How is 'enthalpy' defined in thermodynamic systems?

Enthalpy is defined as the total heat content of a system, which encompasses not only the internal energy of the system but also the product of its pressure and volume. It is a crucial concept in thermodynamics as it serves as a useful property for understanding heat transfer in processes occurring at constant pressure. When heat is added to a system at constant pressure, the change in enthalpy reflects the total energy change, including the energy related to the work done by the system due to volume changes.

In practical applications, especially in power engineering and thermodynamics, knowing the enthalpy helps in analyzing energy systems, calculating efficiencies, and designing processes such as boilers, turbines, and heat exchangers. The focus on enthalpy rather than merely temperature, pressure, or volume is because it encapsulates the system's ability to perform work and exchange heat, which are fundamental in energy conversion processes.