Bally Refrigerated Boxes BVC Generation C – Direct Drive Air-Cooled – Vertical Air - Manual (Page 22)

- 22 -
Open Drive - This term is given to a compressor
where its driving motor is separate from the
compressor. In this type of compressor, motor heat
is not transferred to the refrigerant.
Refrigerating Effect - the total amount of heat
absorbed by the evaporator. This heat includes both
latent heat and superheat. This value is usually
expressed in BTU/Hour, (BTUH), or 1000
BTU/Hour (MBH)
Saturation - occurs whenever the refrigerant exists
in both a vapor and liquid state, example: a
cylinder of refrigerant is in a saturated condition or
state of equilibrium. Any heat removed from a
saturated vapor will result in condensation.
Conversely, any heat added to a saturated liquid
will result in evaporation of the refrigerant.
Temperature pressure charts for the various
refrigerants indicate saturation values. For a single
component refrigerant, each temperature value can
only have one pressure when the refrigerant is
either a saturated vapor or saturated liquid.
A single component refrigerant can not change
state until it approaches its saturation temperature
or pressure. For refrigerant blends, the pressure-
temperature relationship is more complex. Simply
stated, Dew point temperature (saturation point in
evaporator-low side) and Bubble point temperature
(saturation point in condenser-high side) are used to
define their saturated condition.
Subcool - to reduce a refrigerant’s temperature below
its saturation point or bubble point. Subcooling of the
refrigerant is necessary in order to maintain a solid
column of liquid at the inlet to the metering device.
Subcooling can take place naturally (in the condenser)
or it can be accomplished by a suction liquid heat
exchanger or a mechanical sub-cooler (separate
refrigeration system).
Superheat - to heat a refrigerant above its saturation
point or dew point. The “amount of superheat” is the
difference between the actual refrigerant temperature
and its saturation temperature. This value is usually
expressed in degrees Fahrenheit or degrees Celsius.
Total Heat of Rejection (THR) is the heat absorbed
at the evaporator plus the heat picked up in the
suction line plus the heat added to the refrigerant in
the compressor. Condensers are sized according to
the required THR. Compressor capacity and the heat
of compression are usually enough to determine the
THR.
GLOSSARY OF TERMS