The choice of performance parameters: 1. Flow Q: As a positive displacement pump, the factors that affect the flow of twin-screw pump are speed n, pressure p, and medium viscosity v. 1.1 speed n impact: screw pump at work, the two screw and bushing form a sealed chamber, the screw every one revolution from the import to export a sealed chamber, that is, a sealed chamber volume of liquid is discharged. Ideally, there is no leak inside the pump, so the pump flow is proportional to the speed. That is: Qth = n * qn ---- speed; q ---- theoretical displacement, that is, the volume of liquid discharged per pump per revolution; Qth ---- theoretical displacement. 1.2 pressure â–³ P of the impact: pump the actual work process, its internal leakage, also known as slip. As the pump seal cavity has a certain gap, and the seal chamber before and after the existence of pressure â–³ P, therefore, there is a part of the liquid backflow, that there is leakage, the amount of leakage with Q, Q = Qth- â–³ Q Obviously, with Before and after the sealed chamber, the pressure difference â–³ P increased, the amount of leakage â–³ Q gradually increased. The impact varies depending on the type and structure. 1.3 Effect of viscosity v: Consider: Leach clear water and viscous paste from funnel-type containers in the same volume. Clearly, water leaks faster than paste. Similarly, for the twin-screw pump, viscous fluid smaller than the viscosity of liquid leakage is small, the amount of leakage and medium viscosity has a certain proportion. To sum up, to comprehensively consider the above factors, through a series of calculations to accurately know the actual pump flow meets the requirements of the working conditions. 2. Pressure â–³ P: Unlike centrifugal pumps, the working pressure of twin screw pump â–³ P is determined by the outlet load, which is the outlet resistance. The outlet resistance is matched with the pressure at the outlet of the pump. The greater the outlet resistance, the greater the working pressure. If you want to know the pressure, you need to use the fluid mechanics knowledge of export resistance accurate calculation.
When there is liquid in the Pipette tip, do not place the pipette horizontally or upside down, so as to prevent the liquid from flowing back and corroding the piston spring.In the process of biological experiments, especially in the field of Cell Culture, the pipette is an indispensable laboratory instrument, and the pipette holder is also used very frequently on the laboratory ultra-clean bench or in the biological safety cabinet. The ease of use of the pipette and the pipette holder also affects the ease of experimental operation.
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