Example 6: Water Treatment Plants

In most water pumping stations, filtration plants, and waste water control plants, control of humidity in the pipe galleries, pump rooms, and control rooms is of prime importance. By reducing the dew-point temperature of the air below the temperature of the piping and walls, sweating and condensation can be eliminated. By circulating warm, dry air through the areas, water accumulation is avoided, maintenance for electrical controls, motors, and instruments is reduced, and paint lasts longer on the pipes, valves, and flanges.

A standard rule-of-thumb is used to approximate this type of application load:

The use of an after-cooling coil for the dry air discharge from the dehumidifier can be omit­ted in most installations since the warm, dry air (low rh) will help heat the space during cool or winter conditions. Heat should not build up to an objectionable level because the large piping and wall areas are at the same tem­perature as the water in the system. Warm air also has the advantage of reducing the rh and increasing the air's capacity to carry away moisture.

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