Research On Bubble Behavior In The Process Of Water Boiling By Electrohydrodynamics Effect

Electrohydrodynamics (electro-hydro-dynamics, referred to as EHD) heattransfer enhancement is a kind of active heat transfer enhancement technology, whichhas some advantanges such as low energy consumption, simple structure and can easyto achieve and so on. The behavior of bubble decides the main process of enhancedboiling heat transfer, so the researching of bubble behavior of bubble is the key toresearch heat transfer enhancement EHD technology.In this paper, based on the design and manufacture of visualization experimentaldevice, experimental study of bubble behaviors is conducted under electric field andusing the method of numerical simulation to research the law such as velocity,pressure variation in the process of water from liquid into vapor under electric field.According to the result to analysis the influence of bubble growth and fracture underelectric field, as to explain EHD enhanced boiling heat transfer mechanism.Numerical simulation results show that electric field intensity significantlyaffectes the process when the water from liquid into vapor, mainly displays in: withthe electric filed intensity bringing in, the fluid flow rate, pressure and vapor volumeratio near the heat source increasing; the velocity direction inconsistent degree offluid is more obvious and inconsistent degree increasing with the increasing ofelectric field intensity. The electric field changes the fluid differential pressure, flowrate, etc near heat source, which increases fluid convection and disturbance degreeand increasing the thermal efficiency between heat source and fluid near heat source.As to the improvement of thermal efficiency, which accelerates the process of bubblegrowth, breaking away from heat source as to decrease the thermal resistancebetween heat source and fluid to further to improve heat transfer efficiency.Experimental results show that the bubble is drawed deformation along thedirection of electric field intensity and the deformation is proportional to the electeicfiled intensity; the cycle of bubble decreases with the increasing of electric fieldintensity and density of heat flow rate; the length-diameter ratio of bubble increases with the increasing of electric field intensity and density of heat flow rate, the risingvelocity of bubble tends to a fixed value and the fixed value increasing with theincreasing of electric field intensity, the rising acceleration of bubble tends to zeroand the acceleration rate decreases with the increasing of electric field intensity.Through the above analysis, we can include that the volume of electric forcefield increases fluid convection and disturbance of bubbles, shorten the cycle of thebubbles in the heat source, speed up the escapeing velocity of the bubbles during theboiling. And it also reduces the thermal resistance and increases the heat transferefficiency between the heat source and the fluid so as to exacerbate the degree ofboiling. So EHD can produce some certain effect.