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Performance improvement by reducing compressor work of r 134 a and r22 used refrigeration systems
Performance improvement by reducing compressor work of r 134 a and r22 used refrigeration systems
Performance improvement by reducing compressor work of r 134 a and r22 used refrigeration systems
Performance improvement by reducing compressor work of r 134 a and r22 used refrigeration systems
Performance improvement by reducing compressor work of r 134 a and r22 used refrigeration systems
Performance improvement by reducing compressor work of r 134 a and r22 used refrigeration systems
Performance improvement by reducing compressor work of r 134 a and r22 used refrigeration systems
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Performance improvement by reducing compressor work of r 134 a and r22 used refrigeration systems

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  • 1. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME187PERFORMANCE IMPROVEMENT BY REDUCING COMPRESSORWORK OF R-134A AND R22 USED REFRIGERATION SYSTEMS BYUSING TWO-PHASE EJECTORK.GANESH BABUB.Tech., M.Tech -R&A/C.Assistant Professor,Department of Mechanical Engineering,Sagar Institute of Technology,Chevella, Ranga Reddy – 515002,Andhra Pradesh, India.K.RAVI KUMARB.Tech., M.Tech -R&A/C.Assistant Professor,Department of Mechanical Engineering,All- Habeeb College of Engineering,Chevella, Ranga Reddy – 515002,Andhra Pradesh, India.Dr. Md. AZIZUDDINM.E. (Mech), Ph.D. (Osm.,)Professor & HeadDepartment of Mechanical Engineering,Royal Institute of Science & Technology,Chevella, Ranga Reddy – 515002,Andhra Pradesh, India.ABSTRACTResearch works evidenced that using expansion device in vapour compression refrigerationsystem giving less efficiency and degraded system performance. Present work R-134a and R22 areused as working fluids, Using Engineering Equation Solver (EES) software version 6.883. Computersimulation is carried out in between Simple vapour compression system & 1-Dimensional Two-phaseejector used vapour compression system.Under the optimal values of Ejector area ratio (Ar) = 14, entrainment ratio (U) = 0.53, nozzleefficiency (nn) = 85%, diffuser efficiency (nd) = 85% at operating conditions of Evaporatortemperature Te=-15°C, condenser temperature Tc = 30°C. The COPs of Ejector used vapourcompression (EVCR) system 4.649 for R134a and 4.433 for R22, at the same operating conditions,simple vapor compression system COP 3.733 for R134a. COP Improvement 19.70 % for Ejector usedrefrigeration system than simple vapour compression refrigeration system.Keywords: Vapour compression refrigeration system; R134a; Ejector; EES software; COPINTERNATIONAL JOURNAL OF ADVANCED RESEARCH INENGINEERING AND TECHNOLOGY (IJARET)ISSN 0976 - 6480 (Print)ISSN 0976 - 6499 (Online)Volume 4, Issue 3, April 2013, pp. 187-193© IAEME: www.iaeme.com/ijaret.aspJournal Impact Factor (2013): 5.8376 (Calculated by GISI)www.jifactor.comIJARET© I A E M E
  • 2. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME188I. INTRODUCTIONElectrical energy consumption has become a worldwide research topic because Refrigerationand Air-conditioning systems consuming electrical energy approximately 15%. Ejector used vapourcompression refrigeration system has some special advantages such as the simplicity in construction,high reliability and low cost compare to other refrigeration systems.Throttling loss and Higher power consumption for compressor are the major losses in aconventional vapour compression refrigeration system. Various devices have been held instead of theconventional devices like Capillary tube, Thermostatic expansion valve. Ejector is a device that uses ahigh-pressure fluid to pump a low-pressure fluid to a higher pressure at a diffuser outlet. Its low cost,no moving parts and ability to handle two-phase flow without damage make it attractive for being theexpansion device in the refrigeration system.To reduce the throttling losses of vapour compression cycle we replace the throttling device.Ejector as an expander in that, the process is isentropic. By using ejector devices we are able toreduce the throttling looses and reduces the load on evaporator so that the COP of the combinedcompression refrigeration cycle is increases. The descriptions of ejector are as given below1.1 Two phase ejector:Ejector is an expander which uses an expansion device in vapour compression cycle andreplaces the throttling loss by replacing throttling device in vapour compression cycle. Theappropriate installation of the ejector in vapour compression cycle increases the COP of therefrigeration system by raising the compression suction pressure to a level higher than that in theevaporator and consequently, to reduce the load on the compressor and motor.In the ejector geometry there are three sections of ejector1. Motive Nozzle,2. Mixing tube,3. Diffuser section.In Ejector used Vapour compression refrigeration cycle comprises of the following Ejector,Evaporator, Compressor, Condenser, Separator, etc. Figure.1 shows the configuration of ejector.Ejector is an expression device which replaces the throttling valve in order to reduce the throttlinglosses of expansion device. The ejector is installed at the outlet of the condenser (6 to 1), and themotive fluid (liquid from the condenser) enters into the nozzle at a relatively high pressure.Reduction of the pressure of the liquid in the nozzle provides the potential energy forconversion to kinetic energy of the liquid. The driving flow entrains vapour out of the evaporator. Thetwo phases are mixed in mixing chamber (at point 2) and leave it after a recovery of pressure in thediffuser part of the ejector (at point 3). The liquid portion is directed to the evaporator through a smallpressure-drop expansion device (7 to 8) while the vapour portion enters the compressor suction (3 to4). The lines from points 4, 5, 6 are a series process in the compressor and the condenser. The linesfrom points 7, 8, 9 are a series process in the expander and the evaporator. Points 6 and 1 are the stateof the flow at the exit of the primary nozzle and in the mixing area (point 2) of the ejector while point2–3 is a compression process in Diffuser. The appropriate installation of the ejector increases COP ofthe refrigeration system by raising the compression suction pressure to a level higher than that in theevaporator and consequently, to reduce the load on the compressor and motor.
  • 3. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME189III. SIMULATION ANALYSISBased on the Thermodynamic analysis, a steady-state simulation program for the vapourcompression refrigeration cycle, using EES software (Klein and Alvarda (2006)) is developed.3.1 Solution methodology in engineering equation solver (EES) (Klein and Alvarado (2007))EES is a software package developed by Dr. Sanford Klein of the University of Wisconsin.EES incorporates the programming structure of C and FORTRAN with a built-in iterate,thermodynamics and transport property relations, graphical capacities, numerical integration, andmany others useful mathematical functions. By grouping equations there are to be solvedsimultaneously, EES is able to function at a high rate of computational speed. Ammonia-watermixture properties are calculated in EES using the correlation developed by Ibrahim and Klein(1993). There are two major differences between EES and exiting numerical equations solvingprograms. First, EES automatically identifies and groups equations that must be solvedsimultaneously. This feature simplifies the process for the users and ensures that the solver willalways operate at optimum efficiency. Second, EES provides many built in mathematical and thermophysical property functions useful for engineering calculations. The basic function provided by theengineering equation solver (EES) is the numerical solution of the non-linear algebraic anddifferentials equations, EES provides built in thermodynamics and transport property functions formany fluids including water, dry and moist air. Included in the property database are thermodynamicsproperties for H2O-LiBr and NH3-H2O mixture. Any information between quotation marks [“] or [{}]is an optional comment. Variable names must start with a letter. A code containing a good library ofworking fluid properties suitable for heat pumps is the Engineering Equations Solver (EES). Here theuser must write the equations governing the cycle and make sure the set is well-defined. In the case ofa non-linear set of equations, the user must check the results to make sure that the mathematicalsolutions are also a physical One.3.2 Simulation analysis on Vapour compression refrigeration system:3.2.1 Simulation was performed to evaluate the COP of vapour compression cycle with the followingassumptions1. The refrigerant was at all times in thermodynamic quasi-equilibrium.2. Characteristics and velocities were constant over cross section3. Negligible pressure drop.4. There is no wall friction.5. The processes in compressor, expansion valve area assumed to be adiabatic.6. Saturated state at the evaporator and the condenser outlet.3.2.2 Input parameters for Vapour compression refrigeration system simulation:Evaporator temperature (Te) : -15 0CCondenser temperature (Tc) : 30 0CMass flow rate (m) : 1/60 (kg/sec)Refrigerant : R-134a
  • 4. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME1903.2.3 Flow chart for Vapor compression system simulation analysis:3.2.4 Vapour compression refrigeration system simulation results:Evaporator temperature (Te) = -15 ˚CCondenser temperature (Tc) = 30 ˚CEvaporator pressure (Pe) = 1.64 barCondenser pressure (Pc) = 7.706 barCompressor inlet enthalpy (h1) = 241.5 kJ/kgCompressor outlet enthalpy (h2)= 281.1kJ/kgEvaporator inlet enthalpy (h4) = 93.58 kJ/kgMass flowrate (m) = 0.01667 kg/secCoefficient of performance (COP) == ( )( )1 42 1m h hm h h −  − = ( )( )0.01667 * 241.5 93.580.01667 * 281.1 241.5 −  − = 1 4 7 . 9 23 9 . 6   = 3.733
  • 5. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME1913.3 Simulation was performed to evaluate the ejector used vapour compression cycle with thefollowing assumptions:1. The refrigerant was at all times in thermodynamic quasi-equilibrium.2. Characteristics and velocities were constant over cross section (1-dimensional model).3. All fluid characteristics are uniform over the cross section after complete mixing at the exit ofthe mixing tube.4. There is no external heat transfer to the system.5. There is no wall friction.6. Negligible pressure drop.7. The processes in compressor, expansion valve and ejector area assumed to be adiabatic.8. Saturated state at the evaporator and the condenser outlet.9. One dimensional flow in the ejector.3.3.1 Flow chart for Ejector used vapour compression refrigeration system simulation analysis:3.3.2 Input parameters for Ejector used system simulation analysis:Evaporator temperature ( ) : -15 ºCCondenser temperature ( ) : 30 ºCEjector convergentNozzle efficiency ( ) : 85%Ejector diffuser efficiency ( ) : 85%Ejector area ratio (Ar) : 8Entrainment ratio (U) : 1Refrigerant : R134a
  • 6. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME192Graph.3 Nozzle efficiency (nn=10 to 100 %) Vs COPGraph.4 Diffuser efficiency (nn=10 to 100 %) Vs COP26.626.3826.1625.9525.7325.5225.3125.124.924.69232425262710 20 30 40 50 60 70 80 90 100Compressorwork(Wc)inkJ/kgDiffuser efficiency (nd)Diffuser efficiency(nd) Vs Compressorwork (Wc)in kJ/kgCompressorWork (Wc)in kJ/kgGraph.5 Diffuser efficiency (nd) Vs Compressor work (Wc in kJ/kg)Above Graph.3 shows the decreasing of COP by increasing the nozzle efficiency. Diffuserefficiency is mainly affecting the COP of the system, because the diffuser efficiency increasing meansthe pressure of the refrigerant from diffuser inlet to outlet pressure is increasing with respect toincrease in efficiency shown in Graph.4. But it is going to affect on the refrigerating effect i.e.enthalpies (h9-h8) starts to decrease, again the expansion valve throttling losses coming to matter. Forbetter results the nozzle efficiency is little bit less than or equal to diffuser efficiency.V: CONCLUSIONSIn the present simulation analysis the results has been computed for vapour compressionrefrigeration cycle & ejector used vapour compression refrigeration cycle. The effect of the geometryof the ejector Area ratio with the refrigerant R134a has been analyzed. The maximum COP = 4.649 is
  • 7. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME193obtained for optimum area ratio whose value is around Ar = 14 for ejector used refrigeration systembecause, at this area ratio the COP is maximum and compressor pressure ratio (Pr) is minimum.Optimal entrainment ratio(U) = 0.53 because the compressor pressure ratio (Pr) = 2.362 lowcompared to simple vapour compression system compressor pressure ratio (Pr) = 4.698, the quality ofvapour refrigerant at outlet of ejector x3=0.4366 is optimal at entrainment ratio (U) = 0.53 compare toquality of vapour refrigerant at outlet of ejector x3 = 0.8331 at entrainment ratio (U) = 2. Thesimulation analysis results shows that for a given evaporator temperature (Te) = -15˚C and thecondenser temperature (Tc) =30 ˚C, the vapour compression refrigeration cycle COP = 3.733 is lessthan that of the ejector used vapour compression refrigeration cycle COP = 4.649.The system performance mainly depends on the diffuser efficiency, because the diffuserefficiency increase is increasing the pressure at the outlet of diffuser. This pressure increase isdecreasing the pressure ratio of the compressor. Compressor pressure ratio decreases the compressorwork also decreases. If work decreases the COP of the system will increase.The system performance also depends on the nozzle efficiency. The nozzle efficiencyincrease is decreasing the pressure at the outlet of nozzle. This pressure decrease is increasing thepressure ratio (Pr) of the compressor. Compressor pressure ratio increases the compressor work (Wc)also increases. If work increases the COP of the system will decrease. For better results the nozzleefficiency is little bit less than or equal to diffuser efficiency. The performance increase of the ejectorused vapour compression refrigeration system is 19.70%.VII: REFERENCES:1. Chen, LT. (1988) ‘A new ejector–absorber cycle to improve the COP of an absorptionrefrigeration system’, Applied Energy, Vol.30, pp.37–51.2. Elbel, S., Hrnjak, P. (2006) ‘Experimental validation of a prototype ejector Designed to reducethrottling losses encountered in transcritical R744 system operation’ International journal ofrefrigeration, Vol.32, pp.411-412.3. Huang, B.J., Hu, S.S., Lee, S.H. (2005) ‘Development of an ejector cooling system with thermalpumping effect’ International journal of refrigeration, Vol.29, pp.476-484.4. Klein, S.A., Alvarda, F., (2003) Engineering Equation Solver, Version 6.883. F-chart software,Middleton, WI.5. Li, D., Groll, A. (2005) ‘Transcritical CO2 refrigeration cycle with ejector expansion device’,International Journal of Refrigeration, Vol. 28, pp.766–773.6. Refrigeration and Air-conditioning by R.S.Kurmi7. Refrigeration and Air-conditioning by Domkundwar, Arora, Domkundwar.8. Dr. Ashok G. Matani And Mukesh K. Agrawal, “Performance Analysis Of VapourCompression Refrigeration System Using R134a, Hc Mixture And R401a As WorkingMedium” International Journal Of Mechanical Engineering & Technology (IJMET) Volume 4,Issue 2, PP: 112 – 126, ISSN PRINT : 0976 – 6340, ISSN ONLINE : 0976 - 6359

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