Video: Air Curtain 101: Working Principle, Types, Function, Application and Selection
Figure 1: Air door curtain.
Air curtain, also called air door curtain, air door, is mainly installed at the entrances and exits of public places with air-conditioning environments. It uses a special high-speed motor to drive the fan wheel to generate a powerful air flow barrier, forming an invisible curtain.
1. What is an Air Curtain and How Does Air Curtain Work?
1.1 What is an Air Curtain?
An air curtain is a device used to create a barrier of air across a doorway or an opening. It is designed to separate two different environments, typically maintaining a temperature difference or preventing the transfer of contaminants such as dust, insects, or odors between the two spaces.
Figure 2: Air curtain fan.
1.2 How Does Air Curtain Work?
Airflow Generation
Air curtains are usually installed horizontally above the entrance they are meant to protect. They incorporate a high-velocity fan or blower system that generates a controlled stream of air.
Airflow Direction
The generated air stream is directed downward across the doorway or opening, forming a curtain of air. The direction and speed of the airflow are critical to the effectiveness of the air curtain.
Barrier Effect
The fast-moving air creates a barrier that separates the indoor and outdoor environments. This barrier helps to prevent the exchange of air, temperature, and contaminants between the two spaces.
Temperature Control
In heating applications, air curtains can be used to prevent the escape of heated air from a conditioned space to the outside. This is especially useful in cold climates to conserve energy.
In cooling applications, air curtains can help keep conditioned air inside while preventing warm, outdoor air from entering.
Contaminant Control
Air curtains are effective in preventing the entry of dust, pollutants, insects, and odors from the outside environment into the controlled indoor space.
Energy Efficiency
By creating a barrier of air, air curtains contribute to energy efficiency by reducing the need for heating or cooling in response to outdoor temperature changes.
Variable Speed and Controls
Many modern air curtains come with variable speed controls, allowing users to adjust the intensity of the airflow based on specific needs.
Some advanced models may include sensors or automation features that activate or adjust the air curtain based on factors such as door openings or environmental conditions.
Air curtains find applications in a variety of settings, including retail stores, warehouses, restaurants, industrial facilities, and even walk-in refrigerators. They provide an invisible barrier that helps maintain indoor comfort, improves energy efficiency, and ensures a cleaner and more controlled indoor environment.
Figure 3: Air curtain installation effect diagram.
2. Types of Air Curtains
The air curtain can be divided into the following types according to different classification methods.
2.1 Classified by Fan Type Used
1. Cross flow air curtain
Also known as the tangential air curtain, it has a cylindrical shape. A cross-flow air curtain is a specific type of air curtain that utilizes a cross-flow fan to generate the airflow. In a cross-flow air curtain, the fan is positioned in such a way that the air is drawn in from one side and then expelled in a perpendicular direction. This design allows for a more compact and versatile air curtain system.
2. Centrifugal air curtain
The airflow enters along the axis from one end (or both ends) of the fan wheel and is discharged from the direction perpendicular to the axis. This design allows for increased pressure and airflow control, making centrifugal fans well-suited for air curtain applications.
3. Axial flow air curtain
The airflow mainly moves along the axial direction, that is, it enters and also flows out along the axial direction. The air out of the axial flow air curtain is concentrated and the air volume is large. This type of air curtain is suitable for occasions with low installation height and large space.
Figure 4: Centrifugal air curtain.
2.2 Classified by whether the Outgoing Air Flow is Heated
According to the processing state of the outgoing air flow, it is divided into non-heated air curtains (natural air curtains) and heated air curtains. Among them, a heated air curtain (hot air curtain) can be divided into hot water heated, steam heated and electric heated according to their heat source types.
Natural air curtain
The natural type is more common with relatively simple structure. Since the air outlet is not blocked by the heater, the wind power and air volume are sufficient, and the hanging height can be high. The main goal is to block the outflow of indoor cold air in summer.
Electric heated air curtain
The electric heated air curtain is generally PTC heating. There are also water-heated air curtains. Both types of air curtains can increase the temperature of the entrance and exit.
Figure 5: Cutaway view of a tangential air curtain.
2.3 Other Types of Air Curtain
According to the diameter of the fan wheel, it is divided into 90mm, 120mm, 130mm and 150mm. Different sizes produce different air volumes.
According to the length of the body, it can be divided into 900mm, 1000mm, 1200mm, 1500mm, 1800mm, etc.
According to the installation height, it can be divided into 25, 30, 35, 40, 45, etc., corresponding to the installation height: 2.5 meters, 3.0 meters, 3.5 meters, 4.0 meters, and above 4.5 meters.
According to the direction of air supply: it can be divided into upward blowing and downward suction, side blowing and side suction, downward blowing and upward suction, upward blowing and side suction, blowing on both sides, upper (or downward) suction, blowing on both sides, suction on both sides, upward blowing, side suction, and downward blowing types.
Figure 6: The air flow direction of different air curtain machines.
3. Air Curtain Functions
Thermal insulation function
Air curtains are mainly used in places such as restaurants, shops and entertainment venues where customers often come in and out and doors need to be opened and closed constantly. This can maintain the indoor cold or warm air temperature with 60-80% efficiency. Only small temperature changes are allowed.
Anti-insect function
It can be found that most annoying and harmful insects cannot pass through the air barrier. This makes it easier and better to maintain the hygiene of fruit counters, fast food restaurants, etc.
Dustproof function
If an air curtain is installed in a sophisticated machinery factory or in the foyer of a food store or clothing store facing a busy road, it can effectively shield the dust outside and keep it clean inside.
Figure 7: Functions of the air curtain machine.
4. Application of Air Curtain
The air curtain is installed above the doors of places with refrigeration, air conditioning, dustproof and heat insulation functions, such as shopping malls, theaters, hotels, restaurants, conference halls, constant temperature warehousing and logistics centers, cold storages, freezers, operating rooms, etc. When the machine is started, it can prevent outdoor dust from entering the room, which not only facilitates entry and exit, but also prevents the exchange of hot and cold air indoors and outdoors.
At the same time, it also has the functions of preventing odor, pollution, and mosquitoes and flies. Air curtains have been widely used in electronics, instrumentation, pharmaceuticals, food, precision processing, chemicals, shoemaking, services, commerce and other industries, creating a good business environment for many businesses.
5. Air Curtain Selection Guide
1. What is the purpose of use?
Air curtains are mainly suitable for hotels, restaurants, supermarkets, cold storages, industrial workshops and other environments. Before purchasing, clarify the application industry of the product you want to buy and inform the manufacturer. The manufacturer will recommend suitable types and models to you.
2. How is the usage environment?
What is the environment of use? Whether the air is humid, whether there are corrosive gases or excessive salt in the air. If so, you must choose a stainless steel air curtain, which can extend the service life of the air curtain.
3. What is the situation at the installation site?
The choice of air curtain model is mainly determined by the width and height of the door opening. If the door height is less than 3 meters, you can choose the strong wind type; if it is less than 5 meters, you need to choose the super strong wind air curtain; if it is more than 5 meters , it is recommended to install air curtains on both sides of the door.
Figure 8: Centrifugal air curtain for cold storage.
4. Selection of the quantity of air curtain
The number of air curtains is selected based on the width of the door opening. Generally, the longest width of the air curtain is 1.5 meters. Of course, there are also 1.8 meter and 2 meter air curtains on the market. However, it is generally not recommended to use an air curtain machine that is too long, because if the impeller is too long, the force will be uneven, and over time, the impeller will easily deform and break.
If the door opening is relatively wide, several air curtains can be assembled and used. It is recommended that the installation size be greater than or equal to the width of the door opening, so that there will be no dead corners.
5. What kind of material to choose?
At present, the main materials of air curtains are spray-coated steel plates and SUS304 stainless steel. If the air curtain is used in a normal environment, the steel plate sprayed with plastic can already meet the needs of use. If used in the air with high moisture, high temperature, or heavy salt gas, it is recommended to use stainless steel air curtains, which are more reliable. Generally, food companies currently choose air curtains made of stainless steel.
6. How many ways are there to start it?
(1) Manual start: If the door height is not high, or the air curtain is generally switched off, you can choose to start it manually.
(2) Remote control start: If the installation height of the air curtain is high, remote control start can be used.
(3) Human body sensor: When someone approaches the air curtain, the human body sensor activates and the air curtain starts. When the person leaves, it automatically stops.
