Influence Of Surface Hydrophilic And Hydrophobic Modification On Heat Transfer Performance Of Pulsating Heat Pipe

The heat transfer mode of the pulsating heat pipe is mainly the phase change latent heat transfer of the working fluid and the sensible heat transfer of the pulsating flow,which is an effective way for the heat dissipation of the high heat flux density device in the future.In this paper,the hydrophilic and hydrophobic surface was introduced into the pulsating heat pipe.The pulsating flow heat pipe with hydrophilic and hydrophobic inner surface was fabricated,and the experimental platform for pulsating flow heat pipe visualization was successfully built.Visualization experiments were carried out to observe the flow pattern change and motion characteristics of the working fluid in the pulsating flow heat pipe with different inner surface hydrophobicity characteristics,and the temperature oscillation and the average temperature difference of the heat pipe heating section and the cooling section were measured by heat transfer experiments to analyze the hydrophilicity and hydrophobicity.The effect of modification treatment on the heat transfer performance of the pulsating flow heat pipe and the“dry-out,phenomenon.Through experiments,it can be found that:in the heat pipe of hydrophilic pulsating flow,there are many nucleation points and high boiling intensity in the nuclear state.The heat pipe of hydrophilic pulsating flow has good thermal sensitivity and better start-up performance.In the heating section of the hydrophobic pulsating heat pipe,local dry points will be generated,resulting in the deterioration of heat transfer.In the cooling section,the contact area between the steam and the wall surface will increase,and the condensation heat resistance will be small,resulting in better condensation effect.Under the condition of low heating power,the heat transfer performance of hydrophilic and hydrophobic pulsating heat pipe is lower than that of ordinary pulsating heat pipe,while under the condition of high heating power,the heat transfer performance of hydrophilic pulsating heat pipe is higher than that of ordinary pulsating heat pipe,and the heat transfer deterioration of hydrophobic pulsating heat pipe occurs in advance.For this topic focuses on analyzing the "dry-out" phenomenon,combined with"dry-out" condition of the image tube and the heat transfer can be found on the experimental data,the hydrophobic oscillation occurred easily in the stream tube"dry-out" phenomenon,and hydrophilic surface modification treatment effectively delay the onset of the "dry-out" phenomenon,to avoid the occurrence of prenature deterioration of heat transfer,increase the application range of pulsating flow tube.Compared with the hydrophobic surface,the hydrophilic surface can improve the"dry-out" condition by 47.1%.The hydrophilic surface can increase the "dry-out"condition by 25%compared with the untreated normal surface.