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From: "John Jardine"
Subject: Re: Thermal Resistance/Forced Convection
Date: Wed, 11 Dec 2002 12:51:32 -0000
NNTP-Posting-Date: 11 Dec 2002 12:39:02 GMT
X-Newsreader: Microsoft Outlook Express 5.00.2615.200
Tobias Maier wrote in message
> Hello Together
> I'm a student in an german highschool and at this time i make
> intership in a company, which produces switches for power electronic
> tools (for Black&Decker, Bosch, Hilti,DeWalt etc.).
> I have to construct a windtunnel in which you can simulate the airflow
> in a handle bar.
> My problem is to verify my test results with mathematical and physical
> My question is:
> How can I verify, that the thermal resistance of a heat sink is
> dependent of the airflow velocity????????????????
> I`ve measured the temperatur off a switch without cooling with an
> with an airflow velocity of 2,5m/s i've measured only 60K:
> that means that the thermal resistance is reduced. How can i verify
> this with physical formulas?
> I'm sorry about my bad english but i hope you can understand my
> problem and help me!
> Best thanx before
> Greetings Tobias Maier
Verification can only come from physical measurement.
The second best is the use of finite element heat-flow software where a 3D
model of the actual heatsink is tested under variable external conditions.
Third best is the use of closed form analytical thermodynamic solutions
based on simple structural shapes.
There are *numerous* physical variables involved with calculating any heat
flows and the classical solutions can give only maybe 'ball park' results on
real world items. (fortunately that's good enough for most work!).
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