Enter Thermal Design Inputs
This calculator estimates steady-state internal temperature using geometry, heat generation, conduction, convection, optional measured surface temperature, and a safety margin.
Example Data Table
These sample cases show how geometry, conductivity, and cooling conditions influence internal temperature rise.
| Case | Geometry | Ambient (°C) | Effective Power (W) | k (W/m·K) | h (W/m²·K) | Estimated Core (°C) | Comment |
|---|---|---|---|---|---|---|---|
| Drive module | Cylinder | 25 | 96 | 16 | 25 | 64.14 | Moderate convection with low internal gradient. |
| Insulated block | Slab | 30 | 140 | 4 | 12 | 109.60 | Lower conductivity pushes the center hotter. |
| Compact enclosure | Sphere | 22 | 70 | 45 | 35 | 39.85 | Strong material conduction reduces internal rise. |
Formula Used
Effective Power = Power Loss × (Load Factor / 100)
q‴ = Effective Power / Volume
Rconv = 1 / (h × A)
Tsurface = Tambient + Effective Power × (Rconv + Rcontact)
If a measured surface temperature is entered, that value is used instead.
Slab: ΔT = q‴L² / (2k)
Cylinder: ΔT = q‴R² / (4k)
Sphere: ΔT = q‴R² / (6k)
Tcore = Tsurface + ΔT
Tdesign = Tambient + (Tcore − Tambient) × (1 + Safety Margin / 100)
Bi = hLc / k
This model assumes steady-state conditions, uniform internal heat generation, and one-dimensional conduction behavior for the chosen geometry.
How to Use This Calculator
- Select the component geometry that best matches your part.
- Enter the characteristic dimension in meters.
- Provide ambient temperature, total power loss, and load factor.
- Enter conductivity, convection coefficient, exposed surface area, and body volume.
- Add contact resistance if a thermal interface or poor joint exists.
- Enter a measured surface temperature only when test data is available.
- Set a safety margin and the critical temperature limit.
- Press the calculate button to view the result summary, chart, and export options.
Frequently Asked Questions
1) What does the calculator estimate?
It estimates steady-state core temperature inside a heated engineering part. The model combines internal heat generation, material conduction, surface cooling, and an optional design safety margin.
2) When should I enter measured surface temperature?
Use measured surface temperature when you have test data from a sensor, thermal camera, or validation run. It replaces the estimated surface value and usually improves realism.
3) Why does geometry matter?
Geometry changes the path heat must travel from the center to the surface. Slabs, cylinders, and spheres each have different centerline temperature-rise relationships.
4) What is the purpose of the Biot number?
The Biot number compares internal conduction resistance with external convection resistance. Smaller values suggest weaker internal gradients, while larger values imply stronger internal temperature differences.
5) What does contact resistance represent?
It represents extra thermal resistance at interfaces, joints, pads, or imperfect surfaces. Higher contact resistance increases surface temperature and usually raises core temperature too.
6) Is this suitable for transient heating?
No. This page is intended for steady-state estimation. For warm-up time, cooldown, thermal cycling, or pulse loading, a transient thermal model is more appropriate.
7) Why use a safety margin?
A safety margin helps account for uncertainty in properties, airflow, manufacturing variation, fouling, aging, and measurement error. It supports more conservative design decisions.
8) Can I use this for electronics or mechanical parts?
Yes. It can support early thermal checks for electronics housings, motor parts, blocks, cylindrical components, and compact bodies when the model assumptions are reasonable.