What is the circular collection chamber surrounding the fan wheel of a centrifugal fan called?

The circular collection chamber surrounding the fan wheel of a centrifugal fan is referred to as a scroll. This component is designed to collect the air or gas that is discharged radially from the fan wheel and direct it towards a discharge outlet. The shape of the scroll ensures a gradual increase in air velocity while minimizing turbulence.

The scroll acts by converting the kinetic energy of the air produced by the rotating fan blades into pressure energy. As the air moves through the fan wheel, it reaches the scroll, where the cross-sectional area increases. This design allows for efficient airflow and is instrumental in enhancing the fan's performance.

In contrast, the terms associated with other options denote different components or functions. For instance, a volute is a specific type of scroll that has a spiral shape and is often associated with pumps rather than fans. The diffuser is a separate device that further expands the airflow to convert velocity into pressure, commonly seen in various applications, but not as the primary surrounding structure of the fan wheel. Louvers, on the other hand, refer to slatted devices for controlling airflow, often used for ventilation but unrelated to the main mechanism of centrifugal fan design.