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Airtècnics’ Air Curtains: Engineering Indoor Comfort

06.06.2024

Air curtains are key players in environmental engineering, helping to efficiently manage indoor spaces. Although they often go unnoticed near entrances, the science behind their operation is truly fascinating. Let's dive into how air curtains work, their main components, and the benefits they provide.

Understanding How They Work

An air curtain operates by creating a controlled flow of air that forms a barrier across an opening. This steady stream of air, directed downward, effectively seals off the interior from external conditions. The Coanda effect, where air adheres to surfaces, plays a key role in creating this stable barrier without physical partitions.

(Image by © Airtècnics)

Key Components

Air curtains typically include high-velocity fans, air filters, and optional heating elements. The fans generate airflow, while filters ensure the air is free of contaminants. Heating elements can be added to maintain interior temperatures and reduce energy loss through the opening.

Aerodynamic Design

Designing air curtains involves optimizing performance and energy efficiency. Engineers consider factors such as airflow velocity, directionality, and turbulence to create a barrier that minimizes air exchange while conserving energy.

Factors Affecting Air Movement

Air moves between spaces with different conditions due to temperature and pressure differences, along with external elements like wind and drafts. Adjusting the angle and strength of the air curtain helps counteract these forces, maintaining a stable indoor environment.

Air transfer through doorways occurs due to three main factors:

  • Temperature Difference: Natural convection causes air to move between areas with different temperatures. Warm air escapes through the top of the doorway, replaced by cold air entering at the bottom. Greater temperature differences lead to increased air infiltration and energy loss.
  • Pressure Difference: Equalizing pressure differences is recommended to enhance air curtain performance. However, in some installations, like clean zones, a slight pressure difference helps prevent particles from entering.
  • Wind and Drafts: Modifying the air jet's strength and outlet angle allows the air curtain to counter forced air movements. Excessive incoming air velocity reduces the air curtain's efficiency.
Schematic representation of the main parameters involved in the performance of an air curtain produced by the UPC (Polytechnic University of Catalonia).The efficiency of an air curtain depends on the optimization of performance factors.

Schematic representation of the main parameters involved in the performance of an air curtain produced by the UPC (Polytechnic University of Catalonia).The efficiency of an air curtain depends on the optimization of performance factors.

Maximizing Efficiency

Efficiency is enhanced by focusing on:

  • Turbulence: A low-turbulence jet provides significantly enhanced efficiency and energy savings.
  • Air speed: air velocity should be enough across the doorway
  • Air volume: a wider jet makes the air curtain stronger against air transfer on doorways
  • Angle discharge: according to a situation if jets are well oriented it will increase the energy saving
  • Fan type: axial, tangential wheel, centrifugal, etc. Higher pressure fans create a higher pressure jet that reaches farther. For instance, if we compare an air curtain with tangential fan against an air curtain with centrifugal fan (with same air volume), the jet made of centrifugal fans will be stronger and larger.

UPC University air curtain studies have proven that air turbulences are one of the most important parameters that will affect the distance of the air jet.

UPC University schema shows the air turbulences behaviour:

Optimized shape of the outlet plenum, the position and fans type, the shape of lamellas, etc. substantially affects the air jet performance.

Optimized shape of the outlet plenum, the position and fans type, the shape of lamellas, etc. substantially affects the air jet performance.

Research: Air curtains angle discharge

Tests and University studies have proven that the angle discharge helps substantially helps the air curtain to be more efficient.

When factors like wind, temperature or pressure difference causes air transfer from outside to inside, we can aim the jet towards outside some degree. Then the jet direction against the air entrance will help to keep the air outside. The trajectory of the jet will be parabolic but at the end will reach the floor approximate by the doorway. If we can’t adjust the angle discharge, the jet will be pushed in by the external air forces.

The forces parallelogram theory explains how the forces behave on a doorway. The following diagrams show the difference between air curtains with fixed lamellas against adjustable ones.

Air curtain with fixed lamellas less efficient (1)

(1) The first one, fixed vanes, where the entrance air velocity pushes the jet of the air curtain, the resultant of the parallelogram of forces is diverted inwards. This allows outside air to enter inside.

Air curtain with oriented lamellas more efficient (2)

(2) The second one, adjustable lamellas, when the air jet is oriented against the entrance, the resultant of the parallelogram forces is directed perpendicularly to the floor. This means that outside air does not enter and inside air does not escape. Besides internal temperature level is maintained.

Practical Application

Air curtain technology brings together cutting-edge engineering and everyday practicality. Using principles of fluid dynamics and aerodynamics, air curtains create a simple yet effective barrier that helps keep indoor environments clean and comfortable. These devices not only save energy but also support sustainable living. As businesses increasingly focus on being efficient and eco-friendly, air curtains are becoming a key part of modern, sustainable buildings. They help ensure that spaces stay comfortable for everyone inside.

For more information on our extensive range of Air Curtains and to discover how they can benefit your business by enhancing energy efficiency, improving indoor air quality, and creating a more comfortable environment for both employees and customers, visit Airtècnics North America's website.

airtecnicsnorthamerica.com

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