1. Measurement of airflow velocity in pipes Practice has proved that the 16mm probe of the anemometer is the most versatile.
Anemometer
Its size not only ensures good permeability, but also can withstand a flow rate of up to 60m/s. As one of the feasible measurement methods, the measurement of airflow velocity in the pipeline, the indirect measurement procedure (grid measurement method) is suitable for air measurement.
Anemometer 2. The measurement vent in the exhaust and exhaust will greatly change the relatively balanced distribution of the airflow in the pipeline: a high-speed area will be generated on the surface of the free vent, and the rest will be a low-speed area, and vortices will be generated on the grid. According to the different design methods of the grid, at a certain distance (about 20cm) in front of the grid, the airflow section is relatively stable. In this case, the diameter runner of a large anemometer is usually used for measurement. Because the larger diameter can average the unbalanced flow velocity and calculate its average value over a larger range.
3. In the measurement of the air extraction hole, even if there is no grid interference at the air extraction place, the air flow route has no direction, and the air flow section is extremely uneven. The reason is that the partial vacuum in the pipeline draws the air into the air chamber in a funnel shape. Even in the area very close to the pumping air, there is no position that meets the measurement conditions and can be used for measurement operations. If the grid measurement method with averaging function is used for measurement, and the volume flow method is used for measurement, and the volume flow method is used to determine the volume flow, etc., only the pipe or funnel measurement method can provide repeatable measurement results. In this case, measuring funnels of different sizes can meet the requirements of use. Using the measuring funnel, a fixed section that meets the flow velocity measurement conditions can be generated at a certain distance in front of the sheet valve, and the center of the section is measured and fixed, and the center of the section is measured and fixed, and the center of the section is measured and fixed. here. The measured value obtained by the flow rate probe is multiplied by the funnel coefficient to calculate the extracted volume flow. (eg funnel factor 20)
The specific detection method of wind speed and air volume
A. Air volume and wind speed detection must be carried out first. All purification effects are obtained under the designed air volume and speed.
B. Before testing, check whether the fan is running normally, and measure the size of the tested air outlet and air duct on the spot.
C. For a unidirectional flow (laminar flow) clean room, the air volume is determined by the method of the average wind speed of the room section and the product of the clean product.
(Take the section that is 0.3m away from the high-efficiency filter and perpendicular to the airflow as the sampling section. According to the test point spacing should not be greater than 0.6m, set no less than 5 test points on the section, and the arithmetic mean of all readings is taken as the average wind speed.) Vertical The measurement section of the unidirectional flow (laminar flow) clean room is based on the horizontal section of 0.8m~1m on the ground; the measurement section of the horizontal unidirectional flow (laminar flow) clean room is based on the vertical section of the air supply surface 0.5m~1m; The number of upper test points should not be less than 10, the spacing should not be greater than 2m, and they should be evenly arranged;
D. For the tuyere with a filter, the air volume is determined by the product of the average wind speed of the tuyere section and the net sectional area of the tuyere. (The average wind speed is obtained from no less than 6 evenly arranged test points on the section of the tuyere or the section where the auxiliary duct is cited.)
E. When there is a long branch pipe section on the windward side of the tuyere and holes have been or can be drilled, the air volume can be determined by the air duct method. (Punch holes not less than 3 times the pipe diameter or 3 times the length of the large side before the air outlet;)
F. For rectangular air ducts, divide the measured section into several equal small sections, each small section is as close to a square as possible, the side length is not greater than 200mm, the test point is located in the center of the small section, but the entire section should not be less than 3 tests For circular air ducts, the measurement section should be divided according to the equal-area ring method and the number of test points should be determined; holes should be made on the outer wall of the air duct, and a thermal anemometer probe or pitot tube should be inserted. (By measuring dynamic pressure, it is converted into air volume.)
