Numerical Simulation Of Heat Transfer In Nano - Fluid Heat Pipe

In this paper, from the two aspects of mesoscopic and macroscopic, the heat transfer ofnanofluids heat pipe boiling heat transfer characteristics are simulated.On the mesoscopic research direction, using the theory of lattice Boltzmann, To LatticeBoltzmann method→Lattice Boltzmann model→Multiphase and multicomponent LatticeBoltzmann method→Boundary processing method as the main line, the Boltzmann theory isintroduced and derived in detail,and in the lattice Boltzmann model, Introduced themodification of the lattice Boltzmann model under the reaction conditions, and establishedthe effective migration flow model of nanofluids, from the fluid particles distributionfunction, considering the interaction between particles,combined the nanofluids effectivemigration flow model with the Shan-Chen model,then builded the nano fluid phaseseparation model and the phase separation of nano fluid were simulated. As can be seenfrom the results, nano particle concentration of1%nano fluid compared with pure water,nano fluid due to various forces and potential role between nanoparticles, more uniformbubble distribution, and more bubbles, explain that the addition of nanoparticles isbeneficial to the nucleation to have bubbles. For concentration of nanoparticles were0.1%,1%and0.1%respectively of the contrast between the nanofluids, founded that theseparation efficiency was not increased with the increase of the concentration of particles,The main reason is that the interaction of the surface of the nanoparticles is formed on thecore of the new activation rate and the reduction of the particle deposition caused byactivation of the core. the former is greater than the latter could prompt gas-liquid separation,on the other hand, reduced gas liquid separation.On the macroscopic research direction, by using Fluent software,programming througha UDF definitions of nanofluid phase change source term, boiling process were simulated onnanofluids heat pipe evaporation. In this paper, the pure water was contrasted with thedifferent concentrations of nanoparticles of Al2O3-H2O nanofluids of the boiling flowpattern and the characteristics of boiling heat transfer inside the tube. The results show that,in a certain concentration range, boiling heat transfer coefficient of heat transfer ofnanofluids is greater than the boiling heat transfer coefficient of pure water, and under thesame intensity of turbulence, the boiling heat transfer coefficient of nanofluids is higher thanpure water boiling heat transfer coefficient. Concentration nanoparticles of the nanofluids almost does not affect the flow pattern characteristic, in turn appeared bubble flow, slugflow, stratified flow and wave flow pattern. But at the same interface position, the aircontent of nano fluid is higher than that of pure water, and with the increase ofconcentration of nanoparticles, the boiling heat transfer coefficient shows the tendency ofincrease, so the heat exchange efficiency is also increased significantly.Through the above comparison of simulation results, can prove from the theoreticalresearch of nano fluid is good to strengthen the effect of the convective heat transfer, whichprovide the theoretical basis for experimental study.