8
201 Dryer Circuit Flow Diagram
There are two (2) basic sections, commonly referred to as the high and low pressure sections, in a refrigeration circuit.
The high side begins at the refrigerant compressor discharge port and ends at the expansion valve. The circuit leaving the
expansion valve through the air to refrigerant heat exchanger and up to the compressor suction port is known as the low
pressure circuit.
The compressor takes in low pressure refrigerant gas and compresses it to a high pressure and high temperature gas.
The high temperature gas passes into the refrigerant condenser where it is cooled and liquefied. The refrigerant then
passes through the filter dryer where moisture and any foreign particles are removed.
The refrigerant then passes through an expansion valve where the liquid refrigerant is throttled and a temperature drop will
occur as part of the liquid turns into gas. The cold refrigerant gas and liquid then enters the refrigerant-to-air heat exchang-
er where it absorbs the heat from the compressed air as it evaporates. The low pressure refrigerant gas returns to the
compressor for repetition of the process.
Load Control
The expansion of the refrigerant is controlled by a thermal expansion valve. The expansion valve
responds to the suction temperature; As the suction line temperature increases, the expansion valve is
opened to allow more liquid refrigerant to feed into the evaporator. This increased volume of liquid causes
a greater cooling effect. The suction temperature drops and the valve throttles back. In addition, the circuit
incorporates a hot gas bypass valve. This valve feeds a small amount of high temperature gas from the
high side directly into the air refrigerant heat exchanger to enable easier control of the dryer at light or no
load conditions. As the load increases, the evaporator temperature and pressure begin to rise. The
increase of temperature causes the expansion to open and let more refrigerant into the evaporator. As
this occurs, the increased pressure causes the hot gas valve to close. This will continue until the dryer is
operating at full load at which time the expansion valve has full control and the hot gas valve is closed.
REFRIGERATED AIR DRYER INSTRUCTION MANUAL
Ultra Air Refrigerated Dryers
201 Series Instruction Manual
General Information
The Ultra Air 201 Series Refrigerated Air Dryer is a constantly running, non-cycling type with a hermetic
type refrigeration compressor and is available with a water cooled or air cooled condenser.
The following are the five phases that take place in the drying process:
Phase 1 - Precooling
Warm, saturated air enters the air to air heat exchanger, where it is cooled by outgoing cooled air flowing
in the opposite direction.
Phase 2 - Preseparation
As the air is precooled, some of the moisture condenses. During this phase, all condensed moisture and
oil is separated from the compressed air.
Phase 3 - Chiller
The air then enters and is further cooled in the refrigeration chiller. The air stream is cooled to 35-39ºF
(1.6-3.8ºC), reducing its dewpoint to the same temperature.
Phase 4 - Separation
As the air is cooled in the chiller, the moisture condenses into a liquid. At this point, all liquid, via the sep-
arator is removed from the air stream and drained away with an electronic draining device.
Phase 5 - Reheating
The cold, dry air is reheated by incoming warm air as it passes back through the air to air heat exchanger.
