Airfoils Designs Address Changing Fan Market
January 27, 2009
Due to spiraling energy costs in recent years, the market demand for large, higher efficiency axial fan blades used in industrial cooling systems such as cooling towers, chillers, condensers and air cooled heat exchangers has grown. The key to improved energy efficiency is the cross-sectional shape, or airfoil, that governs the airflow around the fan blade. In an effort to achieve better energy efficiency, the National Renewable Energy Laboratory (NREL) has developed blade root and tip airfoils that transition linearly from root to tip and have progressively changing compatible performance characteristics. These new airfoils are designed to replace the less efficient airfoils still used in many industries today but were originally designed for aircraft many years ago.
The patented NREL design has been licensed by Glocon Inc., a composite fan blade manufacturer based in Parsippany, N.J., and incorporated into its Swifter CTX Series of industrial fan blades. Developed for the OEM and replacement fan blade market, the CTX Series will include designs with fan diameters up to 33', says James Tangler of Glocon Inc. Depending on the size and application, the fan blades are expected to reduce the power consumption for a given flow rate by up to 2 percent, and potentially more for adverse operating conditions and small fan blade applications.
According to the company, key design features of the new fan airfoils focus on greater lift-to-drag ratios and lower drag relative to current airfoils. In addition to the airfoil’s inherent lower non-dimensional drag, the higher lift-to-drag ratio will allow lower rotor solidity, with an 18 percent reduction in blade chord for a given flow rate, that results in lower dimensional drag. A thinner tip airfoil is used for the CTX Series over the outer portion of the blade for lower drag while a thicker root blade airfoil is used in the lower drag root region for structural considerations.
The Glocon airfoils are designed to achieve extensive laminar flow over the suction surface of the blade in order to achieve low drag. A key feature of the airfoils - not present with aircraft airfoils - is the transition of the suction surface laminar flow to fully turbulent flow just prior to maximum lift coefficient. This design feature minimizes the effect of airfoil surface contamination on the maximum lift coefficient. Therefore, the loss of fan performance during unsteady, turbulent, inflow conditions is reduced.
For more information on the Glocon airfoils, call (973) 463-7300 or visit www.swifterfans.com.