Engineering Letter Glossary - New York Blower

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BACKDRAFT DAMPER damper used in a system to relieveair pressure in one direction and to prevent airflow in theopposite direction.BALANCING the process of adding (or removing) weight on arotor in order to move the center of gravity toward the axis ofrotation.BARCOL NUMBER a standard measure of FRP surface hardness.BAROMETRIC PRESSURE a measurement of the pressure ofthe atmosphere; standard is 29.92" Hg.BEARING LOSSES the power losses resulting from friction inthe main bearings.BERNOULLI’S THEOREM the principle that the total energyper unit of mass in the streamline flow of a moving fluid isconstant, being the sum of the potential energy, the kineticenergy, and the energy due to pressure. In terms of airmovement, the theorem states that the static pressure plusvelocity pressure as measured at a point upstream in the directionof airflow is equal to the static pressure plus velocity pressureas measured at a point downstream in the direction of airflowplus the friction and dynamic losses between the points.BI fan wheel design with backwardly-inclined blades.BILLET a section of semi-finished metal or non-ferrous alloy.BLADE LINERS pieces of material added over the wheelblades to reduce abrasion of the blades.BLADE-PASS FREQUENCY the tone generated by the bladespassing a fixed object.BLAST AREA the fan outlet area less the projected area of thecut-off.BOILER HORSEPOWER the capability to evaporate 34.5pounds of water per hour into dry steam at 2 12°F. at sea level;33,500 BTU/Hr.BRAKE HORSEPOWER [BHP] mechanical energy consumedat a rate of 33,000 ft. lbs. per minute; a consumption rating, ascompared to the production rating of horsepower itself.BREAKDOWN TORQUE maximum torque a motor willproduce without a sudden decrease in speed. Often referred toas pull-out torque or maximum torque.BRINELL NUMBER a standard measure of metal surfacehardness; metals with Brinell hardness ratings of 250 or moreare generally considered abrasion-resistant.BTU British Thermal Unit; heat required to raise thetemperature of 1 pound of water by 1 °F. The Btu/hr. required toraise the temperature of a volume of standard air a specificnumber of degrees is calculated by the formula:Btu/hr = Temp. Rise x CFM x 1.085CAPACITOR START MOTOR type of single-phase inductionmotor with a capacitor connected in series with the startingwinding. High-starting and breakdown torque, medium startingcurrent. Used in hard-starting applications; compressors,pumps, etc.CAPTURE VELOCITY air velocity necessary to overcomeopposing air currents or natural flow and cause contaminatedair, fumes, or material to flow in a desired direction.CATALYST the final ingredient that triggers the chemicalreaction known as curing, which converts liquid resin to a solid.CELSIUS a thermometric scale in which water boils at 100°and freezes at 0°, same as centigrade:°C = .5556 x [°F. - 32°]CENTRIFUGAL FAN a fan design in which air is dischargedperpendicular to the wheel’s rotational axis.CFM cubic feet per minute; the volume of flow for a givenfan or system.COATINGS specialty coverings, typically referred to as paints,with varying degrees of resistance to atmospheric or chemicalcorrosion.COEFFICIENT OF CONDUCTIVITY the rate of heat transferthrough a material, expressed in Btu transmitted per hourthrough one square foot of surface per degree difference intemperature across the material. Figures are usually expressedfor basic materials, such as wood or insulation; per inch ofthickness, and called by the symbol “K”.COMPRESSIBILITY a factor used by fan manufacturers tocorrect performance ratings in higher pressure ranges toaccount for the fact that air is a compressible gas that does notfollow the perfect gas laws.COMPRESSION a phenomenon related to positive pressure.When air is forced into a system it is compressed and becomesmore dense. Depending on the volume or weight of airrequired down stream in the positive pressure portion of thesystem, the volume of air at the inlet of a fan may have to beadjusted by the ratio of absolute pressure at the entrance of thefan versus the design requirements in the system.CONVEYING VELOCITY the air velocity required in a ductsystem to maintain entrainment of a specific material.CORROSION the deterioration of a material by chemical orelectrochemical reaction resulting from exposure to weathering,moisture, chemical, or other agents in the environment inwhich it is placed.CRP Certified Ratings Program.CSA Canadian Standards Association. Sets safety standards formotors and other electrical equipment used in Canada.Page 2
CURVE, FAN PERFORMANCE a graphic representation of EFFICIENCY, STATIC the ratio of fan output less the kineticTP x CFMFOOT-POUND (Ft. - Lb.) torque rating or requirement;ME = 6356 x BHP equivalent to the force required to move a one-pound weightstatic or total pressure and fan BHP requirements over anairflow volume range at a stated inlet density and fan speed.energy [outlet-velocity pressure] leaving the fan to the powerapplied to the fan:CURVE, SYSTEM a graphic representation of the pressureSP x CFMSE =versus flow characteristics of a given system and density.6356 X BHPDAMPER an accessory to be installed at the fan inlet or outletfor air-volume modulation.dbA sound-pressure level corrected to the “A” weighingnetwork.DECIBEL the logarithmic ratio between some known referenceELEVATION the distance of the subject site above or belowsea level.END REFLECTION a known value of sound radiated backinto a duct or opening.ENTHALPY the heat content per unit mass of a substance.and some quantity of electric or acoustic signal power.ENTRY LOSS the loss in pressure caused by air flowing into aDENSITY the measure of unit mass equal to its weight divided system; normally expressed in fractions of velocity pressure.by its volume (lbs./ft.3); standard air is .075 lbs./ft. 3 .EQUIVALENT DUCT DIAMETER for rectangular duct withDEW POINT the temperature at which condensation begins to sides a and b is:form as air is cooled.D = (4ab/π) 0.5DFT dry-film thickness usually expressed in thousandths ofan inch (mils).EVASE a diffuser at the fan outlet which gradually increases inarea to decrease velocity and to convert kinetic energy to staticDIFFERENTIAL PRESSURE the difference of static pressuresat the fan outlet and inlet; also see FAN CAPACITY.DILUTION VENTILATING the mixing of contaminated airwith uncontaminated supply air for the purpose of attainingacceptable working or living conditions.DIRECTIVITY FACTOR the number representative of theradiation characteristics of a sound source.pressure [regain.]FAHRENHEIT a thermometric scale in which water boils at212° and freezes at 32°.°F = (1.8 x °C) + 32°FAN a power-driven machine which moves a continuousvolume of air by converting rotational mechanical energy to anincrease in the total pressure of the moving air.DRY-BULB TEMPERATURE the combined temperature of awater vapor and air mixture.FAN CAPACITY performance requirement for which a fan isDUST air suspension of particles [aerosol] of any solidselected to meet specific system calculations given in terms ofACFM at the fan inlet.material, usually with a particle size smaller than 100micrometers.FAN CLASS operating limits at which a fan must be physicallycapable of operating safely.DUST COLLECTOR an air-cleaning device used to removeheavy-particulate loadings from exhaust systems prior to FAN LAWS theoretical constant relationships between CFM,discharge.RPM, SP, and BHP for a given fan used in a given fixedsystem:DWDI double-width, double-inlet fans, Arrangement 3.CFM varies as RPMDYNAMIC BALANCE the mechanical balancing of a rotatingpart or assembly in motion.DYNAMIC INSERTION LOSS a reduction of airborne noiseSP varies as (RPM) 2BHP varies as (RPM) 3FC fan wheel design using forward-curved blades.levels affected by the installation of an acoustical silencer.FINITE ELEMENT ANALYSIS (FEA) computerized analyticalDYNE a unit of force equal to that which would accelerate one technique used to divide a rotating body into many segments togram by one centimeter per second.determine the stress of each segment and therefore thecomplete body.EFFICIENCY, MECHANICAL TOTAL the ratio of fan outputto the power applied to the fan. Can be helpful in selecting fan FLASHING sheet-metal strip placed at the junction of intersectingsize, type, or manufacturer for the same application:exterior building surfaces to make the joint water-tight.one foot in distance, equal to 12 in.-lb.Page 3
Page 4 and 5: FORCED DRAFT how air is provided in
Page 6 and 7: PHENOLIC a thermosetting resin syst
Page 8: TUBULAR CENTRIFUGAL FAN fan with a

Engineering Letter Glossary - New York Blower

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