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design detail options

1/ Membrane diffuser


Two types of diffusers combined into one fabric duct. This membrane flap is made of a lightweight, impermeable material and is attached to a selector operated by two types (heating and cooling). In the case of heating, the motor operates the diaphragm to block the cooling diffuser located at the top of the duct, and heating air is supplied through the hole arranged at the bottom. During cooling, the diaphragm blocks the lower half of the duct, and the cooling air is discharged upward through microperforations and falls down. In this way, the membrane operates two opposing diffusers in one duct.



Used to switch between two modes. It is made of standard or fire-resistant materials, depending on the specific specifications of the duct. The inner connections and outer frame are made of galvanized steel. The length is always 400mm. The flaps are powered by 220V or 24V servo motors.


Diffuser (DIFFUSER)

A membrane always blocks half of the diffuser and the other is open to supply air.

2/ Suction duct system


This system is built for square and triangular exhaust. A solid fabric duct is a must for exhaust duct systems, so use AL-rails, tension bolts, and threaded bolts to pull the duct taut. Air is drawn into the duct through a laser hole, which can be located anywhere in the duct. Adjust the spacing and size of the laser hole for an even intake of air. Suction ducts require regular and proper cleaning. The suction fabric duct can be easily removed while it is supported, and the diffuser is easily separated using a zipper and reassembled after washing. If NMI material is used, the duct has antibacterial resistance.


Note : Only NMS, NMI, and NMR materials can be used

3/ Insulated duct


Insulated ducts are used to reduce heat loss when passing air to the diffuser. It uses a soft polyester material with a thickness of 40mm and is sewn between the inner and outer two layers of the duct. All PRIHODA materials are suitable for external use and can be easily integrated with other systems. During the manufacturing process, the insulation thickness of the existing 40mm is reduced to about 20mm. The maximum possible heat transmission coefficient is 1.8 W/m2K. The standard length of 2000mm is manufactured, and the diameter is produced from 250mm or more. Insulated fabric ducts make an excellent soundproofing material, reducing the noise generated by vibrations. Please contact the head office for details.



4/ double duct


Condensation is mostly avoided with double ducting. The fine airflow (approximately 1‰ of total airflow) ensures that the inner duct is in place. The coefficient of heating airflow reaches up to 3.5 W/m2/K.

5/ Defrost Damper


The defrost damper (DeDa) blocks the front of the cooler during defrost to prevent the defrost steam from escaping to the front of the fan. This helps to make the defrost faster when the fan is not working. Made of NLW material, which provides adequate cooling and prevents frost formation.


1. When the fan operates, the damper opens and the supply air flows, and the air volume decreases little by little due to the damper's adjustment. Fine adjustment of the airflow depends on the airflow bend at the fan and damper installation.  


2. When the fan stops working, the damper retracts and hangs in front of the fan connector. At this time, the fan stops and the air inside the cooler continues to flow through the cooler, which causes the fan blades to continue to rotate. This helps defrost work faster and more effectively.  


3. At the end of the damper there is an adjustable cord with a buckle. You can use this to adjust to the diameter of the outlet. It is important to balance the damper by adjusting the cord over the period of use. This ensures that there is no tremor or movement to minimize pressure drop.

6/ Anti-static design


The anti-static design is used to isolate static electricity in areas where static electricity should not build up. An antistatic system conforms to four criteria:


1. Conductive fabric (PMI and NMI are suitable for conductive material)

2. A high-conductivity strip is installed in the duct.

3. All zippers are made with metal joints.

4. The grounding point is the end of the duct.


7/ Combined semicircular duct


Semicircular diffusers connected side by side in a horizontal orientation. Even a duct with a relatively low height allows for a lot of air exhaust.


8/ Wide range of air distribution with nozzle


   small nozzle

A small nozzle can be used to form a directional air pattern. The airflow is expandable by about 25% compared to a standard laser hole (normal hole), and air dispersion is minimized. Ø Standards are 20, 30, and 40mm, and there are two types, industrial and premium.


Precautions:  Only PMS, NMS, PMI, PMIre, NMI, NMR available



















  large nozzle

  Large nozzles (increasing diameter size) allow air to reach long distances. Range may exceed 20m depending on static pressure and temperature difference. Nozzles can be fixed or adjustable and each nozzle has a very similar shape; The adjustable nozzle is adjustable up to ±45° using 4 belts, and for appearance consideration, the belt can be hidden underneath the finished end. Adjustable dampers are used on all nozzles and allow for different airflow patterns.  

9/ Adjustable product


   Length Adjustment - Pleated

The adjustable length bellows (corrugation) is made of 8 types of materials and is uniformly sewn around the circumference of the round duct.

All 8 types of bellows can be adjusted (increased or shortened) to manually adjust the duct length to suit your installation requirements.



- The length adjustment part can be adjusted up to 1500mm and at least 500mm.

- The duct diameter at the corrugation can be increased up to 25% of the duct diameter in consideration of the pressure loss.

- Applicable only to round ducts with a diameter of >250mm and the minimum duct diameter must be over 250mm.

- Only PMI, PMS, NMS NMI, PLI, PLS, NLI, NLS materials are available.

- Adjustable duct length is difficult to adjust when both enlarged cord suspensions are installed.













  angle adjustment (arch) - curved

  The adjustable length bellows (corrugation) is made of 8 types of materials and is uniformly sewn around the circumference of the circular duct (length adjustment - same as corrugated type). Partially reducing the length of the belt will bend in that direction. By adjusting the bellows in a certain direction according to the proper length of the duct, the angle of the end can be adjusted.














  Adjustable laser hole (normal hole)

This product allows you to manually adjust the aperture size and airflow of the diffuser. The picture below explains how it works. The actual diffuser size and hole pattern will be completely dependent on the requirements of the project. You can use Velcro to fix it in any position you want.




 removable adapter

The connection opening on the top of the semi-circle or quarter circle can be made to move, and the opening can be adjusted up to 80mm. A movable adapter is useful when the air supply inlet of the fabric duct is slightly out of position than expected.






  Air diffuser lantern


Lantern diffusers are designed to supply air to high spaces, such as ceilings. It is installed only in the vertical direction, and air is supplied in 6 horizontal directions. A vertically stretched string is used to adjust the flow rate.



10/ Solutions to Airflow Problems


   Equalizers - Balancers

At the beginning of a fan or fabric duct, the main function of the equalizer is to keep the airflow constant. The equalizer installation can prevent the vibration of the fabric duct, however, additional pressure loss must be considered when installing the equalizer.














  Backflow Pockets

  The backflow type pocket hole is designed to prevent the deflection of the airflow discharged from the normal hole. This solution is based on the intersection of two air streams with similar acceleration forces. The closer the hole is to the pocket, the more air is discharged at a certain angle by the backflow pocket hole, and it balances the air deflection. 


  The damper is a conical shaped product made with a laser hole (normal hole). The inlet is the same size as a normal duct, but the outlet can be adjusted to a smaller size using an adjustable belt. If the discharge port is enlarged to the maximum, the pressure becomes 0, whereas if the discharge port is completely closed, the pressure in that part will drop to the maximum. The damper setting can be adjusted at any time using the zipper depending on the situation in which the duct is being used. When the damper is installed in the duct, the static pressure in the duct is equalized and the air is discharged evenly. Dampers are also used when connecting to other systems using fabric nozzles or connectors.  





 Cooling Enhanced Diffuser

When applying cooling for a ∆t ≥ 6° k, a horizontal air pattern in the fabric duct is recommended. This method can be fabricated by making strip-shaped micro-holes in both ducts at 90° and 270°. When using a horizontal air pattern, you must operate at a specific speed to prevent rapid air descending. If sufficient discharge speed (provided by static pressure) is given, 400W of cooling is supplied per 1m length of duct, and at the same time, the speed can be maintained at less than 0.2m/s in a given space. The airflow patterns are detailed in the photos below, please contact us for specific application instructions.  















  Anti-deflector is a product to prevent the backflow of the airflow discharged from the micropore with a size slightly larger than the thickness of the duct. This product is made of fine mesh and wrapped inside the diffuser. We recommend that you use this product whenever reflux occurs on our software.   





11/ Duct shape reinforcement


   Tensioners - tension control

AL-Rail's screw tensioner is used to flatten the fibers' folds. Fabric ducts are stretchable within 0.5% of their original length. Therefore, the initial fabric duct may be 0.5% shorter than the length specified in the drawing. So the proper length is adjusted through the tensioner. The installation procedure is described in the assembly instructions inside the packaging box.















  Use end tensioner (when duct length is short and hanger installation is not required)









   Curved Rack (Arcs)

  The curved rack is used to extend the shape of the diffuser to some extent without supply air. Both ends of the rack are inserted into the pockets sewn inside the fabric duct, and are fixed by attaching them with vecques. The rack can be disassembled for washing. Racks are less expensive than tire types. 


Tires can be crafted in:

1. Flat aluminum strip - No shape deformation, can be used in all dimensions.

2. Heat-resistant plastic

- 20% or less of shape deformation

- Used as PMI, NMI, PMS, NMS, PLI, NLI, PLS, NLS, NLF, NMF, NMR, NLW material – Diameter 400 - 1250 mm

- NHE material and heat-insulating duct  – Diameter 400 - 710mm

3. Stainless Steel Rod - No shape change, can be used in all sizes.


Products other than round tires can only be made of aluminum.


They are installed inside or outside with a default spacing of 500mm. It can be firmly tightened using Velcro, and can be attached or detached while using.










   internal tensioning system

The internal tensioning system is designed to maintain the appearance of the duct with and without supply air. It consists of a console and a tensioning ring that holds it in shape and is inserted into an aluminum rail. By turning the axial console screw, the tensioning ring pulls the entire duct taut. The basic reinforcement ring is a part included with this system.










12/ Winch


When a winch is used, it is possible to install the entire fabric duct by installing it on only one end. This feature makes installation or dismantling very simple. This is especially useful when installing on the ceiling of a swimming pool or in hard-to-reach places.



13/ Print


You can print something like your logo on the outside of the duct. You can also add Part Identification Numbers to make installation and use easier.

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