Abstract: A rotational speed of a fan is maintained at a preset one when an angle of a flap is at a maximum air-flow angle, increased by a specified value when the angle of the flap has been changed by a specified angle in the direction away from the position of the maximum air-flow angle, and decreased by a specified value when the angle of the flap has been changed by a specified angle in the direction toward the position of the maximum air-flow angle. It is possible to prevent any occurrence of condensation and air-flow pulsating noise without needing any complex control such as load response control and yet without requiring any complicate construction in the flap.

Abstract: A direct contact type multi-stage steam condenser system having a direct contact type high vacuum stage steam condenser disposed above a low vacuum stage steam condenser with a water supplying tank for the low vacuum stage condenser disposed therebetween. In the preferred embodiment, the high and low vacuum stage condensers and the water supplying tank are formed integrally as a single unit. The water supplying tank, which also serves as a gas-tight seal between the condenser stages, is formed above a water sprinkling board provided in the upper portion of the low vacuum stage condenser. Condensed water falls under its own weight thereby eliminating the need for an intermediate pressurizing pumps.