Convection

For a Heated Flat Plate (Context)

The direction of diffusion (conduction) of thermal energy is perpendicular to the plate which is also the direction of momentum diffusion.

If there is a free-stream velocity across the plate, there is a no slip condition enforced at the contact of a fluid at the plate.

Momentum Diffusion
${\mathrm{Re}}_e=\frac{\rho Vx}{\mu }$
Where:

• Re: Reynolds number
• Rho: Density
• V: Velocity
• Mu: Dynamic viscosity

Thermal Diffusion
Generally, the convective heat transfer coefficient h increases with Re.

Just like the Reynolds number we can define a Grashof number which defines the buoyancy force resisting a friction force.
$Gr=\frac{F_{Buoyancy}}{F_{viscous}}$
Generally, h increases with Gr.

Forced vs Natural Convection

The heat transfer coefficient is higher for forced convection!

Convection

The main equation here is…
$Q_{conv}^{\prime }=\overline{h}A\left(T_s-T_{\infty }\right)$