Aerodynamic testing of ventilation systems. Methods of aerodynamic testing

Aerodynamic testing of ventilation systems is an important component of the commissioning of modern buildings and structures. This statement is true both in respect of residential and subsidiary premises of apartments and private houses, and production shops. Tests are conducted after the construction is completed and all the building support systems are installed. Ventilation systems are becoming more complex and diverse, energy efficiency requirements are increasing, so the correct and more accurate adjustment of ventilation systems becomes important.

Types of ventilation

Three types of ventilation are used in buildings and structures . The simplest, at least externally, ventilation is natural. Air enters the room and is removed from it through the window and doorways, ventilation ducts.

Artificial ventilation is a system consisting of supply and exhaust systems that forcibly provide air circulation in the room.

There are options for forced ventilation, when either only the air intake (supply system) or the extractor is provided. The exhaust ventilation system removes exhaust air from the premises. Their composition, as a rule, includes air ducts, which form a network of ventilation ducts, exhaust fans and ventilation grilles.

From the outside, air can be supplied from the ventilation pipes and pipes. This is already a combined system of ventilation and air heating.

Two main types of ventilation systems can be combined in different versions depending on the purposes and tasks, forming the third kind - combined ventilation.

What kind of ventilation is suitable for a particular room is determined at the design stage, based on technical and economic considerations, based on the observance of sanitary and hygienic norms and rules.

The ventilation system of individual rooms and the building as a whole is characterized by four features. This is its purpose, service area, method of air movement and design.

Requirements for ventilation

The main purpose of ventilation is to maintain certain indices of air in the room. This is the purity and humidity level. The air masses should spread evenly, and with this the ventilation system must also cope.

From the room must be removed polluted air with carbon dioxide, dust, smoke, unpleasant odors, and to enter it - fresh, cleaned of impurities.

Air exchange in the ventilation systems is necessarily controlled.

In residential buildings, first of all, proper air exchange in kitchens, toilets and bathrooms is important, then in bedrooms and nurseries.

In industrial premises this process is vitally important when working with harmful substances or in hazardous conditions. This, for example, chemical and steelmaking. In medical institutions and veterinary laboratories, where there can be a high content of pathogenic bacteria in the air, its regular purification is necessary.

To ensure that the characteristics and composition of air comply with the standards, and aerodynamic tests of ventilation are carried out.

Test parameters

In the course of testing, firstly, the correctness of calculation of the design indicators and the correspondence of the actual data to it are checked. The air flow rate, system performance, air exchange rate are checked.

Aerodynamic tests allow you to check the operation of the process equipment and its effect on the ventilation system, adjust the flow of air in it.

During the tests, the equipment is tuned to the design capacity at all calculated points. The current figure is output after measurements and pressure comparison, which the fan develops, with the design ratio.

The detection of installation defects - loosely adhering elements, poorly fixed components, insufficient provision of protection against vibrations and noise - is also a task that aerodynamic tests of ventilation systems solve.

Examination of existing ventilation systems is carried out to check the operation of ventilation systems, to determine the cause of malfunctions and to eliminate breakages.

Documents for testing

To determine the scope of work on the verification of the ventilation system, an explication (a plan with decoding of the areas) and designation of the premises of the building in which aerodynamic tests will be conducted are needed. In addition, a schematic diagram of ventilation is drawn up, which indicates all the branches, nodes, equipment for which passports or certificates of conformity are collected.

If the existing ventilation system is checked , the passport for it is considered.

Independent control of ventilation systems

Work is carried out by workers of special laboratories accredited for carrying out similar tests on certain methods, defined in GOST. Aerodynamic tests of ventilation systems perform certified in almost every major city.

Specialists should be familiar with sanitary norms and regulations concerning administrative, residential and residential buildings, ventilation and air conditioning systems.

Passport for the ventilation system can be filled by the organization that carried out its installation. But there are few firms that test themselves and eliminate shortcomings and possible problems without external pressure. Moreover, shortcomings can appear during the operation of the building systems after a long period of time after the completion of work and completion of settlements with the installation organizations.

Therefore, the control measurements and certification should be performed by independent experts during the acceptance of the system, and not when it is required to determine why the project air balance is missing.

GOST 12.3.018-79

Methods of aerodynamic testing of ventilation systems are defined in the state industry standard, approved in 1979 in the Soviet Union and still in force.

The standard establishes methods for selecting measurement points and processing test results, calculating the measurement error in determining the airflow and loss of its pressure, and safety requirements for work.

Methods for aerodynamic testing include the choice of cross-sections in which measurements are taken. Such measurement points must be located in accordance with the requirements of GOST at a certain distance, multiple hydraulic diameter of the duct section, from obstructions to the air flow (for example, valves and grids) and its rotations in order to avoid distortion of data.

The measured cross-section can also be located in places where the diameter of the channel changes abruptly. In this case, its area is the smallest cross-sectional area in the constriction.

Testing equipment

GOST "Methods of aerodynamic testing" (No. 12.3 .018-79) gives not only a list of necessary instruments for measurements, but also its accuracy classes in accordance with state standards.

The combined pressure receptacle and full pressure receiver are used to measure the dynamic and total pressure in a fast flow at a speed greater than 5 m / s, as well as static pressure in a steady flow.

To measure air humidity, both relative and absolute, gas-dust flows from 10 to 90% of the particle content, air temperature from 0 to 50 ° C, the dew point and the speed of air flow use a combined device that includes an anemometer and a thermohygrometer. You can use these devices separately. This depends on the equipment of a specialized laboratory, for example, the thermohygrometer IVTM-7 M2 and the anemometer with the built-in impeller TESTO 417.

The manometer is used for measuring pressure, difference and pressure differences in gas and air flows.

To measure atmospheric pressure, a metrological barometer is used.

To determine the air temperature, conventional thermometers are used, and its humidity is psychrometers.

The design of instruments, especially when measuring in a dusty stream, should ensure their simple cleaning, best of all with their own hands or with a brush.

Carrying out aerodynamic tests is impossible without a funnel for measuring the volume flow of air. It is used in conjunction with an anemometer. Due to the geometry of the ventilation grids, the homogeneity and direction of the air flows necessary for measurements are violated. Therefore, with the help of this device, the flow is directed to the probe of the probe, which are located in the socket, in the part where the quality of the measurements is most satisfactory.

All measuring instruments undergo periodic checks in the bodies of standardization and certification.

Prepare the system for testing

Aerodynamic tests of ventilation networks are carried out with fully open throttling devices that are installed on both the common duct and all branches from it. Usually in the design of the air distribution units of air-handling units there are built-in regulating devices. They too should be completely open. In such conditions, with a maximum air flow, the fan motor of the forced ventilation system may overheat.

If this happens, the choke on the main stream is covered, and if it is not provided in the structure, insert a diaphragm of thin roofing steel between the flanges, reducing the flow of air on the inflow or removal of air masses.

Then, devices and equipment are installed in the way that GOST specifies. Aerodynamic tests must be carried out so that the readings of the instruments are not distorted due to radiant and convective heat, vibrations and other extraneous factors.

Devices are prepared to work in accordance with the passports on them or the operating manual.

Operating procedure

For compliance with the standards, technical documentation for the construction site in terms of heating, air conditioning and ventilation, passports and certificates of conformity for technological equipment is checked. This is the first stage from which aerodynamic tests of ventilation systems begin.

Then, the laboratory specialists determine the number of necessary measurements, develop the terms of reference, determine the cost of work and make a cost estimate.

At the next stage with the help of instruments and equipment all the necessary aerodynamic tests and measurements are carried out. The pressure and temperature of the air in the room, the dynamic, static and total pressure of the flow, the time during which the anemometer is in the flow and the change in its readings are recorded are measured.

Check the air flow rate, its humidity and flow, the loss of full pressure, the correct installation of grids and various valves in the system; Measured the excess air pressure on the staircases of the lower floors, in the tambours, shafts of elevators; As well as pressure drop on closed doors of evacuation routes; Determines the rate of removal of combustion products and much more. Methods of aerodynamic testing are governed by the state industry standard.

During the work, care should be taken to ensure that no hazardous gases or explosive concentrations are formed during the measurement.

The result of the work is duly executed documents. These are the acts and protocols of the work, if necessary, the passport of the ventilation system and individual installations.

Final Documents

At the initial examination of natural ventilation an act of such a survey is made. After checking the artificial ventilation, a protocol is made for measuring the aerodynamic parameters of the ventilation systems and a conclusion is issued on the conformity of their actual parameters with the design parameters.

Aerodynamic tests of ventilation can be completed with an act that includes information about the operation of the process equipment, its productivity, the frequency of air exchange in buildings, the operation of ventilation ducts and the throughput of air filters, and visual inspection data.

Activate the impeller type and its diameter, pulley speed and its diameter, total flow pressure and capacity for the fan; Type, speed, power, torque transmission method, pulley diameter - for the electric motor; Pressure drop, trapping percentage and throughput - for filters; Type of device, circulation circuit and type of coolant, test results for heaters And air conditioners.

The passport of the ventilation system, which requires sanitary inspections during inspections, should contain information about its purpose and location, performance and other characteristics of the process equipment, test results.

The ventilation scheme with all air distribution units must also be in the passport.

Checking the operating ventilation reveals its breakdown, the need for reconstruction or cleaning.

For what and how to check ventilation systems, methods of aerodynamic testing in general terms and documentation that is drawn up based on the results of tests - general contractors, customers of construction of residential and public buildings, specialists of management companies and heads of engineering services of industrial enterprises, this information is needed, at least, To understand what documentation to prepare, where to apply for certification and verification of ventilation systems.