microwave heating

1. MICROWAVE HEATING
REPRESENT BY : RANA MEHUL
REGD NO : 14MMET24
Under the guidance of prof T.N.RAVAL SIR

2. MICROWAVE HEATING
 INTODUCTION
 PROPERTIES
 ADVANTAGES
 APPLICATIONS
 LIMITATIONS

3. MICROWAVE ELECTRO MAGNETIC SPECTRUM

4. INTODUCTION
 Microwaves are electromagnetic waves whose frequencies
ranges from about 300 MHz – 300 GHz (1 MHz = 10 6 Hz
and 1 GHz = 10 9 Hz) or wavelengths in air ranging from
100 cm – 1 mm.
 The word Microwave means very short wave, which is the
shortest wavelength region of the radio spectrum and a part
of the electromagnetic spectrum.

5. PROPERTIES
 Microwave is an electromagnetic radiation of short
wavelength.
 They can reflect by conducting surfaces just like optical
waves since they travel in straight line.
 Microwave currents flow through a thin outer layer of an
ordinary cable.
 Microwaves are easily attenuated within short distances.
 They are not reflected by ionosphere .

6. ADVANTAGES
1. INCREASE BANDWIDTH AVAILABILITY
 Microwaves have large bandwidths compared to the common bands
like short waves (SW), ultrahigh frequency (UHF) waves, etc.
 For example, the microwaves extending from = 1 cm - = 10 cm
(i.e) from 30,000 MHz – 3000 MHz, this region has a bandwidth of
27,000 MHz.
2. IMPROVED DIRECTIVE PROPERTIES
 The second advantage of microwaves is their ability to use high gain
directive antennas, any Electro magnetic wave can be focused in a
specified direction (Just as the focusing of light rays with lenses or
reflectors)

7. ADVANTAGES
3. Fading effect and reliability:
 Fading effect due to the variation in the transmission medium is more
effective at low frequency.
 Due to the Line of Sight (LOS) propagation and high frequencies, there
is less fading effect and hence microwave communication is more
reliable.
4. Power requirements:
 Transmitter / receiver power requirements are pretty low at
microwave frequencies compared to that at short wave band.

8. ADVANTAGES
5.Transparency property of microwaves:
 Microwave frequency band ranging from 300 MHz – 10 GHz
are capable of freely propagating through the
atmosphere.

9. APPLICATION
 Microwaves have a wide range of applications in modern
technology, which are listed below
1. Telecommunication: Telephone and TV, space
communication (Earth – to – space and space – to –
Earth), telemetry communication link for railways etc.
2. Radars: detect aircraft, track / guide supersonic
missiles, observe and track weather patterns, air traffic
control (ATC), burglar alarms, garage door openers,
police speed detectors etc.

10. APPLICATION
3. Commercial and industrial applications:
 Microwave oven
 Drying machines – textile, food and paper industry for drying
clothes, potato chips, printed matters etc.
 Food process industry – Precooling / cooking, pasteurization /
sterility, hat frozen / refrigerated precooled meats, roasting of
food grains / beans.
 Biomedical Applications ( diagnostic / therapeutic ) – diathermy
for localized superficial heating, deep electromagnetic heating
for treatment of cancer, hyperthermia ( local, regional or whole
body for cancer therapy).

11. MICROWAVE OVEN

12. HOW MICROWAVE USED IN
MICROWAVE OVEN FOR COOKING
 Microwaves cause molecules in food to vibrate. This
creates heat that cooks the food. Heat from the food
warms the container that the food is in.
 Some areas get more microwaves, resulting in uneven
cooking—hence rotating disk helps cook evenly
 Microwaves are attracted to water, fat, and sugar
molecules causing them to vibrate and heat

13. MICROWAVE COOKING
• Waves are emitted from an opening in the metal case.
• Waves are then reflected off the sides and penetrate food in the process.

14. MICROWAVE COOKING
 Food and cookware taken out of a microwave oven is rarely
much hotter than 100 °C (212 °F). Cookware used in a
microwave oven is often much cooler than the food because
the microwaves heat the food directly and the cookware is
heated by the food. Food and cookware from a conventional
oven, on the other hand, are the same temperature as the
rest of the oven; a typical cooking temperature is 180 °C
(360 °F). That means that conventional stoves and ovens
can cause more serious burns.

15. LIMITATION
• Microwaves cannot go through metal, but
they do pass through glass, ceramic, plastic,
or paper.
Hence use glass, ceramic, or plastic dishes
that are safe in the microwave oven.

17. REFRENCES
 METAXAS, A.C. Microwave heating. Power Engineering Journal,
September 1991. pp. 237–247.
 KASHYAP, S.C. and WYSLOUZIL, W. Methods for improving heating
uniformity in microwave ovens. J. Microwave Power and
Electromagnetic Energy,
 Microwave Processing of Materials IV Materials Research Society
Symposium Proceedings Materials Research Society, Pittsburgh, Vol.

18. MICROWAVE HEATING
 So far we have covered following topics in microwave
and microwave heating
1. PROPERTIES
2. ADVANTAGES
3. APPLICATION
4. LIMITATIONS
 Now we will see how microwave is useful for industry
purpose.

19. Application of microwaves in textile
finishing processes
• Microwave device

20. Application of microwaves in textile
finishing processes
 Microwave device
 This system offers passage of textile material in a wide
state through a waveguides. The system consists of 6
centrally sloted rectangular waveguides (dimensions 4 x 8
cm) and 2 magnetrons fed by 500 W. Waveguide is
terminated with water-based dummy load that prevents
leakage of residual microwave energy.

21. Application of microwaves in textile
finishing processes
 With proper design of the waveguides and supporting
equipment, a specific environment (at the particular
wavelength) can be created in order to provide controlled
distribution of the microwave energy, making it possible
to achieve uniform exposure to material passed through a
channel. The leakage of microwave energy is inherently
small due to the fact that waveguide slots are oriented
along the wave guideline of symmetry, and therefore they
cannot act as efficient slot antennas

22. Application of microwaves in textile
finishing processes
 Furthermore, in this way the material lies in the maximum
of the electric field that assures effective coupling to the
flowing microwave energy. In a case that request for slots
symmetry is fulfilled, only the load (textile material)
which passes through the waveguides has an influence on
energy loss. The amount of microwave energy absorbed by
the textile in each waveguide pass depends on the
material thickness and moisture content.

23. Application of microwaves in textile
finishing processes
 Working
 The energy of microwave photons is very low (125 kJ/mol)
relative to the typical energies for chemical bonds (335-84
kJ/mol); thus microwave will not directly affect the
molecular structure. They cannot change the electronic
structure around atoms or among them, but they can
interact with the electronic differences between atoms.

24. Application of microwaves in textile
finishing processes
 Different materials can be divided according to their
response on microwave radiation:
 The materials that reflect Microwave radiation (stayed
cold) .
 The materials that is transparent to Microwave radiation
(non-heated).
 The materials that absorb microwave energy (being
heated).

25. Application of microwaves in textile
finishing processes
 For a microwave electromagnetic field oscillating at 2.5
GHz, which is preferred frequency for heating
applications, the charge changes polarity nearly 5 billion
times per second. Microwave radiation is specially tuned
to the natural frequency of water molecules to maximise
the interactions.

26. Application of microwaves in textile
finishing processes
 The main difference between conventional heating with hot air
and microwave heating is the heating mechanism. While
conventional techniques heat a surface, the microwaves heat
the whole volume of the treated object. During the
conventional heating, the heat is generated outside the treated
product and conveyed by conduction or convection. Hence, the
surface is heated at first and afterwards the heat flows toward
the inside, which always remains colder than the surface. The
required internal temperature can be reached only by sufficient
increase of the surface temperature of the material above the
temperature needed for particular treatment.

27. Application of microwaves in textile
finishing processes
 ADVANTAGE
 Microwave radiation for textile finishing has been used for
the combined desizing, scouring and bleaching processes
,dyeing and drying processes, as well as for eradication of
insects from wool textiles. Additional usage was for
continuous measuring of low humidity. All this
experiments were performed in a resonant cavity

28. Application of microwaves in textile
finishing processes
 REFERENCES
1. Metaxas A.C., R.J. Meredith: Industrial Microwave Heating, Peter
Peregrinus 1983, 111-150
2. Varma R: Solvent- free accelerated organic syntheses using
microwaves, Pure Appl. Chem 73 (2001) 1, 193 – 198
3. Cablewski T. et al: Development and Application of Continuous
Microwave Reactor for Organic Synthesis,.Org.Chem 59 (1994) 3408
3412 Englert R.D., L.P. Berriman: Curing chemically treated cellulosic
fabrics, US Patent 3846845, 1974 1112

29. Application of microwaves in textile
finishing processes
 REFERENCES
4. Bobbin: Microwaves meet wrinkle-free marketplace, October 1995
NatNews
5. anonimno: Microwave Processes for the Combined Desizing, Scouring
and Bleaching of Grey Cotton Fabrics, J.Text.Institute (1996) 3, 602-607

30. Conclusion
 By using microwave we can cook food with uniform
temperature and also it is used for industry purpose like
textile technology for drying, dying , etc.

31. THANK YOU