Calculation Coil Pressure Drop

[emalsyd]

Trying to balance some hydronic coils. I have the design gpm, actual gpm and design water pressure drop. Is there a formula to calculate the actual pressure drop?

 

[MortenA]

generally for a fixed system:

dp(q1)/dp(q2)=(Q1/Q2)^2

that is: pressure drop is proportinal to the flow rate (actually its velocity) squared

Best regrads

Morten

 

[ione]

You can use Darcy-Weisbach formula to evaluate pressure drop in pipes

http://en.wikipedia.org/wiki/Darcy–Weisbach_equation

 

[sheiko]

I have fonud this in a forum:

f(coil) = f (straight pipe) *[1+3.5×(d/D)]

f = Moody friction factor
d =inside diameter of the coil tubing
D= Diameter of the helical coil

Reference: Matthew J.Realff & Jde T sommerfield
Georgia insitute of technology)

In addition, if flow is laminar, dp(q1)/dp(q2)=(Q1/Q2)

"We don't believe things because they are true, things are true because we believe them."

 

[25362]

Data for friction factors in coils depend on their geometry, e.g. helices, flat or cylindrical spirals, turbulent and laminar conditions, newtonian and non-newtonian fluids.

I found another formula for helices:

[ƒ] = 0.076 Re^-1/4 + 0.0073(d/D)^1/2 [±] 10%​

valid when:

0.34<Re(d/D)²<300​

The friction factor, [&fnof;], can be used to estimate friction drop, [&Delta;]p_f, using:

[&Delta;]p_f [&asymp;] 4 [&fnof;] [&rho;] (L/d) v²/2​

Where:

d and D as above; [&rho;] = density; v = velocity.