Example 5: Production of Dry Air for a Specific Purpose

Many applications require a specific quantity of outside air to be delivered at a given moisture content and temperature. This requirement may be a need to make up air exhausted from a space or to supply air for a process such as a drying oven.

Physical Facts

1. Maximum allowable moisture content - 17 gr/lb of dry air
2. Maximum allowable temperature - 115°F
3. Quantity of air required - 6,000 cfm
4. Maximum condition of outside air - 95°F, 130 gr/lb

From the Typical Performance Curves chart it is obvious that 130 grain air cannot be reduced to 17 grains in a single pass through a dehumidifier, without other conditioning. Examination of Chart 1 shows that to produce 17 grains air leaving the dehumidifier, the inlet condition should be 64 grains or less at 60°F or less.

This is accomplished as shown above by installing a cooling coil upstream of the dehumidifier to reduce the temperature and moisture content of the outside air.

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