This specification defines the mechanical, thermal, and environmental design requirements for an outdoor industrial control enclosure equipped with a passive sun shield (radiation shield). The design targets fanless operation, sealed enclosure, and long-term outdoor deployment under direct sunlight.
- Fanless, passive cooling only
- No direct solar radiation on the main enclosure surface
- High thermal isolation between sun shield and enclosure
- IP-rated sealed enclosure (IP65 or higher)
- Suitable for industrial & IIoT equipment
- Main enclosure: primary heat dissipation body
- Sun shield: radiation blocking component (not a heat sink)
- Air gap: thermal isolation layer
- Structural spacers: low thermal conductivity supports
| Element | Thermal Role |
|---|---|
| Sun shield | Block & reflect solar radiation |
| Air gap | Thermal resistance (conduction + radiation) |
| Enclosure body | Dissipate internal heat |
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Material: Aluminum Alloy (ADC12 / A6063 / A5052)
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Minimum wall thickness: 2.5–3.0 mm
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Surface treatment:
- Outdoor-grade powder coating
- Color: Light gray / off-white
- Emissivity ≥ 0.85
- Enclosure acts as primary heat sink
- External surface optimized for natural convection
- No thermal coupling to sun shield allowed
- Target ingress protection: IP65 / IP66
- Operating temperature: -20 °C to +60 °C (ambient)
- Solar load condition: ≥ 1000 W/m²
- Reduce solar heat gain by radiation blocking
- Must NOT be used as a heat spreader
- Must NOT conduct heat into enclosure
| Material | Notes |
|---|---|
| Aluminum (thin) | Requires reflective coating |
| ASA / UV-grade PC | Preferred for isolation |
| FRP | High durability, low conductivity |
- Color: White / light gray only
- Finish: Matte (diffuse reflection)
- Optional: IR-reflective coating
- Sun shield must be mechanically supported with high thermal resistance mounts
- Direct metal-to-metal contact is prohibited
| Parameter | Requirement |
|---|---|
| Material | POM / Nylon / PEEK / FR4 |
| Quantity | 3–4 points |
| Contact area | Minimized |
| Height | 10–30 mm air gap |
- Preferred: Plastic screws
- Alternative: Stainless screws + insulating sleeve
- Mandatory insulating washers on both sides
- Minimum gap: 10 mm
- Recommended gap: 20–30 mm
- Gap must remain open on sides and bottom
- No sealing foam or thermal pad allowed
Purpose:
- Block radiative transfer
- Prevent conductive heat flow
- Avoid trapped hot air accumulation
- Roof-style or canopy-style
- Overhang ≥ 15 mm on all sides
- Sloped top preferred (water & dust shedding)
- Top shading mandatory
- Side shading optional based on installation direction
| Item | Limit |
|---|---|
| Shield-to-enclosure conduction | As low as reasonably achievable |
| Shield contact area | < 1% of enclosure top area |
| Internal temperature rise | ≤ +25 °C over ambient |
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Ambient: 40 °C, no wind
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Solar simulation: ≥ 1000 W/m²
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Measure:
- Shield surface temperature
- Enclosure outer surface temperature
- Internal air temperature
- Enclosure temperature must not exceed component derating limits
- Shield temperature must not significantly elevate enclosure temperature
- Directly bolting metal shield to metal enclosure
- Using thermal pads between shield and enclosure
- Dark or high-absorption coatings on shield
- Fully enclosed shield trapping hot air
The sun shield is a radiation barrier, not a thermal component. Mechanical connection must exist, thermal connection must not.
- External vertical fins on enclosure side walls
- Double-layer shield with ventilated gap
- CFD-based worst-case thermal verification
- Document Type: Engineering Design Specification
- Intended Use: Outdoor industrial control equipment
- Revision: Draft v1.0