Effect Of Surface Tension And Viscosity Of Working Fluid On Pulsating Heat Pipe

Pulsating heat pipe(PHP)has the advantages of small volume,high heat flux,a good application prospect in the field of MEMS technology and waste heat utilization system,which is a hot spot in the research and development in recent years.The key point is to develop a PHP device which can operate stably.In this paper,the effect of the surface tension and viscosity of the working fluid on the start-up characteristics and stable operation characteristics of PHP was studied experimentally.The main contents and results are as follows:1?Study the working principle of PHP,and take a liquid plug as the unit,then establish its stress analysis.The effects of the surface tension and viscosity of the working fluid on the start-up and operation of PHP are analyzed deeply,and its theoretical basis is established.2?Using PFOK and PAM as additives and pure water as the base solution,make up aqueous solution of different concentrations.The start-up characteristics and stable operation characteristics of PHP were studied experimentally,and the experimental results are explained theoretically.Experimental findings:(1)The increase of the viscosity of the working fluid slows down the start-up of PHP,improves the minimum start-up power and the heat transfer limit.(2)There is a linear correlation between the viscosity of working fluid and the heat transfer resistance of PHP,i.e.the higher the viscosity,the higher the heat transfer resistance.(3)With the increase of viscosity,the frequency of liquid slug's transient pause increases.It is shown that the temperature amplitude increases,but after a short pause,the temperature fluctuation is faster and the amplitude is smaller.(4)The decrease of surface tension can effectively reduce the start-up time and heat transfer resistance of PHP.However,due to the increase of viscosity,the effect law curves on start-up time and the heat transfer resistance are “W” type.(5)The decrease of surface tension cannot affect the heat transfer limit of PHP and the minimum start-up power.(6)The decrease of surface tension can make the movement of the liquid plug more active.It is shown that the temperature oscillation frequency increased,and the temperature oscillation amplitude is reduced.3?The experimental data are analyzed and fitted,the surface tension and viscosity of the working fluid are integrated,and the correlation between the surface tension and viscosity of the working fluid,the start-up time and the heat transfer resistance of the PHP is obtained.It is found that the viscosity of working fluid is greater than the surface tension in the experimental range.