Installation, starting and adjustment of ventilation and air conditioning systems A Guide

Antipov Alexey

The applied methods of air distribution are characterized depending on the direction of movement of the air supplied to the premises: "from top to bottom", if the supply occurs in the upper zone, and removal – in the working; "from top to top", if the supply and removal of air occur in the upper zone of the premises, as a rule, this method ensures the movement of the supplied flows above the working level zones, and in the working area, the set air velocity is created by the reverse flow; "side up", etc. When choosing the method of air distribution, the direction of heat flows and the areas of the premises characterized by the maximum intake of heat or moisture are taken into account.

If it’s necessary to provide increased air velocity in air conditioning systems with an increased value of the height of the working area of the premises (hP. Z > 2 m) it’s possible to provide air distribution through conical nozzles.

The aerodynamic coefficient of conical nozzles m varies in a wide range, and its values depend on the angle of taper of the nozzle. Conical nozzles are characterized by the highest (maximum possible) values of the aerodynamic coefficient. As the taper angle increases, the value of m also increases. At the same time, the maximum value of m = 7.7 … 7.8. Simultaneously with an increase in m, the coefficient of local resistance also changes significantly. Figure 5.1 shows a diagram of a cylindrical nozzle with preload.

Supply grilles of various designs, ceiling lampshades and diffusers are also widely used, capable of working as supply and exhaust devices.

In rooms of small height (up to 5 m), air distribution can be carried out through perforated panels mounted in the ceiling. In this case, the normative mobility of air in the working area is achieved with a large multiplicity of air exchange. Perforation holes are made with a diameter of 2 to 10 mm, the area of the living section of the panel does not exceed 10% of the total area of the panel.

In air distributors-lamps, air is released (removed) through fluorescent lamps mounted in the suspended ceiling structure. Such a solution in the case of air extraction reduces the heat input from the lighting into the room, since part of this heat is carried away together with the exhaust air, moreover, due to the cooling of the lamps, it increases illumination.

A sufficiently satisfactory air distribution can be achieved by using perforated air ducts. The holes in the duct of variable cross-section length are located in its lower part.

Local exhaust ventilation is used when the places of harmful emissions in the room are localized and it is possible to prevent their spread throughout the room.

5.3. Devices for adjusting ventilation systems

General-purpose check valves are designed to prevent air from flowing through the branches to the disconnected fans (from the disconnected fans) when the latter are connected to the collectors. When installing valves in a vertical duct, the air flow should be directed from the bottom up. Installation of the valve in the network is allowed at air speeds in horizontal sections V >= 5…6m/s and on vertical V >= 4m/s.

The steel valve lobe valves in the usual design are designed to be installed on the discharge side of axial fans in order to prevent cold air and precipitation from entering the production premises after the fans are turned off. The design of the lobe valve is a housing in the bearings of which the blades are fixed on the axes. The purpose of the bearings is to ensure the free opening of the valve in conditions of negative external temperatures during periodic operation of the fans. When the fan is turned on, the blades are supported in the open position by the action of the airflow. After the fan is turned off, the blades return to their original position and overlap the valve section. In order to reduce the width of the valve, instead of switching from a circular fan section to a rectangular valve section, a transitional diaphragm is provided. The minimum dynamic pressure at which the lobe valve operates is 30…40 Pa.

Valves (dampers) air insulated designed for installation in low-pressure supply (exhaust) ventilation systems to prevent the penetration of outside air into the supply chambers and rooms when the fan is not working and to regulate the amount of air entering the system. The dampers can be either electrically heated or without it. The electric heaters in the valves serve only to warm up the flaps in case of icing, in order to prevent damage to the frozen flaps when opening. The electric heaters of the valves are switched on for 5–7 minutes before opening the valve. Valves (dampers) air insulated consist of a housing, double-walled rotary blades with thermal insulation properties, a drive and a motion transmission system from the drive to the blades. A rubber seal is installed at the interface points of the blades of the sound. An actuator is installed as a drive. It is possible to manufacture a manual-driven system. The maximum allowable pressure drop in the closed position is 1225 Pa (125 kgs/m²). Air passage in the closed position at a pressure drop of no more than 5%.

Resistance coefficient in the open position, not more than 0.2.

Dampers are available in the following types:

• Air unified;

• Round section with electric drive;

• Rectangular cross-section with electric drive;

• Circular cross section with manual drive;

• Rectangular cross-section with manual drive;

Air dampers are designed to regulate the amount of air and are used in air ventilation systems, air heating and other sanitary systems with an operating pressure of up to 1000 Pa.

Questions to Chapter 5

1. For what purpose are air distribution devices used?

2. Name the main characteristics of air distribution devices.

3. What factors are taken into account when choosing the type of air distribution device in the room?

4. What is the value of the dynamic pressure required for the operation of the lobe check valve?

5. What is the purpose of electric heating of air dampers, in which cases it is used?

Chapter VI. Mounting tools, fixtures and accessories for mechanization of installation work

Installation of ventilation systems is carried out by a team. As a rule, the integrated team of ventilation fitters includes two or three people with related specialties of an electric welder and a gas cutter. The numerical composition of the team is usually six to seven people. Each team is provided with a set of tools, which allows the team or its units to independently perform almost the entire scope of work on the installation of ventilation systems.