The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
From: email@example.com (Tim Shoppa)
Subject: Re: luxeon star leds
Date: 25 Nov 2002 09:11:46 -0800
References: <3DDD9A57.58900EFB@RobertsResearchInc.com> <firstname.lastname@example.org> <3DDDB646.96D0D9D2@RobertsResearchInc.com> <3DDE7264.CD48F4F8@RobertsResearchInc.com> <email@example.com> <3DDEB081.884EC92A@RobertsResearchInc.com> <3DE03D65.932BF9BF@RobertsResearchInc.com>
NNTP-Posting-Date: 25 Nov 2002 17:11:46 GMT
Victor Roberts wrote in message news:<3DE03D65.932BF9BF@RobertsResearchInc.com>...
> Watson 'Atto Parsec' Name wrote:
> > I don't buy this convection from the top because I'm using the Luxeon
> > Star/O which has the whole top of the LED covered by the lens assembly.
> You are certainly entitled to your opinion, but don't you
> think that the lens assembly will have convective losses
> when it gets hot? The lens assembly will, of course, get hot
> under steady state conditions if the metal base is not
> conected to a heat sink.
OK, now I think I'm beginning to understand what you're trying to say:
1. Heat conduction is proportional to temperature difference.
2. Heat transfer by convection typically is superproportional to to temperature.
3. After the thing gets hot enough, convection is how most heat loss is done.
But here comes a bigger problem:
> Considering that the lens assembly,
> including its cylindrical holder, has a much greater surface
> area than the top of the "bare" Luxeon Star
In order to lose heat by convection through the lens, you've got to
conduct heat through the lens first. And the lens is a pretty lousy thermal
conductor compared to any reasonable heat sink.
I certainly agree that convective cooling can be effective, but from
an engineering standpoint you do it by first getting a good conductive heat
sink/spreader and then using forced air if necessary.
>, the "convective
> effect" should be more pronounced for a Luxeon with the lens
> assembly than for one without.
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup