Mixing Air Distribution

In this chapter we deal with air distribution in a room, where

L = room length B = room width Hr = room height

See Fig. 8.17.

8.7.2.1Penetration of Horizontal Air Jets Room Length

If the room is to be ventilated by one single air jet, and the jet shall pene­trate across the entire room length, the room length should not exceed1

L<Q.62KiJWHr, (8.22)

Where

A0 is the effective discharge area of the jet (m2)

B = room width (m)

Human Common

Pollutant Room Heat activity air supply Type

Load height load level methods of process

Insignificant

Small

Light

Mixing, horizontal air |ets below ceiling

Mechanical

Assembly

Moderate, >5 m dust and fumes

Moderate

Displacement, low-velocity air supply at floor level

Welding shop

Moderate, <5 m

Solvent

Vapors

Light

Low-velocity supply from above,

Local exhausts

Paint shop

High,

Solvent

Vapors

Light

Piston flow, vettical from a hove

Paint booth

Heavy >10 m

High

Heavy

Displacement, low-velocity air supply at floor level

Foundry,

Melting

Works

Hr = room height (m)

= the decay coefficient of the jet L = room length (m)

Mmax = maximum velocity in jet cross-section (m/s) u0 = discharge velocity of the jet

The constant Kl is the decay coefficient used in the formula

[a

= /8.23)

«o 1 x 1

K± depends on the type of jet, and varies between 2 and 7. Some values are given in Table 8.10. See also Section 7.4, Air jets. If the room is longer, one has to take long-room considerations into account. See Section 8.7.2.2.

Posted in INDUSTRIAL VENTILATION DESIGN GUIDEBOOK


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