How It Works

PGC’s method of control is the same for both reach-in chambers and conditioning systems. In short, the environment to be conditioned is controlled at a targeted dew point temperature and then reheated to a specified air temperature. This methodology follows a proven technique that maintaining a constant dew point and air temperature will produce a very constant relative humidity.

A portion of the air returning from the conditioned area (chamber, modular room, laboratory space) is directed through a water spray area (A), the temperature of which is very closely controlled. The temperature of the water spray is adjusted to maintain the dew point temperature of the targeted condition. As the air passes through the water spray, it is cooled down to the temperature of the water and approaches saturation at that temperature.

The air then leaves the spray chamber through a mist eliminator, which removes any free droplets of water, and is next mixed (B) with air that has by-passed the spray area. After passing over an electric heater (C), to warm the air back to the desired dry bulb temperature, the air is returned to the conditioned space.

Utilizing the above method, a very precise humidity control is achieved. The system does not distinguish between humidifying and dehumidifying; it is always setting a dew point and reheating. If the conditioned air has a higher moisture content than the set point, excess moisture condenses out in the cool water spray and dehumidifies the control air. Conversely, if the conditioned air has a lower moisture content than the set point, moisture evaporates from the water spray and humidifies the control air.

The temperature of the water spray is automatically adjusted by the feedback from a high grade RH sensor in the controlled space. If the set point is lower that the actual condition, the temperature of the water spray will gradually decrease until the RH set point is achieved. On the other hand, when the relative humidity set point is above the actual condition, the water spray temperature is incrementally increased until the RH set point is achieved.

For conditions that require a below freezing dew point, a desiccant dryer is utilized.

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