[Drake] Cooling fans - blow in or out?

[Garey Barrell]

Steve -

Disagree...  ALL the parts involved are designed for convective and 
radiative heat transfer..   The primary purpose of a fan for this type 
of equipment is to AID that "designed" cooling by moving the heated AIR 
(the heat transfer medium) as far away from the source as possible, 
allowing cooler air to come in behind it.  We're not trying to cool 
"surfaces" but remove heated air.

Devices and equipment "designed" for forced air cooling usually have 
multiple surfaces exposed to an air flow.  These surfaces and ducts 
usually tend to impede convection cooling and need air with some 
pressure behind it to force it through these impediments.

73, Garey - K4OAH
Atlanta

Drake C-Line Service Manual
<http://hr99.home.mindspring.com/R-4C_Servicez/>



Steve Thompson wrote:

>Garey Barrell wrote:
>  
>
>>Chris -
>>
>>For a piece of equipment that is NOT  _designed_  to be forced air
>>cooled, the most effective cooling is done by having the fan blow OUT,
>>or better still UP to  _aid_  in getting warm air away from the
>>immediate area.  A fan mounted on the back of the final cage of a
>>Drake transmitter will keep it cool, and greatly extend the life of
>>the final tubes and associated components.
>>    
>>
>Blowing out (or should that be sucking out?) works in a situation like this
>where you want to remove a build up of stagnant, hot air.
>
>If you want to actively cool a component surface, you need to blow onto it.
>Air naturally follows a path of least resistance. Air sucked into a fan
>tends to have a neat, ordered flow and will skirt round components, leaving
>a thin layer of stagnant air right on the surface. Air coming out of the fan
>blades has a lot of turbulence, and it's this that breaks up the stratified
>flow and gets moving air in contact with the component surface.
>
>Steve
>
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>
>  
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