What does "latent heat" refer to in HVAC systems?

Latent heat refers to the specific amount of heat energy absorbed or released by a substance during a phase change, such as the transition from solid to liquid (melting) or from liquid to gas (vaporization), without a change in temperature. In the context of HVAC systems, understanding latent heat is crucial because it directly impacts the efficiency of cooling and heating processes.

When refrigerants change state — for example, when they evaporate in the evaporator coil of an air conditioning unit — they absorb heat from the interior space, which is vital for providing cooling. Conversely, when they condense in the condenser coil, they release this heat, helping to maintain comfortable indoor climate conditions. This phase change is integral to the operation of HVAC systems, as it allows for the transfer of heat effectively while maintaining the desired temperature.

The other options do not accurately describe latent heat: the temperature of a gas at a given pressure pertains to thermodynamic principles but not phase changes; total energy consumed by electrical appliances refers to energy usage rather than heat transfer; and the volume of fluid in a refrigeration cycle relates to the physical capacity of the system rather than the heat involved in phase transitions.