Is this the right calculation?
Is this the right calculation?
(OP)
Hi all,
I'm trying to find the power added to my working fluid (water @ 20 deg C) by a theoretical pump to see how much power I have to apply to the motor.
The pump draws from a bag, through flexible tubing, then out through more flexible tubing and a small plastic nozzle.
The conditions are as follows:
-P1 = 0 psi (ambient, the bag is not pressurized)
-P2 = 30 psi (my target output pressure)
-Q = 0.4 Gal/min (1.5 L/min)
-A1 = .051 sq. in. (tube area at inlet
-A2 = 0.0016 sq. in. (nozzle area at outlet)
-h1 = 0 ft
-h2 = 3 ft (total of +3 ft height change)
My equation for power is:
Power = rho * Q * wp (specific work)
wp = ((P2-P1)/rho)+(1/2)*(V2^2 - V1^2) + g*(h2-h1)
where V2 and V1 are the outlet and inlet velocities
Is this the right equation to use? And when I get 80W of power, does that seem right?
I'm trying to find the power added to my working fluid (water @ 20 deg C) by a theoretical pump to see how much power I have to apply to the motor.
The pump draws from a bag, through flexible tubing, then out through more flexible tubing and a small plastic nozzle.
The conditions are as follows:
-P1 = 0 psi (ambient, the bag is not pressurized)
-P2 = 30 psi (my target output pressure)
-Q = 0.4 Gal/min (1.5 L/min)
-A1 = .051 sq. in. (tube area at inlet
-A2 = 0.0016 sq. in. (nozzle area at outlet)
-h1 = 0 ft
-h2 = 3 ft (total of +3 ft height change)
My equation for power is:
Power = rho * Q * wp (specific work)
wp = ((P2-P1)/rho)+(1/2)*(V2^2 - V1^2) + g*(h2-h1)
where V2 and V1 are the outlet and inlet velocities
Is this the right equation to use? And when I get 80W of power, does that seem right?





RE: Is this the right calculation?
30 psi equates to about 69.2 feet of head
add 3 feet
add your flow resistance, estimated at 10 feet
use the calculator at
http://www.ajdesigner.com/phppump/pump_equations_water_horse_power.php
It looks like 6 watts.
RE: Is this the right calculation?
How do you get your flow resistance estimate?
I think the problem with my original calculation was that the output velocity V2 was 160 ft/s, but when I took my flow and area, that's what I got. That makes me think the application of my equation is incorrect.
Thanks,
Adam
RE: Is this the right calculation?
Size your tubing to obtain an 8 ft/sec velocity and it should be inconsequential in the calculations.
RE: Is this the right calculation?
RE: Is this the right calculation?
http://www.c-spray.com/store/axi-flat-fan-ceramic-spray-nozzle-80.html
Check with the nozzle supplier for the pressure and flow ratings.