What are the performance parameters of the pump inside the tank?
(1) Traffic volume
Also known as displacement, pumping capacity, etc., it refers to the amount of fluid discharged per unit time, which can be expressed in two ways: volume unit and mass unit.
The volumetric flow rate is represented by Q, with units of m ³/s, m ³/h, and L/s.
Mass flow rate is represented by G, with units of: t/h,kg/h.
G=ρ·Q; ρ： Density of fluid: kg/m³.
(2) Head lift
The energy obtained per unit mass of fluid, also known as total head or full head, is expressed in H and is measured in kg · m/kg=m.
For high-pressure pumps, the head can also be approximated by the difference between the inlet pressure and outlet pressure (P2-P1) of the pump, where: H=104(P2-P1)/ ρ, Among them, P2： The outlet pressure of the pump is kg/cm2, P1： The inlet pressure of the pump is kg/cm2.
(3) Rotation speed
Usually refers to the number of revolutions per minute of the pump shaft, expressed in n and measured in rpm;
(4) Power
The shaft power of the pump, which is the power transmitted from the prime mover to the pump, is expressed in N, with the unit of kW. It is the product of the pump's mass flow rate and head: kg/s × m=G × H=ρ· Q · H.
(5) Cavitation phenomenon
Turbomachinery works by rotating the impeller, and if the fluid medium being transported is liquid, it increases the energy (kinetic energy and pressure energy) of the liquid. During the interaction between the impeller and the fluid, velocity and pressure are converted into each other. Usually, the inlet pressure is the lowest and the velocity is the highest. If the pressure of the liquid here is equal to or lower than the vaporization pressure of the liquid at that temperature, a large amount of steam and gas dissolved in the liquid will overflow from the liquid, forming a mixture of steam and gas - small bubbles. For example, in LNG pumps, it is a mixture of methane and light hydrocarbon components or nitrogen dissolved in LNG. When reaching the high-pressure zone, due to the gasification pressure inside the bubble and the surrounding pressure being greater than the gasification pressure, a pressure difference is generated. Under the action of this pressure difference, the bubble ruptures and re condenses. During the condensation process, liquid particles accelerate from all sides towards the center of the bubble, collide with each other, generate high local pressure, and cause noise and vibration during operation, accompanied by a decrease in flow rate, head, and efficiency, while reducing the service life of the pump.
