Abstract: In order to study the surface heat transfer characteristics of TiO2-distilled-water nanofluids in internally ribbed copper tube, nanofluids surface heat transfer experimental system and data acquisition system are designed and built, the core part of which uses copper smooth tube and internally ribbed copper tube, the base fluid and TiO2-distilled-water nanofluids are applied in these two kinds of tube to do surface heat transfer experimental study(Re=3 000-8 000), the results show that: in the internally ribbed copper tube, TiO2-distilled-water nanofluids surface heat transfer coefficient is continuous improving with the increasing fluid velocity, and with the mass fraction of nanoparticles increasing, TiO2-distilled-water nanofluids surface heat transfer effect is getting worse and weaker than that of the base fluid. On the base of the same mass fraction of nanoparticles, nanofluids surface heat transfer effect is strengthened with the increase of the fluid average temperature. Through the comparison of the experimental results of nanofluids in different tubes, it is found that the degree of surface heat transfer effect enhancement of TiO2-distilled-water nanofluids in internally ribbed tube compared with smooth tube is lower than that of the base fluid, so the TiO2-distilled-water nanofluids is not fit for internally ribbed copper tube.

Key words: Heat transfer enhancement, Internally ribbed copper tube, Surface heat transfer coefficient, TiO2-distilled-water nanofluids