A Heat Transfer Research Of Non-newtonian Nanofluid In Spiral Baffle Oval Tube Heat Exchanger

The non-Newtonian fluid is a type of fluid that don’t satisfy the Newton law of viscosity, and shear stress and the shear rate have no linear relationship. Since non-Newtonian fluids is quite common in chemical industry, it is very important to develope the heat transfer enhancement technique of non-Newtonian fluids. Spiral baffle is an efficient and promsing structure of heat exchanger, but there were few reports about the applicantion of spiral baffle in non-Newtonian fluids heat transfer, so it’s necessary to investigate the heat transfer properties in this field.In this paper, we have prepared CMC aqueous solution with different mass fraction, and chose 3wt% CMC aqueous solution as the bass fluid. Then the MWCNTs were dispersed into bass fluid to form different mass concentration of MWCNTs/CMC nanofluids. Rheological properties analysis showed that all fluids were non-Newtonian fluids with shear-thinning rheological behavior: the viscosity decreases with increase of temperature. According to the thermal property analysis, the specific heat capacity of the base fluid and nanofluids are very closed, and the thermal conductivity enhancement increases from 4.2% for the nanofluid containing 0.1 wt% of MWCNTs to 14.6% for the one containing 2 wt % of MWCNTs.We investigated the heat exchange properties of bass fluid and 0.5wt% MWCNTs/CMC non-Newtonian nanofluid in shell side and tube side of spiral baffle oval tube heat exchanger. Experimental results show that the heat transfer coefficient of 0.5wt% MWCNTs/CMC non-Newtonian nanofluid increased 4.3%~11.1% in shell side and 20.8%~44.1% in tube side than bass fluid. Meanwhile, the presure drop of 0.5wt% MWCNTs/CMC non-Newtonian nanofluid increased 3.1%~8.6% in shell side and 4.3%~9.8% in tube side than bass fluid. After data fitting, we proposed the mathematical model of non-Newtonian fluid in spiral baffle oval tube heat exchanger. Most deviation of experimental data and calculated data are less than ±5%. What’s more, we also find that the heat exchange properties in shell side is higher than the tube side.