Hydrothermal performance comparison of modified twisted tapes and wire coils in tubular heat exchanger using hybrid nanofluid

Abstract

A comparative experimental study to examine the hydrothermal behaviors of the double tube heat exchanger with various modified twisted tape and wire coil inserts is performed using Al2O3+MWCNT hybrid nanofluid. The investigation is performed for Reynolds number of 8000–40000, nanofluid flow rate of 5–25 lpm and volume concentration of 0.01%. The effects of using various enhancers (V-cut twisted tapes and tapered wire coils) and hybrid nanofluid on the hydrothermal characteristics are assessed for different enhancer arrangements such as different twist ratios, V-cut depth ratios, V-cut width ratios, converging type (C-type) wire coil, diverging (D-type) wire coil and converging-diverging type (C-D type) wire coil. The test reveals that the pressure drop and heat transfer coefficient increase with reducing twist ratio, increasing depth ratio and reducing width ratio. D-type wire coil exhibits higher heat transfer performance with the penalty of pressure drop than that of other arrangements. V-cuts twisted tape of minimum twist ratio, maximum depth and width ratios yields maximum PEC and FOM. V-cut twisted tapes show a higher performance index than the tapered wire coil as the augmentation in pressure drop is slightly significant. D-type wire coil shows the minimum value of entropy generation among all other arrangements. © 2021 Elsevier Masson SAS