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FIGURE 1. The adiabatic process reduces the coil temperature by applying the first law of thermodynamics for heat exchange. In an adiabatic cooling system, the system can operate in dry mode. When more cooling is needed, water saturates a pad installed on the outside of the coil surface to precool the incoming air via evaporation. | Image provided by Guntner US (Click on image to enlarge.)
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The heat exchangers are sized to meet a specific load. As the ambient temperature and load rise, the fans turn on to reject heat, maintaining the required process temperature. As the ambient temperature rises further, the fans reach their designed capacity.
Once the ambient temperature reaches the designed switch-point, the water will engage and saturate the pad. The higher the switch-point, the longer the cooler will run in dry mode without precooling from the water. With more advanced controls, the adiabatic cooler can engage the water at different fan speeds in order to save energy or water. At the same time, intelligent control systems can minimize water usage overall.
For instance, the water could engage at 100 percent fan speed and then begin saturation and metering in order to save the greatest amount of water. By contrast, in the energy-saving mode, the adiabatic cooler could bring saturation and metering at approximately 40 percent of fan speed. Bringing saturation at 40 percent of fan speed has an advantage in that the air is precooling sooner (at 40 percent of the fan speed). Due to fan laws, reducing speed while maintaining the capacity saves a lot of fan energy but sacrifices slightly more water. If saturation starts at 100 percent fan speed, then water can be saved, but using the fans more sacrifices fan energy.
To extend these benefits, a smart controller can accept inputs for the costs of water...