Glossary
| Term | Meaning |
|---|---|
| Absolute pressure (bar a) | Pressure measured from a perfect vacuum; gauge pressure + atmospheric pressure |
| BTU/h | British thermal units per hour; 1 kW = 3,412 BTU/h |
| Carnot COP | Highest COP possible in theory between two temperatures, using kelvin |
| Condensation | Change from vapour to liquid; releases latent heat |
| Condenser | Heat exchanger where refrigerant condenses and gives heat to water or air |
| Conduction | Heat transfer through a solid, molecule to molecule |
| Convection | Heat carried by a moving fluid (natural or forced) |
| COP | Coefficient of performance: heat delivered ÷ electrical input |
| Dew point | Temperature at which air starts to condense water when cooled |
| Dry-bulb temperature | Normal air temperature read on a thermometer |
| Enthalpy | Total heat content of a fluid per kg, in kJ/kg |
| Evaporation | Change from liquid to vapour; absorbs latent heat |
| Evaporator | Heat exchanger where refrigerant boils and absorbs heat |
| Expansion valve | Device that drops refrigerant pressure between condenser and evaporator |
| Gauge pressure (bar g) | Pressure above atmospheric pressure |
| GWP | Global warming potential, compared with CO₂ over 100 years |
| Heat | Energy that flows because of a temperature difference (kJ, kWh) |
| kcal/h | Kilocalories per hour; 1 kW = 860 kcal/h |
| Kelvin (K) | Absolute temperature scale; 0 K = −273.15 °C |
| kW / kWh | Power (rate of energy) / energy (power × time) |
| Latent heat | Heat that changes phase without changing temperature |
| P-h diagram | Pressure–enthalpy chart used to draw a refrigeration cycle |
| Radiation | Heat transfer by infrared waves, needing no medium |
| Refrigerant | Working fluid that boils and condenses to carry heat in a cycle |
| Relative humidity (RH) | Water vapour in air as a % of the maximum it can hold at that temperature |
| Saturation temperature | Boiling/condensing temperature at a given pressure |
| Sensible heat | Heat that changes temperature |
| Specific heat (cp) | Heat needed to raise 1 kg by 1 K; water ≈ 4.186 kJ/kg·K |
| Subcooling | Liquid cooled below its saturation temperature |
| Superheat | Vapour heated above its saturation temperature |
| Temperature | Measure of how hot or cold something is (°C or K) |
| TR (ton of refrigeration) | Cooling rate of 3.517 kW (12,000 BTU/h) |
| Wet-bulb temperature | Temperature of a wetted thermometer in moving air; ≤ dry-bulb |
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