CFW is an air technology specialist providing high quality air curtains, fan and blower-powered products and ventilation solutions for commercial and industrial applications. We offer economical and robust equipment as well as design, selection, installation and after-sales services. Years of experience with blower design and installation mean that we can make custom air curtains for your application. We offer competitive prices and a variety of parts.
Air Curtains and their Applications
Air curtains (also known as air doors) are used to separate two spaces, for example at the entrance of a building. The usual means is to blow air down across the opening with an axial or cross flow fan.
Air curtains have various uses, including
- Minimizing the influx of outside air, dust or insects. Restaurants, bars and food-related businesses in particular benefit from keeping flying insects out, making compliance with health regulations easier. Some reports also indicate that rodents may be deterred.
- Preventing draughts (e.g. from cold stores) from entering other areas and causing discomfort and lower staff morale.
- Reducing wind chill by adding heated air (this requires ancillary equipment).
- Decreasing the load on HVAC or refrigeration systems where doors need to be kept open.
- Functioning as a component of air curtain destructor (ACD) systems. Used to burn debris from vegetation, ACD is much more efficient and environmentally friendly than using an open fire.
Restaurant, cargo and customer doors, drive-through windows, refrigerated rooms and aircraft hangar entrances might all use air curtains. The need to provide easy access to public buildings and to increase trade means that such entrances must often be left open. Leaving doors open in retail shops and supermarkets has been shown to increase trade by as much as 40%. However, air conditioning in these environments have high costs which are increased by open entrances. Air curtains can be used to reduce these costs.
Saving Money using Air Curtains
Air curtains are most often associated with retaining heat in buildings in cold climates, but can also result in significant energy savings where cooled air is to be retained in hot climates, such as South Africa in the summer. Rising electricity costs make them an increasingly attractive choice.
While automatic sliding doors are sometimes used, they are not energy-efficient, either in terms of power use or thermally. Air curtains consume little electricity for doorway-sized openings (about 300 W) and have a relatively low capital cost. Over the long term, air curtains save money when buildings need to be temperature-controlled and still keep entrances open often. Depending on outside conditions, inside temperature regulation, and the model of air curtain selected, it may be possible to recoup one’s expenditure in as little as a year.
Since air is an excellent insulator and since the mixing of inside and outside air is prevented by the air curtain, air curtains help to maintain temperature differentials between the inside and outside of a building. They also help to prevent moisture transfer between the two spaces.
Most switch on automatically when the door is opened and switch off when it closes. Pressure differences between the spaces, and windy outside conditions, reduce their effectiveness.
If a heating element is added, power consumption will be higher. However, air curtains also help to recirculate heated air, preventing it from settling near the ceiling of a room. This increases the efficiency of any heating that is done. Heat recovery devices such as heat pumps can be used in conjunction with air curtains to lower energy costs significantly.
Selecting and Using Air Curtains
Both standard and custom designs exist. Two or more units can be installed for wide openings. Usually, units are merely bolted to the side of a building, but various installation options exist. The type of installation that is needed partly depends on the application.
Commercial applications, such as customer entrances, require lower face velocities (air speeds) to ensure the comfort of users. Industrial buildings often use high face velocities, as they are more effective at preventing air transfer between the spaces. The most effective kind of air fan, in which the air is recirculated by ducts to the top fans, is ideal for new buildings but more difficult to install in existing ones. Most of the air should return to the space inside the building, while about 30% of the air volume should leave the building to prevent cold draughts near the floor. Temperature and pressure differentials between the two spaces should be calculated to determine the air flow and thus the required velocity of the air curtain’s airstream. This will ensure that the air curtain is correctly sized.
Air curtains used to prevent the entry of flying insects should divert the air stream to about 20° from the vertical using a nozzle and be capable of producing air velocities of at least 8 m/s across the whole opening. This is a relatively “heavy duty” use, and some people might find the airstream produced uncomfortably strong.
In cold stores and refrigeration facilities, doors are often open to store or move perishable products. This can result in considerable losses of cold air, with all the attendant energy and maintenance costs and possible product losses. Air curtains provide a solution: while temperature control is maintained in both staff and refrigeration areas, the access and 100% visibility they provide mean that workers operating forklifts need not get off to open and close doors. Work becomes more productive and energy efficient. The air velocity of cold room air curtains needs to be high enough to compensate for outward pressure generated in the room by air spilling back into the room, thus stabilising the air at the floor. At the same time, there is a tendency for ice to be formed at the floor if air velocities are too high in refrigeration applications. For this reason, the velocity must be carefully controlled, usually with louvers or by using a variable speed fan. To eliminate drafts, air flow must be vertical. The air curtain can be mounted on either side of the cooling space while still being effective. Some experimentation is usually necessary to find precisely the right angle, volume and air velocity for your air curtain.
Contact our sales department for further information about our air curtains.
Cape Town, South Africa (HQ)
3 Parin Road, Parow Industria, 7500, Western Cape
Johannesburg, South Africa
4 Chilworth Road, Founders View North, Modderfontein, Edenvale, 1645, Gauteng
Cape Town, South Africa (HQ)
T +27 (0)21 931 8331
F +27 (0)21 931 3165
Johannesburg, South Africa
T +27 (0)11 452 5830 / 5146
F +27 (0)11 452 5132