A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
F.P.M.: A measure of air velocity in feet per
minute.
FACE VELOCITY: The velocity obtained by dividing
the air quantity by the component face area.
FAN, CENTRIFUGAL: A fan rotor or wheel within
a scroll type housing and including driving mechanism
supports for either belt drive or direct connection.
FAN COIL UNIT (FCU): a small packaged unit for
both heating and cooling one zone.
FAN PERFORMANCE CURVE: Fan performance curve
refers to the constant speed performance curve.
This is a graphical presentation of static or
total pressure and power input over a range of
air volume flow rate at a stated inlet density
and fan speed. It may include static and mechanical
efficiency curves. The range of air volume flow
rate which is covered generally extends from shutoff
(zero air volume flow rate) to free delivery (zero
fan static pressure). The pressure curves are
generally referred to as the pressure-volume curves.
FAN STATIC PRESSURE: The pressure added to the
system by the fan. It equals the sum of pressure
losses in the system minus the velocity pressure
in the air at the fan inlet.
FAN, TUBEAXIAL: A propeller or disc type wheel
within a cylinder and including driving mechanism
supports for either belt drive or direct connection.
FAN, VANEAXIAL: A disc type wheel within a cylinder,
a set of air guide vanes located either before
or after the wheel and including driving mechanism
supports for either belt drive or direct connection.
FEDERAL REGISTER: Publication of U.S. government
documents officially promulgated under the law,
documents whose validity depends upon such publication.
It is published on each day following a government
working day. It is, in effect, the daily supplement
to the Code of Federal Regulations, CFR.
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FEVER: An abnormal temperature of the body above
98.6oF (37oC). Exercise, anxiety, and dehydration
may increase the temperature of healthy people.
Infection, nerve disease, cancer, anemia, and
many drugs may cause fever. No single theory explains
why the temperature is increased. Fever increases
metabolism 7% per oC, meaning more food needs
to be eaten. Convulsions may occur in children
whose fevers tend to rise quickly. Confusion is
seen with high fevers in adults and in children.
It may begin quickly or gradually. The period
of highest fever is called the stadium or fastigium.
It may last for a few days or up to 3 weeks.
FILTER: A device to remove solid material from
a fluid.
FILTER EFFICIENCY: The efficiency of various
filters can be established on the basis of entrapped
particles; i.e., collection efficiency, or on
the basis of particles passed through the filter,
i.e., penetration efficiency.
FILTER, HEPA: High-efficiency particulate air
filter that is at least 99.97 percent efficient
in removing thermally generated monodisperse dioctylphthalate
smoke particles with a diameter of 0.3u.
FLOW COEFFICIENT: A correction factor used for
figuring volume flow rate of a fluid through an
orifice. This factor includes the effects of contraction
and turbulence loss (covered by the coefficient
of discharge), plus the compressibility effect,
and the effect of an upstream velocity other than
zero. Since the latter two effects are negligible
in many instances, the flow Coefficient is often
equal to the coefficient of discharge.
FLUID: Gas, vapor, or liquid.
FOLLOW UP TESTING: the testing designed to confirm
the results of the initial testing using identical
testing devices and similar test conditions.
FREE AREA: The actual measured perpendicular
area between the fins of a grille or register.
FLYWHEEL EFFECT: In HVAC systems, to even out
temperature variations in a building due to the
temperature storage capabilities of the building's
mass.
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FREQUENCY: The number of vibrations, waves, or
cycles of any periodic phenomenon per second.
In architectural acoustics, the interest lies
in the audible frequency range of 20 to 20,000
cps Hertz (cycles per second).
FREQUENCY SPECTRUM: Usually a visual representation
of a complex sound or noise which has been resolved
into frequency components. The detailed nature
of a complex sound may be studied by obtaining
its frequency spectrum. Frequency spectra are
commonly obtained in octave bands, 1/3-octave
bands, and various narrow bands.
FRICTION: Friction is the resistance found at
the duct and piping walls. Resistance creates
a static pressure loss in systems. The primary
purpose of a fan or pump is to produce a design
volume of fluid at a pressure equal to the frictional resistance
of the system and the other dynamic pressure losses
of the components.
FUMES: Airborne solid particles usually less
than 1 micrometer (um) in size formed by condensation
of vapors, sublimation, distillation, calcination,
or chemical reaction.
FUNGI: the unicellular of multi-cellular eukaryotic
organisms embracing a large group of micro-flora
including molds, mildews, yeasts, mushrooms, rusts,
and smuts. Fungi are heterotrophic, i.e., requiring
external food sources, as well as a source of
nitrogen other than atmospheric nitrogen. Most
fungi produce spores, which all broadcast through
the air so that virtually all environmental surfaces
will have some fungal material. Few fungi actually
invade living cells and cause infectious disease.
Most health effects are associated with allergic
responses to antigenic material or toxic effects
from mycotoxins. Another potential adverse indoor
air effect of fungi is their ability to metabolize
substrate material and generate certain volatile
organic compounds.
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