Abstract: In one aspect, a heat exchange apparatus is disclosed having a liquid distribution system configured to distribute liquid onto a liquid absorbent material and an airflow generator operable to cause air to flow through the liquid absorbent material and toward an indirect heat exchanger. The heat exchange apparatus includes a controller configured to operate in a dry mode where the controller inhibits the liquid distribution system from distributing liquid onto the liquid absorbent material and a wet mode where the controller causes the liquid distribution system to distribute liquid onto the liquid absorbent material. The controller is further configured to operate at least one of the liquid distribution system and the airflow generator to inhibit drift of liquid from the liquid absorbent material toward the indirect heat exchanger in response to the controller switching from the dry mode to the wet mode.

Abstract: A water recirculation system operates in a primary mode for evaporatively cooling air. When the water recirculation mode malfunctions, the controller switches a secondary once-through mode. The system includes a sump for collecting water run-off from the evaporative pads, and a pump in fluid communication with the sump. The pump transfers moisture from the sump to the distribution arrangement located at the top of the evaporative pads during the recirculation mode. An automatically operated make-up water valve delivers water to a distribution arrangement on the evaporative pads. A moisture distribution arrangement distributes moisture to the evaporative pads and an automatically operated sump drain valve retains water in the sump when closed and freely drains water from the sump when open. A water level control communicates the sump water level to a control system. A monitoring mechanism detects whether the water-recirculation system has malfunctioned or is operating correctly.

Abstract: A water recirculation system operates in a primary mode for evaporatively cooling air. When the water recirculation mode malfunctions, the controller switches a secondary once-through mode. The system includes a sump for collecting water run-off from the evaporative pads, and a pump in fluid communication with the sump. The pump transfers moisture from the sump to the distribution arrangement located at the top of the evaporative pads during the recirculation mode. An automatically operated make-up water valve delivers water to a distribution arrangement on the evaporative pads. A moisture distribution arrangement distributes moisture to the evaporative pads and an automatically operated sump drain valve retains water in the sump when closed and freely drains water from the sump when open. A water level control communicates the sump water level to a control system. A monitoring mechanism detects whether the water-recirculation system has malfunctioned or is operating correctly.