sheafromme
Mechanical
Hello All,
Longtime reader but this is my first post.
I am designing a prototype of an electronics package that will sit out on a pole in the sun 24/7 with a max ambient temperature of 50˚C and at 30˚N latitude. It produces 50W of internal heat and the electronics are rated to 70˚C. Currently, it is all housed in a grey polycarbonate box (approx. 18"x12"x6" hwd). I have room for a 100W air-to-air heat exchanger (I need to keep the box watertight which also precludes most vents) but from back-of-the-envelope calculations I can already tell that the solar loading will likely overwhelm the exchanger. So, from the outset I have planned on putting a solar shield around the enclosure, but now that I have reached that point in design I realize that my heat transfer skills are more than a bit rusty and I'm having trouble fitting the solar shield into my thermal model. I am just wondering if any of you have any tips, suggestions, or resources on how to incorporate solar shields and what their actual effects are on the cooling of enclosures. Do any of you have any experience with solar shields? I have contacted the major enclosure companies for white papers and did some Googling but it all seems very surface-level with not much being given to the driving theory or secondary considerations such as sky temperature or ground reflections. I am currently leaning towards some sort of aluminum "shell" with an air gap because of its high reflectivity and corresponding reduction of emissivity inwards towards the enclosure, but I have no idea how to translate this concept into harder numbers to make sure I can actually reduce the solar loading to the point that the exchanger can handle it. I should note that I work at a startup so my resources are a bit limited (in terms of consulting and labor) so I've found myself straying outside of my skillset quite a bit.
I appreciate any responses, let me know if I need to include more info.
-Shea
Longtime reader but this is my first post.
I am designing a prototype of an electronics package that will sit out on a pole in the sun 24/7 with a max ambient temperature of 50˚C and at 30˚N latitude. It produces 50W of internal heat and the electronics are rated to 70˚C. Currently, it is all housed in a grey polycarbonate box (approx. 18"x12"x6" hwd). I have room for a 100W air-to-air heat exchanger (I need to keep the box watertight which also precludes most vents) but from back-of-the-envelope calculations I can already tell that the solar loading will likely overwhelm the exchanger. So, from the outset I have planned on putting a solar shield around the enclosure, but now that I have reached that point in design I realize that my heat transfer skills are more than a bit rusty and I'm having trouble fitting the solar shield into my thermal model. I am just wondering if any of you have any tips, suggestions, or resources on how to incorporate solar shields and what their actual effects are on the cooling of enclosures. Do any of you have any experience with solar shields? I have contacted the major enclosure companies for white papers and did some Googling but it all seems very surface-level with not much being given to the driving theory or secondary considerations such as sky temperature or ground reflections. I am currently leaning towards some sort of aluminum "shell" with an air gap because of its high reflectivity and corresponding reduction of emissivity inwards towards the enclosure, but I have no idea how to translate this concept into harder numbers to make sure I can actually reduce the solar loading to the point that the exchanger can handle it. I should note that I work at a startup so my resources are a bit limited (in terms of consulting and labor) so I've found myself straying outside of my skillset quite a bit.
I appreciate any responses, let me know if I need to include more info.
-Shea
