Air System Design

2022-12-06

Air System Design

air system design

1. Air System Design Principles

★It can guarantee the required indoor parameters, that is, it can guarantee to meet the indoor temperature, relative humidity, purification and other requirements under the design conditions and operating conditions.

★The combination of initial investment and operating costs is more economical;

★ Minimize the adverse effects of each room in a system;

★ Minimize the length and overlap of air ducts to facilitate construction, management and testing.

★The system should be consistent with the building partition.

★The design parameter value and heat-humidity ratio of each room or area are close to the same pollutants, so it can be divided into an all-air system. For the single-duct system with constant air volume, it is also required to have consistent working hours and basically the same load variation law.

★The total air system in general civil buildings should not be too large, otherwise the air ducts will be difficult to arrange. It is best not to install the system across floors. When it is necessary to install across floors, the number of floors should not be too many, which is conducive to fire prevention.

2. Air Conditioning Air Distribution

2.1 What factors should be considered in the layout of air ducts?

★Try to shorten pipelines, reduce branch pipelines, and avoid complicated local components to save materials and reduce system resistance.

★To facilitate construction and maintenance, properly handle possible conflicts with the arrangement of air-conditioning water, fire-fighting water piping systems and other piping systems.

2.2 What are the common forms of airflow organization at present, and the main application places of various air supply methods?

Reasonable air distribution in the room mainly depends on the form and location of the air supply outlet. Side panel air supply is the most commonly used form of airflow organization at present. The air duct is located in the upper part of the room, laid along the wall, and air outlets are opened on one or both sides of the air duct. It can supply air upwards and return air upwards, or supply air upwards and return air downwards. Its characteristic is that the tuyere should be arranged on the top to form an attached jet, and the heat exchange is carried out in the return air area. The air return port is located on the same side as the air supply port, and the wind speed is 2-5m/s. When sending hot air in winter, adjust the louvers to make the air flow shoot out obliquely downward.

★Diffuser air supply: The diffuser air supply can be sent horizontally or sideways. It also performs heat exchange in the air return zone. The jet and reflow paths are shorter and generally work better with an attached jet along the top grid. It is suitable for rooms where the top grill is set.

★Slit air supply: the air is supplied through the slit-shaped air supply port, and its range is short. The temperature difference and speed change quickly, which is suitable for rooms with large heat dissipation and only for cooling. For example, textile factories, high-level public civil buildings, etc. all use slit air supply.

★Nozzle air supply: The air treated with heat and humidity is ejected at high speed from several nozzles on one side of the room, and returns after a certain distance. This air supply method has high wind speed, long range, slow speed and temperature attenuation, and uniform temperature distribution. It is suitable for public buildings such as large gymnasiums, auditoriums, theaters and tall factories.

★Orifice plate air supply: Use the space above the top grid as a static pressure box. Under pressure, air enters the chamber through small holes in the metal plate. The return air outlet is located in the lower part of the room. When the orifice plate is sent, the diffusion of the jet and the mixing speed of the indoor air are faster. Therefore, the air temperature and flow rate in the working area are relatively stable, which is suitable for occasions where the regional temperature difference and wind speed in the working area are strictly required, and the room temperature is allowed to fluctuate less.

air system design - 1