Vacuum ejector

Vacuum Ejector

Diagram of an ejector showing the flow of fluids.

A vacuum ejector, also known as an aspirator, is a device that uses the flow of a fluid to create a vacuum. It operates on the principle of the Venturi effect, where a fluid passing through a constricted section of a pipe increases in velocity and decreases in pressure, creating a vacuum.

A typical laboratory aspirator.

Principle of Operation

The vacuum ejector works by converting the pressure energy of a fluid into velocity energy. As the fluid passes through a nozzle, it accelerates, and its pressure drops. This low-pressure region can be used to draw in gases or liquids from the surrounding environment, creating a vacuum.

The device typically consists of a converging section, a throat, and a diverging section. The converging section accelerates the fluid, the throat maintains the high velocity and low pressure, and the diverging section slows the fluid down, increasing the pressure again.

Applications

Vacuum ejectors are used in a variety of applications, including:

• Laboratory Equipment: Aspirators are commonly used in laboratories to create a vacuum for filtration or to remove gases from a system.
• Industrial Processes: In industries, vacuum ejectors are used for degassing, drying, and evacuating air from systems.
• Chemical Engineering: They are used in chemical plants for processes such as distillation and absorption.

Advantages and Disadvantages

Advantages

• Simple Design: Vacuum ejectors have no moving parts, making them reliable and easy to maintain.
• Cost-Effective: They are generally less expensive than mechanical vacuum pumps.
• Versatile: Can be used with a variety of fluids, including gases and liquids.

Disadvantages

• Efficiency: They are less efficient than mechanical pumps, especially at high vacuum levels.
• Fluid Requirement: A continuous supply of motive fluid is necessary for operation.

Related Pages

• Venturi effect
• Vacuum pump
• Fluid dynamics