Summary of Lecture 1 CHEE2695 Heat Transfer

CHEE2695 – Lecture 1


Conduction
- Heat transfer due to a temperature difference between 2 objects in contact.
- Occurs in a single phase.
- Follows Fourier’s Law:
δT
q̇=−kA q̇ (W ) – Heat transfer rate
δn
−1 −1
k (W m K ) – Thermal conductivity
A ( m ) – Area normal to heat transfer
2


T (K ) – Temperature
n( m) – Distance over where heat transfer takes place
δT −1
(K m ) – Partial derivative; temperature distribution. If the following
δn
conditions exist, the following approximation can be used:
o Steady state
o One dimension
o No internal energy sources
δT T 2 −T 1
≈
δn n2 −n1



Convection:
- Heat transfer due to the motion of a fluid.
- Occurs between phases when a solid body is exposed to a moving fluid with a
different temperature
- Can be classified as:
o Forced convection: flow caused by external means.
o Natural convection: flow caused by buoyancy forces related to density
differences in fluids.
- Follows Newton’s Law of Cooling:
q̇=hA (T s−T ∞ )q̇ (W ) – Heat transfer rate
h(W m−2 K −1 ) – Heat transfer coefficient
A ( m ) – Area of fluid contact
2


T s ( K ) – Surface temperature
T ∞ (K ) – Bulk fluid temperature



Radiation: