Fan Size and Energy Efficiency

The use of ceiling mounted circulating fans to provide air movement for cooling in industrial premises and animal houses is particularly essential in warm, humid climates. Methods to substantially improve the efficiency of this approach are demonstrated in this paper. Fan laws are identified as one source of strategies for increasing energy-efficiency of fans. Industrial ceiling fans are used to demonstrate that using larger, slower, fans will not only improve energy efficiency but also reduce fan noise. By using large diameter fans (7.3m diameter) in place of conventional fans, energy savings of over 40% are demonstrated. Field studies of air flow characteristics from ceiling fans are shown to provide further opportunities to increase air flow efficiency in industrial buildings. Utilising lower friction losses associated with the Coanda effect in air flow adjacent to the floor is shown to increase air flow toward the outer limits of the radial outflow. Lower fan mounting heights are also shown to provide increased air flow toward the outer limits of the radial outflow. For situations where the floor plane has numerous obstructions to air flow, CFD software is suggested as a means to simulate air flow before installation of fans. Where possible, validation of CFD software output against physical measurements is advised.