Design of ventilation and ventilation elements
Efficient ventilation is considered as one of the most important infrastructure components for modern manufacturing and housing. It is quite difficult to imagine the life in the gas polluted metropolitan city without air conditioning and ventilation units. You may say that town dwellers live and work in almost hermetic premises due to the use of plastic steel windows.
A well-designed ventilation helps air reach for the nooks in the flat, office or manufacturing premises. It also helps in air cleaning of dust and smoke and, if necessary, maintaining the required humidity level. Modern ventilation systems help maintaining temperature indoors by taking it from the exhaust air, thus helping save on heating expenditures.
At the process of ventilation engineering we take into account not only the customer needs and budget but also the existing regulations. The pricing of the works is straight dependent upon the complexion of the project and its specification.
The main stages of ventilation engineering are:
- Drawing a ventilation connection scheme
- Calculation of necessary air exchange
- Aerodynamic analysis of the air system
- Parameters component calculation
- Control scheme and automated system development
- Equipment selection
The engineering process begins with the selection of a ventilation system.
Ventilation systems are classified as follows:
- By the air deflection method (artificial and natural systems)
- By the designation (combined input-exhaust systems, exhaust and input systems)
- By the construction (mono-block and composed systems)
Natural ventilation is one of the simplest ways of air exchange. In this system air flows without any use of equipment. The flow is implemented by the air difference indoors and outside the building and also by means of the wind intensity. External air flows inside through open ventilation windows, window openings, openings in the structures and is removed by the exhausting channels. As the performance of the natural ventilation is directly dependent on the natural factors, its efficiency is quite unstable. That’s why the use of that type of ventilation is limited by dwelling houses and premises of a low air change rate. To increase efficiency of natural ventilation it is recommended to install inlet valves and ventilation grids on the inflow side. Moreover, it is also recommended to install deflectors (special caps for ventilation ducts) on the exhaust side.
Artificial or mechanical ventilation is the forced way of changing processed air into fresh air. The processed air is removed and the fresh air is fed by means of ventilators. Dust and noise penetration from outside is minimized what makes the comfortable conditions. The mechanically driven input-exhaust ventilation system allows to install balanced air parameters regardless the external temperature. If necessary the air is processed by the following ways: heating, cleaning, drying, cooling, wetting, etc., - all the activities which are difficult to execute on the naturally aspirated ventilation.
General ventilation is commonly used in dwelling and administrative buildings and also in service industry. This type of ventilation is a combination of natural and mechanical ventilations. By using it one can drop power costs on large process areas.
Input ventilation provides a fresh air flow from outside. To do this one may use a calorifer to heat the air, a system of filters to clean air from dust and an evaporator to cool the inlet air.
Exhaust ventilation implements removal of a heated, polluted and processed air from the premises.
We engineer both input and exhaust ventilation systems with the required balance calculated. Input or exhaust ventilations are to be executed separately. Lack of air inflow or exhaust is fulfilled by the natural way. In case there is only an exhaust system installed without the inlet then the air flows inside from the neighboring premises through the openings, transfer grills and gaps in doors and windows. And vice versa, in case there is only an input system without extraction then the air is removed or flows into neighboring premises the same manner. Both the input and exhaust ventilation systems may process local areas (spot ventilation) and all the premises (general ventilation).
The input-exhaust ventilation system is used in the premises where a fresh air from outside is required. The polluted air is removed from the premise simultaneously. This type of ventilation is more effective. It regulates air change inside what allows power costs to be saved by heating the inflow air and by recovering heat. The process is executed with special recuperative heat exchangers.
Local ventilation systems provide air supply to the particular areas (zonal input ventilation). At the same time the contaminated air is removed only from the source of contaminations without spreading all over. Zonal suction units are used for extraction. They may have different covers such as covers in the form of boxes or in the form of lathe housings.
Mono-block ventilation systems are used as a combination of all the system components in one sound insulating unit. They are divided into input-extract systems and input systems. An input-extract unit may be equipped with an integrated recuperative heat exchanger what is necessary for saving energy.
Advantages of the mono-block ventilation system are the following:
- The sound insulating housing secures all the elements what allows the noise level to be dropped making the unit quite compact to be placed in any dwelling areas.
- The functional balance is implemented by the meticulous selection of all the elements with the compatibility tests executed.
- Small sizes and easy installation process.
- Low cost and a small number of necessary consumable materials.
Composed ventilation systems consist of a fan, separate components (an automation system, a silencer, calorifer, filters, etc.) and accessories. As a rule such a system is assembled in a separate ventilation chamber due to its big dimensions and a high noise level. If the unit possesses middle characteristics it may be mounted at the ceiling area. The main advantage of such a system is its versatility, It may be used both in the flats and trade centers.
The key elements of the ventilation systems
External air flows into the ventilation system through the air intake. Air intakes may be round or rectangular depending on the form of the inlet air conduits. Air intakes prevent from rain drops, leafs and foreign particles getting in and also serve as a design element.
To prevent the external air from getting inside when the system is off it is recommended to install an air valve. An air valve is necessary in winter time to adjust cold air flowing from outside. As a rule, input ventilation systems are equipped with electrically driven air valves what makes the system control fully automated – the valve gets open when the ventilation system is launched and vice versa.
To prevent the ventilation system from over, dust, insects it is recommended to install a filter. As a rule, one coarse mesh filter blocking particles with the size of more than 10 microns is enough. In case of high air purity requirements fine mesh filters which block particles with the size down to 0.1 micron may be mounted. The filter material of the coarse mesh filter is the cloth which is made of synthetic fibers, for example, acryl. It is recommended to clean the filter once a month. A differential pressure sensor may be installed to control the air pressure difference on the input and output of the filter.
The blower is the key element of the mechanical ventilation system. It is selected depending on the required performance (amount of the changed air) and the total pressure. Blowers are divided into axial blowers (household standing blowers), radial blowers or rotary blowers. Axial blowers provide sufficient performance but generate a low total pressure, that’s why the air speed reduces significantly when the air flows through the intake grids, valves, etc. Extensive air duct systems use radial blowers of a high air flow pressure. Dimensions and noise level also play an important role in the blowing system. As a rule, such characteristics depend on the model.
A calorifer or air heater serves for air heating in cold periods of the year. Calorifers are divided into hot water heaters, steam heaters, glycol radiators, gas-fired air heaters and electric calorifers. Electric calorifers are recommended for small input air systems because the mounting procedure requires less costs. And vice versa, structures of large areas require hot water calorifers.
As the blower is the source of noise it is recommended to install a silencer to prevent the noise from spreading all over the air ducts. To reduce the noise a sound absorbing material is used. This may be mineral cotton, fiber glass and other sound insulating materials of the set thickness. One or several walls of the silencer are finished with the absorbing material.
To spread the air flow over the premises an air network is used. Such an air network consists of air ducts and precast elements (fittings, crossings and T-joints).
The main characteristics of the air ducts are the following:
- Cross-section area
- Form (circular or rectangular)
- Rigidity (rigid, semi-rigid and flexible)
The flow speed in the air duct shall not exceed the set parameters, otherwise the air duct shall start generating noise. That’s why the dimensions of the air duct shall be calculated based on the air duct calculated value and the maximum allowed air speed. Such rigid air ducts are manufactured of galvanized steel. Semi-rigid and flexible ducts are manufactured of the multi-layer aluminum foil of a round form. These air conduits are used on the short-distant areas – basically to connect air distributors due to their high aerodynamic resistance which is caused by the irregular inner surface.
The prepared air flows into premises through air distributors. As a rule, air intake grids (round and rectangular, wall- or under ceiling mounted units) or diffusers serve as air distributors. The main function of air distributers is an equal distribution of the air flow along the premise or an individual adjustment of the air flow as well as the use as design elements.
The use of all mentioned functions is possible by the qualified engineering and assembly. The neglected quality results in additional costs, discomfort and even a premature failure.
Our top-ranked specialists will help you find the engineering solutions for your projects.
Call +7(812)740-47-75 or write to info@bengs.ru.
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