Glossary Term: Refrigeration & Thermodynamics

The total pressure exerted by a gas or fluid, measured relative to a perfect vacuum (zero pressure). Equals atmospheric pressure plus gauge pressure.

The reduction in refrigeration system capacity due to lower atmospheric pressure at high altitudes. Compressor-based refrigeration systems lose approximately 3% capacity for every 300m of elevation above sea level.

A unit of energy representing the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. In refrigeration, typically expressed as BTU/hour (BTU/h) for cooling capacity.

A theoretical thermodynamic cycle that represents the most efficient possible refrigeration cycle. Real refrigeration systems approach but never achieve Carnot efficiency.

A measure of refrigeration system efficiency, calculated as the ratio of cooling capacity (output) to energy consumed (input). Higher COP indicates better efficiency.

The heart of a mechanical refrigeration system. Compresses refrigerant vapor from low pressure (evaporator) to high pressure (condenser), enabling the refrigeration cycle.

Heat exchanger where high-pressure refrigerant vapor is cooled and condensed to liquid, rejecting heat to the environment (typically ambient air or water).

The temperature above which a gas cannot be liquefied regardless of pressure applied. Each refrigerant has a specific critical temperature.

Periodic process of removing ice buildup from evaporator coils. Ice accumulation reduces heat transfer efficiency and airflow.

Total heat content of a refrigerant, including both sensible heat (temperature change) and latent heat (phase change). Measured in kJ/kg (kilojoules per kilogram).