A vapour compression system consist of four major system components namely; 1. refrigerant compressor 2. condenser (heat exchanger where refrigerant rejects heat and condenses to liquid form) 3. Expansion device (throttling device) 4. Evaporator (heat exchanger where refrigerant absorb heat and evaporates).
HVAC load is a function of numerous parameters and varies continuously with time. Conventionally, capacity control was often achieved by On Off cycles of the compressor. A positive displacement compressor – which often is the case – has a constant volume flow of the gas through. Development of precisely controlled variable frequency drives has created wonders universally for all processes and the concept of variable refrigerant flow system is eventually evolved.