**6. Conclusions**

Heat transfer and fluid flow characteristics through tubes induced with multiple plain twisted tape inserts using water and 0.1 vol.% TiO2/water nanofluid were investigated experimentally and numerically. The investigations were carried out for turbulent flow with Reynolds number ranging between 5000 and 20,000. The findings may be summarized as follows:


Accordingly, the combined technique of twisted tape inserts and nanofluid is recommended for heat exchanger application, as the heat transfer is considerably enhancing, with reasonable penalty in pumping power.
