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Centrifugal Pump Power And Efficiency Calculation

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1. Centrifugal pump shaft power calculation formula

P=flow×lift×9.81×medium specific gravity÷3600÷pump efficiency
Flow unit: cubic/hour,
Lift unit: meter

P=2.73HQ/η,

Where H is lift, unit m, Q is flow, unit m3/h, η is pump efficiency. P is shaft power, unit KW. That is, the shaft power of the pump is P=ρgQH/1000η(kw), where ρ=1000Kg/m3, g=9.8

The unit of specific gravity is Kg/m3, the unit of flow is m3/h, the unit of head is m, 1Kg=9.8 Newton  Then

P=specific gravity*flow*head*9.8 Newton/Kg

=Kg/m3*m3/h*m*9.8 Newton/Kg

=9.8 Newton*m/3600 seconds

=Newton*m/367 seconds

=Watt/367

The above derivation is the origin of the unit. The above formula is the calculation of water power. The shaft power is divided by the efficiency to get it.  Let the shaft power be Ne, the motor power be P, and K be the coefficient (the inverse of efficiency)
Motor power P=Ne*K (K has different values ​​when Ne is different, see the table below)
Ne≤22 K=1.25
22
55

II. Calculation formula for shaft power of slurry pump

Flow Q M3/H
Head H m H2O
Efficiency n %
Slurry density A KG/M3
Shaft power N KW
N=H*Q*A*g/(n*3600)
The power of the motor should also consider the transmission efficiency and safety factor. Generally, the direct connection takes 1, the belt takes 0.96, and the safety factor is 1.2

III. Pump efficiency and its calculation formula

It refers to the ratio of the effective power of the pump to the shaft power. η=Pe/P
The power of the pump usually refers to the input power, that is, the power transmitted to the pump shaft by the prime mover, so it is also called shaft power, represented by P.
Effective power is: the product of the pump head, mass flow rate and gravity acceleration.
Pe=ρg QH (W) or Pe=γQH/1000 (KW)
ρ: Density of the liquid delivered by the pump (kg/m3)
γ: Weight of the liquid delivered by the pump γ=ρg (N/ m3)
g: Gravitational acceleration (m/s)
Mass flow rate Qm=ρQ (t/h or kg/s)

IV. Introduction to the efficiency of Sanitary Centrifugal Pump

What is the efficiency of the pump? What is the formula?
Answer: It refers to the ratio of the effective power of the pump to the shaft power. η=Pe/P
The power of the pump usually refers to the input power, that is, the power transmitted from the prime mover to the pump shaft, so it is also called shaft power, represented by P.
The effective power is: the product of the pump head, mass flow rate and gravity acceleration.
Pe=ρg QH W or Pe=γQH/1000 (KW)
ρ: Density of the liquid pumped by the pump (kg/m3)
γ: Specific gravity of the liquid pumped by the pump γ=ρg (N/ m3)
g: Acceleration due to gravity (m/s)
Mass flow rate Qm=ρQ t/h or kg/s

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