Air exchange in the ventilation system occurs due to the movement of the air flow through the duct network. Depending on the use of ventilation systems, ventilation ducts can be industrial and domestic purposes. Their effectiveness is determined by the stiffness, shape and diameter of the sections. The duct design can be flexible and rigid. To ensure maximum performance of ventilation systems, it is worth getting acquainted with the calculation, methods of installation and maintenance of ducts for ventilation.
Air ducts for ventilation: forms of structures and materials of manufacture
Air ducts for ventilation are a system of pipes of various diameters and shapes of sections, interconnected by fitting elements. Proper selection of air ducts for a particular ventilation system depends on the design features of the design and design parameters, taking into account compliance with building and sanitary standards.
Air ducts for ventilation, given the use of materials for their manufacture, are divided into groups:
- metal. For their manufacture using galvanized or stainless steel. Their advantages include low weight, high degree of heat resistance, corrosion resistance, ease of installation;
- plastic. In the manufacture of such pipes as the duct using polypropylene, polyurethane, polyvinyl chloride. Among their advantages – absolute harmlessness, perfect tightness, ease of installation and maintenance. They are easy to clean and quickly wash;
- corrugated aluminum. Air ducts for ventilation of corrugated aluminum pipes are widely used due to the ability to contract and stretch in any direction and at the required angle. The design of flexible corrugated pipes is such that they retain the rigidity and shape of the section. The advantages of flexible air ducts for ventilation are the absence of numerous connections, ease of installation, and durability;
- textile. The material for the manufacture of these ventilation ducts is a synthetic fabric (polyester). Fastenings are also made of textiles. The fabric prevents the formation of condensation on the surface of the duct and does not require insulation. The advantages are the light weight of the tissue system, quiet operation, maneuverability, simple installation and disassembly. Cleaning of fabric systems is done by washing.
The generally established shapes of air duct sections are rectangular and round sections. If the design of the ventilation system has limitations on the shape and size of the section, flat-oval (elliptical) sections are used for air ducts.
The material for the manufacture of rectangular ducts for ventilation is galvanized steel. The thickness of the walls is applied depending on the size of the section and is regulated by the SNiP. Connect rectangular ducts with and without flange elements. The standard length is 1.25 m, the maximum length is 2.5 m. Due to its compact form, rectangular structures are built in a space limited in height (for example, under a suspended ceiling).
Galvanized steel, plastic, polyester metallized tape with a spiral frame, PVC with a spiral frame, aluminum foil can act as a material for circular air ducts. The diameter of the section varies from 100 to 1250 mm. Connections of flexible corrugated air ducts for ventilation are a tight lock. For convenient transportation, corrugated flexible air ducts can be compressed 5 times.
Helpful advice! The choice of aluminum corrugated duct for use in the ventilation system can significantly reduce the cost of acquiring fittings and installing the duct itself.
Possible repeated changes in the shape of flexible corrugated ducts do not violate their qualities. Spiral flexible structures are connected using flange elements and seals. Do not need additional warming. Scope of application of flexible air ducts – supply and exhaust air in residential and industrial premises.
In order to correctly calculate the diameter of the ventilation duct, it is necessary to draw up a diagram of the entire duct system. It should contain the dimensions of all rooms with an indication of their purpose. The calculation of the required amount of air is produced in m? / H. The air velocity in the natural ventilation system is up to 1 m / s.
Calculate the size of the ventilation ducts:
- air exchange rate (L) – for a kitchen this value is 90 m? / h, for a toilet and a bathroom 30 m? / h;
- average air velocity (V) is 0.3 m / s;
- the calculation of the estimated dimensions of the duct is made according to the formula:
F = L * V * 3600 (the number 3600 is used for communication between seconds and hours);
- to calculate the diameter, we use the formula:
D = 2AB * (A + B), where D is the diameter of the section, A and B are the height and width of the duct.
Calculation of the ventilation duct section:
- the calculation of the area of circular cross section produced by the formula:
S =? * D? / 400, where
S is the area of the actual section (cm?);
D is the diameter of the duct (mm);
- calculation of the area of rectangular section:
S = A * B / 100, where
S is the area of the actual section (cm?);
A, B – the height and width of a rectangular duct (mm).
Competent installation of air ducts provides for the following actions:
- correct calculation of the duct cross-sectional area;
- the choice of an acceptable method of connecting the ventilation duct elements;
- calculation of the number of fittings;
- provide a method of insulation and sound insulation.
Installation of air duct systems involves the use of various fastening elements. Depending on the types of ducts (round, rectangular, flexible), the required number is calculated.
A careful and responsible approach to the installation, operation and maintenance of air ducts is a guarantee of long and trouble-free operation of the ventilation system.