I. Overview
Bosion cloth duct design principle and tradition of the same duct, the main contents include the arrangement of the duct, determine the diameter and the wind design. However, new cloth duct Bo radial air supply along the pipeline, axial fan air supply was to form three-dimensional air mode, the overall air even without air valve air iffusers and other accessories, duct layout than simpler and more traditional duct. (This can not)
1, duct layout:
Bo is the new three-dimensional air duct model, the overall air evenly, duct layout should follow the following principles:
Straight - a straight duct to the main pipe to minimize the number of branch
L-to - air duct to be used when turning the layout of L-type
T-to - air duct to be used to go when the T-branch layout, but not too much the number of branch
2, diameter design:
Bo new duct diameter is calculated as follows:
Q = 3600 V * ¦Ð * D2/20002
V - into the wind speed (m / s)
Q - the total volume flow rate (m3 / h)
D - Inlet diameter (mm)
From the above formula can be seen, when the wind is constant, the Bo new duct diameters of wind speed, whereas the wind speed but also with the tube static pressure, and when the tube static pressure and wind speed does not match, the wind may occur jitter (when the wind speed the greater the static pressure the more powerful the more hours of jitter), which affect the actual air supply.
Bo is the new duct system by the static air, and duct pressure Pt = Pv Ps; Pt - total pressure, Pv - dynamic pressure, Ps - static pressure. Pv and Ps is the pressure of different states can be transformed into each other. Pt constant, Pv increase (speed increase) Ps decreases, Pv decrease (reduction of wind speed) Ps increased.
Therefore, in the air duct design, pipe design wind speed should not be too large (6-10m / s is appropriate) to avoid static pressure into dynamic pressure caused by the static pressure duct is too small jitter.
3, the pressure loss calculation
Bo a complex set of new duct system, generally includes a main pipe and a number of straight pipe, elbows, reducers, tee, plenum chamber and other components. Friction loss, but also includes the loss of local resistance to calculate a new blog this complex duct system should select the most negative loop, the frictional resistance and the sum of local resistance were calculated, the total pressure loss. Accordingly we can calculate the minimum static pressure at the entrance.When Bo fresh air flow through the pipe elbows, reducers, tees and other components, the face or the flow of change, as with conventional air duct will have a corresponding local pressure loss:
Z = ¦Îv2¦Ñ / 2, Z - local pressure loss; ¦Î - coefficient of local resistance (primarily measured by the experiment, similar to traditional wind pipe); ¦Ñ - air density (kg/m3); v - wind speed ( m / s);
Bo in order to reduce the local new duct system losses, we usually carry out some optimal design:A comprehensive variety of factors selected diameter, to minimize the wind pipe.
2 Optimal design of shaped parts, to avoid the flow of change too fast, face rapid change.
According to the construction engineering experience, we conclude that all new duct Bo parts, components of the local resistance values (8m / s).
Bosion impact of the new air duct system pressure factors entrance static pressure, dynamic pressure and pressure loss. Bo dynamic pressure in the duct along the length of the new direction into static pressure, also known as static regain. Pressure loss along the way and the connections referred to local loss caused by pressure loss. Therefore, the average static pressure tube can be considered by the entrance static pressure, static pressure recovery and pressure loss was composed of three.
Import static: Generally provided by the fan inlet static pressure, if the new fan and duct system Bo is not directly connected, the inlet duct static pressure for the new Bo static pressure direct connections; if Bo fan and duct system directly connected to the new, the inlet static pressure is Fan static pressure. In general, the end of the static pressure should be greater than 70Pa, but according to the situation of different projects have different requirements.
According to the experience of a large number of engineering practice, we recommend the duct at different heights to achieve the best use of regional wind pressure gradient appropriate reference values
|
