----- Original Message -----
From: "Eeyore" <
[email protected]>
Newsgroups: sci.electronics.design
Sent: Thursday, December 18, 2008 10:29 PM
Subject: Re: aluminum heatsink anodizing
**** YOU !
I designed audio 2 kW amps in 2u Rack units. I know WTF I'm talking
about.
No you don't. A fan blowing air across a heatsink provides for greater
heat transfer from the sink to the aiir than does the natural convection
moving the heated air away slowly. Obviously Eeyone has never blown air
across a spoonful of hot soup to cool it faster than just letting the spoon
sit in still air!
Now do the sums kiddie ! Heatsinking is an expert area that clearly
no-one else
here has much of a clue about. I've been studying it for over 30 years.
Graham
You haven't learned much or else you are using incorrect terminology and
trying to cover it up by bluster and profanity. Conduction provides most
of the heat transfer from the part _to_the_heatsink_. The heatsink
transfers its heat to the air by _convection_.
As far as experience with heat transfer, I have been designing heat
exchangers and such over 40 years. Heat transfer is a subject rarely ever
taught to electrical engineers and what little there is taught is so
simplified. Have you ever designed with heat pipes which use boiling
liquids to carry away heat using the latent heat of vaporization? I have.
And I have designed with the Thompson CSF Hypervapotron cooling technology
for a 1.5 Megawatt rotating arc reactor for coal gasification. I'l like to
see Eeyore try to get this much heat out of a box around a cubic foot in
volume.
Without looking it up via Google or other online search engine, try to
explain Nusselt and Prantl numbers and how they relate to heat transfer.
Extra credit: explain Rayleigh and Grashof numbers.
By now, Graham, you should have figured out that at least one of my degrees
is in chemical engineering, and that heat transfer is studied more by
chemical engineers than any other engineers. Mechanical engineers do study
quite a bit of heat transfer too, but they are usually only concerned with
just air and water. For some strange reasons, mechanical engineering heat
transfer texts often include dimensions to an equation based on
dimensionless numbers.
Go ahead and keep showing off you temper and ignorance. You are
reinforcing the view of most readers here that your posts are usually not
worth reading.
Barry L. Ornitz, PhD