Effect Of Ultrasound On Convective Heat Transfer Characteristics Of Water-based Graphene Nanofluid

Enhanced heat transfer technology can not only improve the heat transfer efficiency of equipment or systems,but also reduce the size and initial investment of heat exchange devices and energy transmission systems,which is of great significance for solving problems such as energy shortage and environmental pollution.Nanofluids have attracted extensive attention as a new type of efficient heat transfer medium,among which graphene nanofluids have attracted the attention of researchers because of their excellent thermal properties.In view of this situation,this paper configures graphene nanofluids,characterizes and tests the stability and thermophysical parameters of graphene nanosolutions with different concentrations,independently designs circular copper tubes and rectangular channels,and builds continuous A series of experimental studies have been carried out on the experimental bench of graphene nanofluid convective heat transfer under the action of ultrasonic oscillation.The main conclusions are as follows:(1)Graphene nanofluids were prepared by a two-step method and their physical properties were tested.It was found that with the increase of concentration,the stability of graphene solution decreased sequentially.When the mass ratio of dispersant and graphene is2:1,the dispersing effect is much greater than that when the mass ratio is 1:2;the viscosity test result of the configured graphene nanofluid is generally larger than the theoretical value.The thermal conductivity of graphene nano-solution increases with the increase of graphene concentration,but the rate of change gradually decreases.Comparing the enhancement ratio of the test value with the theoretical value of the Maxwell model,the average relative error is3.75%.(2)A graphene nanofluid ultrasonic-enhanced convective heat transfer experimental bench was built to conduct experimental research on the convective heat transfer of graphene nanofluids in circular tubes under the action of ultrasonic waves of different powers.The results show that when the graphene concentration increases,the convective heat transfer in the experimental section The thermal coefficient increases accordingly.When the graphene nanofluid concentration is 0.12 wt%,the heat transfer coefficient increases by 21.20%compared with that of deionized water;the ultrasonic-enhanced heat transfer rate can reach up to 38.54% under the action of 15-60 W ultrasound,and the ultrasonic-enhanced heat transfer rate increases with the increase of ultrasonic power.It increases with the increase of concentration,but first increases and then decreases with the increase of concentration;the Nu correlation equation of graphene nanofluid convection heat transfer under ultrasonic field is fitted,and the average relative error does not exceed 6%;the ultrasonic wave is analyzed along the length of the pipe section.The effect on the convective heat transfer capacity was found to be significantly greater in the fully developed section than in the inlet section.(3)The experimental section of the rectangular channel was processed,and the experimental test was carried out on the ultrasonic enhanced convection heat transfer experimental bench.The results showed that the intervention of ultrasonic waves could enhance the heat transfer.With the increase of ultrasonic power,the convection heat transfer coefficient increased.When 60 W ultrasonic was continuously applied,the ultrasonicenhanced heat exchange rate of deionized water was up to 31.13%.When the concentration of graphene nanofluid is 0.12 wt%,the heat transfer coefficient is increased by 30.14%compared with that of deionized water.The error is not more than 5%;the number of Nu along the route shows a large decrease first with the length of the tube,and then gradually stabilizes at a constant value.The ultrasonic enhancement effect in the fully developed section is significantly greater than that in the inlet section.