Second law analysis of a hybrid nanofluid in tubes equipped with double twisted tape inserts

Thermal and Flow Analysis of TiO2 Nanofluid Flow in Circular and Square Ducts with Multiple Twisted Tape Inserts

A numerical study is conducted to observe the thermal and flow performance of TiO2 nanofluid in the circular and square ducts with different twisted tape arrangements. The presence of the twisted tape in the tube induces swirl flow, which aids in the heat transfer, but at the penalty of a higher friction factor. The results also reveal that the maximum Nusselt number enhancement is obtained in the circular tube when the counter-triple twisted tape arrangement (C-TTs) is adopted while it is co-triple twisted tape arrangement (Co-TTs) for the case of square duct. Besides, the highest friction factor is observed for the Co-TTs for both circular and square ducts. The heat transfer and friction factor in the circular duct are greater than that of the square duct. The highest thermal performance factor of 1.286 is obtained when the single twisted tape and 1.5% nanofluid are used in the circular tube. However, multiple twisted tape inserts in the square duct contributes to improved thermal performance at a relatively lower friction factor when compared to the circular tube. Therefore, it is recommended to implement the square duct with multiple inserts for compact or microchannel heat exchanger for heat transfer application.

Analytical Approach on the Water-Based Nanofluid for the Influence of Dissipative Heat Energy

The current study reveals the influence of both dissipative heat in water-based conducting nanoliquid through an impassioned semi-infinite vertical plate past embedding with a permeable medium. The effect of particle concentration in conjunction with transverse magnetic field and heat source/sink is presented by introducing the flow and heat transfer phenomena. However, various heat transfer assets of the considered nanofluid are exaggerated by assuming the slip condition. The reason is that, for the diminution in the heat transfer, the role of temperature slip is vital. For the transformation of governing PDEs into nonlinear coupled ODEs, it is necessary to assume suitable self-similar transformations. Moreover, a semi-analytical technique such as Homotopy Perturbation Method (HPM) is employed to solve these transformed equations. The novelty of the study is to get a comparison of the result with the results obtained using the MATLAB in-build code bvp5c. The numerical results for the comparison between both the methods have been presented in tabular form and the control of various parameters for the flow phenomena is demonstrated via graphs.

Evaluation of Multiple Semi-Twisted Tape Inserts in a Heat Exchanger Pipe Using Al2O3 Nanofluid

The hydrothermal performance of multiple semi-twisted tape inserts inside a heat exchanger pipe is numerically examined in three-dimensions. This study aims to find the optimum case for having the highest heat transfer enhancement with the lowest friction factor using nanofluid (Al₂O₃/water). A performance evaluation criterion (PEC) is defined to characterize the performance based on both friction factor and heat transfer. It was found that increasing the number of semi-twisted tapes increases the number of swirl flow streams and leads to an enhancement in the local Nusselt number as well as the friction factor. The average Nusselt number increases from 15.13 to 28.42 and the average friction factor enhances from 0.022 to 0.052 by increasing the number of the semi-twisted tapes from 0 to 4 for the Reynolds number of 1000 for the base fluid. By using four semi-twisted tapes, the average Nusselt number increases from 12.5 to 28.5, while the friction factor reduces from 0.155 to 0.052 when the Reynolds number increases from 250 to 1000 for the base fluid. For the Reynolds number of 1000, the increase in nanofluid concentration from 0 to 3% improves the average Nusselt number and friction factor by 6.41% and 2.29%, respectively. The highest PEC is equal to 1.66 and belongs to the Reynolds number of 750 using four semi-twisted tape inserts with 3% nanoparticles. This work offers instructions to model an advanced design of twisted tape integrated with tubes using multiple semi-twisted tapes, which helps to provide a higher amount of energy demand for solar applications.

Investigation of Overlapped Twisted Tapes Inserted in a Double-Pipe Heat Exchanger Using Two-Phase Nanofluid

This study investigated the laminar convective heat transfer and fluid flow of Al₂O₃ nanofluid in a counter flow double-pipe heat exchanger equipped with overlapped twisted tape inserts in both inner and outer tubes. Two models of the same (co-swirling twisted tapes) and opposite (counter-swirling twisted tapes) angular directions for the stationary twisted tapes were considered. The computational fluid dynamic simulations were conducted through varying the design parameters, including the angular direction of twisted tape inserts, nanofluid volume concentration, and Reynolds number. It was found that inserting the overlapped twisted tapes in the heat exchanger significantly increases the thermal performance as well as the friction factor compared with the plain heat exchanger. The results indicate that models of co-swirling twisted tapes and counter-swirling twisted tapes increase the average Nusselt number by almost 35.2–66.2% and 42.1–68.7% over the Reynolds number ranging 250–1000, respectively. To assess the interplay between heat transfer enhancement and pressure loss penalty, the dimensionless number of performance evaluation criterion was calculated for all the captured configurations. Ultimately, the highest value of performance evaluation criterion is equal to 1.40 and 1.26 at inner and outer tubes at the Reynolds number of 1000 and the volume fraction of 3% in the case of counter-swirling twisted tapes model.