Technical FeaTure Figure 11 Temperature gradient in a counterflow film filled cooling tower, showing Figure 12 Water pull-back with fans operating on a counterflow. lower temperature at the perimeter and higher temperature at the center. 60°F Entering Water Temperature Warm Water In - Warm Air Out 58°F 45°F Falling Water Cold Air In Fill 35°F Cold Air In Net 40°F Water In Cold Water Basin prevent excessive icing that can result in cooling tower damage. Icing Control - Crossflow. Figure 8 shows lines of constant temperature in crossflow cooling tower fill. This typifies what must occur in Cell 3 (Figure 5, Page 28) to produce 40°F cold water with 60°F water entering. Water flows downward between fill sheets by gravity. The www.info.hotims.com/49802-4 30 ASHRAE JouRnAl ashrae.org March 2014 Cold Air In Falling Water Cold Air In temperature at the bottom of the air inlet face is about 32°F (0°C), at freezing, even though the average is 40°F (4°C) leaving the cell. Water flow slants in the direction of airflow, as shown in Figure 8, sloping along with the fill. Crossflow film fills are designed to slope at an angle compatible with the pull-back of water toward the air discharge face. Water is CourTesy of sPX Cooling TeChnologies 34°F CourTesy of sPX Cooling TeChnologies 50°F 40°F