Research On Heat Exchange Characteristics Of Nanofluids Under The Spring Inserted Tube

The nanofluids were researched as the main object in this paper,an experimental analysis was carried out to investigate the effect of nanofluids'volume fraction,particle size of the nanoparticles,spring pitch and spring wire diameter on the heat transfer performance.The main contents are generalized as follows:(1)Combined with previous research results,the basic physical properties of the nanofluids were studied.Four different nanofluids'viscosity were measured and then contrasted with the theoretical calculation values of existing model.The results showed adding nanoparticles in base fluids could significantly improve nanofluids'viscosity.The nanofluids'volume fraction and particle size of the nanoparticles were two key factors which affect the nanofluids'viscosity.Configuration of nanofluids by different types of nanoparticles had some different degree to improve the viscosity.(2)An fouling experimental platform was established to analyze and contrast how the nanofluids and helical spring insert affect the enhancement of heat transfer in heat exchanger tube under different physical parameters.The results showed the bigger spring wire diameter contributed to improve heat transfer property.The increase of spring pitch could enhance heat transfer coefficient within a certain scope.Under the experimental conditions,the nusselt coefficient of tube 3~#compared to tube 2~#,tube 4~#,tube 5~#rised by24%?5.6%?7.1%respectively.(3)An PIV experimental platform was also established to analyze and contrast how the nanofluids and helical spring insert affect the flow field characteristics in heat exchanger tube under different physical parameters.The results showed the increased spring wire diameter could increase the mainstream velocity effectively and strengthen the boundary layer disturbance.Spring pitch was one of the factors influencing the flow field in tube,the average velocity of tube 3~#increased by 14.1%compared to the entrance.The nanofluids'volume fraction was an important factors which affected the flow field.With the increase of nanofluids'volume fraction,leaded to the corresponding increase in viscosity,made the tube fluids consume more energy in order to overcome the frictional resistance.(4)Simulation research was used to study the tube flow field and heat transfer performance under various working conditions by employing the FLUENT software,and then the tube velocity field,temperature field of simulation were compared with the experiment.The results showed the nanofluids'nusselt coefficient of tube 3~#could reach a maximum when under the same working condition,which were in conformity with heat transfer experiment and PIV experiment conclusion.