Adequate cooling

[audiostrat]

Hello,

I am planning on building a power supply (posted this in another thread), consisting of 8 stages. I will not go into further details, but provide the following information: the maximum continuous DC total wattage that these 8 LM317/LM350 are going to dissipate, is around 36 watts.

In short, I am going to ensure a 6 volt difference between input and output, and the two LM350's will provide 1.5A current max each, while the 6 LM317's will provide 0.5A max each. So, total wattage on the regulators = 2*6*1.5+6*6*0.5 = 36 watts.

Now, I was thinking of mounting them directly on the aluminium chassis for cooling. The chassis dimensions could be approximated by 50cm x 15cm x 10cm, and it will be 3-5mm thick.

Do you think it would be adequate as a heatsink? The transformer powering the whole system will be a toroidal mounted inside the same chassis.

[payloadde]

barely ...
a square horizontal 25cm x 25cm x 3mm bare aluminum plate has Rth approx. 2.5 K/W for a single heat source in it's center
the body temperature of a single 36W device in the center would therefore be at 90C above room temp
... don't know whether multiple devices distributed is better or worse but it seems that you need something like 1 K/W heat spreader with fins on the outside or backside of your box

[audiostrat]

Then, how about using 5mm aluminium along with mounting a 0.5 K/W heatsink on the back side of the chassis? It is going to be on the opposite side of the regulators, but will it help anyway?

[payloadde]

sounds reasonable