受热降膜Marangoni效应临界状态表征

采用红外热成像技术,研究了水和Na2SO4水溶液受热降膜的Marangoni效应及对降膜流动的影响。发现在降膜的流向和径向都存在热Marangoni效应,但Marangoni数却不能较好地表征Marangoni效应对液膜流动的影响程度。因而引入Marangoni效应影响因子ε。结果表明,ε能较好地表征Marangoni效应对液膜流动的影响程度,且不同溶液受热降膜存在一个近似相同的临界值(εLc)。当εLεLc,降膜流向热Marangoni效应将引起降膜明显的扰动。根据εLc值,可获得临界Marangoni数MaTc,L。

Characteristic of the Threshold of Marangoni Effect on Heated Falling Film

Using a sensitive infrared imaging technique,experimental investigations were performed on Marangoni effect in heated falling films of distilled water and Na2SO4-H2O solution as well as its influence on the film flow.It is found that thermal Marangoni effects exist in both streamwise and transverse directions of the falling films,whereas the magnitude of Marangoni number Ma cannot exactly represent the influence degree of Marangoni effect on the film flow.Thus an impact factor of Marangoni effect ε is introduced.The results show that the ε can well represent the influence degree of Marangoni effect on the film.Moreover,the falling films of various solutions possess an approximately same critical value（εLc）.For εLεLc,the thermal Marangoni effect in streamwise direction will cause the film perceptibly disturbance.According to the εLc,the critical Marangoni number MaTc,L can be obtained.