Development Of Apparatus With Axisymmetric Drop Shape Method For Surface Tension Measurement And Experimental Research On Surface Tension Of Binary Mixtures Of DMSO With Methanol

Surface tension is an important thermophysical property of fluids and thebasic physical quantity used to study the fluid phase interfacial heat and masstransfer phenomena. Accurate data of surface tension has an importantsignificance for design and transformation of efficiency industrial equipmentand optimization of related process. A lot of methods are used to measure thesurface tension, such as capillary rise method, laser scattering method andpendent drop method. Compared with other methods, pendent drop method hasadvantages of low requirement in sample consumption, high accuracy, and easyto implement the measurement in high-temperature and high-pressureenvironment.In this work, a new algorithm which is on the thesis of boundary contourfitting method has been accomplished for surface tension measurement usingpendent drop method. Canny operator has been used to progress edge detection,then the coordinates of drop contour are obtained through coordinate extractionand coordinate exchange; the Young-Laplace equation is solved by the fourth-fifth-order Runge-Kutta algorithm, and the objective function foroptimizing is constructed by searching for the nearest point. Anew profile fittingalgorithm with combination of coordinate alternation method and Newtonmethod is researched and implemented. All of above algorithms have beenprogrammed with MATLAB.A new apparatus for surface tension measurement with pendent dropmethod has been built in this work, which contains image acquisition systemand temperature control system. The system can be used to measure the surfacetension of fluid under the pressure range from0to20MPa and the temperaturerange from20to180℃. The surface tension of n-heptane, n-octane and waterwere measured using this apparatus, and the deviations between experiment dataand literature data were less than±0.2mN·m-1, which proves the reliability andstability of the apparatus. The uncertainty analysis for the measurement of liquidsurface tension is estimated to be0.5%.On the basis of the work above, the surface tension of binary mixtures ofDMSO with methanol whose mass fraction was range from0.1to0.9has beenmeasured in the temperature range from303.15to323.15K. The measurementresults provide important thermophysical properties for the application ofmethanol fuel.