Definitions & Resources

Action Items

• [ ] review resources
  • [x] summarize heat transfer in electronic enclosures
  • [ ] calculate temperature rise and determine level of ventilation needed

    • Updates from Ben

      • [ ] for temperature: estimate the hottest & coldest using: link
        • Hot case: hottest ambient temp found on environment canada
          • assume direct +maximum sun exposure (no shading, largest face of box oriented towards sun, max solar flux in summer)
        • cold case: coldest temp from environment canada
          • smallest face of box pointing towards the sun , use minimum solar flux experienced in winter, all components operate at nominal power levels
        • [ ] Vary case conditions
          • Storage conditions (electronic parts manufacturers include an ‘operational’ & ‘storage temp ranges in data sheet’
      • Assume every component is on & dissipating max amount of power
        • [ ] update laptop info
        • [ ] update each heat dissipation as percent of power output generation (https://instrumentationtools.com/how-to-calculate-heat-load-in-electricalelectronic-panel-enclosure/)
      • [ ] Review the following calculations:

      Sources

      • [ ] Quantify ‘safety’
        • Calculate margins on all the component temperatures to observe position relative to operational and storage limits of components
      • [ ] Re-do calculations

Description

The temperature inside the box depends on the watts of heat generated, the area of the box walls, the material of the box walls and the outside temperature. Purpose is to determine if thermal control can be met with passive methods (natural means, no power, low cost) or forced. Based on ambient temp, may not need to worry about enclosure rising significantly above temp?

• What about keeping the components performing at colder temperatures?
  • This is required when temperatures dip below freezing. Mostly, heating is needed to reduce moisture and related corrosion, the goal of enclosure heating is to keep relative humidity inside the enclosure below 65%.

Ventilation:

• Passive: for smaller device enclosure with lower input power (ie. ventilation holes, louver vents, materials & coatings, heat pipes, insulation, heat sinks & radiators, heat shunts/straps)
• Forced air: larger devices w/higher input power (ie. blower fans)

Conduction, Convection, Radiation

Conduction

• Want sufficient amount of SA to enable thermal control through conduction. Mounted components can better transfer heat dissipating to the structural frame.

• Orientation: Specific heat rises (vertical enclosures) have internal temp differences that make them hotter at top than at bottom. Horizontally mounted enclosures may experience significantly more complex heat transfer mechanisms than vertically mounted enclosures.

• Environmental conditions: outside can increase the internal heat load if the ambient air temperature heats the enclosure material. Outdoor enclosures in direct sunlight may absorb solar heat. Enclosures painted in white or other light colors will absorb less heat than enclosures painted in black or dark colors.

Components

Toronto weather (link) : Over the course of the year, the temperature typically varies from -8 °C to 25 °C and is rarely below -17 °C or above 30 °C.

• Average snow fall: 25mm