The use of a modified Bernoulli equation that includes the interfacial energy density, for the characterization of spraying and atomization (S & A) processes, is considered. Ideal S & A systems are defined with respect to the conversion of the upstream pressure heads to downstream interfacial energy density. Using this modified Bernoulli equation, it is shown that, in an idealized S & A process which is free of dissipation, the smallest obtainable size of sprayed drops is inversely dependent on the upstream pressure head and vice versa. In real systems, the polydispersity of sprayed drops increases the dissipation and kinetic energy losses, and consequently, the efficiency of the S & A process is reduced. Using the concept of interfacial energy density, a generalized enthalpy density, h*, for flow systems that involve interfaces is defined. This enthalpy density is shown to be part of the Bernoulli equation and generally of the free energy balance in conjunction with a work source, and its application for the analysis of S & A systems is considered. It is shown that a work source functioning as a pump in ordinary now systems produces in S & A systems an increase in h*. Finally, the efficiency of production of the interfacial energy density is shown to be inversely related to the dissipation and kinetic energy losses, which are associated with the flow and spraying of the fluid.