| The process of liquid falling freely from a smooth vertical wall or a wall with irregularly shaped expansion surfaces such as channels and lines to achieve heat and mass transfer has the advantages of rapid heat transfer,high efficiency,and small temperature difference,therefore It is widely used in energy,chemical,refrigeration,aerospace,power generation and other fields.The complexity of the wall structure with the irregularly-shaped extended surface leads to the falling film process involving many aspects such as fluctuation,heat and mass transfer and rupture.In particular,the change in the surface shape of the heat transfer element and the difficulty in selecting the free surface position of the liquid film have become important reasons for the imperfect research of the falling film on the surface of the corrugated channel.Therefore,the relevant characteristics need further research.The research object of this paper is two types of triangular corrugated structure packings of number 1 and number 2.First,under the conditions of ignoring the effect of external air on the liquid film,the average thickness of the liquid film during the descent process is constant,and there is no slip.The continuity equation and momentum equation of the dimensional flow are used to establish a physical and mathematical model of the falling liquid film flowing along the corrugated wall surface.Through dimensionless ization,an approximate analysis model is obtained.The flow function is introduced,and the general continuity equation and momentum equation are given.The series of differential equations are expanded in series.By measuring the size of the fillers,the wall structure equations in the form of Fourier series of 2 ? and 1 ? fillers are established,and the relationship between the wall structure effect on the liquid film flow and the free surface of the liquid film is derived.Secondly,this article designs and builds a vertical wall falling film flow visualization observation platform,and studies the falling film flow process on the packing surface of two different corrugated structures under three different inlet methods experimentally.The study found that the presence of lateral wind can appropriately increase the spreading area of water on the filler surface and reduce the thickness of the liquid film.Under the same working conditions,the spreading area of the liquid film on the surface of number 2 filler is generally larger than number 1.The thickness distribution of the two packing liquid films was measured by the white light confocal displacement sensor.The results show that the thickness of the liquid film on the surface of number 1 and number 2 fillers is in dynamic fluctuations,and the change process is always around a certain stable value.The range of its change can be obtained by measuring the uncertainty interval;the amplitude and severity of the fluctuation can be expressed by the displacement and velocity change of the liquid film in the direction perpendicular to the wall surface.The thickness of the liquid film at a certain position is predictable by this method.Under the same working condition,the thickness of the liquid film at different positions of the corrugated wall surface is not the same,but the changing characteristics are similar and have consistency.In general,the thickness of the liquid film in the edge area is generally smaller than that of the mainstream area directly below the inlet;within a certain range,increasing the inlet flow rate can increase the thickness of the liquid film and also increase the volatility of the liquid film flow process.By comparing the experimental data of the two fillers,it can be found that the thickness of the liquid film decreases as the triangular corrugated structure parameter ? increases,combining the correlation and experimental data derived from this paper,the higher the triangular corrugation height,the greater the amplitude of the liquid film,reference results were compared and verified. |
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