Experimental Study of Flow Patterns and Improved Configurations for Pulsating Heat Pipes

A series of experiments were performed on three types of closed loop pulsating heat pipes(PHPs),intending toinvestigate various kinds of flow patterns,and to develop some improved configurations for the PHPs.Opticalvisualization results indicated that there might exist three flow patterns,i.e.bubble-liquid slug flow,semi-annularflow and annular flow,corresponding to different working conditions.For a given geometry and an adequate fillratio,the PHPs had the self-adjusting characteristic for the flow patterns(from slug flow to semi-annular and thento annular flow)to meet the demands of the increasing heat input.Two special configurations,one with alter-nately varying channel diameter,the other equipped with one section of thicker tube,were found to be advanta-geous in establishing and maintaining reliable circulation of the working fluid.The thermal performance of thePHPs was examined over a range of working conditions.Comparing with the normal PHP with uniform diameter,either of the improved PHPs exhibited higher thermal performance.

Experimental study of flow patterns and improved configurations for pulsating heat pipes

A series of experiments were performed on three types of closed loop pulsating heat pipes(PHPs),intending to investigate various kinds of flow patterns,and to develop some improved configurations for the PHPs.Optical visualization results indicated that there might exist three flow patterns,i.e.bubble-liquid slug flow,semi-annular flow and annular flow,corresponding to different working conditions.For a given geometry and an adequate fill ratio,the PHPs had the self-adjusting characteristic for the flow patterns(from slug flow to semi-annular and then to annular flow)to meet the demands of the increasing heat input.Two special configurations,one with alter- nately varying channel diameter,the other equipped with one section of thicker tube,were found to be advanta- geous in establishing and maintaining reliable circulation of the working fluid.The thermal performance of the PHPs was examined over a range of working conditions.Comparing with the normal PHP with uniform diameter, either of the improved PHPs exhibited higher thermal performance.