The fundamental thermodynamic process used in mechanical refrigeration systems, converting electrical or mechanical energy into cooling capacity through phase changes of refrigerant between liquid and gas states. The cycle consists of four stages: compression (raising refrigerant pressure and temperature), condensation (rejecting heat to ambient environment as refrigerant condenses to liquid), expansion (reducing refrigerant pressure through expansion valve), and evaporation (absorbing heat from cargo space as refrigerant evaporates to gas). This cycle repeats continuously while refrigeration demand exists, with system efficiency (COP) determined by temperature differential between evaporator and condenser, refrigerant properties, compressor efficiency, and heat exchanger effectiveness. Understanding vapor compression fundamentals explains why altitude degrades performance (reduced air density impairs heat rejection), why multi-stop operations stress systems (rapid cycling between compression and defrost), and why variable-speed compressors outperform fixed-speed systems (ability to modulate capacity matches variable loads). Professional cold chain operations require engineering-level understanding of vapor compression rather than treating refrigeration as black-box magic that either works or doesn’t.
Related Terms: Mechanical Refrigeration, Transport Refrigeration Unit (TRU), Evaporator, Coefficient of Performance (COP)