Author Topic: thermal resistance calculation  (Read 2068 times)

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Offline aniketTopic starter

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thermal resistance calculation
« on: March 22, 2019, 07:58:33 pm »
hi ,
how do i calculate the thermal resistance for a black anodized aluminum sheet with dimension of 100 x 50 x 5mm.
Considering 167W/m3 of thermal resistance for alu , I reach at 0.0041750 for the sheet intended for my application , but that's the thermal resistance for heat transfer within the aluminum , I need to calculate for aluminum sheet to ambient air at 40C .
I need to dissipate a total of 6W , any help will be highly appreciated .......
 

Offline jonroger

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Offline soldar

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Re: thermal resistance calculation
« Reply #2 on: March 25, 2019, 11:24:12 am »
I need to calculate for aluminum sheet to ambient air at 40C . I need to dissipate a total of 6W

Note that all models are quite simplified.

Aluminum to air will be very variable on whether it is still or moving air, whether the aluminum sheet is vertical or horizontal, one or two sides exposed, etc.

On the other hand, this is very easy to measure. You can just build it and measure it.
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Offline CatalinaWOW

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Re: thermal resistance calculation
« Reply #3 on: March 25, 2019, 03:40:48 pm »
I need to calculate for aluminum sheet to ambient air at 40C . I need to dissipate a total of 6W

Note that all models are quite simplified.

Aluminum to air will be very variable on whether it is still or moving air, whether the aluminum sheet is vertical or horizontal, one or two sides exposed, etc.

On the other hand, this is very easy to measure. You can just build it and measure it.

Just want to double down on Soldar's comment.  Unless you are willing and able to do a detailed finite element analysis of your device and its surroundings you will just be getting a ballpark answer, and even the detail analysis will be dependent on knowing things like the surface roughness of your heat sink and details of the anodize process.  Things which are somewhere between difficult and impossible to get.

So make a test model and measure it.  Be sure your design has margin to deal with manufacturing variation.  Since it is the junction temperature of your silicon that matters make sure you have a way of knowing that in your measurements.  (The diode equation is your friend here).
 

Offline jonroger

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Re: thermal resistance calculation
« Reply #4 on: March 27, 2019, 04:45:05 pm »
I get around 90C junction temperature with airflow on both sides.    But +1 on "details matter".
« Last Edit: March 27, 2019, 04:49:14 pm by jonroger »
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