The wind speed of wind pressure air volume calculation formula

                    The wind speed of wind pressure air volume calculation formula

Air volume (q): the so-called air volume (also known as volume flow rate) refers to the flow rate of the air flow through the cross-sectional 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 (sectional area) = M2
Common conversion formula of pressure: 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 ℃, absolute pressure 760mmhg, relative humidity 65%. This state is called STP for short. Generally, the weight of 1m3 air in this state is 1.2kg.
(2) Absolute pressure of air: it is the sum of the atmospheric pressure shown by the local barometer and the gauge pressure, which is generally expressed in kgf / m2 or mmaq.
(3) Reference state: 0 ℃, absolute pressure 760mmhg, relative humidity 0%. This state is called NTP for short. Generally, the weight of 1m3 air in this state is 1.293kg.
Pressure (1) static pressure (PS): the so-called static pressure is the force exerted by the fluid on the surface of the appliance and perpendicular to the surface. In the fan, it is generally caused by the push of gravity and fan. In use, it is often expressed in kgf / 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 can be positive or negative. If the static pressure value is regular, it means that the air duct is currently expanding. If the static pressure value is negative, it means that the air duct is currently being squeezed.
(2) Dynamic pressure (PV): the so-called dynamic pressure is the pressure formed by the speed of fluid flowing in the air duct. In use, it is often expressed in kgf / m2 or mmaq
(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. In the fan, the total pressure value is fixed and will not change due to the contraction of the air duct
The variation of wind pressure and temperature will affect the density of air. Therefore, when other conditions remain unchanged and 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）
Where, the value on the right side of the equal sign, such as p ', t γ Measured pressure, temperature and air density. The relationship between pressure and speed is as large as the pressure is fixed. It is impossible for the pressure to remain unchanged and the speed to change. Similarly, it is impossible for the calculation formula of fan air volume. The definition of fan air volume is the product of wind speed V and air duct cross-sectional area F Large fans can accurately measure the wind speed with anemometer Therefore, the air volume calculation is also very simple Directly use the formula q = VF Then the air volume can be calculated
The number of fans is determined according to the ventilation rate of the selected room Calculate the total air volume required by the plant Then calculate the number of fans Calculation formula: n = v × N / Q, where: n -- number of fans (set), V -- site volume (M3), n -- ventilation times (times / hour), Q -- air volume of single fan of the selected fan model (m3 / h) The selection of fan model should be based on the actual situation of the plant Try to select the fan model matching the original window size The fan shall be kept at a certain distance from the wet curtain as far as possible (installed on both sides of the gable of the plant as far as possible) Achieve good ventilation effect The exhaust side shall not be close to nearby buildings as far as possible To prevent affecting nearby residents For example, the air brought out from the room contains environmental pollution A sprinkler can be installed at the air outlet The pollutants in the vicinity shall be collected in a centralized manner No environmental pollution