Re: [Amps] re cooling of coils

[R.Measures <r@somis.org>]

On Sep 5, 2004, at 4:31 PM, Will Matney wrote:

> Really, the cooling of the tank circuit can be done numerous ways. 
> However, amateur equipment manufacturers look at the cost. They want 
> to build an amp that they can get the most out of with the less 
> innards. Actually, just sizing the conductors to a large enough value 
> is all thats needed in most cases.

The irony is that it takes little air flow to prevent tank inductances 
from having heat problems.  As I see it, not directing forced air at 
tank inductances is not good engineering practice.  Examples of well 
thought out mechanical designs for an amplifier are the TL-922 and 
SB-220

> The manufacturers try to get buy with the least sizes over one thing. 
> cost. Just like Alpha offering a fan for an option. Why not put the 
> fan in as standard if it's needed?

A better fan is not needed in Antarctica?
t
> The sodium idea was good for transferring heat to the mass of the head 
> on the valves like was mentioned The molten sodium would flow due to 
> the differences in temperatures. Sodium becomes liquid has a low 
> melting point, but higher than what water boils at. Sodium Hydroxide 
> (Lye) will boil with water at 180 degrees when the saturation is mixed 
> correctly and is used to blue steel. It has been used in other 
> industrial applications, including cooling. A refrigerant could be 
> pumped through a coil to do this too, with a heat exchanger on the 
> other end with a compressor. Even water could be pumped through one or 
> the coil be immersed in oil. I think Hal mentioned the vacuum cleaner 
> hose to route an air flow onto a coil. If it wasn't Hal forgive me, my 
> mind is short as other things sometimes. When amps are designed, an 
> experienced designer takes all this into consideration or should. Some 
> doesn't and is seen in the final products.
>
> Generally, fan cooled amps have better tank cooling than do blower 
> cooled amps. In my opinion, a fan should be used with a blower to cool 
> one correctly. Not only does tank components need cooling, the large 
> HV electrolytic capacitors do too.

In 200kW+ amplifiers, the tube, vacuum capacitors and tank inductances 
are typically water-cooled.  It is not unusual for such an amplifier to 
have a 100-gallon per minute water pump as well as a centrifugal blower 
cooling the filament seals.

> Heat is the #1 killer of these. Transformers benefit from an air flow 
> across their coil. Really, any part subject to heat will benefit. 
> What's the price of one fan compared to maybe X2 the life span of the 
> amp? But, if the amp wouldn't wear out, they wouldn't be able to sell 
> more after a while.

Which is why one must build a nearly perfect, no-compromises amplifier. 
  The good news is that doing so promotes one out of the "appliance 
operator" category and it for sure beats the hell out of watching 
"Gilligan's Island" reruns or "reality TV".  .
> Will Matney
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Richard L. Measures, AG6K, 805.386.3734.  www.somis.org

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