Bally Refrigerated Boxes BVC Generation C – Direct Drive Air-Cooled – Vertical Air - Manual (Page 21)

GLOSSARY OF TERMS
Balance point - after a system stabilizes, the heat
added to the refrigerant during the refrigeration cycle
will equal the heat rejected at the condenser. The
balance point usually refers to the actual TD that the
system is operating at. The balance point could
refer to a low side balance or a high side balance.
For example, a system operating with a 120
o F
condensing temperature in a 90 o F ambient will have
a condenser balance point of 30 o F TD.
Circuit - a circuit can be considered a group of
feeds. A condenser may be sized to handle several
refrigeration systems at one time. Each system is
considered one circuit and the number of feeds
required for each circuit depends on the THR for
that particular system. Each circuit has its own inlet
and outlet header. The number of circuits on a
condenser can not exceed the total number of feeds
available.
Compression Ratio - Compression ratio equals
the discharge pressure in pounds per square inch
absolute (psia) divided by the suction pressure in
psia. The compression ratio in a compressor
increases as suction pressure decreases and as
discharge pressure increases. (at sea-level, psia is
equal to psig plus 14.7).
Compressor Capacity - can be defined as the
actual refrigerating capacity available at the
evaporator and suction line after considering the
overall system balance point. Compressor capacity
is mainly affected by the evaporating and
condensing temperatures of the system.
Condensate Line - (also called “Drain Leg”) is a
term that describes the refrigerant line between the
condenser and the receiver.
The condensate line should drop vertically and is
typically larger than the liquid line. This is to
promote free draining of the refrigerant from the
condenser to the receiver.
Condenser Temperature Difference (TD) - is the
difference between the condensing temperature of
the refrigerant and the temperature of the air
entering the condenser.
.
Condensing Temperature (CT) - is the
temperature where the refrigerant vapor condenses
back to a liquid. This temperature varies with
condenser size. Condensing temperature should be
kept as low as possible to maintain higher
refrigerating capacity and system efficiency
Desuperheat - refers to the lowering of refrigerant
superheat. Hot vapor entering a condenser must
first be desuperheated before any condensing of the
refrigerant can take place.
Evaporating Temperature - the temperature at
which heat is absorbed in the evaporator, at this
temperature, the refrigerant changes from a liquid to
a vapor. This evaporating temperature is dependent
on pressure and must be lower than the surrounding
temperature for heat transfer to take place.
Feed - a single path for refrigerant flow inside a
condenser. This path begins at the inlet header and
terminates at the condenser’s outlet header. These
feeds can be grouped together to accommodate one
or more circuits.
Heat of Compression - heat is added to the
refrigerant as it is compressed. Evidence of this can
be observed on the pressure-enthalpy diagram for
the refrigerant being used. The amount of this heat
is dependent on the refrigerant type and
compression ratio.
Additional heat from friction also increases the heat
of compression. All of this heat along with the heat
absorbed in the evaporator, suction line and any
motor heat must be rejected by the condenser.
Latent Heat of Vaporization (also Latent Heat of
Condensation) - refers to the heat required to fully
vaporize or condense a refrigerant. This latent heat
varies with temperature and pressure. Latent heat is
often referred to as
hidden heat since adding heat to a
saturated liquid or removing heat from a saturated
vapor will result in a
change of state and heat
content but not a change in temperature.
Liquid Line - is the piping between the receiver and
the metering device. On systems without a receiver,
the liquid line runs between the condenser and the
metering device.
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