Determination of duct and air speed
Three methods of air duct calculation: static pressure recovery method assumed wind speed method such as friction method of air conditioning wind system pipe design (a) In the design of pipe machine must first understand the three parameters from the product data: air volume, wind pressure, noise. 1. Air volume: To determine the size of the air supply pipe. 2. Wind pressure: also called external static pressure. In order to calculate the parameters needed to overcome the resistance in the process of air supply. Simply, or not exactly, how far the wind can travel. 3. Noise: the noise of the product technical data is only relative, because the noise changes with different conditions. Noise may be generated by the following channels: the fan of the machine itself, the vibration of the machine operation, the excessive pressure of the supply air, etc. (2) The main contents of the design of the air duct system include: reasonable use of the air velocity in the pipe to determine the section size of the air duct, calculation of the resistance of the air system and selection of fans, balance the resistance of each branch of the air duct to ensure that the air volume of each branch of the air duct reaches the design value. So how to choose the wind speed in the pipe? How to determine the size of the air duct? ※ The selection of wind speed in the pipe determines the size of the section of the pipe. The relationship between the two is as follows: F=a×b=L/(3600• V) (Formula 1-1) in the formula: F: pipe section area (㎡) a, b: pipe section length, width (m) L: duct air volume (m³/h) V: wind speed (m/s) The above values are affected by the following aspects: ① building space: In modern buildings, whether multi-storey buildings or high-rise buildings, or high-grade villas, the building space is quite tight, so we are required to improve the wind speed as much as possible to reduce the section of the air duct. (The wind speed in the pipe is inversely proportional to the cross-sectional area of the air duct, that is, the higher the wind speed, the smaller the cross-sectional area of the air duct; on the contrary, the lower the wind speed, the larger the cross-sectional area of the air duct.) (2) Fan pressure and energy consumption: the higher the wind speed, the greater the wind resistance, the greater the energy consumption of the fan, and from this point on to reduce the wind speed. (3) Noise requirements: The influence of wind speed on noise is manifested in three aspects: First, with the increase of wind speed, the fan pressure requirement is higher, which causes the fan operation noise to increase; Second, when the wind speed increases to a certain extent, airflow noise will be generated when passing through the air duct components; Third, with the increase of wind speed, the noise reduction ability of the air duct. In general, the higher the wind speed in the duct, the greater the noise generated. Therefore, the selection of wind speed in the pipe is a result of comprehensive balance of various factors. Through access to relevant information and relevant manuals and according to the experience of the actual project.