Overall Heat Transfer Coefficient⚠ unverified
Physics / Heat Transfer · Compute the overall heat transfer coefficient from total thermal resistance
Parameters
| Input | Symbol | Unit | Default | Description |
|---|---|---|---|---|
| R_total | Rtotal | K/W | 1.0 | Total thermal resistance |
| Output | Symbol | Unit | Description |
|---|---|---|---|
| result | U | W/K | Overall heat transfer coefficient, in watts per kelvin (W/K). Returns 0.0 when R_total is not positive |
The science & history
Understanding the Parameters
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$R_{\mathrm{total}}$ — series network: wall, films, fouling, etc. ($R = L/(kA) + 1/(hA) + \cdots$).
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$U$ — for exchangers often quoted per area: $U_{\mathrm{area}} = 1/(R A)$ if $R$ is the total K/W resistance.
Derivation (Approaching a Proof)
$Q = \Delta T / R_{\mathrm{total}}$. Defining $U$ by $Q = U\Delta T$ forces $U = 1/R_{\mathrm{total}}$ for that $\Delta T$ definition (overall or LMTD).
History
Overall $U$ is the single number in $Q = UA\,\mathrm{LMTD}$ heat-exchanger sizing.
Related Concepts: Heat Exchanger Lmtd, Thermal Resistance Conduction, Thermal Resistance Convection, Heat Exchanger Effectiveness
Notes: Registry calculator overall-heat-transfer-coefficient (unverified). Unit is W/K with
$R$ in K/W — not W/(m²·K) unless $R$ is areal.