Real Life Heat Transfer Problems : Conjugate Heat Transfer

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Real Life Heat Transfer Problems Conjugate Heat
Transfer

• P M V Subbarao
• Professor
• Mechanical Engineering Department
• IIT Delhi

Togetherness is More Powerful .
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Solar Power Towers
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Air Craft Window
Tamb,o -400C
Tamb,i 22 0C
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Surface Temperature Distributions
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Conjugate Heat Transfer Model
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Optimal Insulation for Steam Piping
Tsteam
Tpipe,in
Steam
Ambient Air
Tpipe,out
Design Confusion
Tinsulation,in
Tinsulation,out
Tair
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Cooling of Large Electric Motors
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Structure of Stator and Rotor Cores
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Structure of Core Conductor
Conductor coil bundle
Laminated core
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Air flow Convection Heat Transfer in Axial
Radial Ducts
Air gap
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Air flow network
Model of the air flow in the radial air-cooled
induction motor.
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Simplified Air flow Network
Fluid flow network diagram (simplified).
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Air flow in radial ducts and heat flow to air.
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HEAT TRANSFE IN TURNING

• In recent years there has been a growing interest
  in modelling of metal cutting process.
• It has been accompanied also by the interest in
  modelling of thermal behaviour of the workpiece.
• Thermal expansion affects the machining accuracy,
  hence the latter interest can be attributed to
  the demand for higher accuracy and to the effort
  to improve the ability of its prediction.

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Heat Transfer in Turning
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Location of Thermocouples
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Temperature Distribution
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Electrical Circuit Theory of Heat Transfer

• DefineThermal Resistance
• A resistance can be defined as the ratio of a
  driving potential to a corresponding transfer
  rate.

Analogy Electrical resistance is to conduction
of electricity as thermal resistance is to
conduction of heat. The analog of Q is current,
and the analog of the temperature difference, T1
- T2, is voltage difference. From this
perspective the slab is a pure resistance to heat
transfer and we can define
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Thermal Resistance for Radiation
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The composite Wall

• The concept of a thermal resistance circuit
  allows ready analysis of problems such as a
  composite slab (composite planar heat transfer
  surface).
• In the composite slab, the heat flux is constant
  with x.
• The resistances are in series and sum to Rth
  Rth1 Rth2.
• If TL is the temperature at the left, and TR is
  the temperature at the right, the heat transfer
  rate is given by

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Wall Surfaces with Convection