The characteristics, design methods and comparison of commonly used air-conditioning systems Part Four

3. Calculation method of air distribution

The task of airflow organization calculation is to select the form of airflow distribution, determine the form, number and size of air supply outlets, and make the wind speed and temperature difference in the working area meet the design requirements.

Design Principles and Calculation of Air Conditioning Water and Air System

The cold water supply/return temperature of general comfort air conditioner is 7℃/12℃; The water temperature is 2°C/13°C; the regional cooling water supply/return water temperature is 5°C/13°C

1. Forms and design principles of common air-conditioning water systems:

Open system and closed system Same process system and different process system The air conditioning water system can be divided into regions and heights;

Two-control and four-control systems;

Constant flow system and variable flow system

Primary pump system and secondary pump system

2. Hydraulic calculation of air-conditioning water system

3. Air conditioning system and its hydraulic calculation

4. Design and calculation of air duct system

Before the design and calculation of the air duct system, the location of each air supply (return) point and its air volume, the piping system, the layout of related equipment, and the material of the air duct must first be determined. The purpose of design calculation is to determine the pipe diameter (or section size) and pressure loss of each pipe section, ensure the required air volume distribution in the system, and provide a basis for fan selection and construction drawing.

1) The hydraulic calculation method of the air duct system: assumed flow velocity method, average pressure loss method, equivalent pressure loss method, static pressure recovery method, etc. In general air duct design calculations, the more common methods are the assumed flow velocity method and the average pressure loss method.

2)  Basic design calculation steps System pipe section number. Generally, it starts from the section farthest from the fan, and is numbered sequentially from far to near; usually, the air duct with constant air volume and wind speed is the same pipe section; local pipe fittings (such as elbows, tees, air supply outlets, return air outlets, etc.) within the pipe section.

Choose a reasonable air flow rate

Pre insulated duct making machine is a duct board making machine. Pre insulated duct making machine is equipped with cutting knives to cut the pre-insulated duct panels. Pre insulated duct making machine is the best solution for pre-insulated duct fabricators. Pre insulated duct making machine is also called duct board cutting machine.

Pipeline pressure loss calculation. The pressure loss calculation should start from the most unfavorable loop (the point farthest from the fan).

Pipeline pressure loss balance calculation. The general air conditioning and ventilation system requires that the pressure loss difference between the two pipes should not exceed 15%.

When the pressure loss difference of parallel branch pipes exceeds the above-mentioned regulations, it can be passed through:

①Adjust the diameter of the branch pipe;

② Increase the flow rate of the branch pipe with small pressure loss;

③Adjust the opening of the valve, increase the pressure loss of the branch pipe with small pressure loss, etc. to balance the pressure.

Fan selection. To select a low-noise fan, consider the noise elimination of the fan, not only to meet the indoor noise standard, but also to meet the environmental protection requirements for the noise at the outdoor air intake and exhaust; when selecting a fan, the air volume and wind pressure margin should not be too large ;According to the analysis of operating conditions, determine the economical and reasonable number of units; when conditions permit, frequency conversion fans can be used to reduce operating costs. The air volume of the fan is added.

In addition to meeting the calculated air volume, the air volume of the fan should also increase a certain amount of air leakage from the pipeline, and the additional rate of air leakage is less than 10%. In the calculation of the pipe network, the air leakage of the air duct is not considered.

Fan pressure is added. The total pressure of the fan is the total pressure loss of the system pipe network. Usually, the total pressure loss of the pipe network of the air conditioning and ventilation system considers an added value of about 10%.

Pre insulated duct making machine is a duct board making machine. Pre insulated duct making machine is equipped with cutting knives to cut the pre-insulated duct panels. Pre insulated duct making machine is the best solution for pre-insulated duct fabricators. Pre insulated duct making machine is also called duct board cutting machine. 

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