Experimental Investigation to Evaluate the Optimum Performance of Helical Coiled Tube with Insert and Nano-Fluid

Abstract

In the present work an experimental investigation is carried out to evaluate the performance of helical coiled tube with the swirl flow device using Al2O3nanofluid.The effects of wire coil insert with different parameter on heat transfer and friction loss in the helical tube were examined with Dean number (De) ranging from 700 to 2000. The circular or square coil wire has different cross sections, insertedin the tube with different pitch. The wire coil with Al2O3 nanoparticles with a diameter of 80nm dispersed in distilled water with volume concentrations of (0.08,0.1, 0.2and 0.3 vol.% ) were used as the test fluid. The effects of Dean Number, volume concentration of suspended nanoparticles, and wire coil on heat characteristics were investigated. The results reveal that the use of tabulators leads to a considerable increase in heat transfer and friction loss over those of a smooth tube. The Nusselt number increases with increasing of Dean number and reduction in pitch of wire coil. The square type of wire coil provides slightly higher heat transfer than the circular under the same conditions. Results show that the optimum heat transfer is caused of P=15mm of wire coils. Adding nanoparticles to the base fluid causes a significant enhancement in heat transfer characteristics. The overall enhancement in heat transfer using two mechanisms simultaneously compared to using pure fluid within the smooth helical tube exceeds over 213.2% (180% spring enhancement +33.2%Al2O3). The optimum results were found to be P=15mm, φ=0. 3Al2O3 t=2mm square cross section and De=1889. Finally, empirical correlations are developed of predicting Nusselt number of the flow with and without nanofluid. Comparison between the present result in reference results show good agreement.