Performance Comparison of Destratification Fans for Large Spaces

Ceiling fan is proven to have a beneficial effect on increasing air velocity and reducing temperature stratification and thus saving energy for high ceiling applications. Studies show that the velocities produced by large diameter, ceiling mounted fans do not produce a negative or positive effect on human comfort. Recently, smaller, high velocity fans have been introduced to the market as an alternative to these large diameter fans that provides similar energy savings due to reduced destratification, while still not moving the air fast enough to cause human discomfort, though these products have been studied less. This study simulates and compares the performance of both large and small diameter fans using a validated computational fluid dynamics (CFD) model. Two different types of destratification fans are investigated for their performance in destratifying the air temperatures in warehouse style retail stores. A portion of a retail store is used as a base to create the test environment. Simulations show that the small diameter high speed fan (SDHSF) is very good at bringing a well-mixed column of air all the way to the floor, but the spaces without a fan directly overhead are hardly affected. The large diameter low speed fans (LDLSF) are able to mix nearly the entire space, though they created uncomfortable drafts near head height. Between these two fans, the LDLSF is more successful at destratifying the entire space, though the SDHSF is better at only destratifying a specific, smaller area. Varying the speed of the LDLSF also allows for successful destratification, while maintaining acceptable draft velocities.