u/DeBaum

I am currently planning a heated enclosure for drying 3D‑printing filament. While calculating how much heating is needed to keep a stable temperature I got values that do not make sense to me:

My plan:

• 60 cm × 40 cm × 60 cm wooden box → 1.68 m² surface area
• 12 mm wood with around 0.15 W/(m·K) thermal conductivity (from a quick Google search)
• Inside temperature 55 °C / outside 20 °C → 35 K difference
• Formula : Q = (k · A · ΔT) / L

Q = (0.15 · 1.68 · 35) / 0.012
Q ≈ 735 W (seems way too high to me)

Currently I have a small (22 cm × 12 cm × 16 cm) filament dryer made of plastic (3 mm thick, assuming ABS with 0.2 W/(m·K)) with a 50 W power supply, which comfortably reaches 65 °C at normal room temperature. When I do the same calculation here:

Q = (0.2 · 0.1616 · 45) / 0.003
Q ≈ 485 W (doesn't make sense since it only has a 50 W power supply)

Obviously I am wrong somewhere. Can you help me find out where?