LOCATION OF GENERAL EXHAUST Exhausts in Nonstratified Room Air

In a room with perfect mixing of the air, it theoretically does not matter where the exhaust opening is located (Fig. 8.40). In practice, air seldom mixes as completely as in theory. One reason for this is temperature differences or den­sity differences. The contaminants are often warmer than the room air, and in some cases the density of the contaminant itself differs from the air density. These topics are treated in the later paragraphs. This paragraph will focus on isothermal, non-buoyant cases.

In long rooms, i. e., where the room is slightly longer than the penetrating distance of the supply jet, the best location of the exhaust is opposite to the air supply opening. See Fig. 8.41.

In very long rooms, the exhaust should be located at the opposite end of the room. Otherwise, the air exchange in the far end of the room may be small, resulting in an accumulation of contaminants in that part of the room. See Fig. 8.42.

LOCATION OF GENERAL EXHAUST Exhausts in Nonstratified Room Air

LOCATION OF GENERAL EXHAUST Exhausts in Nonstratified Room Air

FIGURE 8.42 In very long rooms, the exhaust should be placed opposite to the supply opening.

LOCATION OF GENERAL EXHAUST Exhausts in Nonstratified Room Air

FIGURE 8.43

Warm contaminants should be exhausted below the ceiling, and preferably close to the

Source.

8.8.2.2 Exhaust of Cold Fumes

Heavy fumes or gases (i. e., negatively buoyant contaminants) should be exhausted at floor level. This applies to displacement ventilation as well as to mixing ventilation (Fig. 8.45).

LOCATION OF GENERAL EXHAUST Exhausts in Nonstratified Room Air

LOCATION OF GENERAL EXHAUST Exhausts in Nonstratified Room Air

LOCATION OF GENERAL EXHAUST Exhausts in Nonstratified Room Air

A roof above the zones.

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