Working conditions and calculation of natural ventilation

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In order for the ventilation in the garage built with your own hands to work, its design must take into account the volume of air exchange, seasonal temperature changes and wind rose.

Natural ventilation of a car box directly depends on the following parameters:

Temperature difference between the air inside and outside the room. The atmosphere of the garage should be hotter and therefore lighter than the outside air. Then heavy and fresh air will penetrate into the garage through the supply air duct by gravity, trying to replace the less dense volume of the internal atmosphere.
Pressure differences between vertical positions of the supply and exhaust. A difference of more than 3 m between the supply air inlet and the exhaust air outlet is required.
Pressure of the moving air mass (wind). On the windward side of the garage, increased pressure is established, on the leeward side - decreased. It is necessary to place the supply air duct on the side of the prevailing wind direction.
Ignoring the above conditions will result in complete inefficiency of natural exhaust. Therefore, in winter, you should set a higher temperature in the car box in relation to the street and reduce air exchange by adjusting the degree of opening of the air ducts.

In summer, it is necessary to open the supply and exhaust air ducts completely, relying on the wind rose.

The location of the supply air intake and exhaust pipe relative to each other must be either along the length of the box or along its diagonal.

The main parameter of air exchange is its frequency, i.e. the number of complete changes of the volume of the atmosphere in the garage with “street” air.

Knowing the standardized supply and exhaust hong kong mobile database exchange rate (6-10 times) and the internal volume of the car box, it is necessary to calculate the air consumption per hour:

L=n•Vг, where

L – air flow per hour, m3/h;
n – numerical value of the standard for the air exchange rate;
Vg – air volume of the garage, m3.
To determine the volume of air that a garage can hold, multiply its internal dimensions by width, length, and height.

For example, a box 4 m wide, 6 m long and 2.7 m high contains Vg = 4•6•2.7 = 64.8 m3. When choosing, say, seven-fold air exchange per hour, such a garage will require L = 7•64.8 = 453.6 m3.

Knowing the air flow and its speed, you can find the optimal diameter of a round air duct for a garage supply and exhaust system using this diagram.

To select the cross-section of the supply and exhaust air ducts, the obtained value L should be rounded up, achieving a multiple of 5.

Therefore, the air flow value obtained in our calculation must be increased to 455 m3, since this number is divisible by 5 without a remainder – 455:5=91.