Ventilation Channels provide fresh air to the environment by expelling the polluted air in the environment. Air quality in indoor spaces where people or materials are present decreases over time. Parallel to this decrease, the ambient air begins to prevent healthy breathing. Bad weather also begins to damage the materials in the environment and leave an odor. Ventilation applications are made to solve this problem in closed spaces where there is not enough air flow. Ventilation ducts are the devices that enable these applications to be carried out in a healthy way. Air is transported through these channels and released to the environment. The bad air in the environment is thus renewed and becomes healthier. According to the air pressure, the ducts can be classified as low, medium and high pressure. The pressure here is the total fan pressure of the system and includes the losses in the ventilation devices, duct losses and vent losses.
Ventilation ducts are indispensable equipment of ventilation systems. It is the equipment that gives the air outside or the outside air in the environment. Air ducts should be designed according to the structural condition of the space, the number of compartments, factors such as dust, odor, smoke and heat in the environment. In addition to many technical issues such as the air flow to be used in these ducts, the structure of the duct, corners, duct lengths, the decoration of the space is also effective. The structure of the channels to be used should not spoil the decor of the environment. The air sucked in by the ventilators installed in the space compartments or in large areas is transferred to the inside by means of the air ducts drawn from the outside, as well as being thrown out through the ducts.
Ventilation Ducts Materials
Ventilation ducts are passages used in heating, ventilation and air conditioning (HVAC) to distribute and/or remove air. Required airflows include, for example, supply air, return air and exhaust air. Therefore, air ducts are a method of providing thermal comfort as well as acceptable indoor air quality. Channels can be square, prismatic, spiral, etc. can be grouped according to their shape. In addition, ducts can be produced from the following materials.
Galvanized Steel: The standard and most common material used in duct construction because the zinc coating of this metal prevents corrosion and eliminates the cost of painting. For insulation purposes, metal ducts are typically covered with faced fiberglass blankets or externally wrapped with fiberglass blankets. When necessary, a double-walled duct is used. The rectangular duct system is usually produced by special metal workshops. For ease of use, it mostly comes in 4 sections. Round duct is made using a continuous spiral forming machine that can make round duct of almost any diameter and any suitable length using the right forming die.
Aluminium: The aluminum channel structure is light and quick to install. In addition, custom channel shapes can be easily produced on site. The pieces are typically cut at 45°, bent if necessary to obtain different fittings, and finally glued together. Aluminum tape is applied to all seams where the aluminum foil outer surface is cut. A variety of flanges are available to suit various installation requirements. All internal joints are sealed with sealant. Aluminum is also used to make round spiral duct, but is much less common than galvanized steel.
Prizmatik Air Ducts
It is essentially an air distribution apparatus and is not designed as a duct for conditioned air. The term fabric duct is therefore somewhat misleading and fabric air distribution system would be a more precise name. However, it is easy to perceive it simply as a conduit, as it often replaces the rigid duct system. Fabric ducts, usually made of polyester material, can provide a more even distribution and blending of conditioned air in a given area than a traditional duct system. They can also be produced as ventilated or perforated. Fabric channels are available in a variety of colours, with options for screen printing or other forms of decoration, or in porous and non-porous fabric. Which fabric is suitable can be determined by considering whether the application will require an insulated metal duct. Material that removes moisture may be healthier for building occupants. Porous material also tends to require less maintenance as it removes dust and other airborne contaminants. Fabric made from more than 50% recycled material is also available, allowing it to be certified as a green product. The material can also be flame retardant, meaning that the fabric can still burn but will go out when the heat source is removed. Fabric ducts are not rated for use in ceilings or concealed attic spaces. However, there are products to be used in raised floor applications. Fabric ducting is generally lighter than other conventional ductwork and therefore puts less stress on the building’s structure. Lower weight provides easier installation. Cloth ducts require a minimum range of air flow and static pressure to operate.
Polyurethane and Phenolic Insulation Panels: Traditionally, air ducts are made of sheet metal, which is placed first and then insulated. A sheet metal fabrication shop will fabricate the galvanized steel duct and insulate it with duct wrap prior to installation. However, the duct system produced from rigid insulation panels does not need any other insulation and can be installed in one step. Both polyurethane and phenolic foam panels are manufactured with factory-applied aluminum coatings on both sides. The thickness of the aluminum foil can range from 25 micrometers for indoor use to 200 micrometers for external use or higher mechanical properties. A variety of rigid polyurethane foam panels are available, including a water-formulated panel where foaming is achieved by using water and CO2 instead of CFC, HCFC, HFC and HC gases. Most manufacturers of rigid polyurethane or phenolic foam panels use pentane as the foaming agent instead of the gases mentioned above. A rigid phenolic insulation duct system is listed as Class 1 air ducting according to UL 181 Safety Standard.
Flexible Channels: It is typically made of flexible plastic on a coil of metal wire. It has various configurations. In the United States the insulation is usually glass wool, but other markets such as Australia use both polyester fiber and glass wool for thermal insulation. A protective layer surrounds the insulation and is usually composed of polyethylene or metallized PET. It is available in diameters ranging from 4 inches to 18 inches, but the most commonly used are sizes ranging from 6″ – 12″. The flexible duct is well suited for connecting the supply air outlets to the rigid duct. It is usually attached with long zip ties or metal bands. However, the pressure loss is higher than most other types of ducts. Therefore, designers and installers try to keep their installed lengths short. Bends should be avoided in flexible ducts. Some customers choose to avoid using flexible ducting on the return air portions of their HVAC systems, but flexible ducting can tolerate moderate negative pressures. UL181 testing requires a negative pressure of 200 Pa.
PVC Low Profile Ducts: It was developed as a cost-effective alternative to steel low profile duct. Low profile ducts have been widely used in apartment and hotel ventilation for years. The growth of low profile ducting has increased significantly due to reduced usable space in ceiling voids in an effort to reduce cost. Apart from these, for external ducts exposed to the weather, the coating, aluminum or aluminum/zinc alloy coated steel sheet, a multi-layer laminate, a fiber-reinforced polymer or other waterproof coating can be applied.