Thermal Network Lab
Sketch a lumped thermal circuit by naming nodes, fixing at least one boundary temperature, and joining nodes with constant thermal resistances. Give unknown nodes a positive heat injection or negative heat extraction in watts. At steady state the solver balances the heat leaving each unknown node against its source and reports every link's signed heat flow, boundary reaction and residual. It is a deliberately limited linear model, not a product design approval.
Key features
- Edit 2–12 thermal nodes and 1–24 links, including distinct parallel resistance paths
- Solve unknown temperatures from the conductance matrix with fixed-temperature boundaries
- Show each node in °C and K and each signed resistance drop in K with heat flow in W
- Report unknown-node and whole-network energy-balance residuals
- Reject zero/invalid resistances, isolated nodes, unanchored components and below-absolute-zero results
- Download versioned input JSON, solved report JSON and tabular CSV
How to use
- Load the self-created series, parallel or heat-source example, or edit node IDs and connection endpoints.
- Mark temperature boundaries as fixed and enter °C; set heat injection at unknown nodes in W, with extraction entered as a negative number.
- Enter every constant positive resistance in K/W; separate rows may connect the same pair to represent parallel paths.
- Solve and read node temperatures, signed link flows and boundary heat absorbed; confirm residuals are below the reported tolerance.
- Export the input or result, then check material properties, geometry, nonlinearity and real operating conditions before engineering use.
Use cases
- Check an idealized conduction path between hot and cold surfaces
- Compare two parallel heat paths feeding one junction
- Estimate a lumped device temperature with a specified heat generation and ambient boundary
- Inspect energy conservation in a small hand-built thermal network
Frequently asked questions
Which equations are solved?
For each unknown node i, the sum of (Ti − Tj)/Rij over attached links equals its specified heat injection Qi. Fixed nodes impose their temperatures. Links use Qij=(Ti−Tj)/Rij; a dense pivoted linear solve finds the unknown temperatures.
How do °C and K work in a resistance?
Absolute temperatures are displayed in both scales, with K = °C + 273.15. A temperature difference has the same numerical value in kelvins and degrees Celsius. Resistance is a temperature difference divided by heat-flow rate, K/W.
Why does a floating or isolated network fail?
An unknown component without any fixed-temperature boundary has no unique absolute temperature; an isolated node cannot exchange heat. The tool rejects these graphs instead of inventing a temperature.
What does a negative flow or boundary value mean?
Link flow is positive from its From node to its To node. A negative value flows the other way. Positive boundary absorbed W means heat enters that fixed-temperature reservoir; negative means the boundary supplies heat.
Does this model certify a thermal design?
No. Resistances are supplied by the user and held constant. The model omits transient storage, radiation, advection, contact variation, geometry-dependent conductivity and uncertainty; validate all of these separately for a physical design.
Is my network uploaded?
No tool API is used. Editing and calculation run in the browser tab; JSON or CSV is saved only when you request a download.
Privacy
The network and computed values remain in this browser tab. This tool sends no calculation inputs to a server API and downloads only on request.
Comments & questions