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The vortex tube is a device which separates a high
pressure flow entering tangentially into two low
pressure flows, there by producing a temperature
change. The vortex tube has no moving parts and
generally consists of a circular tube with nozzles and
throttle valve. High pressure gas enters the vortex
tube tangentially through the nozzles which increase
the angular velocity and thus produces a swirl effects.
There are two exits in the vortex tube. The hot exit is
located in the outer radius near the far end of the
nozzle and the cold exit is in the centre of the tube
near the nozzle. The gas separated into two layers.
The gas closer to the axis has a low temperature
which comes out through the hot exit.
There are two types of vortex tube:
1. Uniform vortex tube
2. Counter flow vortex tube
It is also called as parallel vortex tube. This
type of vortex tube has both the cold and the
hot exit at the far end of nozzle in the same
side. In this type of vortex tube consist of a
nozzle, vortex tube and the cold exit present
concentrically with the annular hot exit. The
main application of the vortex tube are in
those areas where compactness, reliability
and low equipment costs are the major
factors and the operating efficiency is of no
It consists of a nozzle, vortex tube and hot outlet with a cone
shaped valve which controls the output. The cold exit is present
centrally near the nozzle end. A source of compressed gas at a
high pressure enters into the vortex tube then creates a rapidly
spinning vortex. The length of the tube is typically between 30-
50 tube diameters. As the air expands down the tube, the
pressure drops the sharply to a value slightly above atmospheric
pressure. Centrifugal action will keep this constrained vortex
close to the inner surface of the tube. The air that escapes at the
other end of the tube can be varied by a flow control valve,
usually shaped as a cone. The amount of air released is between
30% and 70% of the total airflow in the tube. The remainder of
the air is returned through the centre of the tube, along its axis
as a counter-flowing stream. Once a vortex is set up in the tube,
the air near the axis cools down while the air at periphery heats
up in comparison with the inlet temperature. This phenomena is
known as temperature separation effect.
Counter Flow Vortex
1. Compressed air is passed through the nozzle in the
tube and it expands and acquires high velocity due to
particular shape of the nozzle.
2. A vortex flow is created in the chamber and air travels
in spiral like motion along the periphery of the hot side.
This flow is restricted by the valve.
3. When the pressure of the air near valve is made more
than outside by partly closing the valve, a reserved axial
flow through the core of the hot side starts from high-
pressure region to low-pressure region.
4. Inside the hot tube, both inner stream of air and outer
stream of air rotates with same angular velocity.
5. However, because of the principle of the conservation of
angular momentum, the rotation of speed of the smaller
vortex be expected to increase.
6. But in the vortex tube the speed of the inner vortex remains
same. Angular momentum has been lost from the inner vortex.
7. The energy that is lost from the inner vortex shows up as heat
in the outer vortex. During this process, heat transfer takes place
between reversed stream and forward stream.
8. Therefore, air stream through the core gets cooled below the
inlet temperature of the air in the vortex tube, while air stream in
the forward direction gets heated up.
9. The cold stream is escaped through the diaphragm hole into
the cold side, while hot stream is passed through the opening of
10. By controlling the opening of the valve, the quantity of the
cold air and its temperature can be varied.
We have fabricated the uniform/ parallel vortex
flow tube. In ordered to Vortex flow tube we
used PVC pipes of the dimension given bellow.
In order to form the vortex, we need to pass the air
tangentially in the larger pipe of the assembly. For
this purpose we drilled 5 small holes tangential
holes in the pipe. So air will first enter the free
space in the coupling and then will pass through
five holes in the pipe. To ensure air to flow in the
larger pipe we reduced the internal diameter of the
smaller pipe. These two pipes are coupled using
coupler. Hole is also drilled in the coupler for the
provision of nozzle. Compressed air is entered in
the nozzle through this hole.
Figure 3: Nozzle for compressed air
Figure 4: Reduced internal diameter of
Temperature difference between air coming from two ends was
very small in the first set up. So we tried another approached.
Instead of drilling 5 holes we drilled only one tangential hole and
directly connected it to the nozzle.
Figure 5: complete set up of vortex flow tube
In order to block air at the other end of the large pipe (Hot end), we
made a provision to have a movable valve. This helps in varying the
area of outlet section of the tube.
Figure 6: Movable Valve
After injecting the air at the pressure of 6
bar, we found out the difference in the
temperature of the air at both the ends
This temperature difference is not noticeable
or not as expected from the vortex flow tube.
As vortex flow tubes generally give the
difference around 70-80 0 C.
One reason for the failure of our set up is the
air leakage. Some amount of air was leaking
from the coupling of the pipes.
In order to form the vortex, air must enter
the pipe tangentially. Our set up might not
able to flow air tangentially in the pipe.
It uses air as refrigerant, so there is no leakage
There are no moving parts in the vortex tube
Vortex tube is simple in design and it avoids control
It is light in weight and requires less space.
Initial cost is low and its working expenses are also
less, where compresses air is readily available.
Maintenance is simple and no skilled labours are
Very simple design can easily be made at home.
Can cool the fluid up to 40 0C.
Its low COP
Small portion of the compressed air
appearing as the cold air limits its wide use in
Vortex tubes are extremely small and as it
produce hot as well as cold air. It may be
used in industries where both are
Low temperatures can be obtained without
any difficulty, so it is very much useful in
industries for spot cooling of electronic
It is commonly used for body cooling of the
workers in mines.