Fan and Blower Glossary

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• Atmosphere  -  The layer of gases that surrounds a planet or celestial body and is held in place by its gravity.  On Earth, the atmosphere is the layer of gases that surrounds our planet and is composed primarily of nitrogen (78%), oxygen (21%), and trace amounts of other gases such as argon, carbon dioxide, and neon.  The Earth's atmosphere is divided into several layers based on temperature and composition.  The lowest layer is the troposphere, which extends from the Earth's surface up to an altitude of about 8-18 kilometers, depending on the location.
• Atmospheric Pressure  -  The force exerted by the weight of the Earth's atmosphere on the surface of the Earth.  It is caused by the gravitational attraction of the Earth on the molecules that make up the air in the atmosphere.  At sea level, atmospheric pressure is approximately 101.3 kilopascals (kPa) or 1 atmosphere (atm).  The pressure decreases with increasing altitude because the mass of the atmosphere above decreases.  At high altitudes, atmospheric pressure is lower than at sea level.

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• Belt  -  A loop of flexible material used to link two or more rotating shafts mechanically, most often parallel.  Belts may be used as a source of motion, to transmit power efficiently, or to track relative movement.

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• Combustion  -  A chemical reaction between a fuel and an oxidizing agent, typically oxygen in the air, that produces heat and light.  In most cases, combustion involves the rapid oxidation of hydrocarbons, such as gasoline or natural gas, in the presence of oxygen to produce carbon dioxide, water, and other combustion products.  The heat released during combustion can be harnessed to produce energy, such as in the form of heat, mechanical work, or electrical power.
• Compressor  -  A mechanical device used to increase the pressure of a gas or air by reducing its volume.  Compressors are used in a wide range of applications, such as in refrigeration systems, air conditioning systems, natural gas processing, and industrial processes.
• Constant Air Volume  -  The air volume coming into the inlet of the fan or mixing plenum box is constant.  The volume coming into
  the fan does not vary so bypass air is not necessary to maintain constant outlet velocity.
• Cross Ventilation  -  The process of air entering a room through an inlet and an outlet forcing air back out of the room.

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• Density  -  The ratio of the amount of matter in an object compared to its volume.  Density is a scalar quantity having magnitude and is independent of any specific direction.
• Downflow  -  Refers to a type of air conditioning system that discharges air downward, directly beneath a raised floor, commonly found in computer rooms and modern office spaces.
• Ductwork  -  System of pipes transports heat from the central air conditioning or heating system to the rest of the building.
• Dust Extraction  -  Dust extraction at manufacturing plants where grinding is performed or powdered materials are used.

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• Economizer  -  Uses outdoor air to reduce refrigeration requirements.  It takes advantage of cool outdoor air weather to assist mechanical cooling or, if outdoor air is cool enough, to provide total system cooling.
• Energy Efficiency  -  A measure used to quantify the energy efficiency of appliances and systems, particularly in the context of energy consumption and conservation.  It provides consumers with a standardized way to compare the energy efficiency of different products and make informed decisions when purchasing appliances.
• Enthropy  -  It is a measure of the disorder or randomness of a system and of its constituent molecules.  In thermodynamics it is a measure of the unavailability of a system's energy fo do work.
• Evaporator Coil  -  Located inside a building.  Removes heat and humidity from the air inside the building.
• Exhaust Fan  -  Fan that discharges air to the exhaust duct, or in the case of a rooftop unit, directly outdoors.  Used to balance the amount of air exhausted from the space with the amount of outside air introduced to the system.

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• Fan Curve  -  A fan’s performance at different flow and pressure settings.  Each fan model has its own fan curve and the curves look different depending on the design and size of the fans.
• Flow Curve  -  The tips of the blades are inclined in the direction of rotation.  Normally used in residential heating and air conditioning systems and light-duty exhaust systems where maximum air delivery and low noise levels are required.

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• Heat Exchanger  -  Transfers heat from one fluid to another without the fluids coming in contact with each other.  Heat transfer occurs in a heat exchanger when a fluid changes from liquid to vapor (evaporator), a vapor to a liquid (condenser) or when two fluids transfer heat without a phase change. The transfer of energy is caused by a temperature difference.
• Horsepower  -  A measure of power or the rate of doing work.  It is typically used to describe the work of an engine or machine and is the equivalent of moving 33,000 pounds through the distance of one foot in one minute.  In the context of engines, horsepower is used to measure the power output of an engine.  It is calculated by measuring the torque (rotational force) produced by the engine and multiplying it by the engine's rotational speed.
• HVAC  -  It refers to the technology, systems, and equipment used to control and regulate indoor environmental conditions, such as temperature, humidity, air quality, and air flow.

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• Impeller  -  An aluminum rotor used within regenerative blowers in order to increase flow and pressure.

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• Pressure  -  A measure of the force exerted per unit area on a surface.  It is defined as the force per unit area perpendicular to the surface over which the force is distributed.

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• Radial Blade  -  Has straight blades that are, to a large extent, self-cleaning, making them suitable for various kinds of material handling and particle-and-grease laden air.  Wheels are of simple construction and have relatively narrow blades.  They can withstand the high speeds required to operate at higher static pressures (up to 12″) but usually are noisier than FC or BI blowers.

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• Static Pressure  -  The pressure exerted by a fluid at a specific point in a flow without considering its motion or velocity.  It represents the pressure energy associated with the fluid's molecular collisions and is independent of the fluid's velocity.
• System Curve  -  The system’s frictional resistance and pressure set-up at a certain volume flow.  The system curve is unique for each application and depends on the design of the system where the fan is to be mounted.

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• Temperature  -  Normally described as the amount of heat or cold, but it is neither heat or cold.  Temperature is expressed as a number that is related to energy and porportional to a type of energy, but it is not energy.  Temperature is a number related to the average kineric energy, but is not kinetic energy.
• Total Airflow  -  The total amount of airflow exiting the windband of the fan.

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• Vacuum  -  A contained space having little or no matter or a volume having a pressure lower than the outside atmospheric pressure.  A perfect vacuum is a theoretical state in which there are no particles at all, not even photons, which are particles of light.  However, this state cannot be achieved in practice because there will always be some residual gas molecules, electromagnetic radiation, or other forms of energy present.
• Variable Air Volume  -  The air volume coming into the inlet of the fan or mixing plenum box is variable.  Usually due to multiple fume hoods being tied into a single fan and the use of the individual fumehoods varies.  The mixing plenum box is commonly used to balance out the airflow with bypass air so that the fan will always see a constant volume and maintain a constant outlet velocity.
• Velocity  -  A vector quantity having magnitude and direction that describes the rate at which an object changes its position with respect to time.  It is defined as the rate of change of displacement with respect to time.
• Ventillation  -  The fan process in which air is moved into, out of and between different areas.  Ventilation is used to replace old, stale, odiferous or contaminated air with fresher, cleaner air.
• Volume  -  A measure of the amount of space occupied by a three-dimensional object.  Volume is a extensive variable whose values depend on the quantity of substance under study.  It is expressed in terms of length cubed, a quantity of three dimensional space occupied by gas, liquid, or solid. 

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• Working Pressure  -  The normal pressure that a system operates at.  It is the maximum allowable pressure at which a system, component, or equipment can operate safely and effectively under normal conditions.  It is used in various industries and applications to ensure the reliability, integrity, and safety of the equipment and processes involved.

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