Efficiency optimal operating for vane-speed parallel flow control system

In a flow control system with a fan, the variable speed drive is becoming popular because of its cost-effectiveness compared with conventional vane or damper flow control systems. But, for the large system which requires the parallel operation of several fans, it cannot always be said that driving all the fans with variable speed is the best or most cost-effective choice. In this regard, a variable speed drive fan and a constant speed drive fan with vane control under conditions of parallel operation are dealt with. The total energy consumed in the vane-speed parallel flow control system depends on the operating points of the fan speed and the vane opening, and three will exist an optimal combination of the speed of one and the vane opening of the other that minimizes the total power consumption. This optimal combination is derived from a mathematical model and tested on actual fans for a generating boiler system. The results confirm the validity of the theoretical analysis