Tube Diameter Research Articles

A correlation of heat transfer for falling film evaporation on the horizontal tube with multiple-precision expansion method

The falling film evaporation of water and seawater outside the horizontal tube is experimentally investigated under non-boiling condition, and the effects of spray density, evaporation temperature, tube pitch, circumferential position and seawater salinity on the falling film evaporation are studied. A competitive mechanism, based on the analysis of liquid film, is proposed to analyze the critical Reynolds number of the spray water, ReΓ, and the dual effects of liquid film on heat transfer coefficient. The experimental data covers tube diameter D=19∼38 mm, tube pitch s/D=1.3∼2.25, evaporation temperature Tsat=50∼70 °C, spray Reynolds number ReΓ=118∼1979, and salinity S=0∼60 g/kg. By summing up a large number of experimental data, the heat transfer coefficient correlation applying both water and seawater falling film evaporation on horizontal tubes is proposed. The correlation is also compared with previous studies about water and seawater, which shows a better and wider adaptability to experimental conditions.

Freeze range of a condensing gas propagating in a liquid helium-cooled tube

Understanding air propagation and condensation following a catastrophic vacuum break in particle accelerator beamlines cooled by liquid helium is crucial for maintaining the operational safety of these facilities. Previous experimental investigations on nitrogen gas propagation in both normal liquid helium (He I) and superfluid helium (He II) cooled copper tubes unveiled a nearly exponential deceleration of the gas propagation. A comprehensive theoretical model incorporating gas dynamics, heat transfer, and condensation mechanisms has been developed, which effectively reproduces various key experimental observations. An intriguing phenomenon uncovered in our model simulation is that the gas propagation appears to nearly stop beyond a certain distance from the location where condensation starts. We refer to this distance as the freeze range. In this paper, we present our systematic study of the freeze range at various inlet mass fluxes and tube diameters. We show that the results can be well described by a simple correlation. The underlying physical mechanism that supports this useful correlation is explained. Knowing the freeze range may allow accelerator engineers to develop protocols for controlling frost-layer contamination in the beamline tubes, which is of great practical importance.

Local control of magnetic microbubble behavior by magnetic field and pulsed ultrasound

The localization of magnetic microbubbles (MMBs) to a target site has been shown to be essential to their efficacy in therapeutic applications such as targeted drug delivery and gene therapy. In this work, the MMBs’ dynamic equations of vibration, horizontal and vertical motion in a fluid-filled tube, subject to a magneto-acoustic complex field, are established by Lagrange method. The responses and capture efficiency under three ultrasonic pulses waveform in a magnetic field are numerically analyzed. The regulation effects of the external field are observed by experiments. The results show that the transport behavior is influenced by bubble size, original position, liquid flow rate, tube diameter, parameters of acoustic and magnetic field. For the same acoustic parameters, square wave pulse can make stronger vibrate compared with cosine wave and sawtooth wave, which pushes MMBs closer to the magnet. In addition, high frequency and large amplitude pulse are benefit to translation, and increasing the cycle number in a single pulse can also promote translation. In practical applications, variable parameters such as bubble speed and magnet length can be used to improve the capture efficiency. The observations of high-speed camera are consistent with the prediction of theoretical model, which indicates the model is mostly correct.

An experimental investigation on R245fa and R1233zd(E) flow boiling at high saturation temperatures in a horizontal small diameter channel

The current study presents an investigation on flow patterns, pressure-drop and heat transfer coefficient for the refrigerants R1233zd(E) and R245fa flowing at saturation temperatures (Tsat) between 75 °C and 95 °C inside a horizontal 2 mm diameter tube. Experimental results are reported for mass velocities of 176–570 kg/m²s and heat fluxes of 18.1–54.5 kW/m². As expected, the pressure gradient increases as the mass velocity increases and the saturation temperature decreases. Flow image analysis indicated that the pressure gradient peak is associated with disturbance interfacial waves damping. Heat transfer coefficient data indicated strong contribution of nucleate boiling effects for most of the experimental conditions. The higher the saturation temperature and the heat flux, the higher the heat transfer coefficient, regardless of the vapor quality range. In general, the effect of mass velocity on the heat transfer coefficient was only marginal, with exception of low Tsat and heat flux conditions. Two of 20 pressure-drop prediction methods predicted more than 90% of the database within error bands of ±30%. Overestimation of heat transfer coefficient data was verified for most of the 16 evaluated prediction methods, especially at high Tsat. Only two methods predicted more than 80% of data within an error band of ±30%.

Methodological errors due to a non-cylindrical surface in a Jones-type cell with a removable center extension tube

The article shows an idealized model of a Jones-type cell with a removable central extension tube. Two main factors leading to the cylindricity distortion of the inner surface of the cell are considered. These are radial displacement and tube diameter inequality. Based on the finite element method (FEM), errors in measuring the resistance of a liquid column caused by the non-uniformity of the current density distribution inside the cell were determined. The methodological error with respect to the idealized model was estimated for each factor separately and in combination. The Authors show that at a radial displacement of 0.6 mm, the error can reach 0.1 %. The same error value occurs when the inequality of the diameters is only 20 μm.

Understanding the synergistic catalysis effect on the dual-metal-N4 embedding single-walled carbon nanotubes from first principles

Developing high-efficiency electrocatalysts for the oxygen evolution reaction (OER) remains a crucial bottleneck on the way to the water splitting for producing clean fuel (H2). Compared with single atom catalysis (SACs), dual-atom catalysts (DACs) have attracted great interest due to higher OER catalytic efficiency. In this work, the OER properties of dual-metal-N4 embedding armchair single-walled carbon nanotubes (D-MN4/CNTs) were systematic studied by density functional theory (DFT) simulations. Our results indicate that CoN4 embedding armchair CNTs exhibit higher OER activity than the corresponding planar structure, especially for CoN4 embedding in armchair CNT (4, 4) (CNT4). For MN4-CoN4 co-embedding CNTs, the TiN4-CoN4/CNTs have good OER synergistic effect with the lowest overpotential. Besides, the diameter of CNTs have a significant impact on the OER efficiency. The lowest reaction overpotential 0.47 V were obtained in TiN4-CoN4/CNT4 with a 5.69 Å tube diameter. Interestingly, compressive stress will further enhance the synergistic effect between two metal atoms in the OER reaction. The OER overpotential of CoN4-TiN4 embedding armchair CNT4 can reduce to 0.40 V under the −4 % uniaxial compression strain. These works were expected to better understand the synergistic mechanisms and design high-efficiency dual-atom OER electrocatalysts.

Crashworthy optimization of skeleton-filled FRP tubes based on back propagation neural network

Lightweight composite tubes have been widely used in vehicle safety systems as energy absorbers. To improve the crashworthiness of tubes, composite skeletons with a variety of cross-sectional profiles were ingeniously designed as internal reinforcements. Herein, a novel composite skeleton comprising cross-ribs and an inner circle (OS-skeleton) was proposed and integrally fabricated through the special assembling molds. The novel OS-skeleton presented a steady progressive failure mode under dynamic impact loads, leading to remarkable material utilization and energy absorption characteristics. Subsequently, finite element analysis (FEA) models were developed. The predicted response curves and deformation modes were consistent with the experimental results. Finally, a multi-objective optimization utilizing the back propagation neural network (BPNN) was then conducted to further enhance the mean crushing force (MCF) and specific energy absorption (SEA) by adjusting several structural parameters. The results showed that MCF and SEA increased with the increasing thickness of the skeletons and the number of circumferential ribs. By comparison, the diameter of inner tube and the number of circumferential ribs showed a non-linear relationship with the energy absorption characteristics due to their combined effects. In sum, the proposed composite tubes filled with OS-skeletons could maximize certain aspects of crashworthiness performance through proper structural design, demonstrating great potential for lightweight energy absorbers.

Heat transfer characteristics of R-1234yf, an eco-friendly alternative refrigerant in condenser for semiconductor chiller

This study aims to optimize a semiconductor chiller condenser that uses R-1234yf refrigerant, focusing on its flow pattern and heat transfer characteristics during condensation while considering the tube diameter. The heat transfer coefficient (HTC) decreases as the pressure of R-1234yf increases. This decline is attributed to changes in its physical properties, such as the density ratio between the liquid and gas phases and the thermal conductivity of the liquid phase, according to the change in saturation pressure. The HTC of R-1234yf increases with the mass flow rate (MFR) because the Reynolds number in the tube increases as MFR increases, enhancing heat transfer. Furthermore, the local condensation HTC (CHTC) of R-134a exceeds that of R-1234yf across the entire vapor quality range, primarily due to the higher liquid-phase density of R-1234yf. The correlations by Dobson–Chato [21] and Bashar et al. [10] were found to be suitable for predicting CHTC values for R-1234yf. The predicted values closely align with the experimental values, with an error range of less than ± 10 %, thus indicating that the correlations by Dobson–Chato and Bashar et al. can be directly applied to the design of condensers that use R-1234yf refrigerant.

Deformable Biomechanics of DMEK Tissue Scrolls Traveling Through Narrow Lumens: The Inverse Relationships Between Fluid Velocity, Scroll Width, and Wall Contact and Their Clinical Implications for Preloading.

The aim of this study was to evaluate Descemet membrane endothelial keratoplasty (DMEK) scroll width and length in relation to variable velocities as the tissue transits through wide and narrow lumen glass tubes. Sets of DMEK tissue were processed using the Iowa Lions Eye Bank standard DMEK protocol and were passed through 2 glass tube widths at variable speeds. Two hourglass-shaped glass tubes were created, one "wide" and one "narrow." A syringe pump, valve, and pressure gauge were used to modulate tissue speed through each tube. For both tube sizes, DMEK tissue was passed through their lumens with incrementally increasing velocity and visualized with a high-speed camera at frame rates from 1000 to 8000 fps. Scroll width and length were measured using IDT Motion Studio software and digital calipers. There was a significant, indirect correlation between scroll velocity and width in both the wide (R 2 = -0.98, P < 0.001) and narrow (R 2 = -0.84, P < 0.001) tubes. There was a significant, direct correlation between scroll velocity and length in both the wide (R 2 = 0.84, P < 0.001) and narrow (R 2 = 0.83, P < 0.001) tubes. The resting widths of the scrolls were 105% and 207% wider than the wide and narrow tubes, respectively. All transits recorded scroll widths that were equal to or smaller than their respective tube's internal diameter. There is a significant, inverse correlation between DMEK scroll velocity and width as well as a direct correlation between scroll velocity and length, allowing DMEK scrolls to transit through a tube that is narrower than its resting width without sustained lumen wall contact.

Optimal evaluation of photovoltaic-thermal solar collectors cooling using a half-tube of different diameters and lengths

Photovoltaic Thermal Solar Collectors (PVTs) combine the advantages of photovoltaic (PV) and solar thermal collectors to produce electricity and heat simultaneously. This study proposes a numerical model to investigate the effectiveness of using half-circular tubes to improve thermal conductivity and increase the interaction area between PV panels and tubes. This enhances heat transfer from the PV panels to the working fluid (water) circulating through the thermal absorber. Additionally, the integration of phase change material (PCM) is explored to further boost thermal conductivity and generate hot water. The research focuses on modeling the cooling of solar PV panels using copper half-tubes. The PV panels measure 870 × 665 × 3 mm and generate a power output of 100 W. The study examines the impact of key variables such as tube diameter (three standard sizes: 10, 12, and 15 mm) and fluid flow rate (0.008 to 0.04 kg/s). Solar radiation equations are incorporated, and the finite volume approach, implemented in the ANSYS 19.0 software's CFX modeling framework, is used as the underlying methodology. The investigation culminates in an optimization process to determine the optimal operating conditions for the PV system. The results show that the highest electrical efficiency (13.15%) is achieved at a flow rate of 0.04 kg/s for 15 mm diameter tubes and 7 tubes in total. The peak thermal efficiency (74.28%) is observed under the same conditions. In conclusion, this study contributes to the understanding of enhancing PV/T system performance through innovative thermal management strategies and provides valuable optimization recommendations for achieving improved electrical and thermal efficiencies.

An international RAND/UCLA expert panel to determine the optimal diagnosis and management of burn inhalation injury

BackgroundBurn inhalation injury (BII) is a major cause of burn-related mortality and morbidity. Despite published practice guidelines, no consensus exists for the best strategies regarding diagnosis and management of BII. A modified DELPHI study using the RAND/UCLA (University of California, Los Angeles) Appropriateness Method (RAM) systematically analysed the opinions of an expert panel. Expert opinion was combined with available evidence to determine what constitutes appropriate and inappropriate judgement in the diagnosis and management of BII.MethodsA 15-person multidisciplinary panel comprised anaesthetists, intensivists and plastic surgeons involved in the clinical management of major burn patients adopted a modified Delphi approach using the RAM method. They rated the appropriateness of statements describing diagnostic and management options for BII on a Likert scale. A modified final survey comprising 140 statements was completed, subdivided into history and physical examination (20), investigations (39), airway management (5), systemic toxicity (23), invasive mechanical ventilation (29) and pharmacotherapy (24). Median appropriateness ratings and the disagreement index (DI) were calculated to classify statements as appropriate, uncertain, or inappropriate.ResultsOf 140 statements, 74 were rated as appropriate, 40 as uncertain and 26 as inappropriate. Initial intubation with ≥ 8.0 mm endotracheal tubes, lung protective ventilatory strategies, initial bronchoscopic lavage, serial bronchoscopic lavage for severe BII, nebulised heparin and salbutamol administration for moderate-severe BII and N-acetylcysteine for moderate BII were rated appropriate. Non-protective ventilatory strategies, high-frequency oscillatory ventilation, high-frequency percussive ventilation, prophylactic systemic antibiotics and corticosteroids were rated inappropriate. Experts disagreed (DI ≥ 1) on six statements, classified uncertain: the use of flexible fiberoptic bronchoscopy to guide fluid requirements (DI = 1.52), intubation with endotracheal tubes of internal diameter < 8.0 mm (DI = 1.19), use of airway pressure release ventilation modality (DI = 1.19) and nebulised 5000IU heparin, N-acetylcysteine and salbutamol for mild BII (DI = 1.52, 1.70, 1.36, respectively).ConclusionsBurns experts mostly agreed on appropriate and inappropriate diagnostic and management criteria of BII as in published guidance. Uncertainty exists as to the optimal diagnosis and management of differing grades of severity of BII. Future research should investigate the accuracy of bronchoscopic grading of BII, the value of bronchial lavage in differing severity groups and the effectiveness of nebulised therapies in different severities of BII.Graphical

Experimental investigation on self-induced jet impingement boiling using R1336mzz(Z)

Pool boiling performance enhancement has attracted considerable interest on high power electronic cooling. In this paper, we introduce a self-induced jet impingement device for practical boiling enhancement, achieved by integrating the guidance tube with an orifice plate. With R1336mzz(Z) as the working fluid, we conduct visualization and parametric investigations on the pool boiling performance, considering the varying characteristics of this device. Visualization snapshots confirm the liquid-vapor separation and indicate that the two-phase flow pattern in the guidance tube eventually stabilizes as a churn-annular flow. Our findings suggest that self-induced liquid jet impingement has a minimal effect on the nucleate boiling heat transfer coefficient (hNB) under a certain heat flux, around 75 % CHF of the standard pool boiling, as the single-phase heat transfer is weakened due to the low thermal conductivity of R1336mzz(Z). As the heat flux intensifies, we observe substantial enhancements in both the Critical Heat Flux (CHF) and the Maximum Nucleate Boiling Heat transfer coefficient (hMNB) resulted from the delayed onset of boiling crisis, owing to the additional liquid supply and the promotion on vapor exhausting. The parametric studies reveal that the flow rate of the liquid jet, amplified by either extending the length or the inner diameter of the guidance tube, or by increasing the number of jet holes, positively impacts the boiling performance. However, these improvements show diminishing returns. Our study shows enhancements in CHF and hMNB of up to 69.5 % and 36.7 %, respectively, compared to the standard pool boiling.

Precise Tuning of Hollow and Pore Size of Bimetallic MOFs Derivate to Construct High-Performance Nanoscale Materials for Supercapacitors and Sodium-Ion Batteries.

Precise control of pore volume and size of carbon nanoscale materials is crucial for achieving high capacity and rate performances of charge/discharge. In this paper, starting from the unique mechanism of the role of In, Zn combination, and carboxyl functional groups in the formation of the lumen and pore size, the composition of InZn-MIL-68 is regulated to precisely tune the diameter and wall pore size of the hollow carbon tubes. The hollow carbon nanotubes (CNT) with high-capacity storage and fast exchange of Na+ ions and charges are prepared. The CNT possess ultra-high specific capacitance and ultra-long cycle life and also offer several times higher Na+ ion storage capacity and rate performance than the existing CNTs. Density functional theory calculations and tests reveal that these superior characteristics are attributed to the spacious hollow structure, which provides sufficient space for Na+ storage and the tube wall's distinctive porosity of tube wall as well as open ends for facilitating Na+ rapid desorption. It is believed that precise control of sub-nanopore volume and pore size by tuning the composition of the carbon materials derived from bimetallic metal-organic frameworks (MOFs)will establish the basis for the future development of high-energy density and high-power density supercapacitors and batteries.

Simulation and experimental research on luminance uniformity in full-field electroretinogram stimulators

Full-field electroretinogram (ERG) is a technique to study the function of the retina. The Ganzfeld is the stimulator used to provide uniform light for light input to the visual system. This study aims to design an improved stimulator and study the effects of its illumination geometric parameters on luminance uniformity. The developed Ganzfeld model was simulated in software ASAP, and then built in the laboratory. An illumination tube with variable parameters was mounted on the integrating sphere to investigate the effects on luminance uniformity. A linear regression method was applied to predict the relationship between luminance uniformity and illumination geometric parameters using ANOVA analysis. The simulated results were verified by the experiments, showing no significant difference (p < 0.05). Illumination tube diameter and angle show positive effects on the luminance uniformity, while height negatively affects the luminance uniformity. An equation indicating the parameter effects was obtained, and optimized luminance uniformity was calculated.

A low-cost, portable 32-channel EIT system with four rings based on AFE4300 for body composition analysis

A proposed low-cost, portable, 32-channel (4 rings of 8-channel) Electrical Impedance Tomography (EIT) system based on the AFE4300 analog front-end for body composition measurement. Each ring allows obtaining the conductivity distribution of 4 cross sections, 4 cm apart; to analyze the behavior of conductivity in a volume. The switching of the 4 rings and the current injection and voltage measurement patterns are done with three Texas Instruments 74HC4067 multiplexers, which are managed by an ESP32 board. The proposed system has an average signal-to-noise ratio of 74.71 dB and a frame rate of 50 fps. The sensitivity tests to impedance and volume changes consisted of introducing 4 tubes of different diameters (2 steel and 2 polyvinyl chloride) into a tank with saline solution; then conductivity distribution images were generated in 4 cross-sections of the tank, using the algorithms Gauss-Newton and Noser. Finally, the global impedance index (GI) is calculated to estimate the volume of each tube inside the tank. The results show that the proposed system is highly sensitive to impedance and volume changes, being a promising system for monitoring tissues, and fluids biological.

An innovative pillow-plate reactor for the synthesis of methanol from biogas: A simulation study

This work investigates the performances of a pillow-plate heat exchanger utilized as reactor for small-scale methanol synthesis. When downscaled, multi-tubular packed bed reactors are complicated to use since they undergo rapid losses in catalyst activity. A possible pathway to improve the unit performances is to diminish the tubes diameter and number. As this kind of reactors is governed by convective heat transfer, though, the use of long tubes is required to keep the mixture velocity high. This leads to the use of very long reactors, which cannot be easily realized with traditional designs. In order to tackle this issue, we propose the utilization of an innovative design, the pillow-plate reactor, increasing heat and mass transfer and the unit compactness. The study compares the performances of a packed-bed and a pillow-plate reactor through temperature profiles and methanol productivity at varying reactor lengths (1 – 6 m). It is proved that the pillow-plate unit, unlike the multi-tubular one, well manages scale reduction: when 1 m long reactors are employed, the outlet methanol fraction is close to equilibrium (5.8% vs. 4.9% for packed beds) and the hot-spots are well controlled (537 K vs. 557 K for tubular reactors). Moreover, it is also shown that the distance of metal layers in the pillow arrangement remarkably influences heat exchange, which is very effective for close layers, with a hot-spot of 518 K with a 3 mm gap, and much worse for the 12 mm design (552 K).

Optimization of anodizing parameters for the morphological properties of TiO2 nanotubes based on response surface methodology

TiO2 nanotube (TNT) morphology is crucial for applications in a variety of fields. In this paper, response surface methodology (RSM) has been utilized to optimize the anodizing parameters i.e., electrolyte concentration (C), anodization voltage (V), and time (t) for morphology (e.g., nanotube diameter and length) of TNTs. Ethylene glycol (EG) based electrolyte has been used for anodization employing ammonium fluoride (NH4F) as a source of fluoride ion (F–) with 2.5 vol% H2O. Reliable regression models have been developed between the input variables and the corresponding responses, namely tube diameter and length with multiple regression coefficients of 0.9649 and 0.9253, respectively, revealing a trustworthy association between the actual and those predicted values using the quadratic model. The predicted values of C (0.31 wt%), V (38.44 V), and t (69.37 min) were found to be the optimum anodization condition preceding a TiO2 nanotubes diameter of 99.31 nm and length of 4572.64 nm. It was observed that the nanotubes diameter and length are more affected by anodizing voltage and time, and less sensitive to NH4F concentration. Therefore, RMS could be an appropriate technique to optimize anodizing parameters for producing TiO2 nanotubes with good morphology.

Surge and lifting analysis of internal transmission gas–liquid two-phase flow lifting pipe

The gas–liquid two-phase flow inside large aspect ratio lifting pipes is often characterized by a complex flow pattern, potentially causing coupling vibration of the lifting pipe. And produce a surge effect, aggravating the vibration of the lifting pipe and thus affecting its fatigue life and the lifting performance of the pipe. In this paper, a combination of numerical simulation and experiment is used to investigate the effects of inlet flow rate (Q) and tube diameter (D) on the vibration and lifting performance of the lifting tube. The obtained conclusions are as follows: with an increase in the inlet gas flow rate, the amplitude of the lifting pipe increases, and the lifting flow increases; with an increase in pipe diameter, the amplitude of the lifting pipe decreases and the overall lifting performance increases. According to the numerical simulation and experimental results, when D = 40 mm lifting pipe at the intake flow between Q = 50-60 L/min, the impact of surge effect is the least, and the liquid lifting quality also reaches the best state at this time, The research presented in this paper provides a reference for the selection of parameters for lifting pipes in engineering applications.

A theoretical thermal model for a heat pump module using evacuated tube solar adsorption

The study focuses on analyzing a novel design of an evacuated glass tube solar adsorption cooling module, which combines an adsorption-based heat pump system and an evacuated glass tube solar collector into a single component module. The module consists of a single-wall evacuated glass tube, with the adsorbent bed (generator) located on one side (top section) and the evaporator/condenser with refrigerant on the other side (bottom section). The study presents a theoretical model of the module, based on previous experimental data, indicating promising results in terms of energy efficiency. The adsorbents examined, both zeolite 13X as well as silica gel type-RD, both adsorbents have an ideal design point in terms of adsorbent bed diameter, radiation heat flux, and glass tube diameter, as shown by the analysis. A comprehensive thermodynamic analysis of an evacuated tube adsorption heat pump module by analyzing the heat transfer mechanisms and energy balance involved in the module's operation. Through thermodynamic analysis, the solar coefficient of performance (COP) of evacuated glass tube adsorption heat pump module for zeolite and silica gel type-RD is 0.11 and 0.2 respectively.

Multi-response optimization of ejector for proton exchange membrane fuel cell anode systems by the response surface methodology and desirability function approach

ABSTRACT In a fuel cell system, the performance of the ejector is limited when it operates under off-design conditions. To improve the performance of the ejector under all operating conditions in the fuel cell system, this study employs a multi-response optimization approach to optimize the structural parameters of the ejector. The optimization objectives are the entrainment ratio under low-power and high-power operating conditions, with the optimization variables including the mixing tube diameter (D m ), primary nozzle exit position (L nxp ), and mixing tube length (L m ). A quadratic polynomial model is proposed to correlate the key structural parameters of the ejector with the entrainment ratio using the response surface methodology based on the Box-Behnken design. The optimal structural parameters of the ejector are obtained using the desirability function approach. The results demonstrate that this optimization approach significantly improves the ejector performance under off-design conditions while the performance remains essentially unchanged under high-power operating conditions.