Investigations on the effect of disturbed flow using differently configured turbulators and Alumina nanofluid as a coolant in a double tube heat exchanger

This paper investigates the effect of the combined passive technique on heat transfer enhancement, friction factor, and thermal performance of a double-tube heat exchanger fitted with differently configured turbulators and using Alumina nanofluid. The performance parameters are studied for fixed flow rate (Re = 2500) of water at constant heat flux in the inner tube (hot fluid) and varying flow rates (500 <= Re <= 5000) of Alumina nanofluid (volume concentrations: 0.05-0.15%) flowing in the outer tube (cold fluid). The configurations tested are a peripherally V-cut twisted tape (Twist Ratio = 20, 13.3, and 9.8) and a propeller turbulator (Number of propellers: 6, 8, and 10). The results show increased Nusselt number by 22.4% and 29.43%, increased Thermal Performance Factor by 1.25 and 1.33, respectively, for decreased twist ratio and increased number of propellers and volume concentration of Alumina nanofluid. The peripherally V-cut twisted tape (TR = 9.8) and propeller turbulator (Number of propellers = 10) with 0.15% volume concentrations of Alumina nanofluid combination give better performance, with a slight penalty in pressure drop. The correlations for the Nusselt number and friction factor are developed from the experimental data, which are fairly in good agreement with the experimental data.

Automated summary

The study investigates the effect of combined passive technique on a double-tube heat exchanger, finding that increasing the volume concentration of Alumina nanofluid, the number of propellers, and decreasing the twist ratio can enhance heat transfer and thermal performance. The experiments also show that a combination of peripherally V-cut twisted tape and propeller turbulator with specific volume concentration of the nanofluid provides the best performance with a slight increase in pressure drop.