Experimental Research On The Heat Transfer Performance Of Nano-Magnetic Fluid By The Coupling Of Magnetic Field And Vibration

As a heat pipe occupying a place in the field of heat transfer,the pulsating heat pipe(PHP)is widely used in electronic heat dissipation equipment,and regarded to be one of the heat dissipation components that have great development prospects under the conditions of extra high heat flow density and power consumption.With the maturity of nanotechnology,nanofluid has also become an innovative research in the traditional field of heat dissipation and heat transfer.However,in actual application engineering,many thermal energy devices are irresistibly affected by various external environments,among which vibration is a considerable factor.However,experimental investigations based on practical vibration conditions are relatively scarce,and the influence law of the movement and heat deliver characteristics of pulsating heat pipes under various vibration conditions has not been fully revealed.Therefore,it is extremely important to explore the influence mechanism and law of different vibration environments on the operation and thermal characteristics of pulsating heat pipes.In this paper,three kinds of experiments are designed based on Fe₃O₄/ethanol-based liquid nano-magnetic fluid plate pulsating heat pipe.Firstly,the visual experimental method is used to explore the flow direction of the working fluid in the pulsating heat pipe and the changing law of different flow types.Secondly,the experimental observation method is used to research the relationship between the running state and the heat transfer characteristics of the magnetofluid in the plate-form pulsating heat pipe.The focus is on the influence law of the gas/liquid two-phase transformation and heat deliver characteristics of the nano-magnetic fluid under various vibration circumstances in the plate pulsating heat pipe.And combined with the magnetic field conditions,the heat transfer performance of the to recorpulsating heat pipe under the coupling action of the magnetic field vibration is further explored.The main research contents and conclusions are as follows:(1)This article first builds a visual experiment procedure,using high-speed cameras to record three flow directions.These three flow directions form four operating states under different external conditions,these four states independently or coexist in the pulsating heat pipe under different heating stages.There are four main bubble flow patterns observed in the experiment:bubbly flow,plug flow,long plug flow and annular flow.The heating power directly affects the complex changes of the gas/liquid two-phase flow.(2)Based on the visual experiment system,this paper loads the Suzhou test shaker to simulate six kinds of vibration environments.Using the experiment of non-vibration conditions as a comparison,it is found that the working medium in the tube has the best heat dissipation effect when it is in the cyclic operation mode.Under vibration conditions,the pulsating heat pipe is mainly affected by the comprehensive action of the driving force and other forces exerted on the working medium in the process of vibration.Whether the vibration plays a specific role in promoting or hindering,it mainly depends on the specific operating state of the working fluid in the tube to make a specific analysis.(3)In this paper,a method of loading magnetic field is proposed to enhance the performance of the pulsating heat pipe under vibration condition only.The results show that the magnetic field has a significant effect on the start-up and operation of the pulsating heat pipe in a vibrating environment.The reason is that the magnetic field not only changes the physical properties of the magnetic fluid,but also exerts a certain magnetic force on the pulsating heat pipe,which better optimizes the heat transfer performance of the pulsating heat pipe and shows a certain degree of shock resistance.This provides a certain amount of innovative thinking and guidance for future practical engineering applications.