To design a sealed thin-sheet BAKSA steel box for a 150W PC with the given ambient temperatures, we need to ensure the box is large enough to dissipate heat purely through conduction and natural convection without exceeding safe internal temperatures.
Key Parameters:
- PC Heat Output (Q): 150W
- Max Internal Ambient (T_internal): 55°C
- Max External Ambient (T_external): 45°C
- Material: BAKSA steel (assuming similar to mild steel, thermal conductivity ~50 W/m·K)
- No fans/vents → Only passive cooling
Step 1: Calculate Required Surface Area for Heat Dissipation
The heat must escape through the steel walls via conduction + convection.
Formula:
Q=h⋅A⋅ΔTQ=h⋅A⋅ΔT
Where:
- Q = Heat to dissipate (150W)
- h = Effective heat transfer coefficient (estimated ~10 W/m²·K for passive steel)
- A = Surface area needed (m²)
- ΔT = Temperature difference (55°C – 45°C = 10K)
Solving for A:
A=Qh⋅ΔT=15010×10=1.5 m²A=h⋅ΔTQ=10×10150=1.5m²
Required Surface Area ≈ 1.5 m²
Step 2: Determine Box Dimensions
We need a box with at least 1.5 m² of external surface area.
Assuming a Cuboid Shape (L × W × H):
A=2(LW+LH+WH)A=2(LW+LH+WH)
To minimize size, let’s assume a cube-like shape (L ≈ W ≈ H):A=6L2→L=A6=1.56≈0.5 m (50 cm)A=6L2→L=6A=61.5≈0.5m (50 cm)
Minimum Internal Dimensions:
- 50 cm × 50 cm × 50 cm (if perfectly cubic)
But PCs are Rectangular → Optimize Shape
If the PC is 30cm × 30cm × 15cm, we can adjust:
- Add 10cm clearance → Internal box = 40cm × 40cm × 25cm
- External Surface Area = 2(0.4×0.4 + 0.4×0.25 + 0.4×0.25) = 0.92 m² (Still too small!)
→ Must increase size further.
Revised Dimensions (for 1.5 m²):
- 60 cm × 60 cm × 30 cm (external)
- Surface Area = 2(0.6×0.6 + 0.6×0.3 + 0.6×0.3) = 1.44 m² (~1.5 m² achieved)
Step 3: Enhance Cooling (If Box Must Be Smaller)
If a 60×60×30cm box is too large, consider:
- Use Copper or Aluminum Heat Spreaders
- Bond steel box to copper plates (better conduction).
- Attach External Fins
- Increases effective surface area.
- Thermal Bridge to External Heatsink
- Pass heat through a metal rod to an external heatsink.
Final Recommendation:
| Requirement | Solution |
|---|---|
| Material | BAKSA steel (1-2mm thickness) |
| Minimum Box Size | 60cm × 60cm × 30cm (external) |
| Internal Clearance | PC size + 10cm on all sides |
| Improvements | Add copper shims, external fins, or heat pipes |
Feasibility Check:
- 150W is a lot for passive cooling!
- Without heat pipes/fins, the box will get very hot (~55°C inside).
- Better Alternative: Use an external heatsink or Peltier cooling.
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