Study Of Effect Of Magnetic Field On Surface Tension And Boiling Heat Transfer Of Water

As a country with a large population,China is faced with the contradiction and many problems among population,resources and environment.Energy conservation,emission reduction and environmental protection have attracted increasing attention from all aspects of the country and society,so it is urgent to develop various reliable heat exchange enhancement methods.Boiling,as a common and efficient heat transfer method,can absorb a large amount of latent heat during the vaporization of liquid working medium,and it is especially suitable for some heat transfer occasions with relatively high heat flux.As a substance that is easily obtained in nature,water is also the most commonly used working medium for boiling heat transfer equipment.Academics have conducted long-term and extensive research on its boiling heat transfer characteristics and mechanism.At present,the boiling heat transfer enhancement methods for water are mainly water-based surfactant solution and nano-fluid formation by adding nanoparticles to water.The basic principle is to reduce the surface tension of the working medium to enhance its boiling heat transfer characteristics,but both of these methods will affect the original composition of the working medium,and nano fluids will also increase the maintenance cost in the later period.After experimental exploration,it is found that magnetic field can reduce the surface tension of water.In this paper,a variety of experimental instruments are used to systematically study the influence of magnetic field on the surface tension of water.And the obtained magnetized water is used for the pool boiling experiment to explore the influence of magnetization on the boiling heat transfer characteristics of water.At first,the author introduces the existing for water boiling heat transfer enhancement methods,mainly divides into adding surfactants in water solution and adding nano particles to form nano fluid,but there are many different kinds of surfactants,and for water boiling heat transfer characteristics of the changes are not favorable,and method of nanofluids is due to the stability of the nanofluids problem,although the study is more,However,it is still impossible to avoid the equipment loss and maintenance problems caused by the agglomeration deposition of nanoparticles.Secondly,the author using the electromagnetic device,systematically explores in detail the influence law of magnetic field on the surface tension coefficient of water,and the best combination under different magnetic field intensity and magnetization time,find the optimum magnetization point,found in the 300 mT,15 min of magnetized conditions,the surface tension of the magnetized water coefficient is the largest decline,decline of 25%.And then the author has carried on the magnetized water pool boiling experiment,found in the offer wall heat flux in boiling and boiling in bottom offer wall heat flux,magnetized water can produce more than the magnetized water boiling bubbles and has better effect of boiling heat transfer,the description of magnetization water boiling heat transfer is a must strengthen effect.In addition,compared with the non-magnetized water,the heat flux required by the magnetized water is lower than that of the non-magnetized water when bubbles are generated and completely separated from the water to form violent boiling,which indicates that the boiling of the magnetized water is earlier than that of the non-magnetized water,which is of great significance in the actual heat exchange equipment.