Refrigeration memory aid
Quick definitions of key concepts, units and practical benchmarks in refrigeration.
Field essentials
Daily-check quantities used for system setup and troubleshooting.
Volumetric flow rate
Volume of fluid passing through a section per unit of time.
Common unit: m³/s (or m³/h)
Mass flow rate
Mass of fluid circulating in a system per unit of time.
Common unit: kg/s (or kg/h)
Density
Mass of a fluid per unit volume.
Common unit: kg/m³
Viscosity
Measure of a fluid's resistance to flow.
Common unit: Pa.s (often mPa.s)
Temperature
Quantity that describes the thermal state of a fluid or medium.
Common unit: °C (or K)
Superheat (SH)
Difference between actual suction temperature and saturation temperature at low pressure.
Common unit: K (or °C)
Subcooling (SC)
Difference between saturation temperature at high pressure and liquid line temperature after condenser.
Common unit: K (or °C)
HP / LP
HP = condensing pressure, LP = evaporating pressure. Core values to read the cycle.
Common unit: bar(g)
ΔT evap. / cond.
Difference between air temperature and evaporating/condensing temperature, used as heat-exchange indicator.
Common unit: K
COP / EER
Efficiency indicators: useful cooling/heating output divided by electrical input power.
Common unit: Dimensionless
Refrigeration capacity
Cooling output delivered by the system (e.g. Q = m_dot x Δh).
Common unit: kW
Relative humidity (RH)
Ratio between actual air moisture and maximum possible moisture at the same temperature.
Common unit: %
Airflow rate
Volume of air moved per unit time through a heat exchanger or room.
Common unit: m³/h
Advanced thermodynamics
Diagram and refrigerant-blend notions useful for deeper analysis.
Isobar
Curve representing a process at constant pressure.
Common unit: None (process curve)
Isotherm
Curve representing a process at constant temperature.
Common unit: None (process curve)
Isochore
Curve representing a process at constant specific volume.
Common unit: None (process curve)
Dew point
Vapor-side saturation temperature of a blend. Used for superheat calculations.
Common unit: °C
Bubble point
Liquid-side saturation temperature of a blend. Used for subcooling calculations.
Common unit: °C
Temperature glide
Difference between bubble point and dew point in a zeotropic blend.
Common unit: K
Commissioning and diagnostics
Practical reminders for safety, adjustment and system verification.
ASHRAE class
Refrigerant safety classification (toxicity/flammability): A1, A2L, A3, B2L, etc.
Common unit: Class code
Oil / refrigerant compatibility
Compatibility between refrigerant and compressor oil type (POE, PAG, mineral...).
Common unit: Oil type
Thermostatic expansion valve (TEV)
Component that regulates liquid flow to the evaporator to maintain target superheat.
Common unit: Opening / setting (qualitative)
Defrost
Cycle used to remove frost from the evaporator (air, electric, hot-gas).
Common unit: Duration (min) / frequency
Evacuation vacuum
Removal of air and moisture before charging to ensure reliability and performance.
Common unit: microns (or mbar abs)