Compute the overall heat transfer coefficient for series thermal resistances (flat-wall model): total resistance R_total = Σ R_i (K/W), thermal conductance G = 1/R_total (W/K), area-based coefficient U = 1/(R_total·A) (W/(m²·K)), and if a temperature difference is given the heat flow rate Q = ΔT/R_total (W). Each R_i is a layer resistance already containing the area factor (e.g. convection R_conv=1/(h·A), conduction R_cond=d/(k·A), fouling R_foul=R_f''/A). Enter one resistance (K/W) per line, at least one, all positive. ΔT may be negative (reverse heat flow); a °C difference equals a K difference, a °F difference is converted by ×5/9.
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Key facts
Category
Math & Numbers
Input types
textarea, number, select
Output type
json
Sample coverage
4
API ready
Yes
Overview
Calculate the overall heat transfer coefficient for thermal resistances in series. Enter one positive resistance per line to find total resistance, thermal conductance, and area-based U-value; optionally add a temperature difference to calculate heat flow rate.
When to use
Estimate heat transfer through a flat wall made of multiple resistance layers.
Calculate U-values for composite walls, insulation, heat exchangers, or fouled surfaces.
Find heat flow from a known temperature difference across a series resistance stack.
How it works
1Enter one or more positive thermal resistances in K/W, with each value already containing its area factor.
2Enter the heat transfer area in m²; the default area is 1 m².
3Optionally enter ΔT and select K, °C, or °F. Fahrenheit differences are converted to kelvins.
4The tool sums the resistances and returns R_total, G = 1/R_total, U = 1/(R_total·A), and, when ΔT is provided, Q = ΔT/R_total.
Use cases
Analyze convection, conduction, and fouling resistances across a composite wall.
Compare insulation or wall designs using total resistance and U-value.
Estimate heat exchanger or wall heat flow when the temperature difference is known.
Examples
1. Three-layer flat wall U-value
Thermal engineer
Background
A flat wall has two convection resistances and one conduction resistance connected in series.
Problem
Find the total resistance, thermal conductance, and overall heat transfer coefficient for the wall.
How to use
Enter 0.02, 0.5, and 0.01 on separate lines, then set the area to 1 m².