Vertical air curtains are introducing systems and create local air ventilation effects limited in the area found harmful source.
Using the most common is the vertical air curtains to prevent cold air intrusion in the room from outside through open doors
Air curtains next to the access doors are a necessity when working areas are close to the door and when there is a movement of people or materials through exterior doors.
Vertical air curtains at the doors are of two types: unilateral and bilateral
Bilateral vertical curtains are preferable for two reasons:
-Dimensions are smaller distribution channels which are important to their location.
-Bilateral curtains door plan covers any situation, even if a means of transport temporarily stationed in the opening, while the curtain is interrupted unilaterally in this situation.
The main element of bilateral vertical air curtains is the distributor slit discharge.
The air displaced slot depends on the size and initial speed v0 in its plan.
Length of the discharge gap is equal to the height adopt constructive door for vertical curtains.
Slot length should be minimal to achieve the economic plant.
Width " b " of the slot is chosen equal to 100 ÷ constructive 200 mm.
Page velocity v0 has values between 10 ÷ 20 m / s.
Over the speed limit resulting plants become uneconomic.
If the current trajectory compound remains outside the opening, the outer door is fully protected at all outside air does not penetrate into the room and gain maximum value yield curtain ή = 1.
Air curtains operate air sucked inside the hall, which is the most economical solution.
Determination of the curtain air flow bilateral vertical slot considering that each serving half the width of the door opening.
(method I.A.Sepelev )
D0 = ή x Ddes / 2 ( 1+ φ B √0.5 B / b ) m3/h
ή: return curtain
D0: The air curtain bilateral vertical
Ddes: airflow entered through the door without curtains
φ B: coefficient for vertical curtains
B: width of door
b: width of the slot
ά 30° 45° 50°
a 0.2 0.2 0.2
φ B 30° 45° 50°
Real case
Exothermic industrial hall.
The door must be protected against the winter cold air from outside intrusion.
Opening dimensions are:
Width = 5.3 m
Height = 4.7 m
Near the door are fixed jobs.
It provides a screen with an angle of inclination bilateral ά = 45 ° and having a slot which produces a turbulent jet by a factor of a = 0.2.
Choose a speed of outside air through unprotected opening, w = 2.5 m / s.
Ddes = S x w x 3600 = 5.3 x 4.7 x 2.5 x 3600
Ddes = 224190 m3/h
Choose curtain output ή = 1
The air displaced by a slot in admitting the flow serves as one half the span and if you choose b = 100 mm then:
D0 = ή x Ddes / 2 ( 1+ φ B √0.5 B / b ) m3/h
0.5 x D0 = 112095 x ( 1+ 0.47 √0.5 x 5 / 0.1) m3/h
0.5 x D0 = 33.462 m3/h
Discharge resulting speed V0 = 33462 / 3600 x 4.7 x 0.1 = 19.77 m / s
V0 = 19.77 m/s
The total flow of the veil created by two slits is :
D0 = 2x 33462= 66924 m3/h
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