Ultrasonic Effect On Heat Transfer Performance Of Oscillating Heat Pipe With Binary Fluids

With the rapid development of China’s shipping industry,the degree of automation has been continuously improved,and the use of electronic components has gradually increased.At the same time,the development of highly integrated,miniaturized and reliable operation of the electronics industry has led to an increase in the heat flux density of electronic components.The heat needs to be dissipated more quickly to meet the requirements of reliable operation.Therefore,the problem of heat dissipation and cooling of electronic components has become an urgently important problem that needs to be focused on.As a promising and potential heat transfer element that is expected to solve the high heat flux density in a small volume,the oscillating heat pipe has excellent performance and simple structure,but the oscillating flow and heat transfer mechanism of the internal working fluid is very complicated,and the thermophysical properties and the external field have an effect on its heat transfer performance.In this paper,the heat transfer performance of oscillating heat pipes with methanol,water and their mixture with different ratios are investigated.In the meantime,the effect of ultrasonic field and external oscillating source on the heat transfer performance of oscillating heat pipes are also explored.Experimental study on the heat transfer performance of oscillating heat pipe with pure working fluid shows that the thermal resistance decreases with the heating inputs increasing,sharply first,flat afterwards and finally tending to a stable value.The resistance gradually decreases with the operating temperature increasing,and the higher the operating temperature is,the faster thermal resistance reaching the stable value and the smaller the heating power.There exists a critical heating input(related to the operating temperature).Below this value,the heat transfer performance of OHPs with methanol as the working fluid shows better.Above this value,the OHPs with deionized water as the working fluid has better heat transfer performance.When the inclination angle is at 30°,60°,90°,the heat transfer performance is obviously better than that of 0°.When the filling ratio is at 30%,the heat transfer performance is better than that of 50%and 70%.The binary mixed fluids with methanol-water at different ratios(1:2,1:1 and 2:1)were prepared.The experimental study on OHPs with different ratios of methanol and water as working fluids shows that the heat transfer performance of OHPs is better with methanol-water at different mixing ratios as the working fluid than that of the OHP with pure working fluid.At low heating input(no more than 60W),The OHP with binary fluids(Water:methanol=1:2)has the smallest thermal resistance.At high heating input(larger than 60W),OHP with binary fluids(Water:methanol=2:1)shows better heat transfer performance.The ultrasonic effect on the heat transfer performance of the oscillating heat pipe was studied.Study shows that the addition of the ultrasonic field enhances the heat transfer performance of OHPs to a certain extent,and the enhancing effect is more obvious at lower heating inputs.When the operating temperature is raised from 30℃ to 50℃,the enhancing effect on the heat transfer capability of OHPs with ultrasonic still appears at lower heating inputs.And the effect is weakened when the heating input is higher.The ultrasonic effect has a certain change on the heat transfer performance when the binary fluids used as the working fluid and more obvious at low heating power.The enhancing effect of ultrasonic is varied at different inclination angles.When the ultrasonic frequency was changed,and the heat transfer performance of OHPs with binary fluid still exists.And the enhancing effect is more remarkable after the double-frequency combination is applied on OHPs.The heat transfer performance of the open-loop OHP with externally oscillating source is studied.The results show that when the applied oscillating amplitude is constant,the thermal resistance decreases with the oscillating velocity(frequency)increasing in general.But within a certain speed range,the thermal resistance at one speed is smaller than the thermal resistance at its adjacent speed.There does exist an optimum oscillating frequency that makes the heat transfer performance of the OHPs exhibit better than others.