Electronics Enclosure Temperature Rise Calculator

For a known enclosure thermal resistance, use ΔT = P × Rθ. For an effective UA model, use ΔT = P/(UA).

Enclosure thermal resistance relates internal heat dissipation to enclosure temperature rise above the external ambient environment.

Add the calculated enclosure temperature rise to ambient temperature: Tinternal = Tamb + ΔT.

Use the actual power converted to heat inside the enclosure. For a power supply, losses are closer to Pin minus Pout, not simply output power.

Use internal dissipated heat from power supplies, processors, drivers, relays, resistors, transformers, converters, and other losses.

Not always. If power leaves the enclosure as useful output, only the losses dissipated inside should be counted as internal heat load.

For the stated steady model, Rθ = 1/UA and UA = 1/Rθ.

U is an effective overall coefficient that can represent wall conduction, inside convection, outside convection, geometry, and surface effects when supplied from data or an empirical model.

Effective surface area is the area that actually rejects heat under the installed condition. It may differ from footprint or simple box surface area.

Use Rθ,max = (Tmax - Tamb)/P. If Tmax is at or below Tamb with nonzero heat generation, a passive finite resistance cannot satisfy the target.

Use Arequired = P/(U(Tmax - Tamb)) when an effective overall U is known.

With known Rθ, use Pmax = ΔTallowed/Rθ. With known UA, use Pmax = UA × ΔTallowed.

Use P = mdot cp ΔT and mdot = ρVdot, so Vdot = P/(ρcpΔT).

Estimate ideal CFM from Vdot = P/(ρcpΔT) and convert m³/s to CFM. Installed fan airflow can be lower than free-air rating.

1 CFM equals 0.0004719474432 m³/s, or about 1.6990108 m³/h.

Yes. A sealed enclosure can reject heat through internal convection, wall conduction, external convection, and radiation. Sealed does not mean infinite thermal resistance.

Yes. Larger effective area or lower thermal resistance generally reduces temperature rise for the same heat load.

Internal air temperature is a representative enclosure estimate. Component junction temperature can be much higher and needs component-specific thermal analysis.

Hot spots, local recirculation, poor airflow, package thermal resistance, PCB heating, and component power density can all raise local or junction temperature.

No. Outdoor or sun-exposed enclosures should add solar heat gain or use a dedicated environmental thermal analysis.

Radiation is not separately solved. It may be included only if the supplied empirical Rθ or U already includes radiation effects.

No. It estimates ideal sensible-heat airflow. Real fan selection requires pressure drop, fan curve, grille, filter, duct, and installation review.

Altitude changes air density, which affects volumetric airflow needed for the same heat load. The air density input is editable for that reason.

THM-010 calculates local surface convection from h and area. THM-011 estimates enclosure-level temperature rise from heat load, Rθ, UA, or ventilation energy balance.