关键词: 熔盐基纳米流体, 热扩散模型, 流动换热特性, 数值模拟

Abstract: To study the flow heat transfer characteristics of Al2O3-HITEC molten salt-based nanofluids in heating tubes with constant heat flux，a computational fluid dynamics ( CFD) simulation was carried out with the singlephase thermal dispersion model． The effects of nanoparticle additions with different mass fractions on the heat transfer performance of molten salt were analyzed，and the heat transfer performance variations were discussed from the respect of the thermal physical properties of the fluid． Comparisons of results show that the thermal dispersion model can be used to simulate the heat transfer performance of molten salt-based nanofluids． Simulations show that the temperature inside the tube with various nanofluids is lower than that with pure molten salt，and the temperature drop is the most obvious with the particle concentration of 0. 063% ． The temperature distributions at the four sections show that under the wall heat flux boundary，the temperature of molten salt with or without nanoparticles increases radially，while the temperature of molten salt-based nanofluids is lower than that of the pure molten salt，indicating nanofluids absorb and take away more heat energy． Moreover，compared with that of pure molten salt，the heat transfer performance of molten salt-based nanofluids increases，proving that the nanoparticle additions can improve the heat transfer performance of molten salt． However，the improvement is not proportional to the increase of nanoparticle concentration． Instead，the nanofluids with a mass fraction of 0. 063% show the greatest heat transfer enhancement，and the heat transfer coefficient in the fully developed region is 6. 5% higher than that of pure molten salt． Finally，the drastic change of specific heat capacity is found playing a key role in the change of heat transfer performance through analyzing the physical properties of molten salt and molten salt-based nanofluids．

Key words: molten salt-based nanofluids, thermal dispersion model, flow and heat transfer characteristics, numerical simulation