3 replies to this topic

[Kiran Das]

The 200 mm duct air velocity is 23 m/sec which is equal to 3206 kg/Hr at 20 oc .

and The DCS reading is showing very less flow compared to the calculated value.

The DCS reading is based on DP value which is 159 mmwc and a Cd of 0.6.

The orifice diameter is 142.9 mm and the line pressure is 1.7 bar (A)

The calculated value is again low using Delta P

 

In Nutshell  the DCS reading is neither showing value calculated with velocity as well as calculated value using delta P.

 

Kindly help to correct the calculation and on what value i shall rely.

 

 

 

[Art Montemayor]

How can we correct a detailed calculation we have not seen?

[breizh]

http://www.efunda.co...wmeter.cfm#calc

 

Hi,

 

Consider Art's reply and show us your calculation. I've added a resource to help !

 

Note : Make sure the properties are calculated at (T,P) .

 

Breizh

[katmar]

I think Breizh has hit the nail on the head regarding the properties (specifically density) because your velocity and mass flow rate do not tie up.  Follow Art's advice and present your calculations in detail so that you can get relevant comments.  You also need to be more specific about your system. Often when HVAC people talk of "air ducts" they refer to square or rectangular cross sections. What shape is your duct? What tappings does your orifice plate have. Without that information we cannot help you.