Which of the following types of fans are classified as centrifugal fans?

Centrifugal fans are specifically designed to move air or gases at a right angle to the intake. They accomplish this by utilizing a rotating impeller that throws the air outward, generating a higher pressure compared to axial fans, which move air along the same axis as the impeller.

The correct classification of centrifugal fans includes forward curved, radial, and backward curved fans. Each of these types has a unique construction and operational mechanism. Forward curved fans are typically used in applications requiring high airflow at low pressure, while backward curved and radial fans are favored for their efficiency at higher pressures. These designs allow centrifugal fans to be versatile in various HVAC applications, from air conditioning systems to industrial ventilation.

Other types like axial fans, portable fans, and exhaust fans serve different purposes and function through different mechanisms. Axial fans move air parallel to the shaft and are generally used for larger air movement at lower pressures. Portable fans are typically small, movable units designed for convenience rather than high performance typically associated with centrifugal types. Exhaust fans are designed mainly to expel air from a space but do not inherently define a centrifugal mechanism since they can utilize axial or centrifugal designs depending on the specific type. Thus, the classification of centrifugal fans correctly identifies the types that utilize the principles of