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Understanding the Principles of Laminar Airflow

Key Takeaways

  • A laminar airflow system aims to reduce turbulence and maintain uniformity in the flow to reduce contamination.

  • The laminar airflow regime can be applied for downflow or crossflow operations.

  • CFD tools can help in identifying turbulent regions and mitigating them with accurate simulations.

Visualizing flow in the airflow system

The concept of laminar flow involves the ability of fluid particles to move in a smooth path, with each layer moving parallel to the other. This concept has been utilized in the design of many aerodynamic and hydrodynamic systems to make them more efficient by reducing friction drag. Laminar airflow follows the exact principle where the air handling units are designed to exhibit uniformity in direction and flow rate as well as ensure consistency.

The significance of laminar airflow is seen in laboratories or during the manufacturing of intricate semiconductors where a sterile working environment is desired. With CFD analysis, the modeling of such laminar airflow systems, including downflow/crossflow chambers, tunnels, and workbenches, can be done efficiently, whereby the governing equations can be solved to predict the velocity, pressure, and temperature suitable for creating a sterile environment. 

Laminar Airflow

Laminar airflow refers to the flow within an air distribution system that follows the principle of laminar flow of air. When gas molecules travel in straight, parallel layers without intersecting or mixing with each other, laminar conditions are formed. In an enclosed space, the uniformity in velocity and direction due to laminar airflow provides the opportunity for creating an efficient circulation system. The circulation of the filtered air within a system is key to keeping a clean and contamination-free environment.

This type of laminar airflow system is usually desired in industries such as chemical or semiconductor manufacturing as well as in medical and biological laboratories where the unidirectional flow of clean air is desired for the utmost protection against external particles. Most air handling units achieve this by applying vertical (downflow) or horizontal (crossflow) laminar airflow regimes.

How Does a Laminar Airflow System Work?

The typical layout of an airflow system includes an enclosed chamber, work station, air filtration system, lights, and fan or blower. The fan or blower sucks the air, which is filtered through the filter pad. This filtered air then passes through the particulate filter, which facilitates the removal of micro contaminants such as bacteria or dust. A sterile work environment can thus be achieved within the working area with a uniform flow of air.

Vertical laminar airflow chamber

Vertical laminar airflow: In a vertical laminar airflow system, the filter is located at the top of the cabinet from where the room air enters the working area. As the filtered air flows vertically downwards towards the work surface, the contaminants, including bacteria or particles, are removed, creating a clean working environment.

Horizontal laminar airflow: In a horizontal laminar airflow system, the filtration unit is located at the side of the cabinet from where the room air enters the working area. The filtered air then flows horizontally towards the work surface, sweeping the contaminants along with the flow. 

Analyzing Laminarity With CFD Tools

While laminarity is the goal of airflow systems, turbulence is a possibility that can lead to contamination due to the lack of flow control. When designing laminar airflow systems, it is important to visualize laminarity and any unwanted turbulence. With CFD tools, a range of Reynolds numbers can be analyzed within a system to check for laminar and turbulent conditions. Any detected turbulent regions during system design can be resolved with an airflow simulation model. In a laminar airflow system, CFD analysis can also help in the calculation of pressure losses, velocity, and other airflow attributes over time. With the mesh generation and simulation capabilities from CFD platforms such as  Pointwise and Omnis, the desired laminarity in an airflow system design can be achieved.

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