friction loss formula into excel 1

[jgreg43]

I am looking to figure pressure loss per foot for sprinkler piping. I have the formula and am trying to figure out how to place it into excel.

p=
4.52 Q to the power of 1.85 over C to the power of 1.85 D to the power of 4.87.

P = friction loss per foot
Q = gpm flowing
D = actual inside dia. of pipe
C = friction loss coefficient

any help in writting this into excel would be appreciated.

 

[btrueblood]

= 4.52*(Q/C)^1.85/(D^4.87)

...but where did you come up with that formula?

 

[jgreg43]

Thanks.

I picked this formula up out of the fire protection design handbook. If there is an easier way then by all means share.

Thanks again.

 

[jgreg43]

I',m also finding out that it really does not work. I should get a number around .0217 for a 1" CPVC flowing 11 gpm.

 

[JStephen]

What are you using for C?

 

[BillPSU]

You'll have to calculate the Reynolds number and determine if the flow is laminar or turbulent and then apply the correct friction factor calculation. You will need to know the absolute or kinematic viscosity and the specific gravity of the fluid. If the flow is turbulent you will probably use a Moody diagram. You will need to know the absolute roughness of the tubing or conductor.

The head loss calculation of the Bernoulli equation is difficult to put into a spreadsheet. There are multiple data types in the kinematic or absolute viscosity data. There is both SI and English units of measure. The turbulent friction factor can be arrived at by using the Moody diagram or a very extended formula. There are numerous formulae required but it can be done.

Then the real challenge begins because you are looking for some answer to come out the Bernoulli equation but sometimes its the pump horsepower, while other times you want some pressure at a second point in the hydraulic system. What I'm driving at sometimes the information is a given variable while the next time it is what you are looking for. Building a spread sheet to handle all cases is tough. I have built one but it is still incomplete and its been a real bear.

 

[quark]

Suppose if you put Q values in cellA2, C values in cellB2 and D values in cellC2 then the formula should be,
=4.52*(POWER((A2/B2),1.85)/POWER(C2,4.87))

Here is a spreadsheet that calculates pressure drop in pipelines. This good spreadsheet was developed by a fellow member of eng-tips.

http://homepage.ntlworld.com/brian.doherty/pipesize.xls

Here is one more spreadsheet by another fellow member of eng-tips.

http://mysite.wanadoo-members.co.uk/pressure_drop2

You can get one spreadsheet for pressure drop calculation and another for solving colebrook's equation from,

http://me.queensu.ca/courses/mech451/losses.htm

Note that these are all good spreadsheets but they are based on Darcy's equation.

Regards,

 

[quark]

btrueblood's formula gives the same result.

 

[CanuckMiner]

The equation given by the original poster is a modified form of the Hazen Williams equation that yields psi per foot of pipe. It matches the formula in my Fire Protection Handbook (which I have used in the past).

Cheers,
CanuckMiner

 

[svanels]

Water sprinkler, laminar flow? that is impossible. We are dealing with water, the Hazen Williams equation is applicable to turbulent flows.
What are the flow requirements of the area to be protected?
to give an idea:
for a 1/2" sprinkler with a nozzle pressure range 10 - 100 psi, the flow range would be 18 - 58 GPM

 

[Allen]

You can also write such formula's in "MathCad" spreadsheets also.