DCS RF48SS, Service Manual, Page: 16 / 74

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1. Principles of the Cold Cycle
1) Compressed Stroke (Adiabatic Compression)
Low temperature and pressure gas absorbed from the evaporator is compressed
rapidly by the piston, the work applied to the gas will be changed into heat and the gas
becomes high temperature and pressure. (It is considered as adiabatic
compression as the heat doesn’t come in or go out in this process.)
2) Condensed Stroke (Isothermal Compression)
High temperature and pressure gas is discharged from the compressor, gets cooled after it
enters the condenser. As it emits the residual heat through the condensation until it changes
to a liquid state, the temperature doesn’t change. Only its state changes.
This state is the isothermal compression. This state is called super-cooling the
temperature of the gas which is completely liquefied at the end of the condenser drops.
3) Pressure Reducing Stroke (Adiabatic Expansion)
When the liquefied gas in room temperature and high pressure goes through rapid throttling
action in the capillary tube, it expands quickly and goes into the evaporator. At this time, its
temperature drops, and it is due to its adiabatic expansion, not to take heat away from its
surrounding during its throttling action.
4) Evaporating Stroke (Isothermal Expansion)
The gas that came into the evaporator has already get cooled, but its liquefied part keeps
evaporating until it gets completely vaporized and takes the residual heat of evaporation away
from the surrounding.
2. Roles of the Cold Cycle Components
Compressor: It compresses gas in low temperature and pressure into that of high temperature
and pressure and circulates the gas in the cycle.
Condenser: It condenses gas refrigerant in high temperature and pressure into liquid refrigerant
in room temperature and high pressure.
Capillary Tube: It decompresses liquid refrigerant in room temperature and high pressure, and
expands it into low temperature and pressure.
Evaporator: The liquid refrigerant in low temperature and pressure takes heat away from its
surrounding, and changes into gas in low temperature and pressure.
■
Throttling Action
When gas passes the area whose resistance is high, the pressure drops to its flowing direction
due to the friction or dispersion of its flow. In other words, the pressure drop at the narrow area
is said to be throttling. The extent of the pressure drop depends on the properties, states and
speed of gas and on the sizes of the capillary whose passage gets narrow.
3. How the Refrigeration Cycle Components Work
■ Condenser
1) Roles: It emits heat to the outside (water/air) to change gas refrigerant in high temperature
and pressure, which is discharged from the compressor, into liquid.
2) Types
A. Air Cooling Type: It condenses air by circulating it naturally or compulsorily.
①
Natural Convection Type: It uses a home refrigerator whose condensing capacity is small.
②
Forced Convection Type: It circulates air using a fan-motor forcibly (large capacity).
B. Hydro-Cooling Type: It passes water coolants into the pipes of the condenser (large capacity).
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