Heat inside a sealed box
Every watt dissipated inside a sealed enclosure has to leave through its walls, so the air inside warms up and every part in it runs hotter than on the open bench. Bigger or vented boxes, or moving hot parts outside, fix it.
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How it works
Box surface A = 304 cm²; natural convection h ≈ 6 W/m²K, so θ_box = 1 ÷ (h·A) = 5.5 °C/W.
Inside = 30 °C + 0 W × 0.0 °C/W = 30 °C. The resistor then runs at that plus its own rise: 30 °C.
Try it on the bench
- Select the Box and change it to 200 × 150 × 100 mm: the inside temperature drops because the walls have more area.
- Set the rating to IP20 (open frame): much cooler, but no protection from dust and water.
- Drag the resistor out of the box: it cools to the room’s 30 °C plus its own rise.
Parts on the bench
- Project enclosure
- Bench power supply
- Resistor
In the course
Zen’s Electronics Design Mastery, module “Capstone — Connected Tracker”.