Classification and application of central air conditioning terminal equipment

1. Classification according to the setting of air conditioning equipment:

(1) Centralized air-conditioning system: The centralized air-conditioning system centralizes various air treatment equipment and fans in a dedicated machine room to centrally process the air, and then the air supply system sends the processed air to various areas. Go to an air-conditioned room.

(2) Semi-centralized air conditioning system: In addition to the centralized air treatment room, there are also secondary treatment equipment in each air-conditioned room to further supplement the air from the centralized treatment room.

(3) Fully decentralized air conditioning system: an air conditioning unit that assembles air handling equipment, fans, automatic control systems, and cold and heat sources, etc., and places it directly in the air-conditioned room to process the air on-site. It is a local air-conditioning method.



2. Classification according to the type of media used to bear the indoor load:

(1) Full air system: an air conditioning system in which all heat and humidity loads in the air-conditioned room are borne by treated air.

(2) All-water system: An air-conditioning system in which the heat and humidity loads in the air-conditioned room are all borne by water as the hot and cold medium.

(3) Air-water system: An air-conditioning system in which the heat and humidity loads of the air-conditioned room are shared by treated air and water.

(4) Refrigerant direct evaporation system: This is an air conditioning system in which the evaporator of the refrigeration system is placed directly indoors to absorb the heat and humidity load of the room.



3. Classification according to different service objects:

Classified according to different service objects: comfort air conditioning and process air conditioning. Comfort air conditioners are usually used in homes or public places; process air conditioners are usually used in factories, laboratories and other places that have special requirements for air.

As shown in the picture is a brand new fan unit, which is a centralized air conditioning system.

Its working principle is: outdoor fresh air (fresh air in the picture) enters the air treatment room (E-air conditioner in the picture) through the fresh air outlet (F-air inlet grid in the picture), passes through the filter to remove dust in the air conditioner, and then After being processed by surface coolers, heaters and other equipment to make the air reach the temperature and humidity required by the design, the air is sent from the air blower through the air volume control system (D-total air volume regulating valve in the picture) into the air duct system (the dimensions are marked in the picture) Pipe) is sent to the muffler device (C-muffler in the picture) to reduce the noise, and then passes through the air volume adjusting device (B-air volume regulating valve in the picture) in each room and is sent to each room through the air outlet (A-orifice air supply port in the picture). In an air-conditioned room, after absorbing the residual heat and humidity in the room, it is discharged to the outside through the air return port and the air duct.



Chapter 2. Technical terminology of central air conditioning system

1.Air duct



Air ducts are pipes made of metal, non-metallic sheets or other materials for air circulation.

(1) Air duct materials commonly used include thin (galvanized) steel plates, stainless steel plates, plastic composite plates, organic (inorganic) fiberglass plates, plywood, aluminum plates, plastic hoses, metal hoses, rubber hoses, etc.



(2) Specifications and dimensions of air ducts

As shown in the figure, the air duct consists of three dimensions: A, B, and L. A represents the width, B represents the height, and L represents the length. The units are mm unless otherwise specified. The formula for calculating the expansion area of the air duct is S=2 (A+B)×L, generally converted into m according to the unit required by the project, for example, A×B×L=500×200×5000 means air duct The width of the duct is 500mm, the height of the duct is 200mm, and the length of the duct is 5000mm. According to the expansion area of the air duct, the calculation formula of S=2(A+B)×L=2 (0.5+0.2 )×5=7㎡ Note: mm (millimeters).



(3) Insulation of air conditioning ducts

Since air-conditioning pipes transport high-quality air, the insulation requirements for the pipes are very high. Therefore, the pipes need to be insulated. Commonly used insulation materials are as follows:



2. Air duct accessories and components:

Air duct accessories refer to elbows, tees, crosses, various types of reducing and special-shaped pipes, guide vanes and flanges in the air duct system. Duct components refer to various air outlets, valves, exhaust hoods, hoods, inspection doors and measuring holes in ventilation and air conditioning duct systems.

3. Air conditioning system terminal equipment and its components:

The terminal equipment of the air conditioning system includes prefabricated air conditioning units and fan coil units. Its main components include fan units, surface coolers, heaters, humidifiers, dehumidifiers, air filters, air distributors, etc.



As shown in the figure, it is a prefabricated air conditioning unit, which is made of various air treatment equipment, fans, air volume control valves, etc. into a unit with a box. These units can be combined by designers according to project needs to form a group. Prefabricated air conditioners that can meet various air treatment requirements.



Prefabricated air conditioning units have various structural forms: horizontal, vertical, angle and stacked. When selecting a prefabricated air-conditioning unit, an air-conditioning unit of appropriate model and structure should be selected based on the total air volume required by the air-conditioning system, the total cooling load of the system, and the area of the air-conditioning room.



(1) Concept of semi-centralized air conditioning system

In addition to the centralized air treatment room, the semi-centralized air conditioning system also has secondary air treatment equipment in the air-conditioned room. This air conditioning method that combines centralized treatment of air with local treatment overcomes the shortcomings of the centralized air conditioning system such as large air processing capacity and large cross-sectional area of equipment and air ducts. It also has the advantage of local air conditioning systems being easy to adjust independently. Semi-centralized air conditioning systems are divided into fan coil air conditioning systems and inducer systems due to different types of secondary air treatment equipment. Among them, the fresh air plus fan coil system is the longest-used semi-centralized air conditioning system. As shown in the figure:



The treated fresh air is sent to the room through the fresh air supply duct. The indoor air is mixed with the incoming fresh air through the return air outlet and then processed by the fan coil unit. After reaching the requirements, it is sent to the room. This continuous cycle ensures that the room usage requirements are met. .

(2) Fan coil unit:

The fan coil air conditioning system consists of a fan coil unit, a fresh air unit, an air supply duct, and a control valve. Among them, fan coil units and fresh air units are often called terminal equipment, and together they constitute a semi-centralized air conditioning system.

1.Types of fan coil units:



2.Parts of fan coil unit:



(3) Parts and components of air conditioning terminal equipment:

1. Fan unit:



2. Surface cooler



3. Heating dehumidifier



4. Heating dehumidifier







5. Air filter Air filters can be divided into coarse-efficiency filters, medium-efficiency filters, sub-high-efficiency filters and high-efficiency filters according to the size of filtered dust particles. According to the appearance characteristics, it can be divided into plate filter, bag filter and scroll filter.



6. Air distributor: including various forms of air valves and air supply and return ports

Chapter 3. Introduction to central air conditioning water system

1.Working principle of central air conditioning water system:



The air conditioning water system can be divided into two forms: open system and closed system, as shown in the figure; the end water pipe of the open system is connected to the atmosphere (left side), while the pipes of the closed system are not connected to the atmosphere (Right). Common water system circulation includes chilled water system circulation and cooling water system circulation.

(1) Chilled water system circulation: For systems using compression chillers and heat exchangers, cold (hot) water does not need to be treated for water quality, because there is generally no possibility of scaling, and even a small amount of scaling is necessary to prevent electrochemical corrosion. protective effect;

For systems using lithium bromide absorption cold and warm water units, softened water should be used according to the manufacturer's requirements. Some projects are equipped with sodium ion exchangers, and some are equipped with electronic water treatment equipment.

(2) Cooling water system circulation: The air conditioning cooling water system refers to the circulating cooling water system composed of the condenser, cooling tower, cooling water tank and cooling water circulation pump of the chiller.

2. Cooling tower

The cooling tower is an important piece of equipment in the circulating cooling water system. There are four types of counterflow cooling towers, cross-flow cooling towers, jet cooling towers, and evaporative cooling towers. The two most commonly used types are counterflow cooling towers (round, square) and cross-flow cooling towers (round, square). kind.



3. Operating principles of cooling towers and cooling tower systems



4.Circular counterflow fiberglass cooling tower



5.Cooling tower packing