Study on Evaporation Characteristics of Water in Annular Liquid Pool at Low Pressures

Abstract

In order to investigate the energy transfer mechanism and the nonequilibrium effect during water evaporation in its own pure vapor at low pressures, a series of precise measurements are conducted to obtain the temperature profile near the liquid−vapor interface and the evaporation rates in an annular pool in a closed chamber. The results show that the interface temperature of the vapor side is higher than that of the liquid side when water evaporates in its own pure vapor at low pressures (ranging from 394 to 1467 Pa), the temperature discontinuity across the interface exists in all experimental conditions. The magnitude of the temperature discontinuity is strongly affected by the vapor pressure. A uniform temperature layer with a thickness of about 2 mm is found below the evaporating interface because of the coupling effect of evaporation cooling and thermocapillary convection. The energy required for evaporation is mainly transferred by thermocapillary convection in the uniform temperature layer. Furthermore, the numerical simulation results confirm that the evaporation flux near the cylinders is much larger than that at the middle region, which implies that most of the latent heat required for evaporation is transferred to the interface near the cylinders.

Modeling for Simple Batch Distillation of Vanadium Oxychloride-Titanium Tetrachloride (VOCl3-TiCl4) Mixture

“…The reduction rate of the W increase with a decrease of the operating pressure, as shown in Figure 6A. This result is attributed to a deviation of the equilibrium state under a change of pressure [18]. At low pressure, the cross association between components in the liquid mixture is reduced, resulting the significant distinction of equilibrium state for these components [19].…”

Testing of a Falling-Film Evaporator for Adsorption Chillers

“…On the other hand, water use at a low evaporation temperature implies low saturation vapor pressure that requires a special evaporator design to maximize the evaporation rate during the adsorption phase. Some studies have demonstrated that the efficient evaporation of water at sub-atmospheric pressure is challenging [3][4][5]. Indeed, its low saturation pressure at the typical operating conditions of adsorption chillers limits high heat transfer rates due to the nucleate boiling.…”