PDA

View Full Version : m=V/v







seanf
14-08-2016, 09:31 PM
Anyone familiar with the relationship between mass flow rate and volume flow rate divided by velocity? m = V/v. Im probably mistaking something though. Thanks.

The word "gasoline" is a mistake in the image, should be "air".
14276

Brian_UK
14-08-2016, 11:01 PM
What has the potental energy of gasoline got to do with the airflow in a duct?

seanf
15-08-2016, 08:33 AM
Hi Brian_UK,

Sorry should have said the word gasoline is a mistake in the question, it should be air

Brian_UK
15-08-2016, 11:39 AM
Okay, panic over, ;)

seanf
15-08-2016, 12:01 PM
Any knowledge of it Brian_UK?

Brian_UK
15-08-2016, 02:22 PM
To be honest, no.

All that says to me is that it depends on the air density to calculate mass, which we knew anyway.

Volume flow rate divided by velocity gives the duct/pipe area.

Sorry I can't be of more help.

seanf
15-08-2016, 04:53 PM
no problem Brian_UK. I will share what else I know in case anyone has a thought.

The only other info that may be relevant that I have is,

P pressure is energy per unit volume in J/m^3
Pv pressure*velocity is energy per unit mass in J/kg

So then the thought is energy per unit mass E/m = Pv
E/m = (E/V) * v
Take reciprocal of both sides
m/E = V * 1/E * 1/v
Multiply both sides by E
m = V/v

But Im not sure thats correct.

Brian_UK
15-08-2016, 08:32 PM
Does this throw any light on it ?

https://www.google.co.uk/url?sa=t&source=web&rct=j&url=https://d3jc3ahdjad7x7.cloudfront.net/m44hBo0bhuxv1s3rkLW1n2DtwCnfuGLwncgXlQjLQrsFjP3b.pdf&ved=0ahUKEwjrjMy4ksTOAhVBLMAKHQlXBWgQFghQMA4&usg=AFQjCNHPZRdckF4IY9wahURr773KKLOXJg&sig2=oXrEg4X1X8XTmxY8f4nr7A

Or is the second 'v' standing for specific volume?

seanf
15-08-2016, 09:39 PM
That would be it, specific volume. Why the hell I thought velocity:confused:. Thanks Brian.

Brian_UK
15-08-2016, 10:53 PM
Oh well, got there in the end, at least one of us knows what you were talking about. :)

Next time it might be me....