Electricity demand for the pumps
Electricity demand for the pumps
(OP)
Hi Folks,
I am trying to calculate the electrical power demand for a process plant. Where pumps and agitator motors are main consumers for the electricity.
Is there some rule of thumb to calculate the electricity demand for the pumps (based on flowrate) and motors.
Thanks in davnce for your input on the issue.
Best Regards
Zahid
I am trying to calculate the electrical power demand for a process plant. Where pumps and agitator motors are main consumers for the electricity.
Is there some rule of thumb to calculate the electricity demand for the pumps (based on flowrate) and motors.
Thanks in davnce for your input on the issue.
Best Regards
Zahid





RE: Electricity demand for the pumps
Power = flowrate * density * pressure differential / efficiency of 0.7
Now divide by motor efficiency = 0.9
and add another 10% for electric losses
"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO, BP
**********************
"Being GREEN isn't easy" ..Kermit
http://www.youtube.com/watch?v=hpiIWMWWVco
http://vir
RE: Electricity demand for the pumps
RE: Electricity demand for the pumps
Power = Volumetric flowrate * pressure differential / efficiency
A quick unit check.
If volume flow rate in m^3/sec and dp in N/m^2 then the product will be in Joule per second as required. If you put density in there you will have something different than power.
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Electricity demand for the pumps
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Electricity demand for the pumps
(a) I repeat, one must be careful with the units' consistency.
To estimate the power input to pumps P = g.ρ.Q.H/η .
For example, given
Q (flow rate) in m3/s,
ρ (density) in kg/m3,
H (head) in m,
η (fractional efficiency) dimensionless, and assuming
g = 9.8 m/s2,
(b) Regarding efficiencies, zamu2010 asked for a ROT, and BigInch submitted one.
RE: Electricity demand for the pumps
RE: Electricity demand for the pumps
I have provided consistent units including differential pressure. You introduced head and density as alternative to differential pressure - also very valid. My only reason for mentioning units was to demonstrate that the previously posted "flowrate * density * pressure differential / efficiency" is not correct (I assumed flow rate represents volumetric.... but also not correct if flow rate was mass, since in that case density would have to go in the denominator).
BigInch knows more about pumps than I'll ever know. I was just pointing out what seems to be a typo.
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Electricity demand for the pumps
"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO, BP
**********************
"Being GREEN isn't easy" ..Kermit
http://www.youtube.com/watch?v=hpiIWMWWVco
http://vir
RE: Electricity demand for the pumps
rmw
RE: Electricity demand for the pumps
OK. Sparkies - fire at will.
"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO, BP
**********************
"Being GREEN isn't easy" ..Kermit
http://www.youtube.com/watch?v=hpiIWMWWVco
http://vir
RE: Electricity demand for the pumps
Bring it on distinguished Sparkies. We are like sponges here.
I may go over to the electrical motor forum and start a thread that says rmw and biginch are all yours over in the pump engineering forum-have at 'em.
rmw
RE: Electricity demand for the pumps
Think of it as the kW demand is determined by the load and the efficiency of the motor and the kVAR demand (the reactive bit) is something inherent in the motor caused by the design of the magnetic circuit in the machine. The reactive power doesn't cross the boundary from the electrical world into the mechanical world so you guys don't have to worry about it other than to pay the 'leccy bill. At an ultra-simplistic level it means that the current drawn by the motor is higher than you would expect based purely on the kW demanded by the load, and we have to size conductors and equipment to accomodate this higher current.
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Electricity demand for the pumps
Actually these sparky guys never give you the same story twice. Something to do with job security I think. It keeps me coming back asking the same dumb questions over and over Opps. I mean, Thank You Scotty!!
"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO, BP
**********************
"Being GREEN isn't easy" ..Kermit
http://www.youtube.com/watch?v=hpiIWMWWVco
http://vir
RE: Electricity demand for the pumps
To electricpete, my message intended to reinforce yours.
RE: Electricity demand for the pumps
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Electricity demand for the pumps
Well ... That's what I was thinking all along. I said it's, "a phenomenon that doesn't actually affect the watts registered at the meter". Why did I get confused this time?
"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO, BP
**********************
"Being GREEN isn't easy" ..Kermit
http://www.youtube.com/watch?v=hpiIWMWWVco
http://vir
RE: Electricity demand for the pumps
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Electricity demand for the pumps
"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO, BP
**********************
"Being GREEN isn't easy" ..Kermit
http://www.youtube.com/watch?v=hpiIWMWWVco
http://vir