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Effect of Dimensional Parameters on the Performance of Vortex Tube

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									Effect of Dimensional Parameters on the Performance of Vortex Tube
                                       1                         2                         3
                   T.Karthikeya Sharma , Dr.M.L.S. Deva Kumar , Dr.K. Vijay Kumar Reddy
       1,2
             J.N.T. University College of Engineering ( Autonomous), Anantapur, Andhrapradesh,India
                         3
                           J.N.T.U. Hyderabad, Department of Mechanical Engineering
                                     (e-mail: karthikeya.sharma3@gmail.com)

 Vortex tube is a non conventional cooling device which will produce cold air and hot air from the source
of compressed air without affecting the environment. When a high pressure air is tangentially injected into
vortex chamber a strong vortex flow will be created which will be split into two air streams one is cold and
another is hot. The main factors that affecting the performance of vortex tubes are inlet pressure, L/D
ratio, cold mass fraction, diameter of nozzle and orifice. In this work an attempt is made to design and
test a simple counter flow vortex tube. The effect of orifice diameter, inlet pressure, L/D ratio on
performance of the vortex tube is investigated and presented in this paper.

1.Introduction

The vortex tube, also known as Ranque vortex tube, Hilsch vortex tube, and Ranque–Hilsch vortex tube,
is a device that enables the separation of hot and cold air as pressurized air flows tangentially into the
vortex chamber through inlet nozzles . Vortex tube was first discovered in 1933 by metallurgist and
physicist Ranque, and the German physicist Rudolf Hilsch improved the design. A Ranque–Hilsch vortex
tube consists of one or more inlet nozzles, a vortex chamber, a cold-end orifice, a hot-end control valve
and a tube. Fig.1 shows the construction of vortex tube. Specially designed vortex chamber’s internal
configuration, combined with the effect of the pressure, accelerates the air to a high rate of rotation (over
a million rpm).

        High pressure gas is tangentially injected into the vortex chamber through the inlet nozzles, a
swirling flow is created inside the vortex chamber. In the vortex chamber, part of the gas swirls to the hot
end and another part exist through the cold end directly. Part of the gas in the vortex tube reverses for
axial component of the velocity and move from the hot end to the cold end. At the hot end, the air
escapes with higher temperature, while at the cold end, the air has lower temperature compared to that of
the inlet temperature pass through the orifice.




                           Fig. 1. Construction of vortex tube
         Vortex Tube has the following advantages compared to the normal commercial refrigeration
device. Simple in constructions, no moving parts, no chemicals, light weight, low cost, maintenance free,
instant cold air, durable for its application. Therefore, if compactness, reliability and lower equipment cost
are the main factors, then the vortex tube are recommended for spot cooling. Now lot of research works is
going on the vortex tube to improve its performance.

       In this work, an attempt was made to fabricate and test a counter flow vortex tube. The
performance of vortex tube was evaluated at different working parameters and geometry parameters. The
Experimental Setup shown in Fig 2.




                                        Fig. 2. Experimental Setup.



2. Design and construction details :

       The design details of vortex tube: Diameter of vortex tube D= 12 mm 15 mm; Length of vortex
tube L= 120mm ( L/D = 8 and 10 ). Diameter of orifice selected Do = 8 mm and10 mm, Diameter of
nozzle DN = 17 mm, No of nozzle= 1, Material= Mild steel , Inlet pressure= 2 bar -12 bar.

3. Experimental part :

        The experimental setup consists of compressor, vortex tube and temperature indicator. A stop
valve at the compressor reservoir exit controls the inlet air to the vortex chamber. The inlet pressure is
measured using pressure gauge. The temperatures of the air at inlet, at cold end, at hot end and ambient
air are measured using thermocouple (copper constantan). Fig. 2 shows the overall view of the
experimental setup. The compressor was initially run for about 20 min. to get a stable compressor air tank
pressure of 2 bar (g). Temperatures at all location are tabulated. Then the same sets of readings are
taken at a pressure of 2, 4, 6, 8 and 12 bar. The temperatures of the air at cold and hot end are the vital
parameters that determine the efficiency of the vortex tube. The experiment is conducted with 8 mm and
10 mm orifice plate at the vortex chamber and with L/D ratios 8 and 10 and with Vortex tube length L 120
mm using Mild Steel as material.
3.1 Tables :
 3.2 Graphs :




4. Results and discussion :

     Fig. 3 shows the effect of orifice diameter and pressure on the ΔT h with L/D = 10. As the inlet the
pressure increases, the temperature difference is increased. At low pressure (6 bar) the entire orifice has
better performance. But at higher pressure the orifice with 10 mm diameter performs well and the
                                                      0
maximum temperature difference is obtained as 27 at 12 bar. Fig. 4 shows the effect of orifice diameter
and pressure on the ΔTh with L/D = 8. As the inlet the pressure increases, the temperature difference is
                                                                         0
increased. The maximum temperature difference is obtained as 29 at 12 bar with orifice of 10 mm
diameter.
     Fig. 5 shows the effect of orifice diameter and pressure on the ΔTc with L/D = 8. As the inlet the
pressure increases, the temperature difference is increased. At low pressure (4 bar) the entire orifice has
better performance. But at higher pressure the orifice with 10 mm diameter performs well and the
                                                      0
maximum temperature difference is obtained as 27 at 12 bar. Fig. 6 shows the effect of orifice diameter
and pressure on the ΔTc with L/D = 10. As the inlet the pressure increases, the temperature difference is
                                                                         0
increased. The maximum temperature difference is obtained as 24 at 12 bar with orifice of 10 mm
diameter.
      From Fig.3, Fig.4, Fig.5 and Fig.6 it is observed that the pressure is the main factor for the energy
separation. As the pressure drop is more, the temperature drop is increased. Because in the vortex
chamber, the air which is nearer to the wall will be compressed and air in the center region will be
expanded. Hence, the outer core will be heated and the inner core will be cooled. Since, the pressure
ratio P2/P1 is directly proportional toT2/T1, the temperature difference is increased for higher pressure.
   The diameter of the orifice influences the expansion that takes place in the vortex chamber. When the
diameter of the orifice is 10 mm, it produces best cooling effect and heating effect compared to 8 mm
diameter orifice. L/D ratio of the vortex tube influences the Cooling and heating effects produced. The
best cooling and heating effects are produced at L/D = 8 compared to L/D = 10.

5. Conclusion :

        When the inlet pressure increases, the temperature difference in cold end and hot end is
         increased.

        At lower values of L /D ratio the performance of vortex tube is very good.

        Larger size diaphragms are well preferable to have better performance.

Nomenclature:
D diameter of vortex tube in mm
L length of vortex tube in mm
Do diameter of orifice in mm
DN diameter of nozzle in mm
∆Tc = Tinlet - T cold

∆Th = T hot – T inlet



References
[1] Ranque, “Experiments on expansion in vortex with simultaneous exhaust of hot air and cold air”. Le
journal de Physique et le Raiuum(paris)pp 112-114(1965)
[2] Hilsch , “The use of expansion gases in centrifugal field as a cooling process.” Review of scientific
instruments. 18(2)pp108-113 (1947)
[3] Takahama H. “studies on vortex tubes.” Bull Jpn Mech Engg 8 (31);433-440( 1965).
[4] Soni and Thomson, “ Optimal design of Ranque-Hilsch vortex tube”. ASME journal of heat transfer, vol
94.,no 2,pp316-317 (1975)
[5] Gao ,” Experimental study on a simple Ranque - Hilsch Vortex tube,” Cryogenics pp173-183(2005)
[6] Ahlborn .B,Grooves.S, “.secondary flow in a vortex tube”,Fluid dynanmics Res 21(2);pp73-86 (1997;
[7] Saidi and Valipur,” Experimental modeling of vortex tube refrigerator,” Applied Thermal
Engg23;pp1971-80 (2002)

								
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