The basic parameters that characterize the main pump performance are the following:
First, the flow Q
Flow is the amount (volume or mass) of liquid delivered by the pump in a unit of time.
Volume flow Q said, the unit is: m3 / s, m3 / h, l / s and so on.
Mass flow Qm said, the unit is: t / h, kg / s and so on.
The relationship between mass flow and volume flow is:
Qm = ÏQ
Where Ï - liquid density (kg / m3, t / m3), Ï = 1000kg / m3 room temperature water.
Second, lift H
The head is the pump unit pumping the weight of liquid from the pump inlet (pump inlet flange) to the pump outlet (pump outlet flange) energy value. Which is the effective energy of a Newtonian liquid through the pump. The unit is N · m / N = m, which is pumping liquid pumping column height, used to refer to as rice.
Third, the speed n
Speed ​​is the number of revolutions per unit time of the pump shaft, indicated by the symbol n, in r / min.
Fourth, NPSH NPSH
NPSH, also called net positive nozzle, is the main parameter of cavitation performance. Naphthenic margin used domestic Δh said.
Fifth, power and efficiency
Pump power usually refers to the input power, that is, the prime mover shaft pump power, it is also known as shaft power, with P said;
Effective power pump, also known as output power, with Pe said. It is the unit of time delivered from the pump liquid in the pump to obtain effective energy.
Since the head is the unit of pump output, the effective weight of the liquid from the pump, the product of the head and the mass flow and the acceleration of gravity is the effective energy obtained from the liquid output from the pump per unit of time - that is, the pump Effective power:
Pe = ÏgQH (W) = γQH (W)
Where Ï - pumping liquid density (kg / m3);
γ - pumping liquid heavy (N / m3);
Q - pump flow (m3 / s);
H - pump head (m);
g - Gravity acceleration (m / s2).
The difference between the shaft power P and the effective power Pe is the loss power in the pump, which is measured by the efficiency of the pump. Pump efficiency for the effective power and shaft power ratio, expressed with η.