Passive Cooling on metal surface equipment

TigerBoy · August 18, 2020

I have a router and some switches that go from 60-71 Celsius (140-160 Fahrenheit).

Switch A) It is not ideal putting a fan in the location due to limitations for one of them. I noticed the metal case (material not specified) is really sucking up a lot of heat to the point you can't put your hand on it for more than 5 seconds. This is a small switch so it is hard to cool with a fan.

Switch B) (See picture A) I placed a fan on the bottom that will cool down 50% inside the chassis (via the side vents) and 50% the metal case. Heat currently goes out the side vents (top) and some heat stays at the upper portion of the metal chassis. This has dropped the temps to 47 Celsius from 71 Celsius. Also added an image of the internal layout and side vents.

Questions:

1) Switch A) I would like to ask if slapping on a thermal pad would help dissipate heat at all even by a few degrees or does it not work without a heat sink or an active cooling source?

2) Switch B) Does it still help cool it down further if I slap a thermal pad on? Do I need to add in a heatsink for it to generate any additional benefits? Or is everything futile with this?

Jenko32 · August 18, 2020

You could take a look at these type of fans https://www.aliexpress.com/item/4000099669773.html?spm=a2g0o.productlist.0.0.33129a2dP9RhYP&algo_pvid=c4c276c3-ee90-43ee-9453-158cc0dc93ec&algo_expid=c4c276c3-ee90-43ee-9453-158cc0dc93ec-1&btsid=0b0a050115977913636976922ec127&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

They are typically found in rack servers/routers/switches which tend to be flat and long. They move a lot of air when they run at max power

If you put maybe two of these, one on top and another one on the left side they could work as exhaust and intake. Or maybe only one as introducing fresh air might be what they need

TigerBoy · August 18, 2020

8 minutes ago, Jenko32 said:

You could take a look at these type of fans https://www.aliexpress.com/item/4000099669773.html?spm=a2g0o.productlist.0.0.33129a2dP9RhYP&algo_pvid=c4c276c3-ee90-43ee-9453-158cc0dc93ec&algo_expid=c4c276c3-ee90-43ee-9453-158cc0dc93ec-1&btsid=0b0a050115977913636976922ec127&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

They are typically found in rack servers/routers/switches which tend to be flat and long. They move a lot of air when they run at max power

If you put maybe two of these, one on top and another one on the left side they could work as exhaust and intake. Or maybe only one as introducing fresh air might be what they need

Hi Jenko, Thanks for the update! I plan on replacing the Switch B Setup with two 40mm noctua fans once the import borders open up again from where I am.

Trying to think if it is worth using thermal pads for now or just a complete waste. I have two large sheets of 2mm thick pads and wanted to see if that would help.

Jenko32 · August 18, 2020

4 minutes ago, TigerBoy said:

Hi Jenko, Thanks for the update! I plan on replacing the Switch B Setup with two 40mm noctua fans once the import borders open up again from where I am.

Trying to think if it is worth using thermal pads for now or just a complete waste. I have two large sheets of 2mm thick pads and wanted to see if that would help.

21 minutes ago, TigerBoy said:

This is the photo of the inside right?

Do you know if it's it the transformer (on top) or the chip with the heatsink that is heating up? (If you check with your hand after use beware of the high voltage capacitor which might kill)

A thermal pad alone will not help radiating heat away. Thermal pad (as thermal paste) are used as an interface to make two metals exchange heat, you might try connecting the heatsink with the metal case of the switch.

Even if the metal case feels hot to the touch that might just mean that given the hot air radiating from the heatsink/transformer it becomes hot too, instead if you add a thermal pad between the heatsink and the metal case you might make the chip dissipate through the case, with this setup you should be able to keep it cooler since the metal case is in contact to the fresher air outside the enclosure. The mini fans will probably be way more effective anyway so my advice might only work as a temporarily replacement.

TigerBoy · August 19, 2020

31 minutes ago, Jenko32 said:

This is the photo of the inside right?

Do you know if it's it the transformer (on top) or the chip with the heatsink that is heating up? (If you check with your hand after use beware of the high voltage capacitor which might kill)

A thermal pad alone will not help radiating heat away. Thermal pad (as thermal paste) are used as an interface to make two metals exchange heat, you might try connecting the heatsink with the metal case of the switch.

Even if the metal case feels hot to the touch that might just mean that given the hot air radiating from the heatsink/transformer it becomes hot too, instead if you add a thermal pad between the heatsink and the metal case you might make the chip dissipate through the case, with this setup you should be able to keep it cooler since the metal case is in contact to the fresher air outside the enclosure. The mini fans will probably be way more effective anyway so my advice might only work as a temporarily replacement.

It is the heatsink mainly. It would definitely benefit to put two smaller fans inside to push the hot air out instead. I know for gear like these it is mainly intakes due to the even dimensions of the chassis. Is there any benefit doing a push pull with 40mms or is it better to go push push for the two 40 mms to also cool the power components? (or maybe experiment and go from there)

May just hold off on switch B for now as the border is not allowing imports. My problem now is switch A... Found a picture of it open. It is quite small which makes fan cooling impractical. This one goes around the 60 degree range without load which is too hot. Do you think it would benefit from sticking a heatsink on the chassis? I am not too sure how thick of pads I need for this... thinking 1mm or .5mm is ideal as the heat is not too intense. What do you think?

Jenko32 · August 19, 2020

18 minutes ago, TigerBoy said:

It is the heatsink mainly. It would definitely benefit to put two smaller fans inside to push the hot air out instead. I know for gear like these it is mainly intakes due to the even dimensions of the chassis. Is there any benefit doing a push pull with 40mms or is it better to go push push for the two 40 mms to also cool the power components? (or maybe experiment and go from there)

May just hold off on switch B for now as the border is not allowing imports. My problem now is switch A... Found a picture of it open. It is quite small which makes fan cooling impractical. This one goes around the 60 degree range without load which is too hot. Do you think it would benefit from sticking a heatsink on the chassis? I am not too sure how thick of pads I need for this... thinking 1mm or .5mm is ideal as the heat is not too intense. What do you think?

As for the fans, you will have to experiment, so try everything it seems logical to you. If you experiment remember to use it in the same scenario, like transferring a big file back and forth many times

As for the thermal pads, the more there are in between the less efficient it will be, as it's really difficult to calculate I guess that you can only try and see, we have to remember that not only you would need a thermal pad inside between the heatsink and the chassis but even between the external heatsink and the chassis. and let's not forget that the chip itself as some kind of thermal interface to the black internal heatsink, it would be a complex system to calculate the variables and only if you try it you will see if there are benefits. You would need to make holes (or use some kind of clamp?) for the external heatsink to compress the thermal pad and make good contact

If it's something you want to put effort in, you could create a wood/plastic taller case for it with a hole for a fan on the top and many mini holes as side vents to exhaust the heat.

Or put it in a box where it fit and make the mini holes to emulate side vents and put a fan there

TigerBoy · August 19, 2020

5 hours ago, Jenko32 said:

As for the fans, you will have to experiment, so try everything it seems logical to you. If you experiment remember to use it in the same scenario, like transferring a big file back and forth many times

As for the thermal pads, the more there are in between the less efficient it will be, as it's really difficult to calculate I guess that you can only try and see, we have to remember that not only you would need a thermal pad inside between the heatsink and the chassis but even between the external heatsink and the chassis. and let's not forget that the chip itself as some kind of thermal interface to the black internal heatsink, it would be a complex system to calculate the variables and only if you try it you will see if there are benefits. You would need to make holes (or use some kind of clamp?) for the external heatsink to compress the thermal pad and make good contact

If it's something you want to put effort in, you could create a wood/plastic taller case for it with a hole for a fan on the top and many mini holes as side vents to exhaust the heat.

Or put it in a box where it fit and make the mini holes to emulate side vents and put a fan there

Awesome feedback! I think I will go back to the drawing board on this as all plans plans are somewhat not ideal (within the realm of keeping the warranty). I doubt there will be any issues as it came out the factory like this and all users experience this. It just really feels off having switches reach these temps. I may circle back to this after the warranty is gone.

Thanks Jenko and stay safe!