Anemometer - Calculation formula of wind speed
V=Q/{(D/2)^2*3.14*3600} V-wind speed (m/s);
Q-air volume (m3/h);
D-pipe diameter (m);
Inverted V means power.
Air volume (Q): The so-called air volume (also known as volume flow rate) refers to the flow rate of air passing through the cut-off area of the air duct, which is generally expressed by the following formula: Q=60VA Q (air volume)= m3/min; V (wind speed) = m/sec; A (cross-sectional area) = m2 Pressure common conversion formula 1Pa=0.102mmAq 1mbar=10.197mmAq 1mmHg=13.6mmAq 1psi=703mmAq 1Torr=133.3pa 1Torr=1.333mbar Common unit conversion Table - Air Volume 1m3/min (CMM) = 1000 l/min = 35.31 ft3/min (CFM)
Description of common terms
(1) Standard state: 20°C, absolute pressure 760mmHg, relative humidity 65%. This state is called STP for short, and the air weight of 1m3 in this state is generally 1.2kg.
(2) Absolute pressure of air: It is the sum of the atmospheric pressure displayed by the local barometer plus the gauge pressure, generally expressed in kgf/m2 or mmaq.
(3) Reference state: 0°C, absolute pressure 760mmHg, relative humidity 0%. This state is called NTP for short, and the air weight of 1m3 in this state is generally 1.293kg.
pressure
(1) Static pressure (Ps): The so-called static pressure is the force exerted by the fluid [laugh and cry] on the surface of the appliance and is perpendicular to the surface. In the fan, it is generally caused by gravity and the push of the fan. It is often expressed in kgf in use. /m2 or mmaq, and can be obtained directly through measurement. In the air duct of the fan, the static pressure value in any direction is a fixed value and there are also positive and negative points. If the static pressure value is positive, it means that the Shizhou air duct is currently being expanded. If the static pressure value is negative, it means The air duct is currently being squeezed.
(2) Dynamic pressure (Pv): The so-called dynamic pressure is the pressure formed by the velocity of the fluid flowing in the air duct. It is often expressed in kgf/m2 or mmaq in use.
(3) Total pressure (PT): The so-called total pressure is the sum of static pressure and dynamic pressure, which is often expressed in kgf/m2 or mmaq in use. The total pressure value in the fan is fixed and will not change due to the shrinkage of the air duct. Wind pressure and temperature Temperature changes will affect the density of air. Therefore, when other conditions remain unchanged, when the temperature changes, the wind pressure must be corrected according to the following relationship to obtain the wind pressure value under standard conditions: P = P'[(273 + t)/ 293] (mm Aq) Similarly, when the air density changes, the wind pressure value can be corrected as follows: P = P'(1.2/γ) (mm Aq) In the formula, the value on the right side of the equal sign is like P', t, γ equivalent measured pressure, temperature and air [shut up] air density.
The relationship between pressure and speed: the speed is fixed as much as the pressure, it is impossible that the speed will change if the pressure remains unchanged.
The formula for calculating the wind volume of the fan The definition of the air volume of the fan is: the product of the wind speed V and the cross-sectional area F of the air duct. Because the wind speed can be accurately measured by the anemometer for large fans, the calculation of the air volume is also very simple. The air volume can be calculated directly by using the formula Q=VF.
Determination of the number of fans: According to the number of air changes in the selected room, calculate the total air volume required by the plant, and then calculate the number of fans. Calculation formula: N=V×n/Q Among them: N--the number of fans (sets), V--the volume of the site (m3), n--the number of air changes (times/hour), Q--the number of the selected fan model Single air volume (m3/h).
