Overall Heat Transfer Coefficient
Overall Heat Transfer Coefficient Formulas |
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\( 1 \;/\; U \; A = (1 \;/\; h_1 \; A_1) + ( l_1 \;/\; k \; A) + (1 \;/\; h_2 \; A_2) \) \( U = 1 \;/\; (1 \;/\; h_1) + ( l_1 \;/\; k_1) + (1 \;/\; h_2 ) \) (heat transfer through the plane wall and disregarding radiation) \( U = 1 \;/\; (1 \;/\; h_1) + ( l_1 \;/\; k_1) + ( l_2 \;/\; k_2) + (1 \;/\; h_2) \) (heat transfer through the plane composite wall, no thermal contact resistance and disregarding radiation) |
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| 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.
Tags: Heat Transfer Coefficient Heat