Igor Palymskiy
Siberian State University of Telecommunications and Information Sciences, Russia
Title: About convection stability of the gas-vapor mixture at the temperature close to critical
Biography
Biography: Igor Palymskiy
Abstract
The intensive investigations of convection modes in the homogeneous gas have been performed. However, the condensation and evaporation of liquid often accompany the moving of gas. The amount of the liquid in the vapor state is defined by saturated vapor pressure. The last comparatively quickly grows with the temperature increasing at growing density of the gas. The gas is considered to be ideal so after evaporation of the whole liquid (the critical point) density gas falls off with growing of the temperature. In the critical point the heat expansion coefficient has the change of its sign. The convection of the oxygen O2 with liquid-vapor cyclohexane C6H12 mixture is considered in a horizontal layer at heating from below, it is supposed that the cyclohexane condensation occurs on the horizontal isothermal boundaries and that the partial pressure of the oxygen is to be constant. The layer is divided into two sublayers by critical temperature moreover the temperature of the lower horizontal boundary is above critical and upper boundary - below. For study of convection stability the Galerkin method is applied. It is shown that at sufficient value of Rayleigh number the convective instability may be observed in unstable lower sublayer. At decreasing of the relative thickness of the unstable lower layer τ the level of convective instability decreases and vice versa. The asymptotic behave of neutral curve, position of the instability boundary on the wave plane, critical Rayleigh number and corresponding critical wave number, the increment of most dangerous disturbance is investigated at parameter τ close to 1 and 0. The asymptotes at τ close to 0 are derived numerically and at τ close to 1 - analytically as expansion in powers of (1- τ)3.