Twisted Tube Research Articles

Thermo-fluid characteristics and exergy analysis of a twisted tube helical coil

AbstractIn the present investigation, the exergy of an innovative technique involving the integration of curved helical tubes with twisted passages was experimentally presented. This technique aims to improve the thermofluid characteristics by involving the swirl intensity of fluid flow in a twisted tube helical coil (TTHC). Six identical geometries with different pitch ratios $$\Upsilon$$ of 36 mm, 54 mm, and ∞ (smooth/no twisted) were experimentally explored at two different inner tube profiles of triangular and square cross-sections in counter flow arrangements. The experimental runs were carried out at 10,300 ≤ Rei ≤ 37,800 and 2400 ≤ Reo ≤17,600 for both the inner and annulus fluids, respectively. The results showed that the Nusselt number, Nu, increased by 39.6% and 41.5% for triangular and square inner twisted cross-section profiles, respectively, at a $$\it \Upsilon$$ of 36 mm at the expense of increasing f by 37.6% and 60.7%, respectively. The results also showed that the thermal performance factor reached 1.3 and 1.25 for a $$\it \Upsilon$$ of 36 mm for the triangular and square inner twisted tube profiles, respectively. A comprehensive study is performed to analyze the TTHC from thermal, frictional, and exergetic viewpoints. New correlations for expecting the annulus Nuo and fo are presented.

Twisted-tape inserts of rectangular and triangular sections in turbulent flow of CMC/CuO non-Newtonian nanofluid into an oval tube

Purpose This paper aims to study numerically the non-Newtonian solution of carboxymethyl cellulose in water along with copper oxide nanoparticles, which flow turbulently through twisted smooth and finned tubes. Design/methodology/approach The twisted-tape inserts of rectangular and triangular sections are investigated under constant wall heat flux and the nanoparticle concentration varies between 0% and 1.5%. Computational fluid dynamics simulation is first validated by experimental information from two test cases, showing that the numerical results are in good agreement with previous studies. Here, the impact of nanoparticle concentration, tube twist and fins shape on the heat transfer and pressure loss of the system is measured. It is accomplished using longitudinal rectangular and triangular fins in a wide range of prominent parameters. Findings The results show that first, both the Nusselt number and friction factor increase with the rise in the concentration of nanoparticles and twist of the tube. Second, the trend is repeated by adding fins, but it is more intense in the triangular cases. The tube twist increases the Nusselt number up to 9%, 20% and 46% corresponding to smooth tube, rectangular and triangular fins, respectively. The most twisted tube with triangular fins and the highest value of concentration acquires the largest performance evaluation criterion at 1.3, 30% more efficient than the plain tube with 0% nanoparticle concentration. Originality/value This study explores an innovative approach to enhancing heat transfer in a non-Newtonian nanofluid flowing through an oval tube. The use of twisted-tape inserts with rectangular and triangular sections in this specific configuration represents a novel method to improve fluid flow characteristics and heat transfer efficiency. This study stands out for its originality in combining non-Newtonian fluid dynamics, nanofluid properties and geometric considerations to optimize heat transfer performance. The results of this work can be dramatically considered in advanced heat exchange applications.

Investigation of the hydraulic performance heat improvement in 3D pipe by variable of novel twisted tape configurations based on CFD and DoE analysis methods

Enhancing heat transfer is a key area that is closely related to economically efficient systems in various forms of energy saving. The insert of twisted are regarded as thermal method. Goal of the current study was to thoroughly assess how using several approaches at the same time affected the tube heat exchanger’s thermal flow, and thermal enhancement. Different twisted configurations were used such as twisted width, thickness of twisted, turn numbers, and thickness of inward are the modified geometrical parameters. Design of the experiments approach is used to investigate how different geometrical parameters affect the improvement of heat and hydraulic thermofluid pattern in twisted tube heat exchangers as the output variables. The Response Surface technique was also used to investigate and identify various outcome models. Taguchi analysis was applied to optimize the experimental design by investigating changes and executing orthogonal arrays. Additionally, the experimental study design was the orthogonal array L16. The performance parameter was optimized separately, and then the DoE methodology was combined with Taguchi method (TM) and response surface methodology (RMS) to optimize all parameters. In this work, the ideal twisted tape design is discovered through the application of CFD numerical approach in conjunction with RSM and TM. Compared results to traditional pipe, improvement in heat is roughly 42.81 % and 42.72 % for temperature differentials and heat transfer rate performance, respectively.

Novel twisted hexagonal tubular crystallizer used for thiourea cooling crystallization: Improving crystal qualities

The stirred-tank crystallizer (STC) is the widely used apparatus in industrial crystallization. However, it presents notable challenges, including a broad crystal size distribution (CSD) and fouling. Herein, the twisted hexagonal tube (THT) was employed for thiourea cooling crystallization. The THT exhibited superior heat transfer performance compared to the circular tube (CT) under identical conditions. Furthermore, the THT exhibited longer induction times and wider metastable zone width compared to STC and CT, indicating that the THT can effectively mitigate the nucleation rate. Crystals formed in the THT exhibited elliptical shapes, with a purity of 99.3 % and a target-product (425 μm) proportion of 78 wt%. Thiourea crystallized using the THT met the first-class in China standard HG/T 3454–2013, whereas those crystallized using STC and CT met the second-class standard. Consequently, the THT, as a novel tubular crystallizer, demonstrated considerable potential.

Numerical analysis on the flow and heat transfer characteristics of heat exchanger with cruciform tube

The heat exchanger (HE) is widely used in energy and power industries, which has a vital impact on the stability and efficient operation of relevant industrial systems. Different shaped heat exchange tubes are often designed specially to improve the thermal–hydraulic efficiency of HEs. In the study, two new geometries named the cruciform twisted tube and cruciform straight tube are introduced, and the heat & mass transfer properties of liquid lead (Pb) and supercritical carbon dioxide (s-CO2) in the HEs are numerically studied to assess the thermal–hydraulic efficiency and application prospect of two kinds of cruciform tube HEs. The results demonstrate that the unique cross-section geometry of the cruciform tube improves the uniformity of the flow field, and the spiral structure of the cruciform twisted tube effectively improves the blending and turbulence of working fluid. The cruciform tube can improve the comprehensive performance of the HE by more than 12%.

Enhancing thermal efficiency in twisted tri-lobe double pipe heat exchangers via integrated CFD and AI approaches

Industrial energy efficiency relies on precise heat exchanger design. Engineers aim to enhance heat transfer while minimizing pressure drop. Twisted tube Double Pipe Heat Exchangers (DPHEs) excel, inducing secondary flows that disrupt boundary layers and enhance fluid mixing. This investigation aims to provide insights into the relationships among specific factors and the thermal performance of a DPHE with twisted tri-lobe tubes, utilizing water as the working fluid. This is accomplished by employing an approach that integrates computational fluid dynamics with an artificial neural network, coupled with a single-objective genetic algorithm. Data inquiry was facilitated using response surface methodology, considering five design variables including the Reynolds numbers of the outer and inner twisted tubes, outer and inner twist ratios, and twisting direction. The simulation employed the turbulent k-ω shear-stress transport model, and the governing equations were solved using the finite volume method. The results underscored the efficacy of the developed multi-approach algorithm in maximizing the Performance Evaluation Criterion (PEC) both within the specified domain (10000 ≤ Re ≤ 20000 & 5≤twist ratio≤20) and beyond the domain (5000 ≤ Re ≤ 50000 & 2.5≤twist ratio≤25) of design variables. In the specified domain, a PEC of 1.16 was achieved, demonstrating the algorithm's effectiveness. Furthermore, the proposed method, extrapolated to the data space, yielded a noteworthy improvement in PEC of 16.35 %. In both domains, the optimized set of design variables for maximizing the PEC comprised a minimum outer Reynolds number, maximum inner Reynolds number, maximum outer twist ratio, and minimum inner twist ratio.

A novel approach to improve double-tube thermal energy storage: Impacts of inner tube twisting and its location

Thermal energy storage (TES) systems are a crucial component of solar energy harvesting cycles. Our objective in this study is to enhance the efficiency of a double-tube TES that utilizes lauric acid, a phase change material (PCM), and heated water as a heat transfer fluid (HTF). For the first time, this study examined the effects of utilizing a twisted inner tube inside a double-tube TES containing HTF. The finite volume method based on the enthalpy porosity model was used to investigate the effects of three different cross-sectional aspect ratios (AR = 0.5, 0.75, and 1) of the inner tube, at three different normalized locations along the vertical axis (Y = 0, −0.2, and − 0.4). The results were evaluated based on liquid fraction, temperature, velocity, total melting time, and average Nusselt number. The obtained results revealed that the AR effect of the inner tube varies depending on its location along the Y-axis. It is established that placing the tube at lower Y values in cases where a helical tube is present will yield significantly better results than higher Y values. Finally, the best case with the lowest total melting time occurred when the inner tube was located at Y = -0.4 and AR = 0.5. This case resulted in a total melting time decrease of up to 63 % compared to the reference case (AR = 1 at Y = 0).

Enhancing heat exchanger performance with combined twisted tubes and twisted Tapes: Design and retrofit strategies

This study investigates the application of twisted tubes and twisted tapes as heat transfer enhancement tools in both new designs and revamping of shell-and-tube heat exchangers. This research introduces a new design approach based on published data of thermohydraulic performance of combined twisted tubes and twisted tapes. This work discusses general design considerations and proposes methodologies for the sizing of new heat exchangers and the incorporation of twisted tubes and twisted tapes into existing units. In design, surfaces with the best trade-off between heat transfer enhancement and pressure drop are simple twisted tubes and twisted tubes with triple-channel twisted tape (TT-3C) with a PEC of 3.06 and 2.59 respectively. It is found that for new designs, reductions in area relative to the original units are observed. With twisted tubes alone, the reduction is 19.11 %, while with the incorporation of TT-3C, it reaches 29.70 %. In revamping of existing heat exchangers, the replacement of smooth tubes by twisted tubes and TT-3C results in average thermal load increases of 26.32 % and 27.50 %, equivalent to 19,526 kW and 20,442 kW, respectively. The results reveal significant improvements in heat transfer efficiency without substantial pressure drop increments, making twisted tubes and twisted tapes valuable options for enhancing heat transfer.

Determining of the thermo-hydraulic characteristics and exergy analysis of a triple helical tube with inner twisted tube

An innovative technique to enhance heat transfer as a passive method was investigated. The combination of the twisted tube and helical coil to increase the swirl intensity is presented. The current investigation showed experimentally and numerically the exergy and thermal performance analysis of a new design of a triple tube design called a triple helical tube with inner twisted tube, THTITT. The new design is a modified design of a double helical tube with inner twisted tube, DHTITT which is created by twisting the inner tube. Besides the benefits of adding the third fluid to DHTITT that achieve extra contact surface area per unit length between the intermediate tube and the new passage in the outer tube. In which expected to enhance the temperature gradient between the three fluids and consequently, the thermal characteristics augment occurred. The twisted tube increased the intensity of the swirl flow and more intense disturbance of the fluid in the tube occurred. A 3d CFD model was established to get more insight at a level of detail not always available in the experiment. The effects of twisted pitch ratio, ξ hydraulic diameter, ω, helical coil torsion, α, helical coil inclination angle, φ, as well as Dean number, NDn, h were explored. Four groups of test specimens include various ξ of 5.32, 7.97, and ∞, various ω of 3.8, 6.8, and 9.9 mm, various α of 0.068, 0.095, and 0.121, and various φ of 0°, 45°, and 90° were established, manufactured and examined in this investigation. The investigation covered Reynolds number, NRe,h, for a range of 2450:29300 corresponding to Dean number, NDn, h, for a range of 570:4800. The results showed a higher Nusselt number, NNu, h, of THTITT compared to DHTITT by 61.8 %%, while the increase in fh is approximately negligible. Also, by decreasing ξ from ∞ to 5.32 increases NNu, h by 33.4 %, with an increase in friction factor, fh by 57.6 %. Furthermore, with a decreasing ω from 9.9 mm to 3.8 mm, a significant increase in NNu, h occurs by 20.6 %, at the expense of increasing fh by 36.4 %. In addition, with decreasing α from 0.121 to 0.068, a significant increase in NNu, h occurs by 27.6 %, at the expense of increasing fh by 17.1 %. Finally, the THTITT decreases the heat loss (exergy destruction) between the hot and cold fluids. New correlations to predict NNu,h, and fh are presented.

Investigating the effect of using aluminum oxide nanofluid and twisted tapes with different twisted pitches on the heat transfer efficiency and using perceptron artificial neural networks in data prediction

This study investigates the effect of aluminum oxide nanofluid with 1% and 2% volume fractions (VFs) in four different tubes with identical bending and the uniform, low-high-low, low-high, and high-low-high longitudinal states with twist ratios of 0, 2 and 4. These tubes are affected by a constant thermal flux of 10000 W/m2 and Reynolds numbers of 2000-10000. For the numerical solution of these equations, the finite difference method on the basis of the control volume and the SIMPLEC algorithm and the K-ε-RNG method were applied for the turbulent flow modeling. The determined Nusselt number from the numerical methods were evaluated applying the perceptron neural network. The most optimal increase in the Nusselt number was in the twisted tube with twist ratio of 4 in the Reynolds number of 10,000 and VF of 1% and 2% nanofluid with increasing trend of length from low to high. The most optimal increase in Nusselt number compared to base fluid was about 25%. The sum of squared error and the relative error data obtained from the hyperbolic tangent function for the training and test data were 0.080-1.331 and 0.113-0.675, and from the sigmoid function for the training and test data were 0.093-0.392 and 0.097-0.147.

Numerical investigation of thermal-hydraulic performance enhancement in helical coil heat exchangers with twisted tube geometries

This numerical study examines the thermal-hydraulic performance of helical coil heat exchangers (HCHEs) using twisted tubes versus conventional circular tubes. The effects of Reynolds number (Re = 10,000 to 100,000), pitch length (11, 7.2, 5.5, 3.6 mm), and twisted tube orientation (co-current, counter-current) on heat transfer efficiency and pressure drop were investigated. The results show that higher Reynolds numbers can reduce the Resistance factor by approximately 25 % and improve heat transfer by approximately 35 %. An optimal pitch length of 5.5 mm was found to balance enhanced heat transfer and manageable pumping costs. Twisted tubes demonstrate significant performance advantages at lower Re, with 20–33 % higher Performance Evaluation Criterion (PEC) values compared to circular tubes. However, the benefit diminishes at higher Re, with less than 10 % PEC increase. Implementing counter-current twisted tube configurations leads to approximately 13 % higher Nusselt number and 11 % higher Resistance factor, resulting in a 10 % overall PEC improvement. These findings highlight the superior thermal-hydraulic performance of twisted tubes in HCHE applications, especially at lower Reynolds numbers. Future work could explore different fluids, advanced optimization, energy analysis, cost assessment, and additional geometric parameters to further enhance twisted tube heat exchanger design and performance.

Self-Incompatibility in Devil's Potato (Echites umbellatus Jacq., Apocynaceae) May Explain Why Few Flowers Set Fruit.

Pollinators are needed for the reproduction of Echites umbellatus, and only sphingid moths have mouthparts long enough to reach the nectar at the bottom of the species' long, twisted floral tube. Though plants produce many flowers over a period of several months, one observes very few fruits in nature. We asked: (1) Are plants self-compatible, or do they need pollen from another individual to set fruit and seed? (2) Are cross-pollinations between unrelated individuals more successful than crosses with relatives? (3) How does the relatedness of pollen and ovule parent plants affect fruit set, seed number, and seed quality? We investigated the breeding system of E. umbellatus by collecting fruits from seven sites, growing plants and performing hand pollinations over a period of several years, collecting and measuring fruits and counting seeds. Echites umbellatus is self-incompatible, though some individuals produce fruit by self-pollination. Cross-pollinations between unrelated individuals set the most fruit (59%), and those that were self-pollinated set the least (9%). Fruit set from cross-pollinations between related individuals was intermediate (32%). Although the number of seeds per fruit did not differ significantly among pollination treatments, fruits from self-pollinations had substantially fewer viable seeds than outcrossed fruits, with fruits from sibling crosses being intermediate. There were higher levels of self-compatibility in the fragment populations compared with plants from intact habitats. Self-incompatibility may explain why fruit set is low in this plant species; future investigation into the breakdown of self-incompatibility in smaller populations is warranted.

The reason induced unique characteristics of local Nusselt number in straight and twisted square tubes for laminar flow

The velocity contribution and velocity gradient contribution to the transport of the heat flux defined by Fourier's law, q, are numerically investigated in this paper to investigate the reason induced the unique characteristics of Nusselt number in twisted and straight square tubes for periodically fully developed laminar flow. The reason of local Nusselt number in straight square tube at some regions is larger than that in twisted square tube are reported. It is found that the summation of velocity and its gradient contributions determines local Nusselt number under UWT. Both velocity and velocity gradient contributions are not uniformly distributed in the cross section in straight and twisted tubes. Velocity and its gradient both promote the transport of the local heat flux components along the normal direction of the wall surface which have larger values in straight square tube at some regions and result local Nusselt number has larger values. The summation contributions of velocity and its gradient are much larger in twisted square tube, especially in the region close to the wall surface. Thus the averaged heat flux components have much larger value and averaged Nusselt number in twisted square tube is larger than that in straight square tube.

Influence of the twisting and nano fluids on performance of a triangular double tube heat exchanger

Abstract The hydraulic and thermals performance of flow in a double-tube heat exchanger with an inner twisted triangle tube of length L = 1 m has been studied numerically. Equations for energy, turbulence, and Navier–Stokes were used to model the fluid flow and heat transfer in a double-tube heat exchanger with an inner twisted triangle tube. The Reynolds number range was 5000–30,000 for nanofluid (water-Al2O3) as a working fluid under a turbulent flow regime. The considered configuration was examined by varying the volume concentration of nanofluid while keeping the twist ratio constant (Tr = 5). Different cases of volume concentration of nanofluid are triggered (0.05 %, 1 %, 2.5 %, and 4 %, respectively). The numerical outcomes of a double-twisted tube heat exchanger with an inner triangle-twisted tube are validated with the obtainable numerical data. The governing equations were solved with ANSYS Fluent 18.2. The findings reveal that the larger volume concentration of nanofluid (4 %) gives a greater Nusselt number and vice versa due to the increased thermal conductivity of the nanofluid in the double twist tube heat exchanger compared with a plain tube. However, the nanofluid Nusselt number grows with the rise of both the Reynolds number and volume concentration (Ø), and the best value of the Nusselt number is 210 when Reynolds number = 30,000 and Ø = 4 %. The effectiveness of the heat exchanger grows with an increase in the concentration of the nanofluid and a reduction in the torsion ratio compared to the normal tube. The effectiveness of the double-tube heat exchanger with an inner twist triangle tube increases to the highest value of 0.38 at Reynolds 30,000 and Ø = 4 %.

A case study on effect of twisting technique on heat transfer characteristics in a twisted oval helical tube

Efficient transfer of energy is an important issue addressed by numerous scholars in the literature and various methods have been proposed for enhancing the heat transfer efficiency in heat exchangers. Among many different heat exchangers, helical tubes are one of the most prevalent types of heat exchangers which have many applications in industry. In a case study, effect of twisting technique on the heat transfer in a helical tube with oval cross section has been investigated numerically and the results have been compared with simple circular cross section helical tube. Effect of cross section aspect ratio and twisting ratio in different flow Reynolds numbers has been considered. Results have been presented in terms of Nusselt number, friction factor, PEC, entropy generation and contours of velocity, streamlines and temperature. Results indicate that twisting technique can significantly enhance the heat transfer and all cases have PEC values of above unit which indicates superiority of this method. Also the velocity contours and streamlines indicate that using twisting technique result in higher mixing in the flow which is the reason for higher heat transfer characteristics in twisted oval helical tubes.

Effect of axial preloads on torsional behavior of superelastic shape memory alloy tubes – experimental investigation and simulation/predictions of intricate inner loops

Shape memory alloy (SMA) devices (utilizing wires/rods, springs or tubes) engage unique superelastic/pseudoelastic (SE) phenomenon for large stroke recovery, energy dissipation and damping applications. In particular, SMA components in torsion are also generally subjected to some pre-tension loads and hence understanding their combined effects on the torsional response is vital. In this work, some intricate internal loop and outer loop responses (large twists > 1500°) of SMA tubes under different twisting-untwisting scenarios are investigated to understand the effects of static pre-load on torsional responses. Key SMA hysteretic features like sink point memory (SPM) and return point memory (RPM) have not been well understood under torsion (with and without axial loads) have been investigated here. Further, a modified two variant thermodynamic Preisach modeling approach is proposed to simulate responses of twisted tubes with varying extents of twist and different axial loads. The central principle here is the use of a Gibbs Potential framework to separate the dissipative and thermoelastic parts of the SE responses using well established thermodynamic principles and then utilizing a non-ideal switching type disjunctive Preisach model to fit the nonlinear hysteretic dissipative section of the SE response. By using the outer loop response for model calibration, other complex loading unloading scenarios leading to intricate internal loops and effects of axial loads on these can be predicted. It is also shown that addition of a single interior loop detail for model calibration significantly enhances prediction of other more intricate internal loops. This approach dramatically simplifies the experimental data needed for the simulation of SMA components even under complex loading.

Study of ultrasonic influence on heat transfer and resistance performance of round tube with twisted belt

Abstract In this study, ultrasonic technology is combined with twisted belts to explore the comprehensive performance, and this study also investigated the effect of different Reynolds numbers, ultrasonic frequencies, and number of transducers on the performance of circular and twisted band tubes. It was found that ultrasonic waves applied on the tube plate enhanced the heat transfer performance of the heat exchanger tubes, reduced the flow resistance, and improved the overall performance, and the lower the ultrasonic frequency, the better the heat transfer and resistance reduction ability, and at the experimental condition frequency of 21 kHz, the maximum increase of Nu is 19.06%. With the increase of Reynolds number, the better the ultrasonic enhancement heat transfer performance, but the worse the resistance reduction performance. For different heat exchanger tube structures, the synergistic enhanced heat transfer effect of ultrasonic waves with the twisted belt is better than round tubes, and the synergistic drag reduction effect with the round tube is better than the twisted tape round tube. When the installed ultrasonic transducers are two, the heat transfer performance of the heat exchanger tube is the best, and the maximum increase in the value of Nu was 28.06%.

Employing uniform and non-uniform inner twisted elliptical tubes in a double-pipe heat exchanger

Turbulent hydrothermal characteristics in a double-pipe heat exchanger with an internal twisted elliptical tube (TET) are investigated. The impacts of aspect ratio (AR = 1.4–2), uniform twist pitch (p = 100 mm-400 mm), and non-uniform twist pitch (five cases) on flow stream characteristics and heat transfer of parallel and counter-flows are investigated numerically. Utilizing a TET with a non-uniform twist pitch as an innovative approach yields noteworthy results, particularly in contrast to the traditional use of TETs with uniform twist pitch, owing to the longitudinal asymmetry. The outcomes depict that the pressure drop and heat transfer augment as the uniform twist pitch declines and the AR rises. The counter-flow has a more significant average Nusselt number than the parallel-flow by about 2–4 % without increasing the friction factor. Still, in some cases of non-uniform twist pitch, the average Nusselt number of the parallel flow is even 4 % higher than the counter-flow. The case with p = 100–200–400 mm (three parts with various twist pitches) and parallel-flow exhibits the most significant performance evaluation criterion (PEC) among the non-uniform twist pitch. As the aspect ratio increases from AR = 1.4 to AR = 2, the PEC factor in the counter-flow mode increases; however, there is an out-of-trend point at AR = 2 for the parallel-flow mode. The PEC factor augments about 8.47 % and 6.16 % for the counter-flow and the parallel-flow modes, respectively. The growth of TET twist pitch by 300 % reduces PEC by about 13.3 % in the counter-flow. The most significant PEC value is 1.166, which belongs to the case with the counter-flow condition and p = 100 mm.

Numerical Investigation of Heat Exchanger Enhancement for a Staggered Arrangement with Corrugated Rods in Front

The heat exchanger is used in many industrial and engineering activities.Where, numerous applications confirms on a large heat transfer rate. However, the twisted tube is one of heat transfer rate enhancement methods. Also, the turbulent flows are often used instead of laminar for enhancement heat transfer rate. Therefore, the tube arrangement can be used in a suitable way for utilized this purpose. The shape features of tubes in the heat exchangers are very important for enhancing their performance. As well, the pressure drop and heat transfer rate have a remarkable effect on the thermal efficiency of the heat exchanger. In this research, a numerical investigation with a new way for heat exchanger tube staggered arrangement is presented. Where new solid spiral rods with oval sections are inserted in front of main tubes to induce high turbulent flow intensity as well as redistribution airflow over exchanger tubes. However, the new air distribution will help the airflow pressure over all the tubes to push the thermal boundary symmetrically behind the tubes. Therefore, two different sectional tubes were presented (circular and elliptical). These cross-sectional areas for both types have the same values. The main tubes have no twisted to prevent decreases in pressure. The numerical analysis used the K- ε model at a low Reynolds number to the simulation of this situation. Where, the eddy will generate in the vicinity region to pipe walls due to twisted pipe as well as the obstruction the cross flow. However, there are a good improvement of heat transfer rate without spend any energy depending on the control the shape and arrangement of pipes. The results show that the corrugated rod will increase the Nusselt number at different values of Reynolds. However, the elliptic tube gives the best results for heat transfer rate and maximum Nusselt number. The results compared with others works and give a good agreement.

Multi-objective optimization of twisted tri-lobed tube geometry for enhanced heat transfer and reduced resistance in turbulent flow

This study presents a detailed multi-objective optimization analysis of turbulent flow and heat transfer within a twisted tri-lobed tube, employing an integrated approach that combines Central Composite Design (CCD), Response Surface Methodology (RSM), Non-dominated Sorting Genetic Algorithm II (NSGA-II), Pareto frontier analysis, Linear Programming Technique for Multidimensional Analysis of Preference (LINMAP), and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). The investigation focuses on optimizing key design parameters: Reynolds number (Re), twist pitch (P), and minor circle radius (r), targeting Nusselt number (Nu), Poiseuille number (fRe), and Performance Evaluation Criterion (PEC) as optimization objectives. Our major findings reveal that the developed second-order regression model precisely predicts the influences of these parameters on Nu, fRe, and PEC, with sensitivity analysis showing Re's strong positive impact on Nu and fRe, P's negative effect on fRe, and r's minimal impact. The study notably highlights the significant Nu enhancement with Re increase. Utilizing multi-objective optimization, we identified a Pareto optimal set, and through LINMAP and TOPSIS methods, derived compromise solutions that optimally balance heat transfer efficiency, flow resistance, and overall performance. These outcomes underscore the critical importance of parameter selection to meet specific engineering needs, offering a strategic framework for enhancing twisted tri-lobed tube designs.