cfd analysis on ejector cooling system with variable throat geometry

72
International Journal of Research and Innovation on Science, Engineering and Technology (IJRISET)
CFD ANALYSIS ON EJECTOR COOLING SYSTEM WITH VARIABLE THROAT
GEOMETRY
Srihari Anusuri1
, A.Sirisha Bhadrakali2
, V.V.Kamesh3
.
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 of Mechanical Engineering, Aditya Engineering College, Surampalem, Andhra Pradesh, India.
*Corresponding Author:
Srihari Anusuri,
Research Scholar,Department of Mechanical Engineer-
ing, Aditya Engineering College, Surampalem, Andhra
Pradesh, India.
Email: hari.anusuri@gmail.com
Year of publication: 2016
Review Type: peer reviewed
Volume: III, Issue : I
Citation:Srihari Anusuri, Research Scholar "Cfd Analy-
sis on Ejector Cooling System With Variable Throat Ge-
ometry" International Journal of Research and Innova-
tion 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 flow work contained in the
motive fluid stream into kinetic energy. The motive nozzle
is a converging-diverging design. It allows the high-speed
jet to become supersonic.
Schematic of a typical two-phase ejector design
Depending on the state of the primary fluid, the flow at
the motive nozzle exit might be 2-phase. Flashing of the
primary flow inside the nozzle might be delayed due to
thermodynamic and hydrodynamic non-equilibrium ef-
fects. The high-speed jet initiates the interaction with the
secondary fluid which is inside the suction chamber. Mo-
mentum is transferred from the primary flow to the sec-
ondary flow. For the stagnant suction flow an additional
suction nozzle can be used to pre-acceleration of the rela-
tively. This helps to reduction of excessive shear losses
caused by large velocity differences caused between the
two fluid streams. Depending up on the working condi-
tions, both the flows either primary or secondary flow
might be choked inside the ejector. Due to static pressure
differences, it is possible for the primary flow core to fan
out. To create a fictive throat in which- the secondary flow
reaches to the sonic condition before both streams thor-
oughly mixes in the subsequent mixing section. The mix-
ing section can be designed as a segment, having a con-
stant 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-sec-
tional area of the mixing section. The mixing process is re-
peatedly accompanied by shock wave phenomena which
results in a considerable pressure rise. At the exit of the
mixing section, still have the high flow 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, the total flow exiting at the dif-
fuser has a pressure in between the primary and the sec-
ondary streams entering in to the ejector. Thus, the ejec-
tor acts as a motive-flow driven fluid pump which used to
elevate the pressure of the entrained fluid.
The 2 major characteristics that can be used for determi-
nation of the performance of an ejector are :
i.Suction pressure ratio and
ii. Mass entrainment ratio.
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 fluid by using CFD
(computational fluid 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 fluent14.5.
International Journal of Research and Innovation in
Thermal Engineering (IJRITE)

73
Need for development
• Due to raise in global warming need for development of
highly efficient 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 efficiency
• Improvement of ejector efficiency 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, indus-
trial processes and solar, etc.
The first steam ejector refrigeration system was devel-
oped by Maurice Leblanc in 1910 and gained in popu-
larity for air conditioning applications until the devel-
opment of chlorofluorocarbon refrigerants in the 1930’s
and their use in the vapour compression cycle which was
much more efficient than alternative thermally driven cy-
cles. Research and development continued however and
the ejector technology found applications in many engi-
neering fields particularly in the chemical and process
industries. Systems have been developed with cooling
capacities ranging from a few KW to 60,000 kW but de-
spite extensive development effort the COP of the system,
which can be defined 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 com-
panies 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 efficiency
of the simple ejector cycle more complex cycles have been
investigated as well as the integration of ejectors with va-
pour compression and absorption systems. An example of
this is the Denso transport refrigeration system. Signifi-
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 suc-
tion flow than that of the motive fluid, the term injec-
tor is sometimes used for applications in which the dif-
fuser discharge pressure can actually reach the pressure
of the driving fluid. Other synonyms encountered in the
literature are eductor, diffusion pump, aspirator, and jet
pump. In case the total flow exiting the diffuser consists
of only a single component.
DESIGNING
CATIA - which stands for Computer Aided Three-dimen-
sional 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 world-
wide by IBM.
Designing of Ejector
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 fluid R134a)
IMPORT CATIA MODEL
• Open Ansys Workbench and then Fluid Flow (Fluent) →
double click
• Select geometry and then right click, import geometry
by choosing the → select browse →open part → ok

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Image of imported model in ansys
Image of mesh model
Results → graphics and animations → contours →
setup
Picture explaining wall shear stress
Picture explaining turbulent kinetic energy
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

CFD ANALYSIS ON EJECTOR MODIFIED 1(Working
fluid R134a)
Picturing explaining density
"Flux Report"
-------------------------------- --------------------
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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CFD ANALYSIS ON EJECTOR MODIFIED 2 (Working
fluid R134a)
Picture explaining turbulent kinetic energy
Picturing explaining density
"Flux Report"
--------------------------------- --------------------
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
CFD ANALYSIS OF EJECTOR RESULTS TABLE:
VELOCITY
MAGNITUDE
STATIC PRESSURE STATIC TEM-
PERATURE
MIN 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 DENSITY MASS
FLOW
RATE
MIN MAX
ORIGINAL 2.18E+03 2.43E+00 1.31E+04 1.23E+00 6.24E-06
MODI-
FIED1
4.96E+00 1.00E-03 1.71E+01 1.23E+00 1.86E-06
MODI-
FIED2
0 2.43E+00 1.31E+04 4.24E+00 0.925E-03
CFD ANALYSIS OF EJECTOR GRAPHS:
Velocity Magnitude
The velocity graph shows that original ejector has the
high velocity than the modified. Again in the Modified
ejector Modified-1 has less velocity magnitude than the
Modified-2.So the modified-1 has the least velocity than
others.
Static temperature
As we observe the graph shows there is no change in the
static temperature.
KINETIC ENERGY:
Mimimum Kinetic engergy
As we observe the graph, the minimum kinetic energy is
less for the Modified ejector-1 than the other two ejectors.

76
Density
As we observe the graph, there is change in density ob-
served from the original ejector to the Modified ejector-1
.There is rapid increase in the density is recorded for the
modified ejector-2 .
Mass flow rate
As we observe from the graph , mass flow rate is no change
form original modal to modified 1 and the rapid increase
modified 1 to modified 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 fluid
dynamics (CFD) simulations of a vapor-jet ejector operat-
ing with R134a as the working fluid 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 modified model,
mass flow rates increase in the 2nd modified model and
even if we see the remaining results we can conclude that
the ejector with the diameter of throat inlet 3mm is a bet-
ter product with best material by using R134a.
Future scope
In this paper computational fluid dynamics (CFD) sim-
ulations of a vapor-jet ejector operating with R134a as
the working fluid will be analyzed. The impact of vary-
ing geometrical parameters on ejector performance will be
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 per-
formance when mixing section length and primary nozzle
exit radius, further we can also continue study consider
different working fluids also to increase the efficiency ,
we can also try working fluids with different Nano fluids
which are popular these days
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Author
Srihari Anusuri,
Research Scholar, Department of Mechanical Engineer-
ing, Aditya Engineering College, Surampalem,
Andhra Pradesh, India.
A.Sirisha Bhadrakali,
Assistant Professor, Department of Mechanical Engineer-
V.V.Kamesh,
Associate Professor , Department of Mechanical Engineer-

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