Parallel Duct Pressure Loss

[jwood10]

I am trying to model flow through an electronics cabinet as if the flow channels were ducts. The flow follows a path similar to this:

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with the horizontal lines acting as Ts in the duct. How do you calculate the total pressure loss of the system in order to achieve a system characteristic curve?

 

[trashcanman]

More data please. What is the air velocity entering the cabinet? Within the cabinet? Leaving the cabinet? Changes in the velocity is reflected in changes in Vel. pressure which can be used to approximate static losses.

 

[briand2]

Hydraulic Resistances

P = R*q^2
P is pressure drop, kPa
R is resistance, kPa/(l/s)^2
=r*l
r is unit res,
kPa/m/(l/s)^2
l is length, m
q is flow, l/s (theory kg/s!!)

For pipes look up pressure drop in kPa/m versus flow in l/s (~kg/s!) and calculate r as above (r=P/q^2).

For fittings either use equivalent length of pipe (but this varies with flow and pipe size) or use Kv (m^3/h @ 100 kPa) as R = 1296/(Kv^2).

Series resistances,
Rt = R1 + R2

Parallel resistances,
Rt = (R1*R2)/(sqrR1 + sqrR2)^2

I hope this helps!!

Brian