Performance evaluation of shell-and-double concentric tube heat exchanger

Abstract

Shell-and-tube heat exchangers (STHEX) have been used for several decades. Conventionally to increase the thermo-hydraulic performance of classical heat exchangers, overall length of tubes has to be increased. This contributes major disadvantage in term of classical heat exchangers design particularly considering economical aspect. In this study, the thermo-hydraulic performance analysis of a shelland-double concentric tube heat exchanger (SDCTHEX) is carried out using commercially the available Computational Fluid Dynamic (CFD) software ANSYS FLUENT 14.0. A 3D realizable k–ε turbulence model with scalable wall function treatment is used for the whole numerical simulations. Validation on heat transfer coefficient and pressure drop are done, where the Bell-Delaware method, Gnielinski, and Haaland correlations are compared with CFD simulation values of SDCTHEX and classical STHEX. The SDCTHEX model is then compared with classical STHEX model for their thermo-hydraulic performances for different mass flow rates of the hot fluid. Next, the effects of different inner tube diameters and different arrangement (counter and parallel flows) flows of working fluids flows on the performance of SDCTHEX are investigated. Other than that, the effects of the heat transfer and pressure drop of Al2O3/water nanofluid at different Al2O3 nanoparticle volume concentrations and flow rates flowing inside annulus side of SDCTHEX are also analysed. It is observed that, the percentage of overall heat transfer rate per overall pressure drop of SDCTHEX with inner tube diameter equal to 8/12 mm/mm, is increased nearly 343 % higher than that of STHEX. Also, the overall heat transfer rate per overall pressure drop of SDCTHEX is sensitive to inner tube diameter. It is found that Φ/ΔP for the mass flow rate of 22.5 kg/s is for to be maxed about 400 % higher at inner tube diameter of 12/16 (mm/mm) with respect to the STHEX. On the other hand, the thermo-hydraulic performance for counter flow arrangement of working fluid is also found higher than that of parallel flow arrangement of working fluid at any hot fluid mass flow rate. For the nanofluid effect, the results obtained showed that at the same Re, the heat transfer performance increases by increasing the nanoparticle volume concentration and it’s valued higher when compared with water. But when compared at the same mass flow rate, the nanofluid at any nanoparticle volume concentration does not show any enhancement on heat transfer when compared with water.