Study On Spectral Radiation And Flow Characteristics Of Nanofluids

As an excellent heat transfer medium,nanofluid has the advantages of high thermal conductivity,strong radiation absorption,good heat transfer performance and wide application range.This is very important to improve the economics,reliability and miniaturization of the heat exchange system.The study of spectral radiation characteristics of nanofluids is an important aspect of studying nanofluids and has attracted wide attention in the field of spectroscopic radiation.However,the absorption of nanofluids and the internal radiation transmission mechanism are still unclear.Especially,little research has been done on the radiation transport mechanism of nanofluids in non-uniform particle systems,which is ubiquitous in practical applications.In the process of nanoparticle flow,the research on the erosion deposition problem that affects the radiation absorption capacity,the heat exchange efficiency inside the tube and the service life of the heat exchanger has yet to be carried out.Therefore,this thesis conducts theoretical and experimental research on the radiation propagation of beams in non-uniform particle systems and the erosion deposition of nanoparticles.Firstly,a nanofluid translucent medium was used as a research object.A spectral radiation transfer model was established for non-uniform particle system.Based on Matlab and Visual Studio,the Mie theory and the Monte Carlo method are used to solve the uniform particle system and the non-uniform particle system.The spectral radiation characteristic parameter calculation program was carried out to study the spectral radiation characteristics of the uniform particle system and the non-uniform particle system.The effect of using a simplified uniform particle system instead of an actual non-uniform particle system on the spectral characteristics of nanofluids is compared.By comparing the experimental data with the theoretical calculation results,it is found that the calculation program results of the spectral characteristics of the non-uniform particle system are more in line with the actual test results,and more accurately reflect the spectral transmission characteristics.Secondly,the 90° elbow is taken as the research object.Computational fluid dynamics software is used to study the flow characteristics of nanofluids under liquid-solid two-phase flow and the erosion characteristics of the wall.Calculate the different axial sections of the characteristic pipe sections,the flow velocity distribution and particle concentration distribution of the two-phase flow.The effects of different velocity distributions and particle concentration distributions on wall erosion and deposition were analyzed.The results show that the hot spot area of the 90° elbow deposition is the axial angle of 45°?75°,circumferential angle of 345°?15°,120°?150°and 210°?270° bending.The erosion hot spot area is 45°?75° axial angle,120°?150° circumferential angle and 210°?270°.Therefore,in the application of nanofluids,erosion hot spots should be protected.Finally,this paper established a nanofluid erosion deposition test bench.A 90° test elbow was designed and fabricated to test different axial and axial angle corrosion deposits.The 14 hour erosion deposition test was carried out.Detection of erosion deposition behavior of nanofluids on characteristic sections by X-ray photoelectron spectroscopy and inductively coupled plasma spectrometry/mass spectrometry,and the deposition amount was quantitatively analyzed.The results show that the most severe erosion deposition area is an axial angle of 30°?75°,circumferential angle of 345°?15° bending,which is consistent with the same numerical analysis.