Author Topic: Mirror fan and smoke test  (Read 148 times)

unmoharib

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Re: Mirror fan and smoke test
« Reply #15 on: January 31, 2018, 01:35:20 AM »
Smoke and mirrors. Stan Brower would howl when anyone lit a cigarette anywhere near his optics, claiming the particles immediately were deposited on the surface.
Alan Adler demonstrated a cross-the-face fan system to rid the boundary layer, right around the time the Brian Greer article was published in S&T.

Junee Hunt

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ichpezafi

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Re: Mirror fan and smoke test
« Reply #17 on: February 02, 2018, 10:07:52 PM »
Quote
Just a comment that may or may not be applicable. I worked in power conversion electronics for over 40 years and when forced air cooling was used for various "box" enclosures, blowing the air into the box created more turbulent conditions in the box than if the fan was oriented to "suck" air out of the box. This latter method produced more internal laminar air flow which, in the case of thermal cooling of heat sinks, is the least efficient way to cool. Turbulent flow tends to "scrub" the heatsinks resulting in better heat transfer. With laminar flow, an insulating boundary layer is formed between the air flow and the hot element that the laminar flow is next to. This effect reduces cooling efficiency. Not sure if this applies to cooling telescope mirrors/tubes but I thought I would mention it.

Frank
Tucson

Thats right, within a telescope laminar flow has no advantage at all over turbulent air, only disadvantages. The atmosphere might be a different story...