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
Thanks in advance for your insights
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
Thanks in advance for your insights





RE: Fan CFM Computation
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
H. Bruce Jackson
ElectroMechanical Product Development
UMD 1984
UCF 1993
RE: Fan CFM Computation
= = = = = = = = = = = = = = = = = = = =
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
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
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
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).
another day in paradise, or is paradise one day closer ?
RE: Fan CFM Computation
RE: Fan CFM Computation
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
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
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.
RE: Fan CFM Computation
I am now considering the replies you've given and need some help on the computations of Heat transfer.
Idea now is to compute the Air GAP so that the Heat (30watts) or Temperature (60C)entering the Housing is Less (*shown on the Sketch)
I was trying to use and figure out the solution using the formula
dQ/dT = AΔT/(L1/k1+L2/k2+L3/k3) but was stuck
Any advice here?
RE: Fan CFM Computation
maybe a refresher is needed ? maybe something online ??
another day in paradise, or is paradise one day closer ?
RE: Fan CFM Computation
1) How is your ABS plastic attached to the metal bit?
2) You will have radiative heat (infra red if you like) from the hot metal surface as well as air convection.
3) What is the air doing? moving, staying still?
If you put some really skinny tubes made of some sort of low heat conductivity material between the steel and your ABS and blew lots of ambient temp air in between the two at a gap of say 60 or 70mm then you might just keep the temperature below 60C, but the mechanics of working it out are complex.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Fan CFM Computation
Why not keep your temperature sensor remote from your electronics package that could be mounting at a cool location? Having a fan to cool an electronics package for a grille, even a commercial one, seems like a tough and expensive application!
Walt
RE: Fan CFM Computation
Are you sure?
RE: Fan CFM Computation
Ha! When I replied, I assumed the application involved protecting instrumentation for studying/testing a consumer product, like in a lab setting, not a permanent part of the product.
In my defense, I'm not sure what's actually more bizarre...a grill that requires 20 CFM of compressed air...or a grill with food ID vision system.
RE: Fan CFM Computation
RE: Fan CFM Computation
https://www.newmantools.com/vortex.htm
TTFN (ta ta for now)
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RE: Fan CFM Computation
What happens if the end user says "I don't have compressed air, but I'm hungry, so I'm going to use the barbecue anyway"?
Something needs a fundamental re-think.
- Eliminate whatever the fancy electronic gizmo is that warrants temperature control in the first place. My barbecue sure doesn't have, nor need, any such thing.
- If for whatever reason that's not viable, redesign the gizmo so that it's not attached to the high-temperature part of the barbecue. If there's a sensor that needs to sense something, use one that can handle the heat and mount it remotely.
RE: Fan CFM Computation
Dan - Owner
http://www.Hi-TecDesigns.com
RE: Fan CFM Computation
This salmon had become more distracting to babysit than if I’d just cooked it on my own. This salmon had become a metaphor for Silicon Valley itself. Automated yet distracting. Boastful yet mediocre. Confident yet wrong. Most of all, the June is a product built less for you, the user, and more for its own ever-impending perfection as a platform. When you cook salmon wrong, you learn about cooking it right. When the June cooks salmon wrong, its findings are uploaded, aggregated, and averaged into a June database that you hope will allow all June ovens to get it right the next time. Good thing the firmware updates are installed automatically.
It amuses me that a certain segment of the user base (like, say, me - if somebody bought one for me) is likely to think it funny to, for instance, put yesterday's newspaper in the oven, tell the oven software that it's filet mignon, and proceed to reduce said paper to charcoal...and have the oven update its database accordingly.
Back to YOUR proposed device: why a lithium battery and not something less prone to exploding if it gets a bit hot, and easier for consumers to replace (e.g. standard alkaline cells)? I like Mike's suggestion, and thought myself of a periscope up one side of the chamber, with camera safely ensconced down below the hot grill casing.
RE: Fan CFM Computation
Dan - Owner
http://www.Hi-TecDesigns.com
RE: Fan CFM Computation