Table 1 shows an R-134a refrigeration system with an overcharge of refrigerant. Notice the 30 degrees of liquid subcooling backed up in the condenser. Because of the overcharge of refrigerant, the condenser will have too
much liquid backed up in its bottom, causing high condenser subcooling. By overcharging a system with too much refrigerant, increased liquid subcooling amounts will be realized in the condenser.
However, just because a system has increased subcooling amounts in the condenser doesn’t necessarily mean the system is overcharged. This will be explained in the next two system checks. Remember, the condenser is where refrigerant vapor is condensed and liquid refrigerant is formed. This backed-up subcooled liquid at the condenser’s bottom will take up valuable condenser volume, leaving less volume for desuperheating and condensation of refrigerant vapors.
Too much liquid subcooling at the condenser’s bottom will cause unwanted inefficiencies by raising the head pressure and the compression ratio. Higher compression ratios cause lower volumetric efficiencies and lower mass flow rates of refrigerant through the refrigeration system. Higher superheated compressor discharge temperatures will also be realized from the higher heat of compression caused from the high compression ratio.
Remember, most conventional condensers’ functions are to:
- Desuperheat compressor discharge vapors
- Condense these vapors to liquid, and
- Subcool refrigerant at its bottom.