Tube Parameters Research Articles

Experimental Study on Convective Heat Transfer and Pressure Drop Characteristics of an Alternating Cross-Section Flattened Tube with Different Twist Angle

In this research, the heat transfer coefficient (HTC) and pressure drop of alternating cross-section flattened (ACF) tubes were investigated experimentally and compared with the same parameters of a circular tube. Three different ACF tubes were fabricated from circular copper tubing with an internal diameter of 4.5 mm, a thickness of 1 mm, and a length of 400 mm. The twist angles were 30, 45, and 90°. The experimental ranges covered a mass flux of 729–1,434 kg/m2s and a heat flux of 12–30 kW/m2. The results showed that the HTC and pressure drop increased with mass flux. The HTC decreased with increments of heat flux, but the pressure drop did not change. The HTC and pressure drop of the ACF tubes were higher than those of the circular tube. The ACF tube with 90° twist angles produced the highest HTC, and the thermal performance of that tube was about 27% better than the thermal performance of the circular tube.

Crashworthiness design of CFRP/AL hybrid circular tube under lateral crushing

The metal hybrid method can effectively solve the problem of low energy absorption efficiency of CFRP under lateral crushing load, and the application prospect of the hybrid tube can be better explored through the related crashworthiness design. Therefore, the CFRP/AL hybrid circular tube parameters were analyzed in this paper and propose single, antisymmetric, and hybrid wrapping methods (Sap, Aap, and Hap). Based on the nonlinear progressive damage theory, the finite element model is established, considering intra- and inter-ply damage. The results show that the calculated results of the FE model are basically consistent with the experimental data, and can accurately capture the failure mode in the actual collapse. Increasing the wrapping angle can significantly improve the energy absorption of the CFRP/AL hybrid tube, with 40° antisymmetric wrapping (Aap-40) being the best, which can increase the specific energy absorption (SEA) by 54% compared with the initial hybrid tube. Finally, the parameters of the AL tube were studied, and the energy absorption mechanism of hybrid tubes with different thickness of the AL tube was revealed.

Research on heat transfer and frost resistance performance of the closed wet cooling towers tubes

The closed wet cooling tower used as refrigeration equipment should not only consider its heat transfer effect, but also its frost resistance performance in cold winter, so as to operate safely and stably in the low temperature season, thus saving electric energy. Fluent is used to simulate the falling film flow pattern on the outer wall of the heat exchange tubes, the heat transfer performance differences of the oval tube with different nominal axis ratios (major axis/minor axis) and the traditional circular tube were compared. And also the effect of spray density on the heat transfer outside the tubes has been discussed. The type of oval tubes with better thermodynamic performance was given. Then, the ANSYS static structure module is used to analyze the elastic-plastic properties of heat exchange tubes with different materials and tube types, and the tube parameters with better frost resistance are proposed. Combining the performance of heat transfer and frost resistance, it provides a reference for the design of closed wet cooling tower tubes for refrigeration.

Experimental study on sound absorption performance of microporous aluminum square tube space absorber

The aluminum square tube is one of the ceiling materials that have been produced in recent years. It has become the most popular product in the decoration market because its lines are bright and clean with distinct layers, reflecting the simple modern style, and it is easy to install and dismantle. However, the aluminum square tube used in the market is mostly a single aluminum panel structure, mainly used for decoration, without sound absorption and noise reduction. In order to improve the sound absorption properties of the aluminum square tube, a microporous aluminum square tube space absorber is proposed. The reverberation chamber method is used to investigate the sound absorption properties of the microporous aluminum square tube. The results show that the sound absorption performance of the aluminum square tube can be greatly improved by the formation of micropores on it. The sound absorption performance of the aluminum square tube perforated on three sides is better than that of the aluminum square tube perforated on only two sides. In the case of perforation on only two sides, with the increase in the height of the perforated surface, the peak value of sound absorption is gradually increased. In addition, the sound absorption peak gradually shifts to the low-frequency direction as the distance between the perforated surfaces increases. The reasonable design of structural parameters of microporous aluminum square tube can make it have beautiful decorative effect and good sound absorbing effect.

Study on Flame Suction Behavior of High-Pressure Gas Well under Self-Excited Negative Pressure Effect

Summary Placing a flow tube on the wellhead to suction flame during a well control operation is key to creating a safe environment near the wellhead. Aiming at the problem that the internal flame of the flow tube can easily leak during the rescue of a high-pressure gas well, we propose in this paper to use the self-excited negative pressure effect to improve the capacity to suction flame. Based on the coupling method of the Reynolds averaged Navier-Stokes equation and mixed combustion model, a gas well combustion model is established. The accuracy of the model is verified by proportional scaling experiment. Furthermore, the sensitivity analysis of key structural parameters of self-excited negative pressure flow tube is carried out, and the structure of the flow tube optimized. The result shows that the optimized flow tube has a suction flow about twice that of the horn flow tube, and the suction scope is increased by 61.5%, which greatly improves the flame suction capacity. The research work can provide guidance for structural design and optimization under self-excited negative pressure effect.

Optimization of mechanical properties of rotary friction welding parameters of low alloy steel tubes using design of experiments concept

Optimization of mechanical properties of rotary friction welding parameters of low alloy steel tubes using design of experiments concept

A Comprehensive Assessment of Two-Phase Flow Boiling Heat Transfer in Micro-Fin Tubes Using Pure and Blended Eco-Friendly Refrigerants

This review study examines flow boiling heat transfer in micro-fin tubes using mixed and pure refrigerants with zero ozone-depleting potential (ODP) and minimal global warming potential (GWP). This investigation focuses on the extraordinary relationship between heat transfer coefficients (HTCs) and vapor quality. Since the introduction of micro-fin heat exchanger tubes over 30 years ago, refrigerant-based cooling has improved significantly. Air conditioning and refrigeration companies are replacing widely used refrigerants, with substantial global warming impacts. When space, weight, or efficiency are limited, micro-fin heat exchangers with improved dependability are preferred. This review article discusses flow boiling concepts. The researchers used several refrigerants under different testing conditions and with varying micro-fin tube parameters. Micro-fin tubes are promising for improved heat transfer techniques. This tube increases the heat transfer area, fluid disturbance, flow speed, and direction owing to centrifugal force and HTC. As the focus shifts to improving heat transfer, pressure drop, mean vapor quality, and practical devices, this subject will grow more intriguing. A radical shift will reduce equipment size for certain traditional heat transfer systems and bring new products using micro-scale technologies. This suggested review effort helps comprehend saturation flow boiling through micro-fin tubes and find the right correlation for a given application. This domain’s challenges and future relevance are also discussed.

THE APPLICATION OF ARTIFICIAL INTELLIGENCE TO ANALYZE THE LINER PRODUCTION PROCESS

The paper demonstrates a technique that combines the use of artificial intelligence and the finite element method to analyze the production process of the liner – the seamless part of composite overwrapped pressure vessels obtained by tube forming. Instead of expensive physical experiments, computer simulation was used, which made it possible to quickly obtain "big data", including the main technological parameters of tube forming process, some metal flow features and the tendency for defects to appear. The processing of the data array was carried out in MATLAB using neural networks and a genetic algorithm for the multi-objective optimization problem. As a result, the influence of technological parameters on the formation of the liner geometry was determined, and the optimal variant of their manufacture was proposed, which is of practical interest to companies producing metal-composite cylinders.

Effect of guided Ahmed glaucoma valve implantation on corneal endothelial cells: A 2-year comparative study.

To compare the effects of guided and non-guided Ahmed glaucoma valve (AGV) implantation on the corneal endothelium. Medical records of patients who underwent AGV implantation in the anterior chamber (AC) were reviewed retrospectively. The eyes were divided into two groups depending on the use of a guidance technique with spatula and a 4-0 nylon intraluminal stent. Specular microscopy was performed to measure corneal endothelial cell density (ECD) loss after surgery, and the rate of ECD change was calculated. Tube parameters were measured using anterior segment optical coherence tomography (AS-OCT). The ECD loss during 2 years of follow-up was significantly lower in the guided AGV implantation (gAGV) group than in the non-guided implantation (ngAGV) group, and the rate of ECD change was -0.62 ± 1.23 and -1.42 ± 1.57%/month in the gAGV and ngAGV groups, respectively (p = 0.003). The mean tube-cornea distance (TCD) and mean tube-cornea angle (TCA) were significantly greater in the gAGV group than in the ngAGV group. The frequency of tube repositioning within 2 years after surgery was 0% in the gAGV group and 12.66% in the ngAGV group (p = 0.005). The use of a guidance technique can reduce corneal endothelial loss during the first 2 years after AGV implantation in the AC. The tube was positioned at a more distant and wider angle from the cornea in the eyes of the gAGV group, which may have contributed to the reduced need for tube repositioning to prevent corneal decompensation.

Effect of fin density and fin height on flow-induced vibration behavior of finned tube arrays subjected to water cross flow

PurposeThe prediction of critical velocity at instability threshold for shell and tube heat exchangers is important to avoid failure of tubes as a result of flow-induced vibrations due to water cross flow. The flow-induced vibration in finned tube heat exchangers is affected by various parameters such as fin height, fin pitch, fin material, tube array, pitch ratio, fin type, fluid velocity etc. In this paper, an experimental investigation of fluid elastic instability in shell and tube heat exchangers is carried out by subjecting normal square finned tube arrays of pitch ratio 1.79 to water cross flow.Design/methodology/approachThe five tube arrays, namely plain array, two finned tube arrays with 3 fpi and 9 fpi fin density, and two finned tube arrays with 3 mm and 6 mm fin height are tested in the experimental test setup with water flow loop and vibration measurement system. The research objective is to evaluate the effect of fin density and fin height on the instability threshold. The critical velocity at instability threshold is determined to characterize the fluid elastic instability behavior of different tube arrays. The vortex shedding behavior of the tube arrays is also studied by determining Strouhal number corresponding to the small peaks before fluid elastic instability.FindingsThe fluid elastic instability behavior of the tube arrays was found to be the function of fin tube parameters. The experimental results indicate that an increase in fin density and fin height results in delaying the instability threshold for finned tube arrays. It is also observed that critical velocity at instability is increased for finned tube arrays compared to plain tube arrays of the same pitch ratio. The design modifications in the outer box have resulted in further reduction in the natural frequency. This enabled to reach clear instability for all the five-tube arrays.Originality/valueThe research data add the value to the present body of knowledge by knowing the effect of fin height and fin density on the fluid elastic instability threshold of normal square finned tube arrays subjected to water cross flow.

OPTIMIZING THE STRUCTURAL CHARACTERISTICS OF DRAFT TUBE IN A SPOUTED BED REACTOR FOR BEST PHOTOCATALYTIC DEGRADATION OF TOLUENE AND CO2 SELECTIVITY USING RESPONSE SURFACE METHODOLOGY

In this study, toluene degradation efficiency and carbon dioxide (CO2) selectivity in a spouted bed reactor with a porous draft tube were optimized using the response surface methodology. For this purpose, titanium dioxide (TiO2) was used as a catalyst for photocatalytic degradation of gaseous toluene in a dynamic mode under ultraviolet (UV) irradiation. The influence of draft tube parameters' (including height, diameter, gap, and porosity) on toluene degradation efficiency and CO2 selectivity (as the response variables) was investigated by central composite design. Analysis of variance (ANOVA) was applied to evaluate the significance of the variables' effects and the interaction between them. Results showed that maximum toluene degradation efficiency of 78.1 % and maximum CO2 selectivity of 88.7 % were obtained at 1.99 cm draft tube height, 1.3 cm draft tube diameter, 1.3 cm gap, and 60 % draft tube porosity. The highest F-values indicated that the gap is the most important variable affecting the toluene degradation efficiency and CO2 selectivity, while the draft tube diameter is the second important variable. The results of experiments at optimal levels of parameters with three replications showed a maximum toluene degradation efficiency of 78.8% (SD= 0.62) and maximum CO2 selectivity of 89.1 % (SD= 0.46). The study revealed that the spouted bed reactor with a porous draft tube has a good stability for volatile organic compounds (VOCs) degradation and mineralization.

Experimental and numerical study on an enhanced swirl cooling with convergent tube wall and local dimple arrangements

This paper experimentally and numerically investigates an enhanced swirl cooling structure, featuring multiple connected convergent swirl tubes and dimpled wall. The dimpled swirl tube adopts a novel local dimpled wall scheme, only arranging dimple arrays under the tangential jets, which takes advantage of the heat transfer potential of the individual dimple. A counterpart multistage convergent swirl tube without dimples is also studied as a comparison baseline to clarify the action of local dimple arrays on swirling flow. The spatially resolved heat transfer data are measured by applying transient thermochromic liquid crystal (TLC) technique. Four channel Reynolds numbers (Re = 20,000 to 50,000) are tested based on the maximum tube parameters. The results show that the enhanced dimpled swirl tube performs a synergistic reinforcement of the high-speed swirling flow over the dimple arrays, which produces many local high Nusselt number patterns. Under the individual injection slot, the upstream dimples have a better enhanced heat transfer performance. For the studied working conditions, the globally averaged Nusselt number of the dimpled swirl tube can be increased by 6.0%–11.5% in comparison with the baseline convergent swirl tube. Besides, the dimpled wall also suppresses the swirl intensity, which leads to the weakening of wall-fluid shear stress action and the disappearance of downstream vortex breakdown, and consequently reduces the pressure loss by 2.0%–10.2%. Based on the well-validated CFD results, the dimpled wall under incoming jets redistributes the contribution of the near-wall turbulence and the forced convection due to the near-wall flow motion to the heat transfer enhancement in the swirl tube, which achieve an ideal cooling performance of high heat transfer in combination with low pressure loss. This provides a new inspiration for the design and optimization of swirl cooling device.

1153: BLIND NG TUBE INSERTION WITHIN 1 MINUTE OR 3 ATTEMPTS MINIMIZES MUCOSAL INJURY DURING RESUSCITATION

Introduction: Patients under resuscitation are at high risk for aspiration of gastric contents which causes ventilator-associated pneumonia. Therefore, blind nasogastric (NG) insertion is performed for decompression, however minimal trauma to the laryngopharynx can sometimes lead to severe bleeding in patients with a bleeding diathesis. Recently, the usefulness of NG tube placement under the assistance of a Video-laryngoscope (VLS) has reported. However, NG tube insertion is still performed blind, and insertion techniques to minimize mucosal injury during resuscitation are not well understood. We investigated laryngopharyngeal mucosal injury associated with blind NG tube insertion during resuscitation and considered practical blind NG tube insertion guidelines to minimize mucosal injury. Methods: We included patients (n = 84) with cardio pulmonary arrest on arrival in whom blind nasogastric tube insertion was possible within 120 s in the Blind group and those in whom it was not possible in the Difficult (Dif) group. In the Dif group, VLS-assisted nasogastric tube insertion was performed. The laryngopharyngeal mucosal condition was recorded after NG tube insertion using VLS. Patient background, success rates, insertion time, the number of insertions, and injury scores were evaluated. A single regression analysis was performed, and practical blind NG tube parameters for insertion during resuscitation were assessed. Results: Success rates in the Blind and Dif groups were 98.5% and 76.5%, respectively, and insertion times were 48.8 ± 4.0 and 54.8 ± 3.0 s, respectively. The number of insertions (2.1 ± 0.2 vs. 8.1 ± 0.8) and injury scores (1.04 ± 0.21 vs. 6.40 ± 0.64) in the Blind group were significantly lower than those in the Dif group, respectively. Mucosal injuries were most severe in the retropharyngeal wall in both groups. The number of insertions and insertion time both showed strong positive correlations with injury scores. Conclusions: The severity of laryngopharyngeal mucosal injury increased with increased insertion time and the number of insertions. Blind nasogastric tube insertion performed within 1 min or for a maximum of two or three attempts may minimize laryngopharyngeal mucosal injury, and VLS-assisted insertion should be considered if these limits are exceeded.

Numerical study on the cooling performance and inlet mass flow rate per unit area of Ranque–Hilsch vortex tubes with different area ratios

The development of the Ranque-Hilsch vortex tube has stagnated since the 1950s, when Hilsch improved the vortex tube proposed by Ranque. Consequently, the performance of vortex tubes has remained constant for the past 70 years. In addition to the unclear flow structure and energy separation mechanism of vortex tubes, the lack of a mature design method for vortex tubes has also limited its widespread adoption for industrial applications. The inlet nozzle and main tube parameters have been studied extensively, and matching the inlet with the main tube is considered an important step in the design of a vortex tube; however, this process has not been studied extensively. In addition, although the temperature drop at the cold exit is a commonly adopted performance benchmark, it is not possible to establish a close relationship between this parameter and the geometric parameters of a vortex tube. This study investigates the relationship between the cooling performance and the area ratio of a vortex tube. The results indicate that the inlet mass flowrate per unit area has a positive correlation with the cooling performance, and its influence on the performance of a vortex tube is higher than that of the distribution of the reverse flow boundary. Therefore, the inlet mass flowrate per unit area can potentially be a geometric performance benchmark. However, further studies are required to develop better guidelines for optimizing the design and to obtain a deeper understanding of the energy separation mechanism of vortex tubes.

Numerical simulation study on the influence of scroll design parameters on helicopter intake system

Based on the numerical simulation theory, this paper establishes the two-phase flow calculation model of sand and air mixture in the sand control vortex tube, and combined with CFD numerical simulation, studies the influence rules of various design parameters of the vortex tube on the total pressure loss and sand dust separation efficiency of the helicopter intake system, optimizes the structural parameters of the vortex tube separator, and puts forward a set of vortex tube design method, it provides a basis for the design optimization of vortex tube.

Experimental study on forming process of the high-precision high-alkali glass tube

Rigid optical fiber products (optical fiber panels, image inverters, etc.) are a kind of image coupling and transmission device with excellent performance, which is formed by regular arrangement and fusion of tens of millions of optical fibers with a diameter of 3 to 6 μm. As the basic material for optical fiber, the high-alkali glass tube is one of the cores of optical fiber technology. The geometric parameters and precision of the high-alkali glass tube are completely determined by the molding process. This paper summarizes the influence of a single process parameter on the geometric parameters of the glass tube by studying the aspects of temperature, pressure in the tube, and traction speed, and systematically analyzes a large number of experimental data to establish an overall forming control theory, which provides a theoretical basis for actual production and proposes an improvement plan for high-precision high-alkali glass tube forming equipment to improve product quality.

Research on the evaluation method of lunar soil disturbance based on the fitting of Gaussian surface

It is crucial to maintain the layer sequence information on in situ lunar soil during the lunar soil sampling. In this paper, a discrete element model for direct push sampling of the lunar weathering layer is established, and the relationship between the perturbation rate of the lunar soil layer sequence information and the sampling depth is obtained. A quantitative evaluation method of the perturbation rate of the structural information on the lunar soil layer sequence based on the Gaussian curvature is proposed by reconstructing the center-of-mass point cloud model of the marked layer lunar soil particles in MATLAB. The proposed method can accurately describe the perturbation rate of lunar soil layer sequence information and can analyze the degree of lunar soil disturbance according to the displacement of the sampling tube and mechanical parameters in real-time inversion during the sampling process. When the sampling depth is 40 mm, the minimum and maximum perturbation rates of sampling along the penetration direction of the machine are 5.261 % and 27.649 %, respectively. The perturbation rate shows a trend of first decreasing and then increasing. The method proposed in this study could effectively solve the problem that the disturbance of lunar soil bedding information was difficult to evaluate in the sampling process of lunar regolith.

Design of Ventilation Systems in a Single-Family House in Terms of Heating Demand and Indoor Environment Quality

In buildings with good-quality thermal insulation of external partitions, the main component of the building’s heat balance is the heat demand for ventilation. The reduction of this energy demand cannot be achieved at the expense of thermal comfort of the occupants and indoor air quality. The aim of this article is to analyze the impact of various ventilation strategy (natural and mechanical) on heating demand, thermal comfort, and CO2 concentration in a single-family house located in Poland. The benefits of using fans integrated with the earth tube were tested. The study was based on the numerical energy simulation of a multi-zone building model for the entire calendar year. Contam, EnergyPlus, and Python programs were used to perform calculations. The thermal model was validated on the results of temperature measurements in the building. To obtain the best solutions, the parameters of the systems considered have been optimized with the use of genetic algorithms. Various optimal parameters of the earth tube (diameter, length, and foundation depth) were obtained during this research. The highest number of thermal discomfort hours was obtained in the naturally ventilated building with automatic window opening. This system supplied to the rooms a large amount of cool outdoor air in winter and warm air in summer, causing instantaneous rapid fluctuations in indoor temperature. Supplementing the mechanical ventilation control system with CO2 concentration sensors resulted in a much higher amount of ventilation air supplied to the rooms compared to systems controlled only by temperature sensors, resulting in an increase in heat demand.

Effect of trigger mechanisms on the quasi-static axial crushing behavior of glass epoxy/polyvinyl chloride hybrid composite tubes

This paper investigates the effect of trigger mechanisms on the crashworthiness parameters of glass epoxy/ polyvinyl chloride hybrid composite tubes. Quasi-static axial compression tests are conducted to determine these parameters for composite tubes with nine different specimen configurations. These configurations include; specimens with no triggers, specimens with three distinct chamfer triggers, and specimens with five different double-step triggers, respectively. The double-step trigger is a novel trigger mechanism introduced in this study. The specimen tubes were fabricated using a five-axis filament winding machine. The results showed that both trigger mechanisms could significantly improve the crashworthiness performance of the tested hybrid composite tubes. Additionally, the performance of the double-step trigger surpassed that of the conventionally used chamfer trigger. Overall, the DST7.5 specimen configuration exhibited the best performance of all the tested samples. The initial peak force of this specimen configuration was about 43.8% less, its crush force efficiency approximately 92.3% more, and its SEA about 28.1% higher than that of the non-trigger specimen configuration.

Theoretical and experimental research on valve-less piezoelectric pump with arc-shaped tubes

In order to apply a valve-less piezoelectric pump in navigation equipment, this work first revealed a valve-less piezoelectric pump with arc-shaped tubes and then researched the relationship between the main structural parameters of arc-shaped tubes and the output flow rate. According to the velocity difference between clockwise and counterclockwise directions of liquid in circular arc-shaped tubes, the flow characteristics of liquid in circular arc-shaped tubes are analyzed in this paper, and the velocity difference model and flow equation of a piezoelectric pump are established. By using three-dimensional printing technology, five types of prototypes with different parameters were made, and the experimental research was carried out. The results show that at the optimal frequency, the pump output flow is the largest. The output flow is proportional to the driving voltage, the base circle radius, and the cross section area of the pipe. The low-cost and miniaturized navigation equipment made by using the piezoelectric pump has potential application value in unmanned aerial vehicle and intelligent vehicle navigation.