The basic parameters of the pump
The basic parameters that characterize the main performance of the pump are as follows: 1. Flow rate Q Flow rate is the amount of liquid (volume or mass) delivered by the pump per unit time. The volume flow is expressed by Q, and the unit is: m3/s, m3/h, l/s, etc. The mass flow rate is expressed by Qm, and the unit is: t/h, kg/s, etc. The relationship between mass flow and volume flow is: Qm=ρQ where ρ-the density of the liquid (kg/m3, t/m3), and clean water at room temperature ρ=1000kg/m3. 2. Head H Head is the unit weight pumped by the pump The increase in energy of the liquid from the pump inlet (pump inlet flange) to the pump outlet (pump outlet flange). That is, the effective energy of a Newtonian liquid obtained by the pump. The unit is N•m/N=m, that is, the height of the liquid column of the liquid pumped by the pump, which is often referred to as meter for short. 3. Rotation speed n Rotation speed is the number of revolutions of the pump shaft per unit time, represented by the symbol n, and the unit is r/min. 4. NPSH NPSH NPSH NPSH, also called net positive tip, is the main parameter indicating cavitation performance. The NPSH has been expressed by Δh in China. 5. Power and efficiency The power of a pump usually refers to the input power, that is, the power on the shaft of the prime mover to support the pump, so it is also called shaft power, which is represented by P; the effective power of the pump is also called output power, which is represented by Pe. It is the effective energy obtained in the pump by the liquid delivered from the pump per unit time. Because the head refers to the effective energy obtained from the pump by the unit heavy liquid output by the pump, the product of the head, mass flow rate and gravitational acceleration is the effective energy obtained from the liquid output from the pump per unit time-that is, the pump Effective power: Pe=ρgQH(W)=γQH(W) where ρ-the density of the liquid conveyed by the pump (kg/m3); γ-the gravity of the liquid conveyed by the pump (N/m3); Q-the pump’s Flow rate (m3/s); H-pump head (m); g-gravitational acceleration (m/s2). The difference between the shaft power P and the effective power Pe is the power loss in the pump, and its magnitude is measured by the efficiency of the pump. The efficiency of the pump is the ratio of the effective power to the shaft power, expressed by η.