Goomer
Member
Does anyone know the formula for figuring out what your GPM flow is out of your wand?
Are PSI and jet size the only factors?
Are PSI and jet size the only factors?
GPM wand flow formula
- Thread starter Goomer
- Start date
Nate The Great
Member
goomes said:
The steamway guys will also say 3/8" solution hose. Right Loren???
Ryan
Member
- Joined
- Jun 29, 2009
- Messages
- 2,415
Your pump can only put out so many GPM and your 1/4 solution line will restrict it to around 2 GPM tops.
I have heard guys talk about using larger jets even though it won't put out any more water it will reduce the "atomization" or mist effect or your spray.
sweendogg
Member
Do your own bucket test, at different pressures.
roro
Member
Try this one and when done convert it from metric shiteatinggrin or just do the bucket test....
"Data you need if it is exclusively within 1 pipe:
L: Length: (m)
D: Diameter: (m)
A: cross section area = pi*D^2/4 if circular
e: Pipe roughness: (m)
You also need to know details of all local loss components (valves, elbows, tees, unions, return bends, entrances/exits, etc.) as well as any substantial altitude changes.
Fluid properties:
rho: density (kg/m^3)
mu: dynamic viscosity (kg*m/sec)
If it is exclusively within 1 horizontal pipe with no local losses:
Find Reynolds number to classify flow
Re = rho*v*D/mu
To find velocity, use
v = m_dot/(rho*v*A)
Ultimately, Reynolds number for circular pipes. Since you do not know the flow rate, make a guess and iterate.
Re = 4*m_dot/(Pi*D*mu)
If Re < 2100, it is laminar. Otherwise it is turbulent.
If it is laminar, find friction factor f, by (only for circular pipes)
f = 64/Re
If turbulent, use the Haaland equation to find f:
http://en.wikipedia.org/wiki/Darcy_frict…
Once you've found f, find the pressure differential by:
dP = f*L/D*(rho*v^2/2)
Flatten this formula to
dP = 8*f*L*m_dot^2/(D^5*rho*Pi^2)
If dP equals the desired pressure drop, you are done, otherwise, iterate by guessing a different m_dot until you get a balance."
"Data you need if it is exclusively within 1 pipe:
L: Length: (m)
D: Diameter: (m)
A: cross section area = pi*D^2/4 if circular
e: Pipe roughness: (m)
You also need to know details of all local loss components (valves, elbows, tees, unions, return bends, entrances/exits, etc.) as well as any substantial altitude changes.
Fluid properties:
rho: density (kg/m^3)
mu: dynamic viscosity (kg*m/sec)
If it is exclusively within 1 horizontal pipe with no local losses:
Find Reynolds number to classify flow
Re = rho*v*D/mu
To find velocity, use
v = m_dot/(rho*v*A)
Ultimately, Reynolds number for circular pipes. Since you do not know the flow rate, make a guess and iterate.
Re = 4*m_dot/(Pi*D*mu)
If Re < 2100, it is laminar. Otherwise it is turbulent.
If it is laminar, find friction factor f, by (only for circular pipes)
f = 64/Re
If turbulent, use the Haaland equation to find f:
http://en.wikipedia.org/wiki/Darcy_frict…
Once you've found f, find the pressure differential by:
dP = f*L/D*(rho*v^2/2)
Flatten this formula to
dP = 8*f*L*m_dot^2/(D^5*rho*Pi^2)
If dP equals the desired pressure drop, you are done, otherwise, iterate by guessing a different m_dot until you get a balance."
Lee Stockwell
FOJL
Thanks for simplifying that for us RoRo!
Shawn Forsythe
RIP
From a practicality standpoint, Al and David are right on.
You can use pressure and opening size, but you have to measure the pressure at just behind the opening. Most think that they can simply use the pressure gauge on the machine, and the jet size stamped on the jet. Here are the problems with that;
1. Worn jets
2. Inaccurate gauge
3. Restrictions downstream of the gauge resulting in downstream pressure drop, including but not limited to hose and hose length, fittings, disconnects, bends, interior roughness, chemical buildup, scale buildup, and the differential check valve.
The bucket and stopwatch test will take less time than even thinking about it all.
The jet flow chart that Ryan posted is great for reference when outfitting a wand, especially when you have a fair idea of the pressure at the jet opening.
You can use pressure and opening size, but you have to measure the pressure at just behind the opening. Most think that they can simply use the pressure gauge on the machine, and the jet size stamped on the jet. Here are the problems with that;
1. Worn jets
2. Inaccurate gauge
3. Restrictions downstream of the gauge resulting in downstream pressure drop, including but not limited to hose and hose length, fittings, disconnects, bends, interior roughness, chemical buildup, scale buildup, and the differential check valve.
The bucket and stopwatch test will take less time than even thinking about it all.
The jet flow chart that Ryan posted is great for reference when outfitting a wand, especially when you have a fair idea of the pressure at the jet opening.
