液体的莱顿弗罗斯特效应及贝纳德对流试验研究

摘要

This paper introduces the experimental work being awarded the first prize in the Physical Experimental Competition in November 2015 among Beijing College students.The Leidenfrost effect of NaC1 solution is studied through equipments installed by authors.Leidenfrost points are measured to be proportional to the solution concentrations.If the surface is dirty with the left solid NaC1 or dust,the Leidenfrost phenomena will not happen even the temperatures of surface are higher than Leidenfrost points,which indicates that the rough degree of heating plate surface greatly influences the Leidenfrost effect.When the heating plate surface is smooth,we find that the droplet size has no effect on the Leidenfrost effect.The Bernard convection phenomena are showed through the simply equipped devices too.We replace the NaC1 solution by the silicon oil and drop the oil to the surface of heating plate.The Bernard convection phenomenon is observed when the thickness of silicon oil layer reaches a certain value and the temperature difference between its upper and lower surfaces reaches a critical value.As soon as the Bernard convection phenomenon occurs,thickness of silicon oil layer and the temperature difference between its upper and lower surfaces are measured.The measured results coincide with the theoretical simulation given by reference.Through the process of designing and fulfilling of the experiments,students know two important experimental phenomena of liquid,that is,Leidenfrost effect and Bernard convection.Their interests to science are inspired.Their abilities of thinking and practicing are promoted.Innovative experimental teaching plays an important role in training students' scientific literacy.%本文介绍了作者于2015年11月在北京市大学生物理实验竞赛中获得一等奖的实验工作.通过自行设计的实验装置,演示了溶液的莱顿弗罗斯特现象,测量了溶液莱顿弗罗斯特点及其随溶液浓度的变化.当加热板表面有污渍,变得粗糙时,同样的溶液滴到表面,即使温度升高到莱顿弗罗斯特点之上,也不会产生莱顿弗罗斯特效应,说明加热板表面粗糙程度对溶液莱顿弗罗斯特效应有很大影响.当加热板表面光滑时,液滴体积的大小对莱顿弗罗斯特效应没有影响.还演示了连续介质的贝纳德对流现象,用二甲基硅油代替氯化钠溶液,滴到加热器皿里,当硅油层厚度达到一定值,上下表面的温差也达到一个临界值时,观察到贝纳德对流现象,测量了对流现象发生时硅油层的厚度及其上下表面温度差.通过设计并完成整个实验过程,学生系统地认识了液体的菜顿弗罗斯特效应及贝纳德对流,拓展了学生的视野,激发了学习兴趣,锻炼了学生的创新思维和动手能力.创新性实验教学在培养学生科学素养方面起着重要的作用.