Convection over plate (top and bottom)

[jofree87]

Homework Statement

Consider a flat plate subject to parrallel flow (top and bottom) characterized by u_∞ = 5 m/s and T_∞ = 20°C.

Determine the average convection heat transfer coefficient and convective heat transfer rate with an L = 2m long and w = 2m wide flat plate for airflow and surface temp T_s = 50°C

Homework Equations

Re_L = V*L/v

h = Nu*k/L

The Attempt at a Solution

My question is what should the L be to calculate the Reynold's number and conventive coefficient. Is it 2m or 4m since fluid flows over the top and bottom?

 

[LawrenceC]

The L is measured from one surface so L is 2 m.