Air socks are used both for air distribution and transportation with nearly identical efficiency.
- through permeable fabric;
- through microperforation – holes less than 1 mm in diameter;
- through perforation – holes over 1 mm in diameter;
- through an exit adapter: air exits in a direction perpendicular to the flow's direction – through an open end – the air is supplied into another fabric duct.
- Perforated ceiling panels (diffusers)
Various methods exist for air distribution in textile systems.
Microperforation provides a means to supply and disperse air at a small distance away from the duct’s surface while perforation, of a larger diameter, offers the ability to provide air emission a greater distance away and in a particular direction. If there is a need, one can combine dispersed and directional air emission.
The vast majority of ventilation systems works with a small excess pressure somewhere between 70 and 300 Pa. However, the parameters of facilities, in particular the distance from the ducts to the work area, may differ greatly. Air distribution conditions also differ, for instance, for air conditioning, heating, or ventilation. Correspondingly, this could involve emitting cooled air in a facility with a low ceiling; meanwhile, warm air in a facility with a high ceiling must be emitted differently. Since when air distribution of the same principle is used in these two cases, the speed of the air in the work area will differ greatly.
Depending on where the textile ducts are used and for what purposes, TEXAIR uses different air distribution systems for its projects.
Low-speed air distribution system
The primary feature of these systems is the emission of air with a relatively low-range stream distance. The air is emitted through micro holes created by a laser on the surface of the fabric. Meanwhile, both air permeable material and air impermeable material can be used. The outflow of air through each individual micro hole is very little, so the air loses its speed very quickly as it exits.
The result of this is that there is practically no draft, which is especially important while the cool air is being supplied. In the event that such air distributors are placed on the ceiling, the cold air will slowly descend.
However, should one choose such a system of air distribution, one should keep in mind that due to the short range of microperforation, there will be a relatively low degree of mixing in the air. There are also restrictions in the air’s emission for each line meter in such ducts, so, often times, when the dimensions of a cooler room are particularly large, or when the company needs to emit a significant amount of cold air, they rather choose a combination of microperforation and additional perforation with a certain specially calculated diameter of holes.
The slow speed of the flow of air conditioning in the work zone is one of the main conditions not only for people to comfortably reside in the room, but also for many technological processes. These may be the processes of cheese ripening, cutting and packing sausages and meat products, prepackaging fruits and berries, and much more. In such facilities air socks play not only a ventilation role but can also be a crucial part of the technological process.
As an example of the efficiency of such air ducts, one can take a look at a sausage ripening factory. Sausage is stored suspended in a room with a particular temperature and humidity. Meanwhile, along with fermentation, a process takes place in which the moisture is extracted from the product, so in the event of an improperly calculated supply system, the air can blow against the product with a higher speed and the moisture removal process may take place quicker than needed. Even if these losses amount to a mere several excess grams per kilogram of the finished product, in the event that the factory has a volume of dozens of tons, this could entail substantial financial losses for the producer.
High-speed air distribution system
For high-speed systems, the recommended height of ducts’ suspension above the floor level ranges from 3 to 10 meters. Such air ducts are most efficient when used for ventilation and air heating.
This system is distinguished by the much greater range of its air stream compared to the low-speed system.
The physics of the air distribution process itself also differs. Due to the excess pressure inside the fabric air duct, the air exits the holes at a high speed, the diameter of which varies from 4 to 12 mm. The high speed at which the air exits the holes and the significant volume allows the air flow to reach the work area located at a significant distance away from the textile air duct. The way this system operates is similar to the operation of an injector in a modern combustion engine. With the help of the injector, a well-blended mixture of air and gasoline steam is fed into the engine. In a similar way, the movement of the air stream takes place from the holes of the duct in a high-speed system. This injection principle provides for the high-quality mixture of the air located in facility. Meanwhile, the friction of the layers and the whirling of the air flow renders the heat (cold) emission process more efficient than in traditional systems with grids and diffusers.
One could provide as an example an air heating system for a finished product warehouse implemented using air socks. At the project’s implementation stage, the customer encountered difficulty with the use of metallic ducts, since the construction that they needed to attach them to was self-supported. It couldn't handle the weight of the metallic ducts and it would be financially very expensive to attach them onto additional columns. Yet another condition was the location of the ducts which were 7 meters above the floor in order to avoid impeding the movement of the loading equipment. In order to tackle this task, air socks were used which, due to their light weight, were attached right onto the roofing construction. The resulting implemented high-speed air heating system also came with significant financial implications for the customer...
Hybrid type air distribution
The hybrid type air distribution system combined low-speed and high-speed types. Its use is worthwhile in cases where the objective is to distribute air in a facility into different work areas at once, located at varying distances from the duct emitting the air. Meanwhile, the speed in these work areas will not exceed the required values. To ensure this, a calculation of the air distribution is computed for each zone separately, taking into account the distance of each work zone from the emitted air, the required air speed in each zone, the static pressure figure in the channel, as well as the temperature data.
Such types air distribution find use in facilities with a large amount of equipment and zones for servicing where people work as well as in facilities where it is technically impossible to divide supplied ventilation according to different zones.
Air socks are used both for air distribution and transportation with nearly identical efficiency. When they are used as a transition system, they are made out of material with low air permeability in order to avoid the formation of condensation. To combine it with metallic ducts, various shapes of elements will be used, which are also manufactured out of fabric.
In the drawing transition elements are shown in bright grey while the emission elements are in blue.
If a significant amount of fresh air is not required in the facility according to the air exchange calculation, but at the same time it occupies large areas that are not being used for a productive amount of work, then equal air emission across its entire volume may not be well-advised. In such cases, air socks are used with the ability for local air emission along with transition sections. This is especially crucial in office facilities without borders where workspaces alternate with hallways. TEXAIR air ducts can be designed in such a way as to ensure the most comfortable possible conditions for employees and implement them in one of the office facilities. If the flow of air is constant along the entire length of the fabric air ducts, then in order to ensure comfortable conditions for the employees, one has to go with the a more powerful and expensive setup; however, in the case of local air emission, there is no need. One can do without the former and adopt a much more low-cost solution.