Cooling Effectiveness of High-Volume Low-Speed Fans Versus Conventional Fans in a Free-Stall Dairy Barn in Hot, Humid Conditions

Abstract

High-volume low-speed (HVLS) fans use less energy and are quieter than conventional high-speed fans; however, data on the cooling effectiveness of these fans in a dairy free-stall barn in a hot, humid climate is limited. A 4-row free-stall dairy barn located in Tifton, Georgia was fitted with 2 redundant mechanical cooling systems. The first system utilized 0.9-m diameter high-speed cooling fans installed over the feeding area and over the free stalls 6m apart (conventional system). Each fan was equipped with 4 high-pressure mister nozzles. The second system utilized 7.3-m diameter HVLS fans installed over the center drive-through aisle at 18-m spacing (HVLS system). Evaporative cooling was provided with the same nozzles used in the conventional system. Misters were automatically turned on for both systems when relative humidity was below 85% and temperature was above 24°C. Two groups of 64 cows each were cooled randomly by one system or the other during 2 tests conducted in 2004 and 2005. Four cows within each group were fitted with vaginal temperature probes to monitor the deep body temperature every 5min on 4 consecutive d. Temperature and relative humidity inside the barn were also recorded every 5min. Air speeds in the barn were measured with each system operating separately. Observed air speeds were lower for the HVLS system (0 to 8.1 km/h) than for the conventional system (0 to 13 km/h), although air speed was more evenly distributed with the HVLS system. Body temperature was 0.2°C higher (P < 0.01) with HVLS fans compared with the conventional system. These results indicate that the HVLS fans were less effective at cooling cows than the conventional system under extremely hot, humid conditions.