SOLAS Refrigeration key terms

The process of removing heat from a space or substance so that its temperature falls below that of the surroundings, and keeping it there.

A form of energy that moves from a warmer body to a cooler one. Refrigeration does not create cold; it moves heat from one place to another.

Heat that changes the temperature of a substance without altering its state. It can be felt and measured with a thermometer, unlike latent heat.

Heat absorbed or released when a substance changes state, such as boiling or condensing, with no change in temperature during the change.

The fluid circulating in a refrigeration system that absorbs heat by evaporating at low pressure and releases it by condensing at high pressure.

The pump that draws low-pressure vapour from the evaporator, raises its pressure and temperature, and delivers it to the condenser. It is the heart of the system.

The heat exchanger where high-pressure refrigerant vapour gives up heat to the surrounding air or water and condenses into a liquid.

The heat exchanger in which low-pressure liquid refrigerant boils and absorbs heat from the space or product being cooled.

A metering device that reduces refrigerant pressure and controls the flow of liquid into the evaporator, regulating how much refrigerant enters.

A modulating metering valve that senses evaporator outlet temperature and pressure and adjusts refrigerant flow to maintain a set superheat.

The number of degrees a vapour is above its saturation temperature at a given pressure. Measured at the evaporator outlet, it shows how well the valve is feeding.

The number of degrees a liquid is below its saturation temperature at a given pressure. It confirms the condenser has fully liquefied the refrigerant.

The temperature at which a refrigerant boils or condenses at a particular pressure. It changes with pressure and is read from a pressure-temperature chart.

A table or graph listing the boiling and condensing temperatures of a refrigerant at various pressures, used to set superheat and diagnose system faults.

The pipe carrying low-pressure vapour from the evaporator back to the compressor. It should be insulated to prevent unwanted heat gain.

The pipe carrying high-pressure liquid refrigerant from the condenser to the expansion valve. It usually includes a filter drier.

A device in the liquid line that traps moisture, dirt, and acid so they cannot reach the expansion valve and cause blockages or corrosion.

A sight glass element that changes colour to warn of moisture in the refrigerant circuit, helping to confirm the system is dry.

A small viewing window in the liquid line used to check that the refrigerant is clear and free of bubbles, indicating a full liquid column.

The total amount of heat that must be removed from a space or product to maintain the required temperature, including transmission, product, and internal gains.

The process of controlling the temperature, humidity, cleanliness, and movement of air in an enclosed space for human comfort or process needs.

The amount of water vapour in the air expressed as a percentage of the maximum it could hold at that temperature, a key comfort and process measure.

The temperature at which air becomes saturated with water vapour and condensation begins. Cooling below it produces liquid water on surfaces.

The process of removing frost or ice that has built up on an evaporator coil, restoring heat transfer and airflow. Common methods are off-cycle, electric, and hot gas.

Ice crystals that form on evaporator surfaces when coil temperature falls below the dew point and freezing point of the moisture in the air.

Lubricant circulating with the refrigerant to reduce friction and seal clearances inside the compressor. Its level and condition must be checked regularly.

A device fitted on the compressor discharge that removes oil from the hot gas and returns it to the crankcase, keeping the evaporator free of oil.

The lower housing of the compressor that stores lubricating oil. Its heater prevents refrigerant from condensing into the oil during shutdown.

A safety or control device that opens or closes an electrical circuit in response to high or low refrigerant pressure, protecting the compressor from damage.

Devices such as high-pressure switches, low-pressure switches, and thermal protectors that shut down equipment before unsafe conditions cause damage or injury.

A temperature-sensing control that switches the cooling system on and off to hold the space at a set temperature.

Adding refrigerant to a system to reach the correct charge. It may be done by weight, by subcooling, or by sight glass and superheat readings.

Removing refrigerant from a system into a suitable container for reuse, recycling, or disposal, rather than venting it to the atmosphere.

A pressure-rated container for storing refrigerant, marked with its contents and never filled above the safe limit. It must be handled as a pressure vessel.

The process of finding where refrigerant escapes, using electronic detectors, soap solution, or dye, so the leak can be repaired and charge restored.

A pressure below atmospheric, created with a vacuum pump to remove air and moisture from a circuit before charging it with refrigerant.

A set of gauges and valves used to read high-side and low-side pressures and to connect service equipment for evacuation, charging, and testing.

A document supplied with a refrigerant or chemical that lists its hazards, safe handling, first-aid measures, and required personal protective equipment.

Protective clothing and gear such as gloves, goggles, and face shields worn when handling refrigerants and working on pressurized systems.