1. Proceedings of the 25th
CANCAM
London, Ontario, Canada, May 31 – June 4, 2014
NUMERICAL INVESTIGATION OF JET PUMP WITH TWISTED TAPES
Arpita Srivastava
Department of Mechanical
Engineering
Indian Institute of Technology
Chennai, Tamil Nadu, India
arpita.sri.lko@gmail.com
Shaligram Tiwari
Department of Mechanical
Engineering
Indian Institute of Technology
Chennai, Tamil Nadu, India
shaligram@gmail.com
Mani Annamalai
Department of Mechanical
Engineering
Indian Institute of Technology
Chennai, Tamil Nadu, India
mania@iitm.ac.in
ABSTRACT
Jet pump is used to transfer momentum from a high velocity
primary stream to a secondary stream that gets entrained. It is
packaged with the advantage of geometrical simplicity
without any moving parts. It comprises mainly of a nozzle,
mixing chamber and diffuser. It is used in numerous
applications, one such being desalination systems, where it
helps in creating vacuum inside the flash chamber without
employing conventional oil vacuum pump. Aim of the
present study is to carry out three-dimensional numerical
investigations of two phase flow jet pump in presence of
twisted tapes under optimized conditions of the parameters
such as upstream and downstream pressures, primary jet
mass flow rate, entrained secondary stream mass flow rate,
geometry of the ejector, etc. Investigations of swirling
turbulent jet flows are carried out using suitable turbulent
model in ANSYS FLUENT. This investigation helps in
predicting the flow behavior at the exit of nozzle with respect
to different nozzle profiles causing dispersion in jet and also
due to introduction of the swirl. At first, the three-
dimensional numerical computations have been carried out to
validate the existing literature without introduction of swirl
in primary stream. Further investigations are carried out to
identify the effect of tape with respect to the case without
tape. Water and air have been used as fluids in the primary
and secondary streams respectively. Nozzle profiles selected
is conical. The mean diameter of nozzles are kept to be 4mm
and 6mm. Results in present study suggest that the
momentum exchange achieved by the swirl causes significant
enhancement efficiency of the jet pump.
KEYWORDS: Jet pump, nozzle profile, two phase flow,
twisted tape.
INTRODUCTION
The ejectors employed in jet pumps causes a complex flow
physics and hence it is preferably modeled in 3D
incorporating CFD which gives us the advantage over
neglecting 1D assumptions and predicted very near to actual
situation. Several investigations have been reported for
enhancing its efficiency. Many researchers carried out
valuable experiments to determine the conditions at which
improvements can be achieved. Pfliedderer [1] proposed that
the pressure ratio and air flow rate are independent of each
other. Martinelli et al. [2] reported that increase in air flow
rate at secondary inlet with an increase in flow rate of water
at the primary side is due to increased pressure at primary
motive fluid. Many researchers have performed studies on
multi hole nozzle. Decay of primary jet flow as well as length
of potential core depends on how the phenomenon of
momentum exchange occurs between two fluids stream in
mixing zone near to primary nozzle exit. Sharma [9] in his
work experimentally verified that, for lower area ratio,
nozzles having elliptical profile are capable of producing
higher efficiency then nozzles with circular or conical
profile. He experimented with different area ratio of nozzle.
The geometrical design for the present study is taken from
Sharma’s experiment. Hansen and Kinnavy [5] performed
experiments on ejectors keeping different area ratio and then
studied different parametric effect. It was concluded that area
ratio has major role to play in ejector efficiency than any
other parameter.
Abdus Samad [10] investigated the influence of the
introduction of swirl low performance of an ejector and
concluded that it enhance the jet breakup resulting in higher
suction rates at different optimized swirl angles.
GOVERNING EQUATION AND NUMERICAL
TREATMENT
Governing equations solved are the mass and momentum
conservation equations. For steady state, incompressible flow
with constant viscosity, these equations can be expressed as
(1)
(2)
In these equations, ui refers to the mean velocity along xaxis,
P the static pressure and the kinematic viscosity of fluid.
CFD helps to formulate the required governing equations
involved in fluid flow into numbers such as to get a final
desired description of the complete flow field under
observation numerically. The observation and results
obtained out of CFD are near to actual flow and it has been
proved in large number of applications. Riffat et al. [6] have
employed CFD tools and application to determine the
optimum design of the ejector. Not only this, he examined
the various performance characteristic obtained during

2. simulation to compare using primary nozzles of various
geometries with different types of working fluid. Later, the
performance of ejector in a compressible flow was studied by
varying the nozzle position with respect to mixing chamber
by Riffat and Omer [7] for a refrigeration system using CFD
model. Gas powered Jet pump performance also depends on
its diffuser design which was analyzed by Neve [11]
numerically using CFD tools.
Ouzzane and Aidoun [12], investigated on ejector and put
forward one-dimensional flow model involved in their
studies. Bartosiewicz [8] performed numerical analysis on
the ejector with working fluid as air, using CFD software
FLUENT. They validated the existing CFD results obtained
with the experimental investigations made. Further these
studies were extended to optimize the turbulent model to
capture more physical realistic situation occurring in flow
field. Many studies has proposed that introduction of swirl in
the primary jet may increase the overall efficiency of jet
pump by improving the entrainment of secondary fluid.
STATEMENT OF THE PROBLEM
The present numerical validation studies have conducted
with the results of Sharma’s experimental work [9]. Problem
is being defined numerically considering it to be a steady
flow, incompressible situation. The pressure-based steady
flow Navier-Stokes solution’s algorithm has been followed to
reach out the solution.
The efficiency of the jet pump was calculated by considering
upstream pressure, pressure at diffuser, secondary and flow
ratio.
(3)
Figure1: Schematic cross section of jet pump
It excludes the effect of pipes and connecting elements used
in the experimental setup. The steady state of the jet pump is
modeled maximum evacuation of air in the vacuum chamber
is achieved. The 3-D geometry is simulated to ensure that
maximum physical turbulent flow field can be captured and
studied. The major details of the dimensions of the ejector
employed are given in Table 1. The profile of the nozzle is
changed keeping other geometrical parameters as the same.
For validation, nozzle of circular, elliptical and conical
profiles, with 4mm nozzle diameter, are compared and found
that elliptical nozzle has better efficiency than others.
Table 1.Design parameters of nozzle
Notation Name Dimension
Do Nozzle diameter 4 mm and 6mm
Dsuc Suction chamber diameter 21mm
Dmt Mixing tube diameter 10mm
Dst Inlet diameter of supply tube 21mm
Lmt Length of the mixing tube 265mm
S Distance between nozzle and mixing tube 31mm
Ld Length of the diffuser 135mm
Dd Diameter of the diffuser at outlet 21mm
 Diffuser semi cone angle 2°30’
This geometry is termed as the ‘base geometry’ in this study
as shown in figure 1. For the studies with twisted tape in
conical nozzle, the diameter of the mixing tube (Dmt) and the
diffuser element downstream of the mixing tube were kept
constant.
For the present study CFD software ANSYS Fluent is used
which incorporates a finite volume code for the preset
simulations. This code solves the discretized equations in a
segregated manner, with SIMPLE algorithm. The first-order
upwind scheme is taken for momentum, volume fraction,
turbulent Kinetic energy and turbulent dissipation rate
discretisation. The solutions were assumed to have
converged for the residual level of 10-4
for continuity, x-
velocity, and y velocity and 10-6
for k -epsilon.
Creation of the geometries was carried out in Solid works
and then imported to ANSYS Workbench for meshing of the
computational domains. To ensure better insight view of
fluid flow and mixing grid independent study was carried out
for ejector with conical nozzle incorporating twisted tape.
For performing the grid study, geometries with mesh size of
167231cells, 257111 cells, 430017 cells 707808 cells,
864906 cells, 1072648 cells and 1755598 cells were
numerically analyzed. Minimum orthogonal quality was kept
at 0.5.The grid size was optimized by head difference. It was
observed that for the geometries with higher mesh size,
variation in head difference was almost negligible. Since
after 7.8lakhs grid size there was no such significant
difference in pressure contours this was fixed as grid size for
all the further simulations which include swirl generators
also. Boundary conditions used for each simulation are
known static absolute pressure. Turbulent intensity was
selected 5 % and respective hydraulic diameters were used at
each of the flow boundaries.
DESCRIPTION
To get the swirling flows single and double twisted tapes, as
shown in figures 2 to 3, has been used in figure 4. The
twisted-tapes are characterized by the twist ratio defined by
the ratio between the tape turn length of 180º along its axis
and the tube diameter. The length of twisted tape is 40mm
and width is 18mm.Thickness of the tape used are 1mm and
Mixing Chamber
Secondary
Inlet
Primary
nozzle Diffuser

3. 1.5mm Single Twisted tapes, used in current study, are 90
degree tape turn with twist ratio 1.11.
Similarly double twisted tapes are also used in primary flow
such as two tapes right angled to each other are twisted at 90
degree.
Figure 2: Single twisted tape
Figure 3: Double Twisted Tape
Figure 4: Pictorial representation of double twisted tape
incorporated in primary nozzle
RESULTS AND DISCUSSION
On performing numerical studies, the ejector incorporating
double twisted tape is found to be highly efficient
comparatively to other ejector combination. It is also found
that single twisted tape has the lesser efficiency than double
twisted tape but better than without tape. The Table 2.shows
the comparative parametric studies carried out along with
performance obtained. The twisted tape studies are
performed for higher area ratio in conical nozzle as for higher
diameter of nozzles are found more efficient than smoother
profiled nozzle by Sharma [9]. The velocity, turbulent kinetic
energy and vorticity magnitude graphs have been plotted
against the length of the ejector, as shown in figures 5 to
7.The velocity contours in figure 8 shows that the maximum
velocity was attained in the conical nozzle with double
twisted tape having thickness 1.5mm. Efficiency of this
arrangement is increased by 10% when compared with
nozzle, without any tape.
Table 2: Comparison of various operating parameters and
performance
Parameters
Without
tape
Single twisted tape Double twisted
Tape
1mm 1.5mm 1.5mm 1mm
Water flowrate
Qw(lps)
1 1 1 1 1
Air Flowrate
Qa(lps)
1.6 1.63 1.63 1.8 1.72
Flow Ratio 1.7 1.63 1.63 1.8 1.72
Upstream
Pressure(Bar
absolute)
8.9 8.9 8.9 8.9 8.9
Downstream
Pressure(Bar
Absolute)
1.81 1.81 1.81 1.81 1.81
Suction
Pressure(Bar
Absolute)
1.01306 1.01311 1.01311 1.01306 1.01306
Efficiency ɳ
(in %)
18.4 18.4 18.4 20.4 19.5
Position (mm)
Figure 5: Velocity profiles for jet pump with different twisted
tape
CONCLUSIONS
It has been observed that there is a change in flow behavior
after the nozzle when twisted tapes are inserted in the
upstream primary fluid and more pressure drops after the
nozzle is observed due to high vorticity magnitude. This
enhances the volume flow rate of the secondary air which
ultimately results in better entrainment.
Double
Twisted
Tape
Nozzle
exit
Secondary Inlet
Velocity(m/s)
Primary
Inlet

4. Position(mm)
Figure 6: Turbulent kinetic energy profiles for jet pump with
different twisted tape
Position (mm)
Figure 7: Vorticity magnitude profiles for jet pump with
different twisted tape
Figure 8: Velocity contours at the mid plane for different Jet
pumps
REFERENCES
1. Pfleiderer, C., “Experiments on jet pump for its
performance”, C. Zeit, VDI, 58, 965 &1011.
2. Martinelli, R.C., Boelter, L. M. K., Morrin, E. H.,
“Theoretical and experimental analysis of ejectors
Trans. ASME, 66, pp. 139-151.
3. Senthil Kumar, R., Mani, A., Kumaraswamy, S.
2004, “Selection of Pumps for Vacuum Desalination
System Utilizing Ocean Thermal Energy, 31st
National Conference on Fluid Mechanics and Fluid
Power, Vol. 1, pp. 409–416.
4. Senthil Kumar, R., Mani,A., Kumaraswamy, S.,
2007, “Experimental Investigation on Two-Phase
Jet Pump used in Desalination System ” ,
Desalination, 204, pp. 437-447.
5. Hansen, A. G., and Kinnavy, R. 1965, “The design
of water jet pumps part I – experimental
determination of optimum design parameters”.
ASME Paper 65-WA/FE-31.
6. Riffat, S. B., Gan, G., and Smith, S., 1996,
Computational fluid dynamics applied to ejector
heat pumps, Journal of Applied Thermal
Engineering, 16, 291-297.
7. Riffat, S. B., and Omer, S. A. 2001, CFD modeling
and experimental investigations of an ejector
refrigeration system, Int. Journal on Energy
Research, 25, 115-128.
8. Bartosiewicz, Y., Aidoun, Z., Mercadier, Y., 2006,
“Numerical assessment of ejector operation for
refrigeration applications based on CFD”, Applied
Thermal Engineering, n 26, pp.604–612.
9. Sharma, V. Kumar., Kumaraswamy, S., Mani, A.
2012, “Effect of Various Nozzle Profiles on
Performance of a Two Phase Flow Jet Pump”. Int.
Journal of Mechanical and Aerospace Eng,6, p.136-
142.
10. Samad, A., Omar, R., Hewakandamby, B., Lowndes
I., and Short, G. 2012, “Swirl Induced Flow
Through a Venturi-Ejector,” ASME 2012 Fluids
Engineering Division Summer Meeting
(FEDSM2012), Puerto Rico, USA.
11. Neve, R. S. 1993, “Computational fluid dynamics
analysis of diffuser performance in gas-powered jet
pumps”, Int. Journal on Heat and Fluid flow, 14,
401-407.
12. Ouzzane, M., and Aidoun, Z. 2003, Model
development and numerical procedure for detailed
ejector analysis and design, Journal of Applied
Engineering, 23, 2337-2351.
Turbulentkineticenergy
(m2
/s2
)
Vorticity(1/s)
Velocity, m/s