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# Fan CFM Computation

## Fan CFM Computation

(OP)
Guys,

I need some help regarding the Fan size needed for my Sensor Module (unit size of 5x3x1 inch) project
The product is mounted on the Lid of a Oven/BBQ Grill which is place outdoor
The temperature inside the Grill or on the Lid surface is max at 350C and the Ambient/surrounding is at 40C
Then, inside the Sensor module are electronics that need to maintain an internal temperature of 60C so that it will not damage the components
I need some help on how to get the right CFM size in order to control the temperature below 60C

### RE: Fan CFM Computation

This is not really an engineering question, but I doubt there is any way to cool this unit reliably to 60C. Conduction of heat through the metal? body is far more efficient than blowing 40C air at it.

Simply not going to be feasible for such a small device IMHO

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

### RE: Fan CFM Computation

NFW you're going to get the temperature inside that sensor to 60C if the surface it's mounted on is going to be 350C, no matter what size fan you use!

H. Bruce Jackson
ElectroMechanical Product Development
UMD 1984
UCF 1993

### RE: Fan CFM Computation

It depends on how effective and thick the insulation pad between them is.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

### RE: Fan CFM Computation

OP just say "mounted on". Hence why you could blow 100 cfm at it and it will still be rather hot. ....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

### RE: Fan CFM Computation

At the extreme this is asking how much airflow is required to drop the temperature of the contact patch to 60C, so it first depends on the conducted, radiated, and convected heat flow to that patch and the conductivity of the metal and ceramic coating of the lid. Since one is looking to create a delta T of 290C with a delta T of 20C using a material with low thermal mass, that would indicate a huge volume of air is required.

The usual approach is to look at ways to limit the size of that patch to minimize the heat-flow. This is done with standoffs to limit conducted heat flow and insulation to limit radiated and conducted heat flow.

### RE: Fan CFM Computation

Insulation and careful design of the housing would be helpful.

For cooling, investigate "vortex tube" devices. To my simple mind, they operate on witchcraft. Compressed air in...hot air out one side...cold air out the other...no moving parts.

I cannot take credit for the idea, though. I recall that somebody proposed using this approach to protect accelerometers mounted on hot engine parts.

### RE: Fan CFM Computation

is this work or "work" ?

can you get a surplus space shuttle tile ?

an air gap of 1" isn't probably going to work (with the electronics mounts on ceramic stand-offs).

### RE: Fan CFM Computation

60C junction temperature is very low, can you get components with a higher rating? What is it that needs to stay below 60C?

### RE: Fan CFM Computation

(OP)
Thanks Guys for the replies
These are enlightening.
I'd like to share a similar product in the Market that is currently working.
This is the June Life Oven which has internal camera attached to the wall (internal oven temp reaches 500F)
What we want is to somehow use that approach.
Yes, there will be insulation in between the Lid and the Product (plan to use Fibre glass fabric or embedded with Aerogel) to protect the Product Housing form direct heat.

Regarding the Grill Lid temperature, since this is exposed to surrounding which is 40C, isn't it that the temperature above the Lid will not be that Hot as compared with the internal since it has been dissipated by ambient air (my rough simulation say's 200C)

BTW, there is Lithium Battery inside so 60C is required to maintain.

### RE: Fan CFM Computation

I won't get into how silly I think the product is, but...

#### Quote:

Using deep learning neural networks which run in real time on the 192 CUDA Cores, the camera and NVIDIA GPU work together to recognize over 25 foods and recommend the best Adaptive Cook Preset for them.
Overkill, for sure... just to recognize 25 foods that are more easily recognized by a human and selected from a menu

Corning Museum of Glass created a special ceramic window that could withstand the heat of a molten glass crucible, while allowing a camera to view the pool. They designed/created it for some electric crucibles that were placed on three cruise ships, which gave daily shows on glassblowing (I really loved that cruise... 14 days of geeking out in a glassblowing studio, with awesome food and "other" entertainment). The windows slowly failed over several months and required replacement, to the tune of several thousand \$s per window... but your thermal and size needs are considerably less. Something that may be worth looking into...

Dan - Owner
http://www.Hi-TecDesigns.com

### RE: Fan CFM Computation

Well if you look at the oven camera you will find that it is
a) very small
b) behind a glass screen
c) almost certainly isn't attached to the metal hot part of the oven
d) only has a very small amount of heat entering its domain.

your current design has none of those things, what ever it is.

The electronics of the camera will be mounted on the outer shell well away from the internal hot oven casing and even then will probably get pretty hot unless they blow cooling air around the inner oven which will be completely covered in insulation, unlike your BBQ

you need to sketch your anticipated design out a bit to see what it looks like, but for me and as noted above, you will need a awful lot of air moving over a big heat sink.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

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