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NORA Advanced Air Flow

National Oilheat Research Alliance 3 Advanced Airflow Fans and Air Flow Airflow and the components to create it (fans, motors and ducts) move heated, cooled, or otherwise conditioned air throughout a building and return it to be treated again. Factors that affect airflow can either positively or adversely affect system performance, efficiency and reliability. A heating or cooling system will perform no better than its air distribution system. All adequate air distribution systems must: • Supply the right amount of air to each conditioned space • Supply the air in each space so that air motion is adequate but not drafty • Condition the air to maintain proper comfort • Return air from all conditioned spaces • Operate efficiently without excessive power consumption or noise • Operate with minimum maintenance Most air distribution systems are forced-air systems. The primary components that make up a system are the furnace, air supply system and the grilles and registers that allow the circulated air to enter the conditioned space and return it to the heating or cooling system. The air is moved through the system by the force of a fan. In older gravity systems, air was moved by heating it. Since hot air is lighter (less dense) than cold air, it rises up into the building from the heat exchanger through the supply ducts. The cooler return air, being heavier, falls back to the furnace through the return ducts. In modern systems, air moves through ductwork because the fan creates a pressure difference in the airstream: lower pressure in the return and higher pressure in the supply. The amount of air the blower can move and the amount of energy needed to move the air is controlled by the resistance to airflow from the ductwork and all the components in the airstream. In general, fans have the highest capacity when they are in open air, without any restrictions to airflow. The capacity of the fan decreases when it moves air against a pressure difference. Such a pressure difference is created when air is constrained by ductwork. The three different pressures that exist in a duct system are static pressure, velocity pressure and total pressure. Static Pressure The definition of the word static is “lacking in movement or change.” When a balloon is blown up, the air within pushes out evenly in all directions, creating static pressure inside the balloon, causing it to expand. The air that makes up the earth’s atmosphere has weight. It pushes down on the surface at about 14.7 pounds per square inch at sea level. This is called atmospheric or barometric pressure. The static pressure inside an inflated balloon is pushing against the atmospheric pressure outside the balloon. If the static pressure is greater than the atmospheric pressure, the balloon inflates. When the fan blows air into the ductwork it creates static pressure on all the interior sur


NORA Advanced Air Flow
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