Measuring air flow

[Coanda]

I'd like someone to check my mathematics.

 

It's a long time since I left school.

 

I'm using 90mm ducting, which has an ID of 78mm so the radius is 39mm

 

39 by 39 by 3.14 gives an area of 4775.94 mm2

 

Divide by 1,000,000 gives 0.00477594 M2

 

Call it .005 cause my anemometer only has three decimal places.

 

Extract from the kitchen shows 0.7 CMM  and same from the bathroom. Total extract 1.4 CMM

 

Supply to the living room. bed room and junk room is 0.5,0.4 and 0.5 CMM also for a total of 1.4 for the sake of balance I'm going to leave it there meantime.

 

Multiply these numbers by 60 and presto total out, 84 CMH and total incoming the same.

 

I'm going to leave it like that for few hours to see what the numbers at the unit look like regarding temps in out etc.

 

Tomorrow I'll try opening the ceiling vents to see if any more comes through.

 

84 CMH, if my maths are correct is probably good enough for ventilation but I'd need something in reserve for boost.

 

 

 

 

 

 

 

 

 

[JohnMo]

1 hour ago, Coanda said:

CMH

or m3/h

Lots of calculations on here

https://www.omnicalculator.com/math/area-of-a-circle

 

[Coanda]

4 hours ago, JohnMo said:

CMH or m3/h

Lots of calculations on here

https://www.omnicalculator.com/math/area-of-a-circle

 

Are they not the same thing?

[JohnMo]

One the correct units the other not 

[Coanda]

58 minutes ago, JohnMo said:

One the correct units the other not 

Pardon my dimness, but isn't the difference between a Cubic metre per hour and M3h about the same as the difference between a ML and a CC?

[SteamyTea]

SI units save confusion.

 

Volume = m³

 

Time = s

 

Mass = kg (the odd one out)

 

Temperature = K

 

Electrical current = A

 

Amount of substance = mol

 

Luminous intensity = cd

 

 

You will notice that there are no units of volts or force, for instance.  This is because they are derived units.

A volt is kg⋅m²⋅s⁻³⋅A⁻¹ and force is kg⋅m⋅s⁻²