What does the term "enthalpy" refer to in HVAC physics?

The term "enthalpy" refers to the total heat content of a system, which is a key concept in HVAC physics. In essence, enthalpy integrates the internal energy of a system with the product of its pressure and volume, encapsulating all forms of energy contained within a substance. This includes the energy associated with thermal heat transfer and the energy stored in the system due to phase changes, such as from liquid to vapor.

In HVAC applications, understanding enthalpy allows professionals to calculate and optimize energy transfer processes, such as heating and cooling within a building. It helps in designing systems that effectively manage energy consumption and thermal comfort. For example, during the refrigeration cycle, changes in enthalpy signify how much energy is absorbed or released by the refrigerant as it transitions between different states, which is critical for effective system performance.