MicrowaveMicrowave

welcomes welcomes You..You..

Facts and statistics..Facts and statistics..

Agricultural production during 2001-02 was 209MT.Agricultural production during 2001-02 was 209MT.

Agro and food processing sector ranks fifth in India’s GDP.Agro and food processing sector ranks fifth in India’s GDP.

Employs around 18% of country’s industrial force.Employs around 18% of country’s industrial force.

Export growth from 2,821cr (91-92) to 10,770cr (2000-01).Export growth from 2,821cr (91-92) to 10,770cr (2000-01).

Largest live stock population in the world.Largest live stock population in the world.

Second, fifth and sixth largest producer of fruit &vegetables, eggs, & fish Second, fifth and sixth largest producer of fruit &vegetables, eggs, & fish

respectivelyrespectively in the world in the world

[ The Hindu oct-12, 2002 ]

Weakness of Indian food sector..Weakness of Indian food sector..

High wastage levels leading to low processing levels.High wastage levels leading to low processing levels.

High seasonability & perishability – low profit margin.High seasonability & perishability – low profit margin.

Lack of requisite packaging quality and presentability required for Lack of requisite packaging quality and presentability required for

marketing.marketing.

Lack of ready acceptance in international marketing.Lack of ready acceptance in international marketing.

Higher cost of processingHigher cost of processing

[ The Hindu oct-12,2002 ]

Microwave (MW) Processing..Microwave (MW) Processing..

MW heating refers to use of non-ionizing electromagnetic MW heating refers to use of non-ionizing electromagnetic

waves of certain frequencies to generate heat in material.waves of certain frequencies to generate heat in material.

Microwave processing results in excellent retention of nutritional and Microwave processing results in excellent retention of nutritional and

sensory value besides having other advantages like saving in energy, sensory value besides having other advantages like saving in energy,

cost, time, etc cost, time, etc

The speed with which heating takes place in the microwave oven The speed with which heating takes place in the microwave oven contributes to most to its rapid growthcontributes to most to its rapid growth

UNIQUENESS OF MICROWAVE HEATING TECHNOLOGY

Speed: Processes taking hours by conventional means are

possible in few minutes by mw processing.

Uniform volumetric heating: Heat is generated uniformly throughout

the entire substance

Self regulating and differential heating

Efficiency: Efficiency higher than 70%

Instantaneous control

Lower cost: Reduction in processing time thus saving energy and labour

Compatibility with conventional heating: ( 100-300 % efficient )

Electromagnetic spectrum and Electromagnetic spectrum and their applicationstheir applications

915 MHz ± 13 MHz2450 MHz ± 50 MHz5800 MHz ± 75 MHz24125 MHz ± 125 MHz

Available MW - FrequenciesAvailable MW - Frequencies

1m – 1mm

Corresponding wavelengthCorresponding wavelength

Frequency rangeFrequency range

300MHz – 300GHz

Heating mechanism..Heating mechanism.. Accomplished byAccomplished by

Absorption of mw energy by water molecules (Absorption of mw energy by water molecules (Dipolar rotationDipolar rotation)) (Tries to align with changing polarity- 2.45 b times / sec ,generates heat)(Tries to align with changing polarity- 2.45 b times / sec ,generates heat)

Translation ofTranslation of ionicionic components of foods (components of foods (Ionic conductionIonic conduction) )

Effect of electromagnetic radiation on dipoles

Critical Process Factors in Microwave HeatingCritical Process Factors in Microwave Heating

FoodShape, size, composition (moisture, salt), liquid against solidmultiple components (as in a frozen dinner),

Package Presence of metallic elements such as aluminum foil, susceptor

ProcessPower level, cycling, presence of hot water or air around the food, equilibration time

EquipmentDimensions, shape and other electromagnetic characteristics of the oven, frequency, agitation of the food, presence of mode stirrers and turntables

Conventional Vs microwave heatingConventional Vs microwave heating....

Surface heatingSurface heating

Slow processSlow process

Low thermal efficiency Low thermal efficiency

electric oven - 14%electric oven - 14% gas oven - 7%gas oven - 7%

Non-uniformity heatingNon-uniformity heating

Moisture removal (80-90%)Moisture removal (80-90%)

Low product quality (over heating,Low product quality (over heating, case hardening)case hardening)

Volumetric heatingVolumetric heating

Rapid heatingRapid heating

High thermal EfficiencyHigh thermal Efficiency

mw oven-40%mw oven-40%

Uniform HeatingUniform Heating

Moisture removal (<20%) Moisture removal (<20%)

Better quality productBetter quality product

Interaction of electromagnetic fields with materials

Absorption

Transmission

Reflection

Food, oil, water, wood

Applicators

waveguides

Belts, trays,dishes

Dielectric properties of foodsDielectric properties of foods..?..?

Intrinsic electrical properties that affect behavior of foods with EM fieldsIntrinsic electrical properties that affect behavior of foods with EM fields

ε’ - The relative dielectric constant (ability of material to store energy) ε’ - The relative dielectric constant (ability of material to store energy)

ε” - The dielectric loss factor (ability of material to convert EMW to heat)ε” - The dielectric loss factor (ability of material to convert EMW to heat)

Tan δ - The dissipation factor or loss tangent (ε’/ ε”)Tan δ - The dissipation factor or loss tangent (ε’/ ε”)

Measurement of dielectric properties Measurement of dielectric properties

Optimization and process controlOptimization and process control

Indirect determination of a multitude of material properties. Indirect determination of a multitude of material properties.

The rate of heat generation per unit volume ( wm-3 )

Where, E = Strength of electric field of the wave at that location (volts / unit distance) F = is the frequency ε0 =The permittivity of free space (a physical constant) ε” = the dielectric loss factor .

The rate of temperature increase

kƒE2 ε” ε’ δ Cp

Where, k = constant to define the units of temperature and time ƒ = frequency of the microwaves E = strength of the electric field inside the food δ = density of the food Cp = specific heat of the food

Q=2Π f ε0 ε” E2

!

Dielectric properties and penetration depth (cm) of various Dielectric properties and penetration depth (cm) of various foods @ 2,450 MHzfoods @ 2,450 MHz

Material ε' ε” Tanδ Dp

Water (distilled, 25°C) 78.0 12.0 0.15 1.4

Ice (-12°C) 3.2 0.003 0.001 1160.0

Beef (cooked, 30°C) 30.5 9.6 0.31 1.1

Potato (raw, 25°C) 57.3 15.7 0.27 0.9

Potato (mashed, 30°C) 72.5 24.0 0.33 0.7

Wheat (20°C, 5% moisture) 3.3 0.50 0.15 7.1

Corn Oil (25°C) 2.5 0.14 0.06 21.9

Cottonseed Oil (20°C) 2.6 0.18 0.07 17.5

Butter (salted, 20°C) 4.6 0.60 0.13 6.9

Butter (unsalted, 20°C) 2.9 0.45 0.16 7.4

Bread Dough 22.0 9.00 0.41 1.0

Bread 4.6 1.20 0.26 3.5

Microwave ovenMicrowave oven

External view & Internal parts of the domestic microwave system

600-1400w 2450mhz

• Magnetron converts 50-60 Hz AC to higher frequency EMW• Applicators waveguides, coaxial tube

Sectional view of a typical magnetron..Sectional view of a typical magnetron..

Antenna

Electrons form a rotating patterns

Equivalent circuit of one resonant cavity

[ http:www.dtx.net 1999]Internal parts of magnetron

Microwave industrial conveyor systemMicrowave industrial conveyor system

High energy power source with long life.

The system has internal protection features

Forced-air system accelerates the removal of moisture quickly and efficiently.

A straight-through conveyor assures uniform exposure to the microwaves.

Because of its high processing capacity, unit costs are much lower than with the batch process

Microwave conveyor system..Microwave conveyor system..

FDU-543VD54kW 2450MHz6kW x 9 units

Dimensions (approx): 5.5 x 0.41x 1.52 (meters)

Material of Construction: SS - 300 grade

Conveyor Belt:Width (0.30m) link polypropylene belt

Conveyor Opening: H x w (0.03 to 0.08 x 0.32 m)

Elevation of Belt: 1.02 m

Belt Speed: 0 to 50 ft./min

Shipping Weight: 1180 Kg.

Conveyor Drive:0.75 HP motor driven sprocket and chain

Controller Panel:

Solid state controls digital read out, convent belt speed forward and reverse stop start, inverter voltage supply to drive motor

Electrical Requirements:230V single/ three phase 50- 60 Hz Ac

Microwave Heating Power: 12 kW at 2450 MHz

Safety Interlocks:Heating chamber, and Panel

interlocks

Removable end Panels:Entry and exit tunnels and side covers removable for cleaning

Capacity- 0.5kg/min

[www.microwavereasearch.com]

A REPRESENTATIVE MICROWAVE APPLICATIONS SCENARIOA REPRESENTATIVE MICROWAVE APPLICATIONS SCENARIO

MICROWAVE (MW)

INFORMATION

POWER

COMMUNICATION

MICROWAVE HEATNG MICROWAVE PROCESSING

NON- THERMALTHERMAL

MOISTURE MEASUREMENTSEED treatmentInsect control

INDUSTRIALDOMESTIC OVEN

FOOD PROCESSING

pasteurizationSTERILIZATION

TEMPERINGDRYINGBAKING

cookingblanching

MICROWAVEHEATING

MICROWAVEPROCESSING

Microwave food processing applications..Microwave food processing applications..

PROCESS PRODUCTS

Tempering Meat, fish, poultry

Cooking Bacon, meat patties, sausage, potatoes

Drying Pasta, onions, egg yolk, snack foods

Vacuum drying Orange juice, grains, seeds

Freeze drying Meat, vegetables, fruits

Pasteurization Bread, yoghurt

Sterilization Pouch packed foods

Baking Bread , donuts

Roasting Nuts, grains

Blanching Vegetables, potatoes, corn, fruits

Rendering Lard, tallow

Drying chamber

GENERATOR

Schematic of the combined microwave conventional drying system

Mixing Fan

3-way circulator

Tuning screws

Air Outlet

Air

Power metersElectrical Heaters

Blower

Economics of microwave drying system..

mw system varies between 3-4 lakhs / kW for a basic drying system

1 kW of mw energy removes 1.5 kg of water/h

mw system has coupling efficiency of 75%

conversion efficiency of electricity to mw energy is 45-50 %

losses

conversion from AC to DC 4%

DC to mw 40%

waveguide and applicator 10%

Energy Cost/hour = (utility rate/kwh) (kw of system) (efficiency)

Limitations of microwave heating..

High capital investment:

Initial cost of equipment is very high but has lower operating cost,

and increased output.

More complex technology devices:

Requires skilled personnel for repair and operation.

Mw radiation problem:

By proper shielding the radiation can be brought down to safer limit.