>
>2 wrote:
>>
>>>
>>>2 wrote:
>>>>Red or green ink turns toast brown at high temperature. In a typical
>>>>SB-220 (blowing fan) or TL-922 (sucking fan), the marking ink on the
>>>>3-500Zs is still in 'mint' condition after even a decade of use.
>>>
>>>Can you remind us where the markings are in those two amps, for each of
>>>the tubes, in relation to the 'upstream' side? (Just wondering how much
>>>difference that makes.)
>>>
>>?Ǩ Blow air on one side of a cylinder and it flows smoothly around the
>>cylinder. Thus, it does not matter where the ink is placed on the glass.
>> Have you tried blowing out a candle with a cylinder betwixt your lips
>>and the flame?
>
>Yes, I'm aware that happens - but what that party trick demonstrates is
>that at *low* velocities the airflow remains attached to the surface and
>flows smoothly around it to join up again at the far side.
>
>Unfortunately that isn't at all relevant to forced-air cooling, where
>the airflow is very turbulent and the flow pattern is quite different.
>
? fasten seatbelts
>Air is blasted at the upstream side of the tube, cooling it well, but
>the flow breaks away from the surface half-way around to form a
>turbulent wake.
? Not with the quiet, slow speed fan in a SB-220, Ian..
>The downstream side is only cooled by eddies in the
>wake, and there may even be negative pressure on the opposite side.
>
>There is absolutely no doubt that cooling is less good on the downstream
>side.
? The colour of the ink on the 3-500Z glass does not indicate this.
>The only questions are: how much less good, and does it matter?
>That's why I was looking for separate evidence whether the color of the
>markings is dependent on the orientation of the tube.
>
? Denial of reality - the greatest glitch in the human psyche. Alas.
- R. L. Measures, 805.386.3734, www.vcnet.com/measures.
end
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