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2 fans double CFM

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mike93lx

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Depends on if you have enough flow through the box to support the fans. If not, you'll generate some pressure in the box as the air can't all get out easily.

Wow, that little box is expensive...$800ish?
 
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cleaner

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Assuming that the air mass flow rate in and out of the box is balanced (no accumulation of air mass in the box) that does not mean that you are removing 2X the heat relative to a single fan model. Heat transfer is more complex than just moving air through the box.

You can approach this problem empirically by building a box measuring the parameters of interest (mass flow rate, temperature, pressure) and get some idea of what works best as you make changes to the design. Change only one thing at a time and record the measures and then analyze the data to determine what configuration performs best.
 
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jjrbus

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mike93lx said:
Depends on if you have enough flow through the box to support the fans. If not, you'll generate some pressure in the box as the air can't all get out easily.

Wow, that little box is expensive...$800ish?
Click to expand...
Don't forget shipping!
 
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The Tool Tyrant

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Unless it's a trick question then yes, no different than 1 garden hose filling a bucket compared to 2 hoses (on separate hose bibs) filling the same bucket. But as other have mentioned, the incoming air must be able to flow out unrestricted.
 
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Honch

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Very interesting product, a "soundproof box" that lowers noise by "approximately 6-10db". It also apparently cannot be used inside or outside.

1680615075916.png

Must be lost in the translation...
 
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cleaner

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The Tool Tyrant said:
Unless it's a trick question then yes, no different than 1 garden hose filling a bucket compared to 2 hoses (on separate hose bibs) filling the same bucket. But as other have mentioned, the incoming air must be able to flow out unrestricted.
Click to expand...
Your analogy (hose filling bucket) only considers conservation of mass. Heat transfer phenomena is not only a function of mass flow so making this assumption may lead to unexpected results in practice.

An enclosure is not going to allow for unrestricted flow when forcing a fluid through it. Even if the box were empty, it still restricts flow.
 
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The Tool Tyrant

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cleaner said:
Your analogy (hose filling bucket) only considers conservation of mass. Heat transfer phenomena is not only a function of mass flow so making this assumption may lead to unexpected results in practice.

An enclosure is not going to allow for unrestricted flow when forcing a fluid through it. Even if the box were empty, it still restricts flow.
Click to expand...
I am assuming there is enough allowable opening in the box as not to restrict incoming flow...basically 'flow through ventilation'
 
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cleaner

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jjrbus said:
If I build a box to house an item that generates heat and add 2 fans to push heat out of the box will the cfm of the fans be doubled? Aluminum box, lined with composite foam acoustic
insulation, housing a Honda EU2200. Yes I know it cannot be a sealed box and Honda does it.

https://www-honda-co-jp.translate.g...tr_sl=ja&_x_tr_tl=en&_x_tr_hl=en&_x_tr_pto=sc
Click to expand...
Simply knowing the cubic-feet-per-minute requirements is not enough when choosing fans

Here is an overview of fan selection for thermal management of enclosures for those interested to learn more about how to approach this problem. This addresses electronics enclosures, but the problem is the same regardless of the heat source within the enclosure. Since the generator has an ICE you will also need to consider the intake air to the engine, does the Honda box have a snorkel or plenum for the intake?

I would expect that the box has some internal features to direct the airflow to the "right" areas to optimize heat transfer to the forced airflow.

Often in these designs you are better off adding the second fan to force air into the box rather than using both to evacuate air. This is not always the case but is an often-used strategy to increase thermal transport.

https://www.machinedesign.com/autom...1834244/sizing-fans-for-electrical-enclosures
 
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jjrbus

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Thanks for the input, always appreciated. The little grill you see on the honda box is the intake vent, nothing hidden. How they do the exhaust in only a couple inch's has me baffled. I cannot seem to do it without using 8 inch's of the box. The plan at the moment is to put the fan/fans on the intake side of the generator. I have built 2 quiet box's so far but changing the design quite a bit on this one. It is not my idea I am only doing what others have done. The fan is likely not necessary, I do not like the heat build up in the generator when it stops running so looking to help cool the generator.

 
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