International Journal of Research and Innovation on Science, Engineering and Technology (IJRISET)
International Journal of Research and Innovation in International Thermal Engineering (IJRITE) CFD ANALYSIS ON EJECTOR COOLING SYSTEM WITH VARIABLE THROAT GEOMETRY
Srihari Anusuri 1, A.Sirisha Bhadrakali 2, V.V.Kamesh 3. 1 Research Scholar, Department of Mechanical Engineering, Aditya Engineering College, Surampalem, Andhra Pradesh, India. 2 Assistant Professor, Department of Mechanical Engineering, Aditya Engineering College, Surampalem, Andhra Pradesh, India. 3 Associate Professor, Department Department of Mechanical Engineering, Aditya Engineering College, Surampalem, Andhra Pradesh, India.
Abstract The vapor jet ejector cooling cycle driven by waste heat. It is a very auspicious approach of producing ‘free cooling’ by utilizing low-grade energy sources. The mechanism behind the ejector-based on waste heat cooling is very unique, when compared to absorption or adsorption cooling technologies. They are also aimed at producing heat driven cooling. This type of ejector cooling system is actually more closely related to vapor compression technology. In this paper simulations of a vapor-jet ejector operating with refregerent R134a as the working uid by using CFD (computational uid dynamics). The impact of varying geometry parameters on ejector performance will be considered. Different mixing section radii will be considered for the analysis. 3D modeling is done by using Catia V5 and analysis is done by Ansys uent14.5.
*Corresponding Author: Author: Srihari Anusuri, Research Scholar,Department of Mechanical Engineering, Aditya Engineering College, Surampalem, Andhra Pradesh, India. Email: hari.anusuri@gmai
[email protected] l.com Year of publication: 2016 Review Type: Type: peer reviewed Volume: III, Issue : I Citation:Srihari Anusuri, Research Scholar "Cfd AnalyCitation:Srihari sis on Ejector Cooling System With Variable Throat Geometry" International Journal of Research and Innovation on Science, Engineering and Technology (IJRISET) (2016) 72-77
INTRODUCTION EJECTOR WORKING PRINCIPLE As outlined in a typical ejector consists of a motive nozzle, a suction chamber, a mixing section and a diffuser. The working principle of the ejector is of converting internal energy and pressure related ow work contained in the motive uid stream into kinetic energy. The motive nozzle is a converging-diverging design. It allows the high-speed jet to become supersonic. supersonic.
Depending on the state of the primary uid, the ow at the motive nozzle exit might might be 2-phase. Flashing of the primary ow inside the nozzle might be delayed due to thermodynamic and hydrodynamic non-equilibrium effects. The high-speed high-speed jet initiates the interaction with the secondary uid which is inside the suction suction chamber. MoMo mentum is transferred from the primary ow to the secsec ondary ow. For the stagnant suction ow an additional suction nozzle can be used to pre-acceleration of the relatively. This helps to reduction reduction of excessive shear shear losses caused by large velocity differences caused between the two uid streams. Depending up on the working condi tions, both the ows either primary primary or secondary ow might be choked inside the ejector. Due to static pressure differences, it is possible for the primary ow core to fan out. To create a ctive throat in which- the secondary ow reaches to the sonic condition before both streams thoroughly mixes in the subsequent mixing section. The mixing section can be designed as a segment, having a constant cross-sectional area but often has a tapered inlet section. Most simulation models either assume mixing at constant area associated with pressure changes or mixing at constant pressure as a result of changes in cross-sectional area of the mixing section. The mixing process is repeatedly accompanied by shock wave phenomena which results in a considerable pressure rise. At the exit of the mixing section, still have the high ow velocities. Thus, a diffuser can be used for recovering the remainder of the KE and to convert it in to the PE, there by increases the static pressure. Typically, Typically, the total ow exiting at the dif dif fuser has a pressure in between the primary and the secondary streams entering in to the ejector. Thus, the ejector acts as a motive-ow driven uid pump which used to elevate the pressure of the entrained uid. The 2 major characteristics characteristics that can be used for determidetermination of the performance of an ejector are :
Schematic of a typical two-phase ejector design
i.Suction pressure ratio and ii. Mass entrainment ratio.
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International Journal of Research and Innovation on Science, Engineering and Technology (IJRISET)
Need for development
Designing of Ejector
• Due to raise in global warming need for development of highly efcient eco-friendly systems is increased • Ejector Cooling system is one of the eco-friendly system developed to reuse waste gases • But ejector cooling system is rarely used because of high set up cost and low efciency • Improvement of ejector efciency will boost up the use of ejector cooling systems Literature review As we know that ejector principle is known from 100 years. Since, ejector has the capacity of generating low pressure and then lifting pressure, it can be relegated the refrigeration purposes to applications where waste heat is easily available from sources such as automobiles, industrial processes and solar, etc. The rst steam ejector refrigeration system was devel devel-oped by Maurice Leblanc in 1910 and gained in popularity for air conditioning applications until the development of chlorouorocarbon refrigerants in the 1930’s and their use in the vapour compression cycle which was much more efcient than alternative thermally driven cy cles. Research and development continued however and the ejector technology found applications in many engineering elds particularly in the chemical and process industries. Systems have been developed with cooling capacities ranging from a few KW to 60,000 kW but despite extensive development effort the COP of the system, which can be dened as the ratio of the refrigeration effect to the heat input to the boiler, if one neglects the pump work which is relatively small, is still relatively low, less than 0.2. Ejector refrigeration systems are not presently commercially available off the shelf but a number of companies specialise in the design and application of bespoke steam ejector systems that use water as a refrigerant for cooling applications above 0° C. To improve the efciency of the simple ejector cycle more complex cycles have been investigated as well as the integration of ejectors with vapour compression and absorption systems. An example of this is the Denso transport refrigeration system. Signi cant effort has also been devoted to the development of solar driven ejector refrigeration systems. Depending on the application, injector is synonymously used for ejector. The main difference in this case is the discharge pressure at the diffuser exit. While the diffuser exit pressure of the ejector is closer to that of the suction ow than that of the motive uid, the term injec tor is sometimes used for applications in which the diffuser discharge pressure can actually reach the pressure of the driving uid. Other synonyms encountered in the literature are eductor, diffusion pump, aspirator, and jet pump. In case the total ow exiting the diffuser consists of only a single component. DESIGNING CATIA - which - which stands for Computer Aided Three-dimensional Interactive Application - is the most powerful and widely used CAD (computer aided design) software of its kind in the world. CATIA is owned/developed by Dassault Systems of France and until 2010, was marketed worldwide by IBM.
Wire mesh model of ejector body with dimensions
Isometric view of ejector body
Wire mesh model of motive nozzle
Isometric view of motive nozzle solid model
CFD ANALYSIS ON EJECTOR ORIGINAL MODEL (Working fuid R134a) IMPORT CATIA MODEL
• Open Ansys Workbench and then Fluid Flow (Fluent) → double click • Select geometry and then then right click, import geometry by choosing the → select browse →open part → ok
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International Journal of Research and Innovation on Science, Engineering and Technology (IJRISET)
Image of imported model in ansys
Picture explaining density
Mass Flow Rate Results "Flux Report" Mass Flow Rate (kg/s) -------------------------------- ------------------contact_region-src 0.08155416 contact_region-trg -0.08155416 inlet 0.16042796 interior-5 0.081554092 interior-____msbr -0.76828504 outlet -0.16042171 wall-10 0 wall-11 0 wall-____msbr 0 -------------------------------- -------------------Net 6.2435865e-06 Image of mesh model
Results → graphics and animations → contours → setup
Picture explaining wall shear stress
CFD ANALYSIS ON EJECTOR MODIFIED 1(Working fuid R134a)
Picturing explaining density
Mass Flow Rate Results "Flux Report"
Picture explaining turbulent kinetic energy
Mass Flow Rate (kg/s) -------------------------------- -------------------contact_region-src 0.0017365188 contact_region-trg -0.001736518 inlet 0.0045788959 interior-5 0.0017365182 interior-____msbr -0.0098826187 outlet -0.0045770342 wall-10 0 wall-11 0 wall-____msbr 0 --------------------------------- -------------------Net 1.8625287e-06
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International Journal of Research and Innovation on Science, Engineering and Technology (IJRISET)
CFD ANALYSIS ON EJECTOR MODIFIED 2 (Working fuid R134a)
CFD ANALYSIS OF EJECTOR GRAPHS:
Picture explaining turbulent kinetic energy Velocity Magnitude
The velocity graph shows that original ejector has the high velocity than the modied. Again in the Modied ejector Modied-1 has less velocity magnitude than the Modied-2.So the modied-1 has the least velocity than others.
Picturing explaining density
Mass Flow Rate Results "Flux Report" Mass Flow Rate (kg/s) --------------------------------- -------------------contact_region-src 0.067236863 contact_region-trg -0.056789029 inlet 0.099116139 interior-5 0.056845825 interior-____msbr-3 0 .9338875 outlet -0.10031085 wall-10 0 wall-11 0 wall-____msbr 0 --------------------------------- -------------------Net 0.0092531256
Static temperature
As we observe the graph shows there is no change in the static temperature. KINETIC ENERGY:
CFD ANALYSIS OF EJECTOR RESULTS TABLE: VELOCITY MAGNITUDE
STATIC PRESSURE MIN
STATIC TEMPERATURE
MAX
ORIGINAL
6.72E+02
-2.77E+05
2.07E+05
3.00E+02
MODIFIED1
1.76E+01
-1.92E+02
1.03E+02
3.00E+02
MODIFIED2
1.74E+02
-2.93E+03
1.01E+03
3.00E+02
SHEAR STRESS
KINETIC ENERGY
MIN
DENSITY
MASS FLOW RATE
MAX
ORIGINAL
2.18E+03
2.43E+00
1.31E+04
1.23E+00
6.24E-06
MODIFIED1
4.96E+00
1.00E-03
1.71E+01
1.23E+00
1.86E-06
MODIFIED2
0
2.43E+00
1.31E+04
4.24E+00
0.925E-03
Mimimum Kinetic engergy
As we observe the graph, the minimum kinetic energy is less for the Modied ejector-1 than the other two ejectors.
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International Journal of Research and Innovation on Science, Engineering and Technology (IJRISET)
considered. The geometrical parameter is different mixing section radius will be considered for the analysis We can also study the behavior of the ejector cooling performance when mixing section length and primary nozzle exit radius, further we can also continue study consider different working uids also to increase the efciency , we can also try working uids with different Nano uids uids which are popular these days REFERENCE 1. Addy A.L., Dutton J.C., Mikkelsen C.D., 1981, Supersonic ejector-diffuser theory and experiments, University of Illinois at Urbana-Champaign, Report UILUENG-82-4001, Urbana, IL, USA
Density
As we observe the graph, there is change in density observed from the original ejector to the Modied ejector-1 .There is rapid increase in the density is recorded for the modied ejector-2 .
2. American Society of Heating, Refrigerating, and Airconditioning Engineers (ASHRAE), 1983, Handbook: Equipment, Chapter 13: Steam-jet refrigeration equipment, Atlanta, GA, USA 3. Bartosiewicz Y., Aidoun Z., Desevaux P., Mercadier Y., 2005, Numerical and experimental investigations on supersonic ejectors, Int J Heat Fluid Fl, Vol. 26, pp. 56-70 4. Beithou N., Aybar H.S., 2000, A mathematical model for steam-driven jet pump, Int J Multiphase Flow, Vol. 26, pp. 1609-1619 5. Bergander M.J., 2005, New regenerative cycle for vapor compression refrigeration, Final Scientic Report, DOE Award DE-FG36-04GO14327, DE-FG36-04GO14327, Madison, CT, USA 6. Butrymowicz D., 2003, Improvement of compressor refrigeration cycle by means of two-phase ejector, 21st IIR International Congress of Refrigeration, Paper ICR0310, Washington DC, USA 7. Chunnanond K., Aphornratana S., 2004, Ejectors: applications in refrigeration technology, Renew SustEnerg Rev, Vol. 8, pp. 129-155
Mass ow rate
As we observe from the graph , mass ow rate is no change form original modal to modied 1 and the rapid increase modied 1 to modied 2 model. CONCLUSION In this paper we have designed a ejector with geometrical parameter it is different throat radius, at the nozzle will be considered. And the analysis in computational uid dynamics (CFD) simulations of a vapor-jet ejector operating with R134a as the working uid will be analyzed. The impact of varying geometrical parameter such as throat radius on ejector performance is considered. As we compare the results obtained for the 3 types of analysis graphs and tables we can observe that the stress is very less an even negligible for the 2nd modied model, mass ow rates increase in the 2nd modied model and even if we see the remaining results we can conclude that the ejector with the diameter of throat inlet 3mm is a better product with best material by using R134a. Future scope In this paper computational uid dynamics (CFD) sim ulations of a vapor-jet ejector operating with R134a as the working uid will be analyzed. The impact of vary vary ing geometrical parameters on ejector performance w ill be
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International Journal of Research and Innovation on Science, Engineering and Technology (IJRISET)
13. Elbel, S., Hrnjak, P., 2007, Experimental investigation of transcritical CO2 ejector system performance, 22nd IIR International Congress of Refrigeration, Paper ICR07-E1-72, Beijing, China
Author
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Srihari Anusuri, Research Scholar, Department of Mechanical Engineering, Aditya Engineering College, Surampalem, Andhra Pradesh, India.
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A.Sirisha Bhadrakali, Assistant Professor, Department of Mechanical Engineering, Aditya Engineering College, Surampalem, Andhra Pradesh, India.
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V.V.Kamesh, Associate Professor , Department of Mechanical Engineering, Aditya Engineering College, Surampalem, Andhra Pradesh, India.
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