Effects of Interfacial Phenomena and Conduction on an Evaporating Meniscus

An overview of some of the theoretical models describing the effects of chemical potential, excess free energy, free energy gradient, film thickness profile, temperature profile, superheat, thermal conduction, concentration gradient, velocity profile, slip velocity, apparent contact angle, and kinetic theory on the phase change heat transfer processes in an evaporating meniscus are presented. The relative importance of the parameters is demonstrated. Experimental techniques and confirming experimental data are also presented. In essence, the microscopic thickness profile of the evaporating meniscus is measured optically to obtain the details of the liquid pressure field and modeled to give the fluid flow rate and the evaporative heat flux. The macroscopic temperature field of the substrate is measured and numerically modeled to give the microscopic temperature field and a complementary calculation of the evaporative heat flux. For closure, the values of the slip velocity and concentration change on evaporation need to be correctly assumed. The interfacial transport processes are very sensitive to small interfacial temperature and concentration changes, which are difficult, if not impossible, to measure directly. However, the liquid pressure gradients can be directly measured. The effects of the interacting phenomena on the phase change processes are demonstrated using these complementary experimental-modeling procedures. The processes are found to be very complex and simple modeling/experiments can only confirm the general phenomena and give insight.