Experimental Study On The Surface Wettability Effect On The Heat Transfer Performance Of An Oscillating Heat Pipe

With the continuous development of automatic systems on board ship,more electronic components and big power equipment will be used on large modern ships to improve its safety and speed ability,which lead to the high heat flux dissipation problem.Oscillating heat pipe(OHP)has aroused widespread focus through the world as an efficient heat transfer element that can solve the high heat flux dissipating problem.The working fluid inside the oscillating heat pipe can self-oscillate to drive the heat from the heating side to the cooling side.Currently,many research have been carried to explore factors affecting oscillating heat pipe's performance,and the surface wettability affect the performance of an oscillating heat pipe significantly,but few of them on the wettability of surface which hindered the development of oscillating heat pipe.In this paper,the experimental investigation of the heat transfer performance of an oscillating heat pipe on the effect of wettability was carried.Firstly,chemical etching and self-assembly methods were used to prepare the oscillating heat pipe with super-hydrophilic,super-hydrophobic,super-hydrophilic/hydrophobic combined and gradient wettability surface.Secondly,the dynamic temperature,oscillating frequency and amplitude in different heat power were detected.Thirdly,the heat transfer performance of all the four oscillating heat pipe were compared and the mechanism of the effect of the wettability on the oscillating heat pipe was illustrated from the point view of thin film evaporation and dropwise condensation.Through the experimental study the following conclusions can be got:(1)Oscillating heat pipe with superhydrophilic/hydrophobic combined surface get a better performance at the startup condition.Because the surface of this oscillating heat pipe in adiabatic section and condensation section are superhydrophobic which can drive the working fluid easily with the drag reduction effect.(2)The superhydrophilic surface inside the tube can let the generation of thin film more easily and the increase of contact area between fluid and tube has a positive role for both evaporation and condensation.In superhydrophobic surface,however,the thermal contact resistance between liquid slug and heat pipe is high which have a bad influence on the sensible heat transfer.So,the Oscillating heat pipe with superhydrophilic surface has a better heat transfer performance than the oscillating heat pipe with superhydrophilic/hydrophobic combined surface.(3)With the growth of surface wettability,the heat transfer performance of the oscillating heat pipe increase.The oscillating heat pipe can achieve a super heat transfer ability under the superhydrophilic condition(contact angle is 0°),which heat resistance can reach 0.246?/W under 100W heat input.