Force balance droplet entrainment model for the horizontal stratified flow condition

Abstract

Under the horizontal stratified flow condition, a droplet with a large interfacial area influences the mass, momentum, and heat transfer between the gas and liquid phases. In this study, we developed a force balance droplet entrainment rate model applicable to the horizontal stratified flow condition. This model is based on the balance of forces that act on the interfacial wave, which consists of an interfacial shear force, a surface tension force, and the force of gravity. In addition, the force balance droplet entrainment rate model includes constitutive relations for the parameters that are related to the geometry and the characteristics of the interfacial wave. This includes the wave frequency, wave height, wave slope, the wave velocity along the flow direction, and the lateral length of the interfacial wave along the circumferential direction of the flow pipe. The prediction of the onset of entrainment by the proposed force balance droplet entrainment rate model was compared to that with the existing models. Subsequently, the model was evaluated with the latest droplet deposition rate correlation from the literature against the experimental data obtained under the horizontal stratified flow condition. It showed a good prediction capability with a MAPE of 15.34%. Finally, the applicability of the force balance droplet entrainment rate model to a large-sized pipe was investigated. The force balance model showed a reasonable prediction performance. The applicable ranges of the gas and liquid Reynolds numbers (Reg and Rel, respectively) proposed by droplet entrainment rate model are 65,500–571,400 and 170–11,000, respectively.