CONSERVING ENERGY IN AIR HANDLING SYSTEMS.

The first step in an air handling system energy conservation program is to analyze the plant's current needs. Many plants use heated, cooled, process, or ventilation air for several functions simultaneously. Requirements or operations may have changed since the system was installed, and airflow should be selected to satisfy the current job needing the greatest amount. Five factors determine necessary airflow: heat-transfer capacity, terminal velocity, conveying velocity, dilution, and makeup quantity. More than one must be evaluated in almost all industrial applications. Once the correct plant air requirement is determined, a pitot tube traverse of each duct must be taken to calculate current air volume accurately. Even fairly small reductions in airflow produce substantial energy savings because fan horsepower is proportional to air volume cubed. Fan speed is usually adjusted by changing sheaves and belts to attain maximum savings when reducing airflow.