Aerodynamic tests of ventilation systems are an important component of the commissioning of modern buildings and structures. This statement is true both in relation to residential and utility rooms of apartments and private houses, and production workshops. Tests are carried out after the construction is fully completed, and all 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
In buildings and structures, three types of ventilation are used. The simplest, at least outwardly, ventilation is natural. Air enters the room and is removed from it through window and doorways, ventilation ducts.
Artificial ventilation is a system consisting of supply and exhaust units, which forcibly provide air circulation in the room.
There are options for forced ventilation when either only an air flow (supply system) is provided, or an exhaust hood. Exhaust ventilation systems remove 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.
Heated air can be supplied through ventilation pipes and mains from the outside. This is already a combined ventilation and air heating system.
The two main types of ventilation systems can be combined in different versions, depending on the goals and objectives, forming the third type - combined ventilation.
What kind of ventilation is suitable for a particular room is determined at the design stage, on the basis of technical and economic considerations, based on compliance with sanitary standards.
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 moving air and design.
Ventilation requirements
The main purpose of ventilation is to maintain certain air indices in the room. This is cleanliness and humidity. The air masses must spread evenly, and the ventilation system must also cope with this.
Contaminated air with carbon dioxide, dust, smoke, unpleasant odors should be removed from the room, and fresh, cleaned of impurities, to enter it.
Air exchange in ventilation systems is necessarily controlled.
In residential buildings, the first thing that matters is proper air exchange in the kitchens, toilets and bathrooms, then in the bedrooms and the nurseries.
In industrial premises, this process is vital when working with hazardous substances or in hazardous conditions. This, for example, chemical and steel production. In medical institutions and veterinary laboratories, where there may be a high content of pathogenic bacteria in the air, regular cleaning is necessary.
In order for the characteristics and composition of the air to comply with the standards, aerodynamic tests of ventilation are carried out.
Test parameters
During the tests, they check, firstly, the correctness of the calculation of design indicators and their compliance with the actual data. Checks the air flow, system performance, air exchange rate.
Aerodynamic tests make it possible to check the operation of technological equipment and its effect on the ventilation system, to regulate the air flows in it.
During testing, the equipment is tuned to design capacity at all design points. The current indicator is displayed after measuring and comparing the pressure that the fan develops with the design coefficient.
Identification of installation defects - loose fit elements, poorly fixed components, insufficient protection against vibration and noise - this is also the task that aerodynamic tests of ventilation systems solve.
A survey of existing ventilation systems is carried out to check the operation of ventilation systems, determine the cause of malfunctions and eliminate damage.
Testing Documents
To determine the scope of work on checking the ventilation system, an explication (a plan with deciphering the areas) and the purpose of the premises of the building in which aerodynamic tests will be conducted are needed. In addition, a ventilation scheme is compiled, where all the branches, components, equipment for which passports or certificates of conformity are collected are indicated.
If the operating ventilation system is checked , the passport for it is also considered.
Independent control of ventilation systems
The work is carried out by employees of special laboratories accredited to conduct this kind of tests according to certain methods defined in GOST. Aerodynamic tests of ventilation systems are carried out certified in almost every more or less large city.
Professionals should be well aware of sanitary norms and rules regarding administrative, domestic and residential buildings, ventilation and air conditioning systems.
The passport for the ventilation system can be filled out by the organization that performed its installation. But there are few firms that test themselves and eliminate shortcomings and possible problems without external pressure. Moreover, shortcomings can occur during the operation of building systems over a long period of time after the completion of work and the completion of settlements with installation organizations.
Therefore, control measurements and certification should be carried out by independent experts during the acceptance of the system, and not when it is necessary to determine why there is no design air balance.
GOST 12.3.018-79
Methods of aerodynamic testing of ventilation systems are defined in the state industry standard, approved back in 1979 in the Soviet Union and still in force.
The standard establishes methods for selecting measurement points and processing test results, calculating measurement errors in determining air flow and pressure losses, and safety requirements for work.
Aerodynamic test methods include selecting the cross sections in which measurements are taken. Such measurement points in order to avoid data distortion should be located in accordance with the requirements of GOST at a certain distance, a multiple of the hydraulic diameter of the duct section, from obstacles in the air flow path (for example, valves and grilles) and its turns.
A measured cross-section can also be located in places of a sharp change in the diameter of the channel. Moreover, its area is considered to be the smallest sectional area in the narrowing.
Test Equipment
GOST "Methods of aerodynamic testing" (No. 12.3. 018-79) gives not only a list of the necessary equipment for measurements, but also its accuracy classes in accordance with state standards.
The combined pressure receiver and full pressure receiver are used to measure dynamic and total pressure in a fast flow with a speed of more than 5 m / s, as well as static pressure in a steady stream.
To measure air humidity, both relative and absolute, gas and dust flows from 10 to 90% of the particle content, air temperature from 0 to 50 ° C, dew point and air flow velocity, a combined device is used, which includes an anemometer and a thermohygrometer. You can use such devices individually. It depends on the equipment of a specialized laboratory, for example, an IVTM-7 M2 thermohygrometer and an anemometer with a built-in impeller TESTO 417.
The pressure gauge is used for measuring pressure, pressure difference and pressure drops in gas and air flows.
A metrological barometer is used to measure atmospheric pressure.
Conventional thermometers are used to determine the air temperature, and psychrometers are used for its humidity.
The design of the instruments, especially when measuring in a dusty stream, should ensure their easy cleaning, best with their own hands or with a brush.
Aerodynamic testing is not possible without a funnel for measuring air volumetric flow. It is used in conjunction with an anemometer. Due to the geometry of the ventilation grilles, the uniformity and direction of air flow necessary for measurements are violated. Therefore, using this device, the flow is directed to the probe sensor, which are located in the socket, in that part where the quality of measurements is most satisfactory.
All measuring instruments undergo periodic inspections in standardization and certification bodies.
Preparing the system for testing
Aerodynamic tests of ventilation networks are carried out with fully open throttling devices that are installed on the common duct and on all branches from it. Typically, the design of the air distributors of the supply systems has built-in control devices. They must also be fully open. In such conditions, with a maximum air flow, the fan motor of the forced ventilation system may overheat.
If this happens, the throttle on the main stream is covered, and if it is not provided for in the design, a diaphragm made of thin roofing steel is inserted between the flanges, reducing the air flow at the inflow or removal of air masses.
Then, instruments and equipment are installed as stipulated by GOST. Aerodynamic tests must be conducted so that the readings are not distorted due to radiant and convective heat, vibration and other extraneous factors.
Devices are prepared for operation in accordance with their passports or the instruction manual.
Operating procedure
For compliance with the standards, the technical documentation for the construction object is checked in terms of heating, air conditioning and ventilation, passports and certificates of conformity for technological equipment. This is the first stage from which aerodynamic testing of ventilation systems begins.
Then, the laboratory specialists determine the number of necessary measurements, develop the terms of reference, determine the cost of the work and make an estimate of the costs.
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 in the room, the dynamic, static and total pressure of the flow are measured, the time during which the anemometer is in the flow and the change in its readings is recorded.
The air flow rate, its humidity and flow rate, the loss of full pressure, the correct installation of gratings and various valves in the system are checked; excess air pressure is measured on the stairwells of lower floors, in vestibules, elevator shafts; as well as the pressure drop across the closed doors of the escape routes; Determines the rate of removal of combustion products and much more. Aerodynamic test methods are regulated by the state industry standard.
During the work, it is necessary to ensure that during the measurement process hazardous gases or explosive concentrations are not formed.
The result of the work are properly executed documents. These are acts and protocols of the work, if necessary, passports of the ventilation system and individual installations.
Final documents
During the initial examination of natural ventilation, an act of such examination is drawn up. After checking the artificial ventilation, a protocol for measuring the aerodynamic parameters of the ventilation systems is drawn up and a conclusion is issued on the conformity of their actual parameters to the design ones.
Aerodynamic tests of ventilation can be completed with an act that includes information on the operation of technological equipment, its productivity, the rate of air exchange in buildings, the operation of ventilation ducts and the capacity of air filters and visual inspection data.
The type of impeller and its diameter, the revolutions of the pulley and its diameter, the total flow pressure and the fan performance are activated; type, speed, power, method of transmitting torque, pulley diameter - for an electric motor; pressure drop, capture rate and throughput - for filters; type of device, circulation pattern and type of coolant, test results - for heaters and air conditioners.
The passport of the ventilation system, which is required by inspections by sanitary authorities, 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 devices must also be in the passport.
Checking the existing ventilation reveals its breakdown, the need for reconstruction or cleaning.
Why and how are ventilation systems checked, aerodynamic test methods in general terms and the documentation that is issued based on the test results - to general contractors, customers of residential and public buildings, specialists of management companies and heads of engineering services of industrial enterprises, this information is needed if only in order to understand what documentation needs to be prepared, where to go for certification and verification of ventilation systems.