Research On Performance Optimization Of Non-uniform Diameter Pulsating Heat Pipe For Heat Dissipation Of Electronic Equipment

Pulsating Heat Pipe(PHP),with its advantages of simple structure,excellent temperature homogeneity and flexible environmental applicability,has a strong application potential in the field of electronic equipment heat dissipation with high integration and high heat flux,and has attracted extensive attention from scholars at home and abroad.The results show that the non-uniform structure can change the velocity and pressure distribution of the PHP and improve the performance of the PHP.Therefore,this paper establishes the PHP with non-uniform pipe diameter structure for numerical simulation,and explores the influence of several key factors on PHP performance,in order to improve the heat transfer performance of PHP and ensure the safe and efficient operation of electronic equipment.The specific research work of this paper is as follows:This paper presents and simulates uniform diameter PHP,single contracting-expanding PHP and double contracting-expanding PHP.The manifold variation and the Venturi effect of contracting-expanding structure in single loop PHP with different geometry structure is analyzed.The start-up characteristics,flow characteristics,oscillation characteristics,circulating power,temperature uniformity and heat transfer performance of pulsating heat pipes with different geometric structures were compared.Finally,the influence of the single contracting-expanding PHP on the circulation direction at the contracting-expanding structure’s position(left and right),the heat transfer performance of different tube diameter ratios(1.5:3,2:3,2.5:3)and different filling rates(40%,50%,60%,70%)are compared and analyzed.The results show that the pressure and velocity distribution of the contracting-expanding structure accord with the Venturi effect,which can affect the velocity and pressure distribution of the PHP and improve the circulation power of the PHP.The single contracting-expanding PHP has better performance in starting time,flow velocity,temperature uniformity performance and circulation power.In terms of heat transfer performance,the average heat transfer coefficient of each circulation is more stable,and the total average heat transfer coefficient is the largest,which is1576.99W/(m~2·K).In terms of the influence on the direction of circulation,the single scale structure can make the single loop pulsating heat pipe form a stable circulation in a single direction and strengthen the flow trend.By comparing the effects of different pipe diameter ratio and filling rate on the performance of single contracting-expanding PHP,it is found that with the decrease of pipe diameter ratio,the flow velocity and differential pressure in pipe are larger,the Venturi effect is more obvious,and the heat transfer performance is better.With the increase of filling rate,the cyclic dynamic force is enhanced,the homogenization performance is improved,the thermal resistance is reduced,and the heat transfer performance is improved.