CEMS CHILLER · 30.10.2026
A chiller does more than cool water: it transfers heat from a production process or air-conditioning system to another environment under controlled conditions. Understanding its diagram helps clarify component functions and define a project’s requirements.
A vapour-compression chiller contains a refrigerant circuit and a chilled-water circuit. The refrigerant transports heat through pressure and phase changes. Water or a suitable water-glycol mixture carries heat from the process equipment to the evaporator. In normal operation, the fluids do not mix: heat passes through the heat exchanger surfaces.
An air-cooled chiller rejects condenser heat to outdoor air. A water-cooled chiller needs a separate condenser-water circuit and a suitable heat-rejection system. The air-cooled schematic below therefore does not represent the exact piping arrangement of every unit.
Low-pressure vapour from the evaporator enters the compressor. Compression raises its pressure and temperature and maintains refrigerant circulation. Selection of scroll, reciprocating or screw compressors depends on capacity, operating temperatures, refrigerant and load profile.
Preventing liquid carryover, maintaining lubrication and respecting the manufacturer’s operating envelope are essential. Multiple compressors or variable-speed control can help match capacity to demand in a suitable design; not every model uses the same control arrangement.
Hot, high-pressure vapour leaving the compressor releases heat in the condenser and condenses. In an air-cooled unit, fans move air across the coil. The heat rejected includes heat absorbed in the evaporator as well as energy transferred to the refrigerant by the compressor.
Dirty coils, restricted airflow or recirculation of hot discharge air can impair heat rejection. Installation clearances and permissible ambient temperatures must follow the specific model’s technical documentation.
As liquid refrigerant passes through the expansion device, its pressure falls and a portion flashes into vapour. A low-pressure liquid-vapour mixture enters the evaporator. A thermostatic or electronic expansion valve, with an appropriate control arrangement, regulates refrigerant feed and evaporator outlet superheat.
The valve does not produce cooling on its own; it operates as part of the complete cycle. Refrigerant, capacity and pressure differential affect selection. Valve and superheat settings must not be adjusted arbitrarily by the user.
Inside the evaporator, refrigerant absorbs heat from the water circuit and evaporates. Cooled water is supplied to the process or HVAC load. Plate and shell-and-tube heat exchangers serve different applications; selection considers water quality, pressure drop, capacity, service access and freezing risk.
Insufficient flow, an unsuitable fluid or incorrect temperature settings can increase freezing risk. Flow monitoring, temperature sensors and suitable freeze protection must be considered together. Where glycol is needed, its type and concentration must suit the project, with its effects included in capacity and pump calculations.
A filter drier helps control moisture and certain contaminants. Where installed, a sight glass allows observation of refrigerant and, with suitable types, a moisture indicator; it does not prove correct refrigerant charge on its own. Solenoid and check valves provide functions such as flow control and prevention of reverse flow.
A liquid receiver, suction accumulator and oil separator have different roles and are not required in every chiller. A receiver supports liquid refrigerant management; an accumulator helps reduce the risk of liquid returning to the compressor; an oil separator supports oil return in a suitable arrangement. Verify the actual equipment and locations against the unit’s circuit diagram.
The circulation pump provides the required flow and overcomes circuit pressure losses. Motor power alone is not a pump-selection criterion: flow and head at the operating point must be considered together. A strainer or suitable filter helps protect the heat exchanger but requires regular inspection and cleaning.
A buffer tank can increase system water volume and thermal stability. An expansion vessel accommodates temperature-related volume changes in a closed hydraulic circuit; the two are not interchangeable. Air removal, filling and draining points, appropriate safety devices and service valves are defined for the project.
A flow switch or sensor monitors acceptable flow conditions. A running pump does not by itself prove that the evaporator receives sufficient flow. The illustrated pump position is indicative; actual placement depends on the hydraulic design.
The controller coordinates compressors, fans, pumps and valves using temperature, pressure and flow information. High- and low-pressure protection, motor protection and electrical monitoring depend on the unit design. Sensor readings must be assessed alongside actual operating conditions.
Do not bypass safety devices or repeatedly reset recurring alarms to keep a unit running. Work on electrical and refrigerant circuits must be carried out by qualified personnel following the manufacturer’s procedures.
Define cooling duty, entering and leaving water temperatures, flow, piping pressure losses, fluid type, ambient conditions and changing load together. Two units with the same nominal capacity may perform differently at different water and ambient temperatures.
A technical review with CEMS Chiller should cover hydraulic connections, control requirements and maintenance access as well as the refrigeration circuit. Confirm the final equipment list, electrical diagram and piping diagram against project-specific documents.
Illustrative air-cooled cycle, not an installation or service drawing. Colours distinguish fluid states, not actual temperatures or pressures. Water and refrigerant do not mix. Auxiliary components are omitted for clarity.
Low-pressure vapour from the evaporator enters the compressor. Compression raises its pressure and temperature and maintains refrigerant circulation. Selection of scroll, reciprocating or screw compressors depends on capacity, operating temperatures, refrigerant and load profile.