Unit installation

14
BASIC REFRIGERANT FLOW AND PROCESS & INS. DIAGRAM
These chillers work on the concept of Vapor Compression Refrigeration. At the start of operation cycle, the water (or
other liquid) flows through the water piping system, the flow switch contact is made, and if the controller calls for
cooling and all safety devices are closed, the compressor will start.
The compressor raises the pressure of the refrigerant and it is pumped to the condenser. Since this (high side)
refrigerant temperature is higher than the temperature of the air being passed through the condenser, heat flows from
the hot refrigerant gas to the condenser air. Thus, heat is absorbed by the condenser air from the refrigerant and the
high pressure refrigerant gas changes its phase to high pressure liquid. The high pressure liquid refrigerant then flows
through a filter drier, sight glass/moisture indicator, economizer (if provided) and then liquid line solenoid valve (which
should be open now). The system pressure then forces the liquid into an expansion valve which causes a large
pressure drop and also meters the liquid refrigerant through the evaporator/cooler. The refrigerant then passes
through the tubes inside the cooler while water flows over these tubes, thus heat transfers from the higher
temperature water to the lower temperature refrigerant. The water gets chilled and the liquid refrigerant evaporates
into a gas. The refrigerant is returned back to the suction side (low side) of the compressor as a low pressure gas and
is then ready to be recycled again through the compressor.
Notes:
1. This P & I diagram illustrate a single refrigeration circuit. Total number of these circuits in a particular chiller shall be as
many as the number of compressors provided in that chiller.
2. This P & I applicable for a chiller with standard features. For chillers provided with optional features like pressure gauges,
hot gas bypass system, cooler heater, etc. suitable changes in this diagram should be envisaged.
3. If ‘Economizer’ is provided in a refrigerant circuit, it optimizes the system capacity by further sub cooling the high pressure
liquid refrigerant which increases its thermodynamic efficiency. This is accomplished by a refrigerant to refrigerant brazed
plate heat exchanger in which a portion of the high pressure liquid refrigerant is vaporized thereby sub cooling the remaining
liquid refrigerant. Although this has little effect on the suction capacity of the compressor but the effective refrigerating
capacity of the compressor is boosted by the increased heat absorption capacity of the liquid entering the evaporator/cooler.
4. The ‘Liquid Injection Circuit’ is provided to allow refrigerant injection for oil cooling. The solenoid valve and liquid injection
valve provided in this circuit open in response to demand sensed by the discharge line temperature sensor (i.e. open when the
refrigerant discharge temperature rises above the set point). The liquid injection valve is required/ provided in the LI circuit
when the refrigeration circuit includes an economizer. In case the refrigeration circuit does not have an economizer, the liquid
injection valve is not required/ provided and the process of liquid injection is accomplished by the LI solenoid valve alone in
conjunction with the chiller controller.