Characteristics of multiple-fan ventilation networks

Summary The definitions of system pressure loss (mine head) and system resistance, which are traditionally associated with single-fan networks, are applied to multiple-fan ventilation networks. The system characteristics, relations among air power, pressure loss, air quantity and resistance, are analysed by introducing the concept of subsystems. These subsystems are associated with the fans located in a cutset of the network.For a multiple-fan network, the resistances for the subsystems and total system are dependent on the quantity ratios of the subsystems. In general the pressure loss of a subsystem or a total system does not vary as the square of the corresponding air quantity. If the quantity ratios of subsystems are all held constant, then the resistances become constant and the pressure losses are predictable from the quantities employing the square law. The system resistance has a minimum value under the natural-splitting flow pattern. Being independent of the value of system quantity, the minimum system resistance provides a basis for comparing the different networks.