Numerical And Experimental Study On The Characteristics Of Pulsating Pipe

The development of high-performance stratospheric airships has once again been put on the agenda,and the requirements of research for high-speed permanent magnet brushless DC motors have also become urgent.One of the most important problem is heat dissipation in motors.Based on this engineering background,considering the widespread application of pulsating heat pipes in high heat flux miniaturization equipment,the scheme that a motor heat dissipation using pulsating heat pipes was proposed.Although the pulsating heat pipe has an efficient heat transfer performance,there is still a lack of understanding of its working mechanism.Based on reasonable assumptions,a three-dimensional pulsating heat pipe model was simplified to prepare a design calculation program for one-dimensional pulsating heat pipe.The temperature and pressure of the pulsating heat pipe in different diameters,different working media,different boundary conditions,and different initial design parameters were calculated.Changes in the position of the gas-liquid interface,flow rate,and latent heat transfer can quickly give design results under specific conditions.The calculation results show that the higher the wall temperature of the heating section is,the larger the fluctuation of the flow rate of the working fluid in the tube and the less frequent the frequency fluctuation of the temperature.Under the small pipe diameter,the latent heat transfer power of water is slightly higher than that of ethanol and methanol,and the difference is not large.Under the large pipe diameter,the latent heat transfer power is much higher than that under the small pipe diameter,and the latent heat transfer power of water is ethanol.About twice as much as methanol.In order to better understand the mechanism and influencing factors of gas-liquid two-phase phase change heat transfer in pulsating heat pipes,a visual test method was used to study the flow of methanol,ethanol,deionized water,and CTAC solutions at different heating powers and liquid filling rates.Morphology,start-up characteristics and thermal properties.The results show that the bubble-like flow,elastic flow,semiannular flow and annular flow were observed in the visual experiment.As the heating power increases,the working characteristics of different working media become better and the start-up time becomes shorter.Under low heating power,the thermal resistance under different conditions is not much different.Under high heating power,the thermal resistance is much lower than that under low heating power.Based on the knowledge of the visualization experiment results,the influence of the pulsating heat pipe on the thermal performance under different heating power,different liquid filling rates,different vacuum degrees,different placement angles and other parameters was studied.The results show that within a certain range,the higher the heating power,the higher the liquid filling rate and the higher the vacuum,the lower the thermal resistance when placed vertically.The pulsating heat pipe has the best thermal performance.