CALCULATORS / HEAT TRANSFER AND TEMPERATURE

Thermal-resistance network calculator

Series thermal resistances at steady heat flow.

thermal-thermal-resistance.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	totalK/W	temperaturedegC
	3.5	60
	3.5	53

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

temperature budget60.00 degC✓ passes

BASELINE INPUTS

heat10 Winterface0.5 K/Wsink3 K/Wambient25 degC

CALCULATED

total3.5 K/W

temperature60 degC

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Thermal-resistance network
# Scope: Series thermal resistances at steady heat flow.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

heat = 10 W
interface = 0.5 K/W
sink = 3 K/W
ambient = 25 degC

total := interface+sink [K/W]
temperature := ambient+heat*total [degC]

check temperature budget: temperature <= 80 degC

scenario alternative: heat = 8 W

Calculated from your source · not saved

Baseline · Baseline

temperature budget60.00 degC ✓ passes

alternative · alternative

temperature budget53.00 degC ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

total: total = interface+sink [K/W]
temperature: temperature = ambient+heat*total [degC]

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

heat: 10 W
interface: 0.5 K/W
sink: 3 K/W
ambient: 25 degC

Calculated

total: 3.5 K/W
temperature: 60 degC

Assumptions and limits

Series thermal resistances at steady heat flow.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: Thermal-resistance network. Inputs: thermal resistances; heat sources; boundary temperatures. Outputs: node temperatures; heat flows. Model scope: Lumped or low-dimensional thermal models with explicit properties. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: thermal resistances, heat sources, boundary temperatures
Outputs: node temperatures, heat flows
Modes: calculate, compare, sweep
Drawing: Temperature and heat-flow plot

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS