This paper presents an experimental study to investigate the heat transfer enhancement in a horizontal circular tube using three metal oxide (ZrO2 (80 nm), γ Al2O3 (20 nm), CuO (40 nm)–distilled water) nanofluids and fitted with three types of twisted tape (typical twisted tape, twisted tape with V-cut and clockwise-counter clockwise twisted tape) with twist ratios (TR=4, 6, 8). The studied concentrations of nanofluids are (φ = 0, 0.01, 0.05, 0.1, 0.5, 1, 2, 3% by volume) under fully developed turbulent flow and uniform heat flux condition.
The experimental test rig includes all the required instruments to study the heat transfer enhancement. All the tests were carried out with Reynolds number range (2490-20100) and uniform heat flux (2108-9280 W/m2). The experimental study also includes preparation and measurement of properties of density, viscosity and specific heat of nanofluids. The pressure drop, wall temperature, flow rate, heat flux and temperature of nanofluids.
For nanofluid, the maximum enhancement in the heat transfer (Nusselt number ratio) was (7.5), and the maximum thermal performance factor was (3.9) using (CuO)–distilled water nanofluid, clockwise-counter clockwise twisted tape with twist ratio (TR=4) at Reynolds number (2490) and concentration (φ=3%). The average Nusselt number and friction factor with Reynolds number, nanofluid concentration and twist ratio were correlated for each type of the used nanofluid.