Training Manual on Energy Efficiency - APO Asian Productivity ...
Training Manual on Energy Efficiency - APO Asian Productivity ...
Training Manual on Energy Efficiency - APO Asian Productivity ...
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8. ENERGY EFFICIENCY IN FANS<br />
8.1 INTRODUCTION<br />
Fans and blowers provide air for ventilati<strong>on</strong> and industrial process<br />
requirements. Fans generate a pressure to move air (or gases) against<br />
resistance caused by ducts, dampers, or other comp<strong>on</strong>ents in a fan system.<br />
The fan rotor receives energy from a rotating shaft and transmits it to the air<br />
as pressure energy.<br />
Figure 8-1 Basic diagram of a fan<br />
Difference between fans, blowers, and compressors:<br />
Fans, blowers, and compressors are differentiated by the method used to move<br />
the air, and by the system pressure they must operate against. As per the<br />
American Society of Mechanical Engineers (ASME), the specific ratio—the ratio<br />
of the discharge pressure over the sucti<strong>on</strong> pressure—is used for fans, blowers,<br />
and compressors. Accordingly, fans offer a pressure rise up to 1136 mmWg,<br />
blowers offer from 1136 to 2066 mmWg, and compressors offer pressure rises<br />
even higher than blowers.<br />
8.2 FAN TYPES<br />
Fans fall into two general categories: centrifugal flow and axial flow. In<br />
centrifugal flow, airflow changes directi<strong>on</strong> twice: <strong>on</strong>ce when entering the fan<br />
and again when leaving (forward-curved, backward-curved or -inclined, and<br />
radial types). In axial flow, air enters and leaves the fan with no change in<br />
directi<strong>on</strong> (propeller, tube axial, vane axial).<br />
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