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HEAT
TRANSFER
SKMM 3443
HEAT TRANSFERHEAT TRANSFER
CCHH
AA
PP
TT
EE
RR
44DrDr Mazlan 2016Mazlan 2016
LECTURER: ASSOC PROF. DR. MAZLAN ABDUL WAHIDhttp://www.fkm.utm.my/~mazlan
TEXT: Heat and Mass TransferFundamental and Applications, 5th Edition by Cengel & GhajarMc Graw Hill
HEAT
TRANSFER
ASSOC. PROF. DR. MAZLAN ABDUL WAHID
Transient Heat Conduction
CCHH
AA
PP
TT
EE
RR
44DrDr Mazlan 2016Mazlan 2016
2
2
ASSOC. PROF. DR. MAZLAN ABDUL WAHIDC24-333
Towards an Entrepreneurial University
Recap
• Generalized Heat Conduction Equation
• Steady-one dimensional
• Including heat generation• Including heat generation
Transient Heat Conduction
Lumped capacitance
methodSpatial effects
method
Lumped capacitance Spatial effects
Lumped Capacitance Method
“Analysis tool for solids with negligible
temperature gradients”
Lumped capacitance Spatial effects
Lump?
Synonym of lump: combine, put, group, bunch,
aggregate, unite, pool, mix, blend, merge, mass,
join, fuse, conglomerate, coalesce, consolidate,
collect, throw, collect, throw,
Lumped capacitance Spatial effects
Capacitance analogy
Capacitors store
electric charge
Solids store
heat
Lumped capacitance Spatial effects
Energy balance
Lumped capacitance Spatial effects
Energy balance
Lumped capacitance Spatial effects
Thermal time constant
Lumped capacitance Spatial effects
Thermal time constant
Lumped capacitance Spatial effects
Thermal time constant
Lumped capacitance Spatial effects
Heat transfer rate
Lumped capacitance Spatial effects
Validity of Lumped Capacitance
Method
Relate the temperature change in the solid to
the temperature change between surface and
fluid
Lumped capacitance Spatial effects
Biot Number
Lumped capacitance Spatial effects
Non-Conservative Characteristic
Length
Lumped capacitance Spatial effects
Conservative Characteristic Length
Lumped capacitance Spatial effects
Biot Number
Lumped capacitance Spatial effects
Biot Number
Lumped capacitance Spatial effects
Biot Number
Lumped capacitance Spatial effects
Biot number
Which one can we apply LCM ?
Lumped capacitance Spatial effects
Biot number
Which one can we apply LCM ?
Lumped capacitance Spatial effects
Example (Problem 4-21)
Lumped capacitance Spatial effects
Spatial Effects: One dimensional
Large plane
wallLong cylinder Sphere
Lumped capacitance Spatial effects
Fourier Number (Revisit)
Lumped capacitance Spatial effects
Transient, one dimensional conduction
Lumped capacitance Spatial effects
Plane wall : Transient, one dimensional
conduction
Lumped capacitance Spatial effects
Plane wall : Transient, one dimensional
conduction
Lumped capacitance Spatial effects
Plane wall : Transient, one dimensional
conduction
Lumped capacitance Spatial effects
Plane wall : Transient, one dimensional
conduction
Lumped capacitance Spatial effects
Plane wall : Transient, one dimensional
conduction
Lumped capacitance Spatial effects
Approximate analytical solution
Lumped capacitance Spatial effects
One term approximation
Lumped capacitance Spatial effects
One term approximation
Lumped capacitance Spatial effects
One term approximation
Lumped capacitance Spatial effects
One term approximation
Lumped capacitance Spatial effects
Lumped capacitance Spatial effects
Lumped capacitance Spatial effects
Lumped capacitance Spatial effects
Lumped capacitance Spatial effects
Example (Problem 4-39)
