Static pressure calculation for aircon duct

[sparo]

Hi i am new here.
can anyone provide me the formula to calculate the static pressure for the aircon ductwork.


Thanks:)

[nh3simman]

Measure static pressure with a u-tube manometer
static pressure = density x gravity x height

if water in manometer
density = 1000 kg/m3
gravity = 9.81 m/s2
height = difference in manemeter levels, meter


typical static pressures in aircon duct
0 to 400 Pascals

Pressure drop due to friction

The correct equation to use is Darcy-Weisbach.

dP = (1/2) density f L V^2 / d
density of air at sea level = 1.2 kg/m3
f = friction factor (typical f = 0.019 )
L = duct length, m
V = air velocity, m/s (typical = 5m/s)
d = equivalent diameter, m

This pressure drop due to friction results in a drop in static pressure.

For your info:

Dynamic pressure = (1/2) density V^2

note the similarity to the dp equation.

Duct Fitting Pressure Drop

pressure loss = C (1/2) density V^2

C is the loss coefficient for the fitting
note that it is just a factor on the dynamic pressure

Simple lookup

There are many table published that give a simple lookup. If you can get hold of the ASHRAE Fundamentals Handbook, you will find a good one.

[Peter_1]

There's s not such a thing as a simple formula.

[Brian_UK]

Hi i am new here.
can anyone provide me the formula to calculate the static pressure for the aircon ductwork.


Thanks:)A couple of questions to help us with your query.

What is the airflow rate?

What is the duct size?