Richard wrote:
>
>
>>Richard wrote:
>>>>I need to know how to determine if the following fans will be adequate
>>>>for an 4cx1000/1500 amp. While I can find the cfm specs, I cannot
>>>>find the back pressure specs.
>>>
>>>Ordinary fans do not create enough air pressure to cool external anode
>>>tubes. A centrifugal blower makes more pressure. I like to mount the
>>>tube/socket in a cardboard box and measure air pressure with a
>>>manometer.
>>>
>>>
>>Agreed about the cardboard box mock-up, just to see if the blower is big
>>enough.
>>
>>Broadening the answer, it is better to measure the cfm directly by
>>letting the exhaust air blow up a thin plastic bag, and timing how long
>>it takes (as recommended here by K6GT).
>
>â?¬ Eimac provides a number of pressure vs cfm points in their spec sheets.
>
These pressure figures only relate to the one particular method of
blowing: upward through the socket, chimney and anode cooler in series.
For other methods of blowing, the pressure drops will be different so
you have to work directly from the cfm specification - remembering that
it's cfm, not pressure, that actually cools the tube (well, OK, strictly
speaking it's the mass flow rate, not the volume).
--
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.com/g3sek
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