Displacement-energy and enthalpy as forms of energy: an upgrade.

Abstract

In order to formulate proper energy balances and uphold the law of conservation of energy, there is a need to account for all forms of energy for any system. A survey of thermodynamic engineering literature reveals little consensus about the energy forms to be taken into account. This paper intends to advance the case for formal and explicit recognition of 'displacement energy' as a form of energy that is either missing from textbooks, implied by some unspecified potential energy, hiding inside enthalpy, or incorrectly designated as 'flow work' or 'pV-work' as work is not a form of energy. An important implication is that contrary to prevailing views, enthalpy can also be deemed a form of energy, thereby justifying its presence in many energy balances, and thus rendering Hess’ law into an energy balance as well. The paper specifies 23 conclusions and recommendations.