HVLS stands for High volume low speed,
HVLS fans are large diameter fans above 7 feet in diameter normally used for cooling or air circulation over large spaces. These Ceiling fans majorly finds application for large area like auditorium, indoor stadium, railway station, airport, public places, School, cafeteria, animal cooling etc
Ceiling fans produces column of air as they rotates (shown in fig-1 air CFD) , the periphery of the column has highest air resistance, Smaller the column higher the resistance and to overcome resistance speed of the fan needs to be increased.
As the speed of fan increases, power increases in proportion of cubic root, thus to maintain air flow high power is required with lower diameter blades / fans.
HVLS can be useful for energy efficient performance with lower power as with the increase in the column diameter resistance of air reduces. As the air resistance reduces a low rpm fan can be able to deliver better performance. Therefore HVLS fans find its application for high volume of air circulation.
Being slow operation HVLS fans are quite in operation.
BLDC Technology in HVLS fans:-
HVLS fans were already energy efficient fans considering no of smaller fans and able to be operated at service value of above 7-8 (m3/min/watt). Now with the use of BLDC motor in the HVLS fans Service value can be increased to 27 (m3/min/watt), which means super efficiency in ceiling fans.
For detail in Energy Efficiency in Fans and BLDC Technology