Answer and Explanation:
In thermodynamics, the overall heat transfer coefficient also referred as film effectiveness is a constant of proportionality between force drive for the heat flow and the heat flux.
It gives the measure of the heat transfer as a result of  convection or conduction. The coefficient of overall heat transfer depends on surface area, resistance of the material, temperature difference, thickness, etc.
It is given by:
Q = UA[tex]\Delta T[/tex]
where
U = overall heat transfer coefficient
Its SI units is [tex]W/m^{2}K[/tex].
