air final velocity

[PaulLag]

Hi there

Hope somebody can help me

Following is the problem

I have a mass of air that is passing through a dehumidifier.

given

section

air mass flow,
air inlet temperature
air inlet RH

water condensed

outlet air temperature
outlet air RH

I am asked about the air outlet velocity

Because of moisture removal from the coil, I assume that outlet mass flow is not as inlet mass flow, I was thinking to realize a balance of mass as follows


inlet mass flow - condensed water mass flow = outlet mass flow

from outlet mass flow, outlet conditions I can derive the air outlet velocity.

please, can anybody confirm my guess is correct ?

thanks in advance

 

[IRstuff]

Is this for school? You need to do the math; you can figure out what the saturation water mass could possibly be for a given temperature

TTFN
faq731-376

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[PaulLag]

many thanks for your answer
Please, may I ask you to be more specific ?
I am afraid I can't get the solution you are kindly proposing me.

Thanks

 

[MintJulep]

Yes, your approach is valid.

 

[PaulLag]

thanks

Please, may I expect the velocity to be lower than inlet one ?

Many thanks

 

[MintJulep]

Do the math and find out for yourself!

 

[PaulLag]

Hello

for sure I have done the math.
Since I have found a result, I am just wondering if the result is reasonable or not.

For this I am asking to the forum.
Should I already know the method, I would not post the question, but maybe answering to a similar post, wouldn't I ?

Thanks in advance !

 

[MintJulep]

So hit us with some numbers.

If you want guesses I'll guess.

Velocity is a volume function.

Water vapor is less dense than air, so removing moisture will increase density.

Dehumidifiers typically work by cooling the airstream and cold air is more dense than warm air.

So it stands to reason that the net result of both processes will be a density increase and mass decrease.

Density is mass/volume, or rearranging Volume is mass/density.

Numerator decreasing and denominator increasing makes a smaller number for volume.

Velocity is volume / time / area.

Assuming constant area it follows that velocity will get smaller.

OK, it's not really a guess.

 

[willard3]

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