Mastering refrigeration starts with the basics. If you're working through Refrigeration 101 or diving into technical manuals and refrigeration books, this glossary provides a clear reference for the essential terms. It's built for technicians, engineers, and anyone needing a fast, accurate way to make sense of the language used in the field.
From compressors and refrigerants to terms like subcooling, superheat, and GWP, this list breaks down what you need to know, without filler or overcomplication. Keep it handy whether you're troubleshooting, designing a system, or just getting started.
Here are the top refrigeration and HVAC terms you should know:
Absorption refrigeration
Absorption refrigeration is a heat-driven refrigeration cycle where refrigerant vapour is absorbed into a liquid, commonly employing ammonia-water or lithium bromide-water solutions, as an alternative to traditional vapour compression systems.
Accumulator
An accumulator is a tank in the suction line that prevents liquid refrigerant from entering and potentially damaging the compressor.
Adsorption refrigeration
Adsorption refrigeration is a refrigeration process driven by heat where refrigerant vapour adheres to a solid surface.
Ambient temperature
Ambient temperature is the temperature of the surrounding environment where refrigeration equipment operates.
Ammonia (NH₃ or R-717)
Ammonia (NH₃ or R-717) is a natural refrigerant with excellent thermodynamic properties, widely used in industrial refrigeration for its high efficiency and low environmental impact.
Brine is a secondary coolant solution, often saltwater or glycol, used to transfer heat in indirect refrigeration systems.
BTU (British thermal unit)
BTU (British thermal unit) is a unit of heat energy representing the amount of heat needed to raise the temperature of one pound of water by one degree Fahrenheit.
Bypass valve
A Bypass valve allows refrigerant to bypass certain system components for operational control or maintenance purposes.
Capillary tube
A capillary tube is a narrow copper tube acting as a metering device, controlling refrigerant flow from the condenser to the evaporator.
Cascade refrigeration system
Cascade refrigeration system has two or more refrigeration cycles, each using different refrigerants, to achieve very low temperatures unattainable by single-cycle systems.
CFC (chlorofluorocarbon)
CFC (chlorofluorocarbon) is a refrigerant class phased out due to ozone depletion, such as R-12.
Chiller
A chiller is a refrigeration machine designed to cool a liquid, which is circulated for air conditioning or industrial processes.
Coefficient of performance (COP)
Coefficient of performance (COP) is a ratio measuring refrigeration system efficiency, calculated as cooling output divided by energy input.
Cold storage
Cold storage is facilities maintaining products at controlled low temperatures, typically for preserving perishables.
Compressor
A compressor is a device that compresses refrigerant vapour to higher pressures and temperatures, enabling circulation through the refrigeration system.
Condensate
Condensate is moisture removed from air when cooled below its dew point.
Condenser
A condenser is a heat exchanger that removes heat from refrigerant vapour, causing it to condense into a liquid.
Condensing unit
Condensing unit is an assembly combining compressor, condenser, and associated controls, typically installed outdoors.
Coolant
Coolant is a fluid used to transfer heat, often interchangeable with refrigerant.
Corrosion under insulation (CUI)
Corrosion under insulation (CUI) is corrosion occurring due to trapped moisture beneath insulation in refrigeration systems.
Defrost cycle
The defrost cycle is the process of removing ice buildup from evaporators to maintain efficient heat transfer.
Desiccant
Desiccant is a drying agent used in filter-driers to remove moisture from refrigeration systems.
Desuperheater (DSH)
A desuperheater (DSH) is a heat exchanger that reduces refrigerant vapour temperature before it reaches the condenser.
Discharge line
The discharge line is a pipe carrying high-pressure, high-temperature refrigerant from the compressor to the condenser.
Dry bulb temperature (DBT)
Dry bulb temperature (DBT) is air temperature measured by a standard thermometer, unaffected by humidity.
Dry ice
Dry ice is solid carbon dioxide used as a refrigerant, sublimating directly from solid to gas at approximately -78°C.
Drier filter (Filter-drier)
A drier filter (Filter-drier) is a component that removes moisture and particulates from refrigeration systems.
Evaporator
An evaporator is a heat exchanger where refrigerant absorbs heat and evaporates, producing the cooling effect.
Expansion valve (metering device)
Expansion valves (metering device) are devices that control refrigerant flow into the evaporator while reducing its pressure and temperature.
Fan coil
A fan coil is an indoor unit that circulates air over refrigerant coils for heating or cooling.
Flash gas
Flash gas is refrigerant vaporizing prematurely when pressure drops, typically at the expansion valve.
Flooded evaporator
A flooded evaporator is an evaporator design where liquid refrigerant fully covers the heat exchange surface.
Freon
Freon is a trademark name commonly used for various CFC and HCFC refrigerants.
Global warming potential (GWP)
Global warming potential (GWP) is a measurement indicating how much heat a greenhouse gas traps compared to carbon dioxide.
Glycol refrigeration
Glycol refrigeration refers to systems that use glycol-based antifreeze solutions as secondary refrigerants for heat transfer.
HCFC (hydrochlorofluorocarbon)
HCFC (hydrochlorofluorocarbon) is a refrigerant with a lower ozone depletion potential than CFCs, like R-22.
Heat exchanger
A heat exchanger is equipment that transfers heat between two fluids without mixing them.
Heat load
Heat load is the heat that must be removed to maintain desired temperature conditions.
Heat pump
A heat pump is a reversible refrigeration system capable of heating and cooling.
HFC (hydrofluorocarbon)
HFC (hydrofluorocarbon) is a synthetic refrigerant with zero ozone depletion but varying global warming potential, such as R-134a.
Hot gas bypass
Hot gas bypass is a capacity control method that diverts hot refrigerant gas around the condenser.
HVAC (heating, ventilation, and air conditioning)
HVAC (heating, ventilation, and air conditioning) is a broad field encompassing systems controlling temperature, humidity, and air quality, including refrigeration.
Ice machine
An ice machine is equipment explicitly designed to produce ice via refrigeration processes.
Industrial refrigeration
Industrial refrigeration is a large-scale refrigeration system used in sectors like food processing, pharmaceuticals, or chemical industries.
Latent heat
Latent heat is the energy required to change a substance's state without a temperature change.
Leak detection system
A leak detection system is a system that detects refrigerant leaks early to minimize environmental impact and inefficiency.
Low-side
Low-side is the refrigeration system section operating at lower pressures, from the expansion valve through the evaporator to the compressor inlet.
Manifold gauge set
A manifold gauge set is a service equipment measuring system for pressures for refrigerant charging and recovery.
Medium temperature (MT)
Medium temperature (MT) is systems maintaining temperatures typically between +2°C and +6°C, common in food retail refrigeration.
Multi-split system
A multi-split system is a single outdoor unit connected to multiple indoor refrigeration or air conditioning units.
Natural refrigerants
Natural refrigerants are environmentally friendly refrigerants naturally occurring, like ammonia, CO₂, and hydrocarbons.
Oil separator
An oil separator is a device that removes lubricating oil from refrigerant vapour before it enters the condenser.
Ozone depletion potential (ODP)
Ozone depletion potential (ODP) is measure of a substance's damage to the ozone layer compared to CFC-11.
Pressure relief valve
The pressure relief valve is a safety device that releases refrigerant when pressures exceed safe limits.
Psychrometrics
Psychrometrics studies air-water vapour mixtures, critical in refrigeration and air conditioning.
Receiver
The receiver is a storage tank for liquid refrigerant on the system's high-pressure side.
Reciprocating compressor
A reciprocating compressor is a compressor that uses piston motion to compress refrigerant vapour.
Refrigerant
Refrigerant is a working fluid that absorbs and releases heat through phase changes in refrigeration cycles.
Refrigeration
Refrigeration is the process of removing heat to lower or maintain temperatures below ambient for preservation or comfort.
Rotary compressor
A rotary compressor is a compressor type employing rotating mechanisms that are quieter and more compact than reciprocating types.
Scroll compressor
A scroll compressor is a type of positive displacement compressor that uses two interleaved spiral scrolls to compress refrigerant. One scroll remains stationary while the other orbits around it, trapping and compressing the refrigerant toward the center. Scroll compressors are known for their high efficiency, quiet operation, and fewer moving parts compared to reciprocating compressors, making them popular in residential and light commercial HVAC systems.
Secondary refrigerant
Secondary refrigerant is a fluid that transfers cooling from the primary refrigerant to the cooling load, e.g., chilled water or glycol.
Split system
A split system is a system that separates the evaporator and compressor/condenser units, which is common in air conditioning.
Subcooling
Subcooling is cooling the refrigerant below the condensation temperature to ensure complete condensation.
Suction line
The suction line carries low-pressure refrigerant vapour from the evaporator to the compressor.
Superheat
Superheat is temperature increase of refrigerant vapor above saturation, ensuring complete evaporation.
Thermostatic expansion valve (TXV)
The thermostatic expansion valve (TXV) is a metering device that automatically maintains a consistent superheat at the evaporator outlet.
Ton of refrigeration
A ton of refrigeration is cooling capacity equivalent to removing 12,000 BTU per hour.
Transcritical system
A transcritical system is a system where the evaporator operates below and the condenser operates above the refrigerant's critical temperature, often used with CO₂.
Vacuum pump
A vacuum pump is equipment that removes air and moisture from refrigeration systems before refrigerant charging.
Vapor barrier
A vapor barrier is a material that prevents moisture migration into insulation in refrigeration systems.
Variable frequency drive (VFD)
Variable frequency drive (VFD) controls motor speeds in refrigeration systems for enhanced efficiency.
Walk-in cooler
A walk-in cooler is a refrigerated space large enough for personnel entry to store perishable goods.
Wet bulb temperature
Wet bulb temperature is the temperature measured by a thermometer covered in wet cloth, indicating humidity levels.
Zeotropic refrigerant blend
Zeotropic refrigerant blend is a mixture of refrigerants undergoing temperature glide during phase changes.
