Tube Configuration Research Articles

Sensitivity analysis of geometrical parameters of supercritical water in twisted spiral tubes

ABSTRACT The high thermal efficiency of supercritical water makes it a promising alternative to water cooled reactors. This study employs numerical analysis, utilizing the SST k-ω turbulence model, to investigate the heat transfer performance of supercritical water (SCW) in various tube configurations and fluid flow conditions across Reynolds numbers ranging from 8,000 to 20,000. This research examines how different geometrical parameters, such as the helical direction, number of lobes, and cross-sectional shape, impact the flow physics and heat transfer performance of different spiral tubes. The outcomes specify that increasing the lobed number in the tube improves the heat flux by about 5%–16%. Furthermore, introducing two direction changes in the twisted tube will cause a slight increase (about 20%) on heat transfer enhancement. Finally, the sensitivity analysis of heat flux and Nusselt number to each of the effective parameters in the heat transfer of supercritical water in twisted tubes has been accomplished and the Response Surface Method (RSM) utilizes the central composite design (face-centered) approach. According to the findings of these two studies, it has been established that the Reynolds number of the fluid flow is the most influential parameter in determining the extent of heat transfer. Specifically, it exerts an effectiveness of 26% and 76% on the Nusselt number and heat flux, respectively. Furthermore, the inscribed circle diameter of tube by 8% effectivity and minor axis length by 5% effectivity on heat flux are more effective than others.

Low-Frequency Acoustic Performance of a Microperforated Panel Integrated Coiled-Up Space Absorber With Subwavelength Thickness

Abstract Low-frequency broadband sound absorption with minimal dimensions and material cost is an ongoing research challenge in engineering acoustics. Common acoustic structures, such as microperforated panels (MPPs) and porous structures, are ineffective in alleviating low-frequency noise. In this context, a sound-absorbing panel consisting of two axially coiled-up tubes and MPP is proposed for effective low-frequency noise abatement. Initially, an electro-acoustic analogy-based analytical approach is developed to predict the acoustic absorption performance of series and parallel configurations of MPP and coiled-up tubes, and the findings are corroborated by full-field finite element simulations. The parametric analyses revealed that by carefully choosing the geometric features of the coiled-up tubes, the absorption spectra of each tube can be coupled with that of MPP. Thus the bandwidth of absorption can be broadened. Furthermore, it is observed that the parallel configuration of MPP and coiled-up tubes significantly lowered the thickness of the absorber without affecting the absorption bandwidth. Importantly, the parallel configuration of MPP and coiled-up space demonstrated more than 80% absorption in the frequency range of 250–350 Hz.

A highly sensitive UHPLC-MS/MS method for determining 15 designer LSD analogs in biological samples with application to stability studies.

In recent years, the rise in the synthesis and distribution of LSD analogs in illicit drug markets, commonly referred to as "designer psychedelics", has contributed to increased recreational use. This trend has resulted in a rising number of global reports, with law enforcement increasingly detecting these compounds in blotter papers and biological samples. In the presented paper, an UHPLC-QqQ-MS/MS method was developed for trace determination (fg mL-1) of LSD, its designer analogs (ALD-52, AL-LAD, LAMPA, LSM-775, LSZ, MiPLA, 1B-LSD, 1cP-LSD, 1cP-MiPLA, 1P-LSD, 1P-MiPLA, 1V-LSD and 2-Bromo-LSD) and its metabolite (2-oxo-3-OH-LSD) with simultaneous separation of structural isomers. Biological samples were prepared using liquid-liquid extraction (LLE) at pH 9 (with ethyl acetate); quantification was performed in multiple reaction monitoring (MRM) mode. LSD-d3 was used as an internal standard. The limit of quantification (LOQ) for all substances was 0.5 pg mL-1. Precision and accuracy did not exceed 15.8% and ±14.4%, respectively. Recovery and matrix effect values were 80.6-118.6% and ±19.4%. A stability study was conducted over 30 days under different storage conditions (25 °C, 4 °C and -20 °C) for blood, urine, plasma, and serum, collected in various test tube configurations and with different preservative agents. It was found that the collection of samples in NaF can effectively stabilize LSD analogs and minimize the conversion of N1-substituted compounds to LSD or MiPLA. The presented method is the most sensitive to date for analyzing designer LSD analogs in biological samples, with potential for routine clinical and forensic use, enhancing detection of emerging illicit compounds. By examining the mass spectra (QTOF-MS/MS) obtained in this study and reviewing the literature on analytical characterization of LSD analogs, we proposed fragmentation patterns to aid in future identification of new designer LSD analogs (NPS).

Experimental study of steel single skin, double skin and dual tubes stub columns filled with rubberized concrete

This experimental study investigates the performance of rubberized concrete-filled dual steel tubular (RuCFDST) short columns under concentric compression, addressing a gap in existing literature. While previous studies focused on single- and double-skin circular steel tube stub columns, the specific behavior of RuCFDST columns remains largely unexplored. The study compares RuCFDST columns with rubberized concrete-filled steel tubes (RuCFST) and rubberized concrete-filled double-skin steel tubes (RuCFDSST). A total of eighteen specimens were experimentally tested, which consisted of three single-tube configuration, three double-skin configuration, and twelve dual tube configuration. The investigation covers rubberized concrete preparation, material testing, precise measurements, test setup, and result analysis. Key parameters include rubberized ratio (0 %, 10 %, 20 %, and 30 %) and concrete mix variations. The results provide insights into failure modes, load-shortening behavior, ductility, and strength index, with comparisons to the design predictions based on the European standard EC4. The inclusion of rubberized concrete enhances ductility, while RuCFDST columns show promise in combining sustainability and strength. The study also evaluates design predictions, revealing good agreement for lower rubberized content but indicating deviations for higher ratios, suggesting the need for refined design approaches in such cases.

Thermal performance of parabolic trough solar collector employing novel absorber tubes equipped with distinct heat transfer fluids: An experimental study

ABSTRACT The current research investigates the thermal performance of a parabolic trough solar collector (PTSC) featuring two innovative absorber tube designs for solar water heating. The research evaluates the temperature profile of the PTSC using water and explores the effectiveness of mixing water with thermal oils, specifically Hytherm 600 and Therminol 55, as heat transfer fluids. To assess the impact of mass flow rate on thermal performance, the PTSC was tested at three flow rates (FR)10, 20, and 30 liters per hour (L/h) with each of the three heat transfer fluids. The investigation focused on two absorber tube designs: S12 (Step-up, Step-down) and S15 (Step-down, Step-up). Instantaneous efficiency, thermal efficiency, and useful energy gain for each tube design at various flow rates and heat transfer fluids were calculated and analyzed. The highest instantaneous and thermal efficiency values were achieved with the S15 tube configuration using Hytherm 600 at a flow rate of 10 L/h as compared to existing PTSC reported. This configuration also recorded the highest water outlet temperature of 84.7°C and an efficiency of 43% during peak sunlight hours as compared to the other existing PTSC, with a maximum useful energy gain of 1516.67 kJ. The efficiency and outlet temperature tend to decrease with higher flow rates, highlighting the importance of optimizing the water flow rate through the PTSC.

Axially loaded rectangular FRP-concrete-steel hybrid multi-tube concrete stub columns: Performance, confinement mechanism, and design-oriented model

This paper presents an experimental investigation of rectangular glass fiber-reinforced polymer (FRP)-concrete-steel hybrid multi-tube concrete columns (MTCCs) subjected to monotonic axial compression to explore their mechanical behavior and confinement mechanism. Sixteen rectangular MTCCs and eight concrete-filled FRP tube columns (CFFTs) were tested. Four experimental variables, namely aspect ratio, FRP thickness, steel volume ratio, and steel tube configuration, were taken into consideration. The experimental results demonstrated that rectangular MTCCs’ load-bearing capacity and deformability diminished with increasing aspect ratio, as it reduced the effective confinement area of FRP tube to concrete. Additionally, the confined concrete’s compressive strength and axial deformability of rectangular MTCC (with a 6.4% steel volume ratio) enhanced by 21.5% and 32.9%, respectively, compared to the corresponding CFFT. This demonstrated the effectiveness of additional steel confinement. Furthermore, the confinement mechanism of rectangular MTCCs was clarified based on the full-range compressive behavior and dilation property of confined concrete. It included unconfined stage, transition stage, and hardening stage. Finally, a stiffness-based design-oriented model for rectangular MTCCs was established with favorable accuracy.

Mechanical adjustment and prediction of metal-composite reconfigurable tubes

FML (Fiber metal laminate) is widely used in aerospace as an advanced composite material. Metal hybrid bistable composites are one type of FML structure. The hybrid bistable composite is not only deformable but also conductive. In this paper, based on a bistable metamaterial tube, it is proposed to control its shape through metal-composite layups. A theoretical prediction model with a metal slip effect is developed. The energy equation of the theoretical model was solved using the principle of minimum potential energy. The curvature variation rules of two configurations of composite tube with different metal layups and different initial curvatures are discussed. Moreover, the finite element model of the metal hybrid composite is established. Finally, the accuracy of the theoretical and finite element models was verified by experiments. The proposed metal slip model is accurate than the classical model. The effect of metal on the bistable tube was determined. The configuration of the bistable tube is controlled by layups without adding any weight. This plays an important role in deformable metamaterials and multi-functional morphing structure applications.

Calibration of pressures measured via tubing systems: Accounting for laboratory environmental variations between tubing response measurement and wind tunnel testing

Accurate pressure measurements on structures via tubing systems during wind tunnel tests are crucial for precise estimation of wind loads. While calibration studies have traditionally focused on the contribution of tubing configuration to pressure distortion, they often overlook the effects of environmental parameter changes between the measurement of tubing response and aerodynamic pressure on structures. However, higher atmospheric pressure and lower ambient temperature can substantially increase tubing response distortion. To address this, this study introduces a dynamic calibration approach that accounts for such laboratory environmental changes. This method integrates the experimental transfer function, obtained under specific environmental conditions, with numerical estimates of the impact of environmental changes, to derive transfer functions for the desired environmental conditions. The effectiveness of this approach was validated using experimental and numerical transfer functions under two distinct environmental conditions. A case study for outdoor open-circuit laboratories revealed that neglecting environmental conditions during dynamic pressure calibrations could lead to overall average deviations in peak pressures across the channels on a building face of up to ≈ 5%, with local maximum deviations reaching ≈ 10%, respectively. Therefore, the proposed calibration method can significantly enhance the accuracy of pressure measurements via tubing systems, particularly when the tubing response and the pressures are measured under different environmental conditions.

Thermal and economic impact of geothermal passive cooling for eco-house applications in the maritime desert climate

ABSTRACT Creating comfortable indoor conditions to avoid heat-related health problems is associated with high power consumption, forcing countries with hot climates to seek alternative solutions. In this study, a geothermal passive cooling system was implemented in the maritime desert climate region in Muscat, Oman. The system consisted of multiple path tube configurations, each 5 m long of 10 cm × 10 cm in cross-section, and was buried 2 m underground. Fins were attached to three tube sides in one path to enhance the heat transfer rate. The path of the finned tube significantly reduced the air outlet temperature. The fins increased the temperature drop by a substantial percentage, often exceeding 100% and sometimes even reaching 300%. Installing the geothermal passive cooling system secured an average temperature drop of 7°C. This drop led to a reduction in electricity bills by 4.58% for finned tubes and 4.17% for unfinned tubes. The overall energy savings achieved by the system was 12.91%, demonstrating its potential for reducing energy consumption in desert climates. Future research should focus on identifying the optimal size for geothermal systems to enhance their thermal performance and economic benefits, developing advanced materials, and integrating the system with renewable technologies to maximize their advantages.

Python-based machine learning estimation of thermo-hydraulic performance along varying nanoparticle shape, nanofluid and tube configuration

In this research article, a Python-based machine learning model prediction study was conducted based on the study results obtained from sudden expansion tubes containing different expansion angles, dimpled fin structures and nanofluids, whose thermo-hydraulic performance was previously examined. In the study, Artificial Neural Network and Ridge regression models were used to make predictions on the average Nusselt number (Nu), average Darcy friction factor (f) and performance evaluation criteria (PEC). Physical variations of the sudden expansion tube were taken into account and a detailed comparison of the results was made. A superior average Nu was acquired as 172.45 %, 22.05 %, 17.18 %, 13.65 %, and 7.76 % compared to Ag-MgO/H2O, Al2O3/H2O (blade), CoFe2O4/H2O, Al2O3/H2O (cylindrical), and Al2O3/H2O (platelet), respectively. The highest Performance Evaluation Criteria (PEC) for Re= 2000 based on Al2O3/H2O (platelet) shows an increase of 4.84 %, 12.08 %, 11.76 %, 66.05 %, and 148.94 % compared to Al2O3/H2O (cylindrical), Al2O3/H2O (blade), CoFe2O4/H2O, Fe3O4/H2O, and Ag-MgO/H2O, respectively. From the results obtained, it was determined that Python-based Machine Learning approach which facilitates custom optimizations showed a significant performance with small margins of error in predicting the heat transfer parameters. The lowest error rates of machine learning and polynomial ridge regression models ranged from 0.2 % to 5.4 % for the unseen test set and the application of Python-based algorithms provided considerable savings in calculation time compared to conventional methods. On the other hand, using machine learning models with feature engineering has been found to increase model performance by at least 30 %. In these years when studies on the predictions of thermo-hydraulic studies are very rare in the literature, this study is intended to facilitate scientists, engineers and academicians who will further study on this subject.

Poynting Flux of MHD Modes in Magnetic Solar Vortex Tubes

Magnetic flux tubes in the presence of background rotational flows, known as solar vortex tubes, are abundant throughout the solar atmosphere and may act as conduits for MHD waves to transport magnetic energy to the upper solar atmosphere. We aim to investigate the Poynting flux associated with these waves within solar vortex tubes. We model a solar vortex tube as a straight magnetic flux tube with a background azimuthal velocity component. The MHD wave solutions in the equilibrium configuration of a vortex tube are obtained using the Shooting Eigensolver for SolAr Magnetohydrostatic Equilibria code and we derive an expression for the vertical component of the Poynting flux, S z , associated with MHD modes. In addition, we present 2D visualizations of the spatial structure of S z for different MHD modes under different background flow strengths. We show that S z increases in the presence of a background rotational flow when compared to a flux tube with no rotational flow. When the strength of the background flow is greater than 100 times the strength of the perturbation, the S z associated with non-axisymmetric (∣m∣ > 0) modes increases by over 1000% when compared to a magnetic flux tube in the absence of a background rotational flow. Furthermore, we present a fundamental property of solar vortices, namely that they cannot solely produce an upward Poynting flux in an untwisted tube, meaning that any observed S z in straight flux tubes must arise from perturbations, such as MHD waves.

Vortex core eccentricity and passive control for separation performance enhancement of a novel circumfluent cyclone separator

We have proposed a circumfluent cyclone separator (CCS) that features a concentric internal cylinder and a gas–solid inlet located at the bottom of the separator shell, as opposed to the conventional cyclone design with the inlet at the upper part. The objective of this study is to investigate the eccentricity of the vortex core within CCSs, its impact on separation performance, and to propose a vortex control method for enhancement of separation efficiency. Our research findings indicate that the eccentricity of the vortex core varies with the vertical position, with the maximum eccentricity observed at the bottom of the cone. Increasing the inlet gas velocity (Uin) results in an elongation of the vortex length and a decrease in the eccentricity of the vortex core. These observations suggest that a high level of vortex core eccentricity negatively affects the separation performance of the CCS. To address this issue, we propose a passive control method to reduce vortex oscillations and enhance collection efficiency. By incorporating a central tube within the CCS, we effectively reduce the eccentricity of the vortex core and alter the characteristics of the power spectral density plot of the instantaneous velocity. Importantly, the addition of a 4–5 mm diameter tube enables the CCS to achieve similar separation efficiency for small particles at a Uin of 18 m/s, compared to the CCS without a central tube operating at a Uin of 24 m/s. Furthermore, the central tube configuration reduces the associated pressure drop by 50%. These findings highlight the effectiveness of vortex control mechanisms in enhancing the separation performance of CCS and other cyclone designs.

Energy and exergy analysis of a newly designed photovoltaic thermal system featuring ribs, petal array, and coiled twisted tapes: Experimental analysis

Photovoltaic systems suffer from electrical efficiency loss due to increases in surface temperature. To tackle this problem, Photovoltaic Thermal, consisting of photovoltaic and tube configurations attached to its back, is suggested. This study attempts to develop a new collector design in photovoltaic thermal systems. The new design features ribs and petal arrays on its inner and outer surfaces and a coiled twisted tape positioned inside it. The study also uses silicon carbide enhanced nanofluid (0.3 % and 6 % volume concentration) and phased changing material (1 % volume concentration) to boost the thermal efficiency further. Using an indoor solar simulator, the study investigates the effects of mass flow rate in the range of (0.1–0.85) kg/s, solar irradiances of (400–1000) W/m2, and coolant types of (water, 0.3 % and 0.6 % SiC enhanced nanofluid, water and nanophase changing materials, and 0.3 % and 0.6 % SiC enhanced nanofluid and nanophase changing materials). Besides revealing the relationship between all the parameters studied, the results report a maximum electrical energy efficiency of 11.2 %, thermal energy efficiency of 86.2 %, and total exergy efficiency of 15.3 %. The system reached optimal power production of 25.99 W using a photovoltaic module with a maximum power rate of 30 W.

Effect of use of cuffed endotracheal tubes on the occurrence of postoperative extubation-related respiratory adverse events in pediatric patients with airway hypersensitivity: a retrospective cohort study.

Whether endotracheal tube (ETT) configuration (cuffed or uncuffed) influences the occurrence of respiratory adverse events (RAEs) in patients at risk remains largely unknown. We investigated the effects of cuffed ETTs on RAE occurrence after extubation in pediatric patients with airway hypersensitivity. Children aged < 8years with increased airway hypersensitivity (defined as upper airway symptoms, recent upper respiratory infection within 2weeks, or a history of asthma) who underwent general endotracheal anesthesia with inhaled agents between January 2021 and December 2022 were included. We retrospectively examined the patients' background and intraoperative anesthesia conditions by comparing the cuffed and uncuffed ETT groups. Multiple logistic regression analysis was performed to estimate the association between ETT configuration (cuffed vs. uncuffed) and the occurrence of RAEs or respiratory interventions (laryngospasm, peripheral capillary oxygen saturation < 92%, oxygen supplementation, epinephrine inhalation, or reintubation) after extubation. Cuffed ETTs were used in 163 patients and uncuffed ETTs in 143 patients. Apart from the frequency of upper airway surgery and intraoperative fluid balance, no significant differences in background characteristics were observed between the groups. RAEs after extubation were observed in 36 (22.1%) and 28 (19.6%) patients in each cuffed and uncuffed ETT groups. After adjusting for known RAE risk factors, no difference was observed in RAEs or respiratory interventions after extubation between both groups (odds ratio, 1.14; 95% confidence interval: 0.64, 2.06). In pediatric patients with airway hypersensitivity, the use of cuffed ETTs did not increase the occurrence of RAEs or respiratory interventions after extubation.

Computational and experimental analyses of pressure drop in curved tube structural sections of Coriolis mass flow metre for laminar flow region

ABSTRACT This research presents a comprehensive investigation into the computational and experimental aspects of pressure drop phenomena within the curved tube structures. Mass flow measurement holds critical significance in process industries to mitigate inaccuracies arising from fluid property variations. The CMFM stands as a reliable instrument for direct measurement; however, its performance has exhibited discrepancies, recording lower fluid flow magnitudes than actual values in laminar flow conditions. This anomaly is suspected to be attributable to a secondary force generated within the sensor's curved tube structure. This study seeks to elucidate this phenomenon by assessing the pressure drop resulting from the secondary flow in four distinct curved tube configurations: U, Omega, Delta, and Diamond shapes under steady-state conditions. The paper underscores the pressure drop characteristics inherent in each tube structure configuration, revealing that Basic U and Omega shaped tube structures exhibit the least pressure drop.

Coupled CFD modeling and thermal analysis of multi-layered insulation structures in liquid hydrogen storage tanks for various vapor-cooled shields

The present study aims to propose a coupled numerical model for analyzing the influence of the configuration of the vapor-cooled shield tubes on insulation performance. The numerical model is developed to calculate the effective thermal conductivity of multi-layer insulation (MLI) and rigorously evaluated. Specifically, the tank evaporation simulation software BoilFAST is manually coupled with the CFD commercial software of ANSYS FLUENT (2020 R2) to accurately determine the mass flow rate and temperature of boil-off gas in a tank, which is then used as inputs for the CFD simulations. This coupling methodology can be used for reliable calculations of boil-off losses for liquid hydrogen and heat transfer inside the MLI structures. Results demonstrate that the estimated effective thermal conductivity agrees with the earlier published data and that increasing the diameter and number of tubes enhances heat exchange between the VCS tubes and MLI structures. Also, the heat flux into the tank is relatively reduced by 32.04 % by increasing the diameter of the tube and 49.14 % by adding the number of tubes. Moreover, the maximum temperature difference of the VCS is estimated to be less than 1 K, indicating nearly uniform distributions of the VCS.

A comprehensive numerical investigation of bi-dimensional analysis of PVT system using square channel absorber

Abstract This paper offers a comprehensive numerical investigation of PVT solar thermal performance using the Finite Difference Method (FDM) for both longitudinal bi-dimensional transient and steady state analysis, which is the unique aspect of this study. Likewise, a thorough analysis of the use of two distinct cooling absorber PVT solar collectors is conducted under realistic climatic conditions. The current modeling methodology can be considered a useful tool that enables rapid bi-dimensional PVT system analysis. The findings show that, in comparison to the PVT tube configuration (587 kWh/m2, 178 kWh/m2), the direct flow square channel has more yearly thermal and electrical gain outputs (608 kWh/m2, 196 kWh/m2). Furthermore, the design of directly flow channels has the advantages of easier integration and effective conduction heat transfer between the fluid and absorber panel. A good agreement between the measured and predicted data was obtained once the current results were compared with theoretical and experimental data in the literature. &amp;#xD;

Thermal-hydraulic analysis of wetted airside plain fin flat tube heat exchangers and the role of vortex generators

This study addresses the demand for efficient and compact heat exchange solutions in industrial applications. Unlike previous studies that predominantly focused on round tube configurations, this research investigates the impact of vortex generators and geometrical parameters on plain-fin flat-tube designs. Using ANSYS Fluent, the study evaluated the effects of fin geometry, vortex generators, and flow conditions on thermal–hydraulic performance. The key findings revealed that vortex generators enhanced heat transfer by 5–48% by promoting fluid mixing and turbulence but also leading to an increment in friction losses reaching 35–62%, depending upon the number of vortex generators. Condensation rates increased downstream of vortex generators due to enhanced mixing with cooler surfaces. In terms of thermal–hydraulic performance, specific plain-fin configurations outperformed others, offering efficient heat transfer with relatively lower friction losses, even when compactness was considered. Some configurations were recommended for applications where heat exchanger size is less important, but high heat transfer is crucial. Lastly, it was discovered that the effect of vortex generators is more pronounced for lower to intermediate pumping powers per unit area. New empirical correlations were also derived to predict thermal–hydraulic behavior based on geometry and vortex generator placement. A comparison with the literature revealed significantly higher performance as compared to convex/concave vortex generators. Lastly, it was discovered that the effect of vortex generators is more pronounced for lower to intermediate pumping powers per unit area. Empirical correlations for “j” and “f” were correlated with all geometric parameters.

Validation of an absorption coefficient measurement technique using two cardioid microphones in any impedance tube

We have proposed a technique for measuring sound pressure and particle velocity using a combination of cardioid microphones and then applied it to obtain the acoustic absorption coefficient in a tube. So far, we have revealed that either using one cardioid microphone measured twice or using a pair of cardioid microphones measured once are both suitable for the measurement and that the calibration of the cardioid microphones is required. If the technique works correctly, this technique holds promise for measuring the acoustic absorption coefficient of various specimens in any tube and with any cardioid microphones. To validate the technique's effectiveness, we conducted experiments in multiple square-section wooden or round-section steel tubes, with specimens of glass wool and polyester terephthalate (PET) wool. As a result, this technique can provide accurate absorption coefficient measurements in any tube configuration.

Effect of phase angle on thermohydraulic performance of an annular tube formed by co-twisted oval tubes

This study introduces a novel annular tube configuration consisting of co-twisted oval tubes with different phase angles between the inner and outer tubes. The effect of the inner tube's phase angle on the flow and heat transfer characteristics was numerically investigated over a Reynolds number range of 1000–10 000. The performance of the proposed annular tube configuration was compared with that of a conventional straight annular tube. The results indicate that the twisted oval tube induces a strong secondary flow inside the tube, which significantly enhances the heat transfer. The average Nu and f values of the annular tube with twisted oval tubes are higher than those of the conventional straight annulus. The phase angle between the inner and outer tubes significantly influences the heat transfer and comprehensive thermal performances, especially within the laminar flow region. As the phase angle increases, the average Nu increases first and then decreases. Optimal phase angles of 60° and 45° exist for Re &amp;lt; 6000 and Re ≥ 6000, respectively, with the largest heat transfer ability and comprehensive heat transfer performance. In comparison with a conventional straight annulus, the twisted annulus exhibits an increase in both Nu and f, with maximum enhancements of 89% and 58%, respectively. Moreover, the highest attainable thermal performance factor for the twisted annular tube was 1.66, reflecting a 66% enhancement in thermal performance compared to the conventional straight annulus.