Overall Heat Transfer Coefficient (1/U=ΣR)

Overall Heat Transfer Coefficient (1/U=ΣR) | Online Free Tool | Elysia Tools

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

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.

Resistances: 0.02, 0.5, 0.01 K/W; Area: 1 m²; Temperature difference: omitted; Decimal places: 4

Outcome

R_total = 0.53 K/W, G = 1.8868 W/K, and U = 1.8868 W/(m²·K). Heat flow is not calculated because ΔT was not provided.

2. Heat flow through a resistance stack

Heat transfer analyst

Background

A three-layer system has a known temperature difference of 50 K across an area of 2 m².

Problem

Calculate the U-value and heat flow rate through the series resistances.

How to use

Enter 0.01, 0.1, and 0.01 on separate lines, set the area to 2 m², and enter ΔT as 50 K.

FAQ

What inputs does the calculator require?

Enter at least one positive thermal resistance in K/W, with one value per line.

What does the area input affect?

Area is used to calculate the area-based coefficient U = 1/(R_total·A).

Can I calculate heat flow rate?

Yes. Enter ΔT to calculate Q = ΔT/R_total in watts.

Can temperature difference be entered in Celsius or Fahrenheit?

Yes. A Celsius difference equals the same kelvin difference, while a Fahrenheit difference is multiplied by 5/9.

Can ΔT be negative?

Yes. A negative ΔT indicates heat flow in the reverse direction.

Resistances: 0.01, 0.1, 0.01 K/W; Area: 2 m²; ΔT: 50 K; Decimal places: 4

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Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Overview

When to use

How it works

Use cases

Examples

1. Three-layer flat wall U-value

2. Heat flow through a resistance stack

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