In the present work an attempt has been made to study the effect of the Twisted tapes as bed internals, on the performance of the gas-solid fluidized beds. Experimental investigation has been carried out in cylindrical column with and without Twisted tapes. Twelve numbers of Twisted tapes of three different widths with four values of the twist ratios for each width were studied at different static bed heights. Twist ratio (y) is the ratio of axial distance for 1800 rotation of the tape (H) and the width (W) of the Twisted tape. By using Twisted tape the change in pressure drop, fluctuation ratio and expansion ratio have been studied as compared to “without Twisted tape”. Incorporation of Twisted tapes as baffle decreases the fluctuation ratio and expansion ratio thereby improving the fluidization quality as compared to the “without Twisted tape”. However the increase in pressure drop due to presence of Twisted tape is only marginal and of the order of, 5.25 to 14.9 percent over that of without Twisted tapes. The maximum decrease in fluctuation ratio (r) for the tapes of various twist ratio has been found to be 11.6 to 20.5 percent based on the case of “without Twisted tape”, thereby indicating a corresponding improvement in the quality of fluidization with reduced degree of bubbling and slugging. Quantitatively the maximum decrease in R for the Twisted tapes of various twist ratios has been found to be 17 to 23 percent based on the case of “without Twisted tapes”. However, the pressure drop, fluctuation and expansion ratio were in general found to decrease with decrease in twist ratio of a Twisted tape. Different correlations have been developed for pressure drop, fluctuation ratio and expansion ratio and compared with their corresponding experimental values. 

Power plants are of great influential industries to the environment which could be studied in many ways. Since the optimum equipment would consume less fuel, the issue is mainly interested to those who are concerned about the environmental effects. Amongst various methods, utilizing Twisted tapes inserts which are of passive type is interested in this effort. Although numerous types of tapes are widely utilized, modifying the tape configuration according to the flow specification is still interested. So here the centercleared and perforated tapes are considered to be compared against the typical type. The 3D numerical simulation of finite volume method was applied to cover the flow field of the problem. The RNG k-e turbulence model was responsible for the turbulent behavior of the flow and its circular trend. In order to develop the performance of the optimum tape performance, AL2O3 nanoparticles of different volume concentrations were added to the base fluid. The results showed that the Nu number was enhanced about 22% by using merely the center-cleared 14cm, while the friction factor was increased about 13%. To develop these amounts for the optimum configuration, adding nanoparticles of 0.1% concentration put and increment of 26% for heat transfer.

The present study aimed to investigate the effects of the semi-circular cut Twisted tape insert in tube type heat exchangers. The study selected twist ratios of 4.5, 5.5, and 6.5mm, and cut diameters of 5mm, 8mm, and 11mm. The Reynolds number ranged from 4000-16000. The study quantitatively demonstrated the impacts of cut diameter and twist ratio in terms of Nusselt number, friction factor, and thermal performance factor. The aforementioned output parameters were employed as metrics to assess the efficacy of the Twisted tape insert. The obtained results reveal that smaller twist generates extra swirl which intensifies heat transfer. Also, as the diameter of the cut increases Nusselt number increases. In a quantitative analysis, it was observed that when Re=4000, the plain Twisted tapes with y=4.5, 5.5, and 6.5 exhibited maximum thermal performance factors of 1.36, 1.32, and 1.21, respectively. On the other hand, for the modified Twisted tapes (having a cut diameter of 11mm), the values were higher, measuring 1.84, 1.77, and 1.68 for the same respective ‘y’ values.

The article presents a practical technique for enhancing thermo-hydraulic performance of a circular tube. In this way, numerical method focusing on laminar tubular flow is used to compare the effectiveness of utilizing center-cleared Twisted tapes instead of typical shape of short width tapes. Numerical analysis represented that using both center-cleared and typical shape of Twisted tapes, Re enhancement reduces the flow resistance. Studying short width Twisted tapes showed that decreasing the width of Twisted tape, reduces the heat transfer and hydraulic performance. Contrarily, using sufficient clearance for center-cleared Twisted tapes can increase the heat transfer. Hence, applying center-cleared Twisted tape as a tool of enhancing heat transfer can be a promising and practical idea.

In this paper, experimentally derived correlations of heat transfer and pressure drop are used in a Pareto based Multi-Objective Optimization (MOO) approach to find the best possible combinations of heat transfer and pressure drop of TiO2-water nanofluid flow in tubes fitted with multiple Twisted tape inserts in different arrangement. In this study there are four independent design variables: the number and arrangement of Twisted tape inserts (N), TiO2 volume fraction ( j), Reynolds number (Re) and Prandtl number (Pr). Seven Twisted tape arrangement in three different categories are investigated. The objectives are maximizing the non-dimensional heat transfer coefficient (Nu) and minimizing the non-dimensional pressure drop (f Re).It is shown that some interesting and important relationships as useful optimal design principles involved in the thermal performance of nanofluid flow in tubes fitted with multiple Twisted tape inserts in different arrangement can be discovered by Pareto based multi-objective optimization approach.