In thermodynamics, what is the actual physical meaning of PV?
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In the formula for enthalpy: H=U+PV. Take an actual example, the air separation compressor. The air is compressed, increasing its pressure, and then cooled by water back to its temperature before compression, resulting in a decrease in potential energy (PV). What is the actual physical meaning of PV?
Pressure * volume: as the flow velocity of a gas decreases, the pressure increases; since the volume per unit area decreases, the pressure potential energy drops
In thermodynamic concepts, P*V represents the work done by external forces on the working substance, commonly referred to as driving work. It is part of the total energy of the working fluid. Since the flow of the working fluid is caused by a pressure difference, the driving work during flow is also referred to as pressure potential energy. The so-called decrease in the PV value means that after compression, P increases, but once cooling takes effect and the temperature drops, V decreases even more, resulting in a decrease in the product of P and V. Therefore, after compression, before cooling or if the cooling is insufficient, the PV value increases. This also means that the total energy of the working fluid increases at this point.