Study On Heat Transfer Performance Of Nanofuilds Heat Pipe With Foam Metal Wick And Its Application

Heat pipe, as an efficient heat transfer component, is widely used in various industrialfields. With the rapid development of the nanofluid and foam metal in enhanced heattransfer technology applications, they are applied to the heat pipe to improve the heattransfer efficiency by more and more researchers. Heat pipe can be used to ameliorate thefriction stir welding (FSW) temperature field to improve the quality of welded jointsbecause of its better temperature uniformity. Based on this background, in this paper, porestructure and morphology of sintered porous metal, metal foam and mesh metals were testedby scanning electron microscopy (SEM) and ultra-depth microscopy. The pore size andporosity were tested by mercury intrusion method and immersion method, and thetheoretical capillary suction force was calculated. With different concentration of NanoAl2O3, CuO and SiO2, three types of nanofluids based on DI water (deionized water),ethanol and ethylene glycol were prepared by means of two-step method. The suspensionstability of nanofluids was investigated through sedimentation method. The influence ofadding anion and cation surfactants on the suspension stability of nanofluids was alsostudied. Meanwhile, the thermal conductivity of the nanofluids were compared byexperiment.The latent heat of vaporization and heat weight of the nanofuilds were measuredby themograbimetric differential thermal spectrometer, the viscosity was also measured bycapillary method. On this basis, copper mesh and porous foam metal wick heat pipes withadding nanofluid were designed, and heat transfer characteristics of different heat pipeswere studied. Through the study on heat transfer characteristics of the heat pipe, differentspecifications of flat heat pipe were designed for friction stir welding and its improvementof friction stir welding temperature field was also researched preliminarily.Research of porous material indicates that sintered porous material formed irregularstacking aperture by sintering particles, which is small and widespread. Due to theformation of half through holes are more, its porosity is low. Porous foam metal has highporosity and wide aperture range, small diameter capillary can provide large suction force,large aperture can guarantee a high permeability. Foam metal holes connect each other, andthere are also a lot of directional holes, with large aperture and uniform distribution, whichis helpful to increase the working medium flow disturbance.In the study of nanofluids stability, as the base fluid, the stability of ethylene glycol is the best, while the deionized water(DW) is the worst. While the DW is choosed as the basdfuild, the stability of CuO-DW nanofluids is the worst, and the stability of SiO2-DWnanofluids and Al2O3-DW is better. The appropriate amount of surfactant can significantlyimprove the stability of the water-based nanofluid suspension, and the role of the cationicsurfactant HTAB is superior to the anionic surfactant SDBS.Thermal performance test of nanofluids shows that Al2O3-ethanol thermal conductivityis best, and Al2O3-DW is the worst in different base fluids. While in the DW base fuilds, thethermal conductivity of Al2O3-DW nanofluids and CuO-DW nanofluids is better thanSiO2-DW nanofluids. As the concentration of nanofluids increasing, latent heat ofnanofluids becomes smaller, and phase-transition temperature gets reduced. The higherconcentration of nanofluids, the greater the rate of mass change is. Viscosity test studyfound that the viscosity of CuO-DW nanofluids is the minimum, followed by A12O3-DWnanofluids, and the viscosity of SiO2-DW nanofluids is the largest.Heat pipe performance tests show that, compared to the copper mesh wick, copperfoam wick can improve the average temperature and the heat transfer limit of the heat pipe,reduce the operating temperature of the heat pipe. Contrast with deionized water workingfluid, nano-working fluid can improve the heat transfer coefficient of heat pipe evaporatingsection and the condenser section. Nano-working fluid can reduce the total thermalresistance of heat transfer in the heat pipe and heat pipe working temperature, and increasethe average temperature of the heat pipe. Among them, the effect of0.5%Al2O3-DW asworking fluid is the best.Flat heat pipe can reduce the peak temperature of friction stir welding test plate weld,and the cooling effect is the best when the condenser section of the heat pipe is cooled withwater. It is not only can cool the temperature of welding starting, but also can transfer thetemperature to welding area for preheating, to make the temperature field of welded jointsmore uniform.