The Low Of Cold Surface Freezing And New De-icing Methods

Icing phenomenon is a kind of inevitable phenomena, it will affect the efficiencyand reduce the reliability, and even cause serious security safety problems if the icestick to the aerospace, power sector and other parts of the surface. Currently, a seriesof research about the anti-icing theory and technology have been carried out by manyfields, but it has not yet formed an effective prevention program because the freezingprocess is very easily to be influenced by complex and multi-factors. To reduce orresolve the hazards of ice sticking, it must be deeply analyzed the influence of thefactors on ice. The paper summarizes the law of freezing by using microscopicobservation and analyzes the factors effect on ice, and proposes a new deicing methodby changing morphology of the substrate to influence the freezing strength. In thispaper, the main research contents and conclusions are as follows:(1)To facilitate the analysis of the influence of environmental factors on freezing,the self-made microscopic observation device is adopted to observe the freezingprocess. The process can be roughly divided into water droplets spreading, freezinglayer occurrence and the droplets beginning to expanding, completely frozen.(2) Compared using the ice cylinder to evaluate the freezing character of ice, thispaper proposes a new evaluation on freezing character of the ice which adaptstitration droplets on the material and the droplets are frozen and stick on the surface.The measured device of freezing strength are designed and conducted by dependingthe evaluation method and experimental requirement.(3) In order to optimize and develop anti-icing methods, the paper has analyzedthe influence of the factors effect on freezing strength. It has tested the adhesionwhich was formed under different initial temperature or different freezing time. Theresults show that the freeing strength will increase and the growth rate gradually getsslower with the lower surface temperature. The freezing strength formed on thesurface with temperature above0℃is significantly greater than the strength that isformed on surface with negative temperature. In experiment, freezing strengthincreases with the freezing time prolonging. However, the ice intensity suddenlyreduces in the process.(4) Based on the phenomenon of freezing phase change, this paper puts forwarda new type thinking of deicing methods which combines the phase expansion of ice with changing the substrate surface morphology. To verify the new thinking ofanti-icing method, corresponding tests had been performed. And the tests show thatchanging the substrate surface morphology would influence the freezing strength onthe sample.(5) To further validate the feasibility of the new thinking of anti-icing technologyand analyze the influence of the structure parameters on freezing strength, it design9kinds morphology on the surface of PMMA and the freezing strength formed ondifferent surface was tested. The results show that the surface with the pits of dot hasthe biggest impact on the freezing strength, and tangential and normal strength formedon the surface with pits of dot have respectively decline41%、29%. By analyzing thetest results, the groove angle and form type in the structural parameters have thegreatest impact on freezing adhesion and the structure which has the most influenceon freezing strength is also determined.(6) The freezing strength on the optimal structure form was measured and it isbasically located in the interval range of optimal test index. With comparing theinfluence of morphology on PMMA and Alloy on freezing strength, the influence ofchanging surface morphology on freezing strength would not change under samestructure parameters existing on surface if the adhesive substrate has different materialproperties. Meanwhile, the impact of surface morphology on freezing strength wasanalyzed. It thinks that changing surface morphology affect the stability of adhesiveinterface layer which exists between ice and substrate, and this results in thecontacting interface generating some stress concentrated areas and changing thefreezing strength.