Microwave Cooking Modeling

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Microwave Cooking Modeling
Heat and moisture transport Andriy
Rychahivskyy
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Outline

• What is a microwave?
• Nature of microwave heating
• Goals of the project
• Model description
• Results
• Conclusions and recommendations

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Scheme of a microwave oven
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What is a microwave?
?
H
?
?
- electric field
H
- magnetic field
?
- wavelength (12.2 cm for 2.45 GHz)
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Microwave cooking principle

• Microwaves act on
• 1) salt ions to accelerate them
• 2) water molecules to rapidly
• change their polar direction

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Microwave cooking principle

• Microwaves act on
• 1) salt ions to accelerate them
• 2) water molecules to rapidly
• change their polar direction
• Foods water content heats the food due to
  molecular friction

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Goal of the project

• Design a model of microwave cooking
• predicting temperature and moisture
• distribution within the food product

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Phenomena to model

• Electromagnetic wave distribution
• Heat transport within the product
• Mass (water and vapor) transport

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Governing equations and laws

• Maxwells equations
• Energy balance equation
• Water and vapor balance equations
• Ideal gas law
• Darcys law for a flow in a porous medium

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Porous medium
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Porous medium
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Geometrical model
top
C MW cavity M food product G waveguide
bottom
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Heat source

• electromagnetic properties e, s (control how a
  material heats up)
• e e i e
• radial frequency ? 2p2.45 GHz

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Heat source
Electric field intensity
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Heat source
Electric field intensity
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Heat source
Electric field intensity Heat source
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Convection-diffusion equation
heat capacity (how much heat the
food holds) thermal conductivity (how fast
heat moves) latent heat (absorbed due to
evaporation) interface mass transfer rate
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Boundary and initial conditions
thermal conductivity (how fast heat moves)
heat transfer coef. (thermal
resistance) latent heat (absorbed due to
evaporation)
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One-dimensional model
with
at
at
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Numerical results /without mass transport/

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Numerical results /without mass transport/

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Numerical results /general 1D model/

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Interpretation of results
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Conclusions

• Electromagnetic source is constant
• Heating-up of the product until 100oC develops
  linear in time
• T at the boundary gtgt T in the kernel
• Moisture loss occurs only in a boundary layer

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Recommendations

• Validate the results
• Extend our implementation
• Perform a parameter study