Stagnation-Point Heat Transfer During Impingement of Laminar Liquid Jets: Analysis Including Surface Tension

Abstract

The stagnation-zone characteristics of an impinging liquid jet are of great interest because the maximum heat transfer coefficient occurs in that region. This paper is an analytical study of the fluid flow and heat transfer in the stagnation zone of an unsubmerged liquid jet. The role of surface tension is emphasized. Stagnation-zone transport is strongly dependent on the potential flow above the boundary layer. Only a few studies have examined the potential flow of an unsubmerged jet, each using approximate potential flow theory and neglecting surface tension. In this paper, numerical solutions for a laminar unsubmerged jet are obtained, using a simulation method for steady, inviscid, incompressible flow with surface tension. A series solution that satisfies the boundary conditions in an approximate manner is constructed in terms of Legendre functions. Numerical solution of the momentum equation shows that surface tension has an effect on the stagnation-point flow field when the Weber number is small. Solutions of the associated boundary layer problem are used to obtain predictions of the influence of Weber number on the stagnation-zone heat transfer. The results are validated by comparison to measurements at high Weber number.