Air curtains are commonly used at the entrances of many buildings, refrigerated warehouses, and food or pharmaceutical processing areas, among others. As we will explain later, this equipment creates an invisible and seamless air barrier from the top of any exterior access. But it is not limited to main doors, but also to any opening such as passage and delivery windows for fast food outlets. Its use is also frequent in loading dock doors, service doors, patio entrances, and internal separations within any building.

What are air curtains?

In essence, air curtains are ventilation systems used to prevent heat or cold loss through large doors and windows. They are also known as “air barriers”, “air screens” or “air doors”. Indeed, these units consist of a device driven by a fan that creates, precisely, an air barrier that blows at considerable speed. Being generally placed above the door and inside the air-conditioned or refrigerated spaces, it separates the outside environment from the inside. Being invisible screens, they do not prevent the access or exit of people or vehicles.

Indeed, we are talking about an effective system that also provides considerable energy savings, because air curtains reduce the cost of heating and cooling by 80%. In parallel, they preserve and protect the interior air conditioning and the comfort of the occupants of a room, since they prevent the entry of air currents. In addition, it prevents the entry of insects and the spread of bad odors.

How do air curtains work?

Now, we will briefly explain the mechanism that allows the units in question to fulfill their objective of separating the ambient temperature of a heated or refrigerated room from the outside temperature. Due to its location, above the access or window, the air that enters through the inlet grill (which often functions as a filter) is compressed by the internal fans. Later, it is propelled by means of the nozzle towards the outlet grate directed towards the access in which the curtain is placed.

It should be noted that there are two types of fans for air curtains: direct drive and belt drive. The most used are axial, centrifugal, and tangential. Likewise, the discharge is adjustable, which increases the performance of the units depending on each situation. And since we are talking about regulation, it is important to say that there are several ways to establish the airflow of these barriers. On the one hand, we can use the manual selector on the remote control that will allow us to adjust the speed and power of the ventilation.

Apart from this, there are thermostatic regulators that control the airflow based on the desired temperature. Furthermore, there are automatic activation systems by door switches. Thus, when the door is closed, the air screen may be off or running at a low intensity or with a lower climate level. When the door is open, the air curtain increases the ventilation speed, saving energy. Today, these units are increasingly connected to home automation systems for energy management in buildings.

This is the mechanism that produces the air courtains

  • First, the air is blown through the filtered intake grill after powering up.
  • The function of the filter is to protect the interior components from particles and dust. Especially the electronic components of the heat exchanger and fans.
  • The air is then directed into the fan casing and compressed and accelerated by the internal fans to expel it through the air outlet.
  • Then, due to the force with which it is propelled, the air creates a uniform flow distribution over the entire width of the discharge tube.
  • In the nozzle of the unit, there are vanes with aerodynamic profiles, whose objective is to form a constant air current, with little turbulence.
  • The air that comes out of the nozzle generates a current that flows toward the ground. Approximately 80% of the air is returned to the side that is at the entrance of the air curtains and 20% runs in the other direction.

It should be clarified that air curtains require electricity for their operation. However, they can provide net energy savings by decreasing heat transfer between internal and external spaces. This is made possible by mass transfer when air mixes at the door sill.

Types of air curtains

We have two classification criteria to differentiate the various types of air curtains. The first of them is because of its operation. According to this, air barriers can be:

  • Of continuous operation. That is, they can be activated manually or with remote control.
  • Units automatically activated with the opening of the doors, by means of sensors.

According to the orientation of the air discharge, we have that the systems can be:

  • Horizontal discharge. Although systems with air discharge from the top down predominate, there are also those that do the process in the opposite direction, from the bottom up. And it is that the horizontal devices coupled to the ground are thermodynamically more effective, however, they are the most expensive option due to the requirements of the installation and the inconvenience that can cause users when crossing the entrance to a space.
  • Vertical discharge. In this mode, the air discharge travels from one side to the other. The equipment can be installed without distinction on either side of the access.

Finally, due to the disposition of the discharged air, the air screens can be classified as:

  • Of recirculation. We are talking about units that capture and return the air discharged to the entrance of the system. Without a doubt, this is the most efficient option.
  • Not recirculating. They are those that discharge the flow of air into the environment.

Where can air curtains be used?

In addition to refrigerated warehouses, pharmaceutical companies and food processing areas mentioned at the beginning, it is advisable to install the equipment in question in:

  • Office buildings
  • Factories that require separate refrigerated or air-conditioned spaces
  • Hospitals
  • Universities
  • Train Stations
  • Airports
  • Hotels
  • Banks
  • Malls
  • Museums
  • Theaters
  • Restaurants
  • Theme parks
  • Stadiums and sports complexes

In short, it is advisable to install air curtains in all those places where the doors must remain open or be opened frequently. In fact, part of the success of some commercial chains is due to maintaining open access and great visibility into the premises. In these cases, there are usually air screens arranged at the entrances. This measure facilitates compliance with the decree on limiting the temperature in heating and air conditioning systems, recently approved by the Government of Spain since it allows for maintaining a stable temperature inside the premises.

At Intersam, we design and develop custom refrigeration and air conditioning systems

Since 1995 we have provided custom-made refrigeration and air conditioning systems and solutions for industry and commerce. During our trajectory, we have assumed large-scale and complex projects, both inside and outside of Spain.