The basic equations of vacuum pump calculation

The flow of different components can be in series and parallel. The pipes, valves, cold traps and other components as part of the vacuum system, have a certain impediment to the flow of gas. The natural flow of gas always flows from high pressure to low pressure. When the pressures at both ends are P1 and P2, respectively, and the amount of gas flowing through is Q, the flow of the component is very large, for example, The pumping speed is defined as the volume of gas that is drawn through the pump port per unit of time under a certain suction pressure. A complete vacuum system, no matter what the application, should have a vessel or chamber to be evacuated, a vacuum unit, a vacuum pump, connecting pipes, valves, cold traps, etc. . Different vacuum system components can be guided through the calculation, simulation, measurement and other methods to determine the vacuum pump is to evacuate the gas inside the vacuum container, but often the pump suction port can not be directly connected with the container being drawn due to process requirements Or to reduce the degree of contamination of the vacuum unit contaminated with oil vapor, must pass through the cold trap, the valve, the pipeline can be connected with the evacuated container, because each vacuum component has a definite conductance, it can be said that the pump must pass a certain The flow guide can be connected to the drawn vessel, as shown in the figure, which, besides its geometry, is related to the flow of the gas. The amount of gas passing through it is not limited, then the pumping capacity of the pump depends on the size of its own pumping speed, according to the basic equations of the vacuum pump can be mathematically obtained two extreme results, that is, when the flow guide U is very large, The effective pumping speed S0 of the vacuum chamber can be approximately equal to the pumping speed S of the pump; when the pumping speed S of the pump is very large, or when the conductance U is very small, the effective pumping speed S0 of the vacuum chamber is approximately equal to the conductance U. The gas evacuated from the suction port of the vacuum chamber must pass through the guide U (that is, the pipeline, the valve, etc.) to be evacuated by the vacuum pump. The vacuum pump has a certain working principle in practical work and is carried out according to certain working principles and methods, Show the important role and performance in the vacuum system and give full play to the good performance and value in the industry. The connection between the pump and the vacuum chamber in the figure may include cold traps and valves. However, the evacuation of gas from the vacuum chamber suction port to the pump port is from high pressure to low pressure flow, and from the vacuum pump port is from low pressure to high pressure based on a certain suction principle of forced flow. This is the same with the pump port directly connected to the vacuum chamber. However, if the pump pumping speed is very large, which is relative to the pump pumping speed U is very small, then the actual pumping capacity of the vacuum pump does not depend on its pumping speed depends on the size of the gas through the guide U Capability, the value of conduction is exactly pump effective pumping speed S0.

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