cold storage engineering

1. FPE 613 Cold Storage Engineering
Thermo electric refrigeration system
Vortex tube
Cooling by adiabatic demagnetization
Presented by
Princess Monica PS
2019671804
PhD-FPE (1st year)
Course Teacher
Dr.N.Venkatachalapathy
Professor And Head
Food Process Engineering
IIFPT
Thanjavur

2. Contents :
 Thermo electric refrigeration system
 Vortex tube
 Cooling by adiabatic demagnetization

3. Introduction
 A thermoelectric refrigerator in the same way is a refrigerator that uses the
Peltier effect to create a heat flux between the junction of two different types of
materials.
 The Peltier effect is a temperature difference created by applying a voltage
between two electrodes connected to a sample of semiconductor material.
This phenomenon can be useful when it is necessary to transfer heat from one
medium to another on a small scale.

5.  copper connection paths to the power supply.
 the heat will be moved (or 'pumped') in the direction of
charge carrier flow throughout the circuit. actually, it is the
charge carriers that transfer the heat.

6.  Thermoelectric cooling devices causes the junction to either cool
down(absorbing heat) or warm up (rejecting heat), depending on
the direction of the current.
 The thermo-element materials are doped semiconductors, one n-
type with a majority of negative charge carriers (electrons) and the
other p-type with a majority of positive charge carriers (holes).
 Behind the thermoelectric module an Heat Sink is fitted which
enables the conduction heat transfer from the hot side of module.

7.  At the cold junction side of the thermoelectric module,
convective heat transfer takes place from air.
 The whole thermoelectric module is fitted in a insulated
chamber
 The whole assembly is connected to DC Power Supply.

8. WORKING PRINCIPLE
 two ceramic substance that serve as a foundation and electrical
insulation for P-type and N-type Bismuth Telluride
 The ceramics also serve as insulation between the modules
internal electrical elements and a heat sink
 Electrically conductive materials, usually copper pads attached
to the ceramics, maintain the electrical connections inside the
module
 The heat pumping action is actual function of the quantity of
electrons crossing over the p-n junction.

9. Method of Heat Transport:
 Electrons can travel freely in the copper conductors but not so freely in the
semiconductor.
 As the electrons leave the copper and enter the hot-side of the p-type, they drop down
to a lower energy level and release heat in the process.
 Then, as the electrons move from the p-type into the copper conductor on the cold side,
the electrons are bumped back to a higher energy level and absorb heat in the process.
 Next, the electrons move freely through the copper until they reach the cold side of the
n-type semiconductor.
 Finally, when the electrons leave the hot-side of the n-type, they can move freely in the
copper. They drop down to a lower energy level and release heat in the process.

10.  Between the heat generating device and the conductor must be an
electrical insulator to prevent an electrical short circuit between the
module and the heat source.
 The electrical insulator must also have a high thermal conductivity so
that the temperature gradient between the source and the conductor
is small.
 Ceramics like alumina are generally used.

11. Disadvantages
 the limit to their cooling capacity and coefficient of
performance which may be restrictive in the future when heat
transfer demands become much larger.
 A DC power supply is needed for the TE cooler.

12. ADVANTAGES
 Effective in spot cooling.
 Environmentally friendly.
 Generate no electrical noise.
 Small size and light weight.
 Compact and reliable.
 No moving parts and fluids.
 Durable and maintenance-free.
 Very long operation life.

13. APPLICATIONS
 Include equipment used by military, medical, industrial,
consumer, scientific/laboratory, and telecommunications
organizations
 Uses range from simple food and beverage coolers for an
afternoon picnic to extremely sophisticated temperature
control systems in missiles and space vehicles.

14. Vortex Tube Refrigeration

15. Vortex Tube Refrigeration
 It is one of the non-conventional type refrigerating systems.
 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.
 simple device with no moving parts

16.  It consists of
1. nozzle,
2. diaphragm,
3. valve,
4. hot-air side,
5. cold-air side.

17.  Chamber is a portion of nozzle that facilities the tangential entry of high
velocity air-stream into hot side.
 Hot side is cylindrical in cross section and is of different lengths as per
design.
 Valve obstructs the flow of air through hot side and it also controls the
quantity of hot air through vortex tube.
 Diaphragm is a cylindrical piece of small thickness and having a small hole
of specific diameter at the center.
 Air stream traveling through the core of the hot side is emitted through the
diaphragm hole.
 Cold side is a cylindrical portion through which cold air is passed.

18. Working:
 Compressed air is passed through the nozzle. Here, air expands
and acquires high velocity due to particular shape of the nozzle.
 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.
 partly closing the valve, a reversed axial flow through the core of
the hot side starts.
 By controlling the opening of the valve, the quantity of the cold
air and its temperature can be varied.

20. Advantages:
 It uses air as refrigerant, so there is no leakage problem.
 Vortex tube is simple in design and it avoids control systems.
 There are no moving parts in vortex tube.
 It is light in weight and requires less space.
 Initial cost is low and its working expenses are also less, where
compressed air is readily available.
 Maintenance is simple and no skilled labors are required.
Disadvantages:
 Its low COP, limited capacity and only small portion of the compressed
air appearing as the cold air limits its wide use in practice.

21. Applications:
 Vortex tubes are extremely small and as it produce hot as well as
cold air. It may be of use in industries where both are
simultaneously required.
 Temperature as low as –50°C can be obtained without any
difficulty, so it is very much useful in industries for spot cooling of
electronic components.
 It is commonly used for body cooling of the workers in mines.

22. Cooling by adiabatic demagnetization

23.  Magnetic refrigeration is based on the magnetocaloric effect,
discovered by E. Warburg in 1881.
 in which a temperature change of a suitable material is caused
by exposing the material to a changing magnetic field.
 Similar to mechanical compression and expansion of gases,
there are some materials that raise their temperatures when
adiabatically magnetised, and drop their temperature when
adiabatically demagnetised.

24.  Temperature very near the absolute zero may be obtained by
adiabatic demagnetization of certain paramagnetic salts.
Each atom of the paramagnetic salt may be considered to be
a tiny magnet.
 If the salt is not magnetized then all its atoms or the magnets
are randomly oriented.

26.  If it is exposed to a strong magnetic field, the atoms will align themselves
to the direction of magnetic field.
 the heat will be absorbed by Helium.
 Now if the magnetic field is suddenly removed, the atoms will come back
to the original random orientation.
 If there is no heat transfer from surroundings, the internal energy of the
salt will decrease as it does work. Consequently the salt will be cooled.

27.  The substance is returned to adiabatic (insulated) condition
so the total entropy remains constant
 the magnetic field is decreased, the thermal energy causes
the magnetic moments to overcome the field, and thus the
sample cools, i.e., an adiabatic temperature change.
 Energy (and entropy) transfers from thermal entropy to
magnetic entropy, measuring the disorder of the magnetic
dipoles.

28.  Paramagnetic salts like gadolinium sulphate are used.
 This gives lower temperatures for a brief instant of time.

29. Advantages
 No compressor and refrigerant gas
 Low running cost
 Less environment impact
Disadvantages
 Initial investment is high
 Protection of electronic components from magnetic fields

30. Applications
 Cryogenic engine
 Magnetic domestic refrigerator , magnetic air conditioning in
building and houses
 Refrigeration in medicine
 Bevarage coolers
 Ice cream cabinets

31. References
 Diana Enescu.2018.Thermoelectric Refrigeration Principles
 Prashant Gour .2012. Experimental Encountering of Major Problems
Associated with Thermoelectric Refrigeration
 Rajendra. P. Patil .2017. Thermoelectric Refrigeration Using Peltier Effect
 Tejshree Bornare Vortex tube refrigeration system Based on Compressed air.
 Chapter 15 Adiabatic Demagnetization
 Lesson 8 Methods of producing Low Temperatures 1 Version 1 ME, IIT
Kharagpur

32. Thank you