Skip to main content

Overall Heat Transfer Coefficient

Overall Heat Transfer Coefficient Formulas
$\dfrac{ 1 }{ U \cdot A } \;=\; \dfrac{1 }{ h_1 \cdot A_1} + \dfrac{ l_1 }{ k \cdot A} + \dfrac{1 }{ h_2 \cdot A_2}$ $U \;=\; \dfrac{1 }{ \dfrac{1 }{ h_1} } + \dfrac{ l_1 }{ k_1} + \dfrac{1 }{ h_2 }$ (heat transfer through the plane wall and disregarding radiation) $U \;=\; \dfrac{1 }{ \dfrac{1 }{ h_1} } + \dfrac{ l_1 }{ k_1} + \dfrac{ l_2 }{ k_2} + \dfrac{1 }{ h_2}$ (heat transfer through the plane composite wall, no thermal contact resistance and disregarding radiation)
Symbol	English	Metric
$U$ = overall heat transfer coefficient	$Btu \;/\; hr-ft^2-F$	$W \;/\; m^2-K$
$A$ = contact area for each fluid side	$ft^2$	$m^2$
$A_1$ = contact area for one of the fluids	$ft^2$	$m^2$
$A_2$ = contact area for the other fluid	$ft^2$	$m^2$
$h_1$ = individual heat transfer convection coefficient for one of the fluids	$Btu \;/\; hr$	$W$
$h_2$ = individual heat transfer convection coefficient for the other fluid	$Btu \;/\; hr$	$W$
$k$ = thermal conductivity of the material	$Btu-ft \;/\; hr-ft^2-F$	$W \;/\; m-K$
$l_1$ = wall thickness	$in$	$mm$
$l_2$ = wall thickness	$in$	$mm$

Overall heat transfer coefficient, abbreviated as U, is the heat transfer between items like walls in buildings or across heat exchangers for the conduction within materials.

Similar Articles

Latest Articles