector (TSE) entrainment ratio. With a higher exit pressure and more secondary/entrained flows, the entrain-ment ratio increases. However, altering the primary flow pressure in ways other than for the design conditions reduces the entrainment ratio.
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Autorzy i Afiliacje

Virendra Kumar
1
ORCID: ORCID
Surendra Kumar Yadav
2
Anil Kumar
3
ORCID: ORCID
Nishant Kumar Singh
4
Lalta Prasad
5

  1. Department of Mechanical Engineering. Harcourt Butler technical University, Kanpur 208002, India
  2. Yadavb, Surendra Kumar: Department of Mechanical Engineering. K R Mangalam University, Gurugram 122001, India
  3. Department of Mechanical Engineeringg. KNIT, Sultanpur 228118, India
  4. Singha, Nishant Kumar: Department of Mechanical Engineering. Harcourt Butler technical University, Kanpur 208002, India
  5. Department of Mechanical Engg. NIT, Uttrakhand 246174, India

Abstrakt

In this work, a new dual-evaporator CO2transcritical refrigeration cycle with two ejectors is proposed. In this new system, we proposed to recover the lost energy of condensation coming off the gas cooler and operate the refrigeration cycle ejector free and enhance the system performance and obtain dual-temperature refrigeration simultaneously. The effects of some key parameters on the thermodynamic performance of the modified cycle are theoretically investigated based on energetic and exergetic analysis. The simulation results for the modified cycle indicate more effective system performance improvement than the single ejector in the CO2vapor compression cycle using ejector as an expander ranging up to 46%. The exergetic analysis for this system is made. The performance characteristics of the proposed cycle show its promise in dual-evaporator refrigeration system.

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Autorzy i Afiliacje

Ezzaalouni Yathreb Abdellaoui
Lakdar Kairouani Kairouani

Abstrakt

An analysis of energy efficiency for transcritical compression unit with CO2 (R744) as the refrigerant has been carried out using empirical operating characteristics for the two-phase ejector. The first stage of the refrigerant compression is carried out in the ejector. The criterion adopted for the estimation of energy efficiency for the cycle is the coefficient of performance COP. The analysis is performed for the heat pump and refrigeration systems. The results of COP for the systems with the ejector has been compared with the COPL values for the single stage Linde cycle.

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Autorzy i Afiliacje

Joachim Kozioł
Wiesław Gazda
Łukasz Wilżyński

Abstrakt

Paper deals with theoretical analysis of possible efficiency increase of compression refrigeration cycles by means of application of a twophase ejector. Application of the two phase ejector in subcritical refrigeration system as a booster compressor is discussed in the paper. Results of exergy analysis of the system operating with various working fluids for various operating conditions have been shown. Analysis showed possible exergy efficiency increase of refrigeration compression cycle.

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Autorzy i Afiliacje

Jarosław Karwacki
Adam Dudar
Dariusz Butrymowicz
Kamil Śmierciew

Abstrakt

In this study a cooling ejector cycle coupled to a compression heat pump is analyzed for simultaneous cooling and heating applications. In this work, the influence of the thermodynamic parameters and fluid nature on the performances of the hybrid system is studied. The results obtained show that this system presents interesting performances. The comparison of the system performances with hydrofluorocarbons (HFC) and natural fluids is made. The theoretical results show that the a low temperature refrigerant R32 gives the best performance.
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Abstrakt

Performance assessment of ejector-expansion vapor compression refrigeration system with eco-friendly R134a alternative refrigerants (R152a, R1234yf, R600a, R600, R290, R161, R32, and propylene) is presented for air-conditioning application. Ejector has been modeled by considering experimental data based correlations of component efficiencies to take care of all irreversibilities. Ejector area ratio has been optimized based on maximum coefficient of performance (COP) for typical air-conditioner operating temperatures. Selected refrigerants have been compared based on area ratio, pressure lift ratio, entrainment ratio, COP, COP improvement and volumetric cooling capacity. Effects of normal boiling point and critical point on the performances have been studied as well. Using ejector as an expansion device, maximum improvement in COP is noted in R1234yf (10.1%), which reduces the COP deviation with R134a (4.5% less in basic cycle and 2.5% less in ejector cycle). Hence, R1234yf seems to be best alternative for ejector expansion system due to its mild flammability and comparable volumetric capacity and cooling COP. refrigerant R161 is superior to R134a in terms of both COP and volumetric cooling capacity, although may be restricted for low capacity application due to its flammability.

Słowa kluczowe

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Autorzy i Afiliacje

Shubham Mishra
Jahar Sarkar

Abstrakt

A measuring system was developed for the measurement of ejector forces in the die casting process. When selecting the sensor technology, particular care was taken to ensure that measurements can be taken with a high sampling rate so that the fast-running ejection process can be recorded. For this reason, the system uses piezoelectric force sensors which measure the forces directly at the individual ejector pins. In this way, depending on the number of sensors, it is possible to determine both the individual ejector forces and the total ejector force. The system is expandable and adaptable with regard to the number and position of the sensors and can also be applied to real HPDC components. Automatic triggering of the measurements is also possible. In addition to the measuring system, a device and a method for in-situ calibration of the sensors have also been developed. To test the measuring system, casting experiments were carried out with a real aluminium HPDC aluminium component. The experiments showed that it is possible to measure the ejector forces with sufficient sampling rate and also to observe the process steps of filling, intensification and die opening by means of ejector forces. Experimental setup serves as a basis for future investigations regarding the influencing parameters on the ejection process.

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Autorzy i Afiliacje

S. Krischke
S. Müller
T. Schuchardt
Y. Kouki
K. Dilger

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