Enhancement of Vapor Absorption into a Solution Using the Marangoni Effect

为了实现先进的吸收式热泵，开发一种新的强化制冷剂蒸气吸收过程中的传热传质技术具有重要意义。在大多数商用机械中，通过添加少量的表面活性剂来实现吸收强化，从而大大降低吸收溶液的表面张力，并在制冷剂蒸汽吸收时在溶液表面附近产生Marangoni对流。本文通过在试验室中质量分数为50%的溴化锂水溶液中加入少量辛醇和正十一醇来测量蒸汽吸收过程中的非稳态温度分布，并用全息干涉法进行可视化实验，阐明了表面活性剂对吸收强化的影响。通过对溶液表面的显微镜观察和表面张力的测定，发现辛醇和正十一醇在溶液表面呈滴状分布，处于高于其溶解度的状态是造成强烈Marangoni对流的主要原因。给出了这种Marangoni对流产生的机理模型，为高效热泵吸收器的开发提供了指导，并将蒸汽吸收过程中的Marangoni对流行为可视化为加入少量辛醇的LiBr水溶液的动态降膜流动。介绍了一种利用双脉冲Luby激光测量动态阶段气膜流动位移的干涉测量技术。为了比较有无表面活性剂(辛醇)的干涉条纹构型，清楚地表明在有辛醇的情况下发生了Marangoni对流。这些基础研究使我们能够设计出高性能的吸振器。

It is highly important to develop a new technology for heat and mass transfer enhancement in the process of refrigerant vapor absorption in order to realize the advanced absorption heat pump. In most commercial machine, absorption enhancement has been done by adding a small amount of various kinds of surfactants, thereby reducing the surface tension of the absorption solution drastically and generating Marangoni convection near the solution surface at the time of refrigerant vapor absorption.This paper clarifies the effect of the surfactant on absorption enhancement by measuring the unsteady temperature distribution in the vapor absorption process by adding a small amounts of octanol and decanol into the aqueous solution of LiBr with 50 mass% contained in a test cell and by conducting a visualization experiment using holographic interferometry. It was found, on the basis of the solution surface observation using a microscope and the measurement of the surface tension, that octanol and decanol in a state higher than their solubilities distributed in the dropwise states on the solution surface were the initial cause of violent Marangoni convection. The model of the mechanism generating this Marangoni convection was presented also a guide dealing with the development of a highly efficient absorber to be used for heat pumps was provided.Furthermore, the effort was made to visualize the Marangoni convective behavior during the steam absorption into a dynamic falling thin film flow of the aqueous solution of LiBr with the addition of small amount of Octanol. An interferometric measuring technique was introduced to visualize the displacement of the film flow in the dynamic stage by using double pulsed luby laser. For the comparison of the interference fringe configurations obtained with and without the aurfactant (Octanol), it was cleary shown the occurrence of the Marangoni convection in case with Octanol. these basic study enables us to design high-performance absorber.