In our daily lives, we may have all been curious about the operation of "vacuuming". Whether it is a necessary step when installing air conditioning or it is widely used in scientific research, medical, industrial and other fields, vacuuming plays a pivotal role. So, what exactly is the principle of vacuuming?

I. Definition of vacuum and vacuuming

First, we need to clarify the concept of vacuum. Vacuum, simply put, is a state of space in which no matter exists. However, in practical applications, the vacuum we usually refer to is not a vacuum in the absolute sense, but refers to a gas space with a pressure smaller than one standard atmospheric pressure, that is, a rarefied gas state.

Vacuuming uses some equipment and methods to extract the gas from the container or space to reduce the internal air pressure and form a vacuum state. This operation is widely used in many fields, such as air conditioning installation, scientific research experiments, medical equipment, etc.

II. The principle of vacuuming

The principle of vacuuming mainly involves the physical properties of gases and the working principle of vacuum pumps.

1) Physical properties of gases

Gas is composed of molecules, and there are interactions between molecules. In a closed container, gas molecules are constantly making irregular thermal motions, colliding with the walls of the container and each other. The pressure generated by this collision is the pressure of the gas. When we pump out the gas in the container, it is equivalent to reducing the number of collisions between molecules in the container, thereby reducing the pressure of the gas and forming a vacuum state.

2) Working principle of vacuum pump

The vacuum pump is the key equipment for vacuuming. Its working principle mainly relies on the principles of mechanical compression, molecular adsorption, gas capture and storage.

• Mechanical compression: Some types of vacuum pumps, such as mechanical pumps, use rotating or reciprocating components to create a changing volume space in the pump body. When the volume space increases, the internal gas pressure decreases, creating a suction force that draws external gas into the pump. These gases are then brought to a high-pressure area and discharged out of the pump.

• Molecular adsorption: Other vacuum pumps, such as adsorption pumps, use the adsorption of gas molecules on the surface of materials to remove gas. These pumps are filled with high-surface-area materials, such as activated carbon or molecular sieves, that capture and lock passing gas molecules.

• Gas capture and storage: There are also vacuum pumps that use cryogenic cold traps or chemical traps to physically capture and store gas molecules. This method is particularly suitable for situations where extremely high vacuum levels are required because it can effectively reduce residual gas.

III. Vacuuming equipment

1) Mechanical pump vacuuming

Mechanical pumps are one of the most common types of vacuum equipment. It uses mechanical force (such as rotation or reciprocating motion) to generate suction to draw out the gas in the container. Mechanical pumps usually have one or more rotors inside, which create a low-pressure area as they rotate inside the pump body. This low-pressure area attracts gas molecules in the container into the pump body, and is then brought to the high-pressure area by the rotor and discharged out of the pump. The advantages of mechanical pump vacuuming are simple structure and easy operation, making it suitable for most laboratory and industrial applications.

2) Diffusion pump vacuuming

A diffusion pump is a device that uses the principle of gas molecule diffusion to evacuate. It consists of a heated diffusion chamber and a cooled collection chamber. When the diffusion chamber is heated, the gas molecules within it gain energy and diffuse around. Due to the pressure difference between the diffusion chamber and the collection chamber, the gas molecules tend to diffuse toward the collection chamber, where they are cooled and condensed into liquid or solid. Diffusion pumps can achieve extremely high vacuum levels and are particularly suitable for applications requiring high vacuum levels, such as semiconductor manufacturing and vacuum coating.

3) Molecular pump vacuuming

Molecular pumps use a high-speed rotating rotor to bring gas molecules from the inlet to the outlet and out of the pump. The working principle of a molecular pump relies on the interaction of gas molecules with the rotor surface. When the rotor rotates, it forms a high-speed airflow channel in the pump body, which brings gas molecules from the low-pressure area to the high-pressure area and discharges them. Molecular pumps have the advantages of fast pumping speed and high ultimate vacuum degree, and are especially suitable for occasions that require high pumping speed and high vacuum degree.

4) Refrigeration pump vacuuming

The freezing pump is a device that uses the principle of low-temperature condensation for vacuuming. It consists of a cooling system and adsorption system. When the cooling system is working, the temperature inside the pump body drops to extremely low levels (usually below -100°C). At this temperature, most gas molecules lose their activity and condense into a solid or liquid. Subsequently, these condensed gas molecules are adsorbed by the adsorption system and remain in the pump body. Cryo pumps are particularly suitable for applications that require extremely high vacuum and extremely low temperature environments, such as superconducting material research and low-temperature physics experiments.

IV. Vacuum application and precautions

Vacuuming has a wide range of applications in many fields. In the installation of air conditioners, vacuuming is an essential and important process before filling the refrigerant. It helps to remove non-condensable gases and moisture in the system and ensure the operating effect of the air conditioner. In scientific research experiments, vacuuming is often used to obtain a high vacuum environment to meet experimental needs. In addition, vacuuming also plays an important role in medical equipment, industrial production and other fields.

However, there are some things we need to pay attention to when performing vacuuming operations. First of all, it is necessary to ensure that the performance of the vacuum pump is stable and reliable to avoid failures. Secondly, appropriate vacuuming methods and equipment should be selected according to the actual situation to ensure operational effects. Finally, safety regulations must be strictly followed during operation to prevent accidents.

V. Conclusion

Although vacuuming seems simple, there are complex physical principles and exquisite technology behind it. By understanding the principles and applications of vacuuming, we can better understand the importance of this operation and apply it in real life.