A cheap radial-vaned centrifugal fan is required to provide a supply of pressurized air to a furnace. The specification requires that the fan produce a total pressure rise equivalent to 7.5 cm of water at a volume flow rate of 0.2 m3 /s. The fan impeller is fabricated from 30 thin sheet metal vanes, the ratio of the passage width to circumferential pitch at the impeller exit being specified as 0.5, and the ratio of the radial velocity to blade tip speed as 0.1. Assuming that the overall isentropic efficiency of the fan is 0.75 and that the slip can be estimated from Stanitz's expression, Eq. (7.34b), determine
a. the vane tip speed;
b. the rotational speed and diameter of the impeller;
c. the power required to drive the fan if the mechanical efficiency is 0.95;
d. the specific speed. For air assume the pressure is 105 Pa and the temperature is 20°C
