THERMOCAPILLARY FLOW WITH EVAPORATION AND CONDENSATION AT LOW GRAVITY.1. NON-DEFORMING SURFACE

The problem of steady motion and thermal behaviour of a volatile, wett ing liquid in an open cavity under low gravity is defined and examined . The domain geometrically approximates a two-phase pore of liquid on a wicking structure surface, and consists of a 1 to 10(2) mu m wide re ctangular cavity bounded by a saturated vapour and liquid reservoir on its upper and lower surfaces, respectively. Thermal non-equilibrium a nd convection are established by symmetrically superheating or subcool ing the pore boundaries by similar to 1 K relative to the vapour. Nume rical analyses show that although thermocapillary flow competes with i nterfacial phase change in dictating the circulation and flow structur e, it tends to reinforce the convective effects of evaporation and con densation on surface temperature and heat transport. In addition, high ly wetting fluids with curved menisci are characterized by greater cir culation intensities and dynamic pressure gradients than a flat surfac e. The magnitude of these gradients suggests that the fixed menisci sh apes assumed in this study are unrealistic, and that the influence of convection on surface morphology should be considered.