ON THE ENERGY PARTITION OF LIQUID-DROPS IN SPRAYING AND ATOMIZATION

The eneryg of sprayed and atomized drops is considered. It is shown th at the efficiency of production of interfacial energy, by a process of spraying and atomization, that involves a conjugate bulk pressure-vol ume energy, cannot exceed a theoretical limit of 60%. The upper limit of conversion of enthalpy and the Gibbs free energy to interfacial ene rgy cannot exceed 60%, regardless of the spraying process by which the latter is produced. This efficiency then depends also on the pressure of the ambient phase and on the entropy density of the drops. Higher levels of pressure and entropy density increase the proportion of the bulk energy in the total energy of the drops. This can result in a dra stic decrease in the efficiency, i.e., of energy conversion to interfa cial energy, from the upper limit of 60%, down to a few percent. A cha racteristic drop radius, for which the levels of bulk and interfacial energy are matched, is defined for sprayed and atomized drops. It is s hown that low efficiency is expected when spraying and atomization pro cess yield drops that are significantly larger than the characteristic size. Moment distribution functions are defined. These functions are used to characterize the relative weight that is carried by different size fractions of the drops regarding their contribution to bulk and i nterfacial energies, and to the efficiency of spraying and atomization processes. Drops that are larger than the expectation of drop size ar e the prime source for the low efficiency of spraying and atomization, whereas the smaller drops enhance the efficiency. Finally, the low ef ficiency of spraying and atomization processes can be attributed to th e properties of the sprayed drops, at this low efficiency is a consequ ence of their inherent energy partitioning and is not due exclusively to the nature of the process by which they have been produced.