Tube Internal Diameter Research Articles

DESIGN AND STUDY OF DIMENSIONAL PARAMETERS INFLUENCE ON VORTEX TUBE BEHAVIOR

Vortex tube is a thermodynamic device, with no moving parts, applied to separate hot and cold air from compressed air injected into the tube. It has many applications in the industry, for example, among others, it can be mentioned electronic systems cooling, machining processes cooling and environmental chambers. This paper presents the design and tube dimensioning based on parameters and data found in the literature. Therefore, a prototype has been made and tested, which allowed the understanding of the influence of internal tube diameter and width on the hot and cold air temperatures while submitted to compressed air with pressure varying from 1 to 2.5bar. Results of tested configurations indicates that the relation between tube length and diameter (L/D) has small influence on vertex tube behavior, meanwhile, 3/8” tube diameter shows lowest temperatures on cold flow (-6.5°C, -8.0°C and -8.5°C) and higher COP (≈ 0.15).

Experimental investigation and parameter analysis of LPG refrigeration system using Taguchi method

In this research work, an attempt has been made to study the liquefied petroleum gas (LPG) as an alternative refrigerant to eliminate the global warming potential causes many dangerous impacts on the environment by conventional refrigerants. An LPG refrigeration experimental setup has been fabricated using different lengths of capillary tubes, pressure regulator, evaporator, LPG supply unit, and gas burner. Initially, the parameters working ranges have been confirmed by conducting Exploratory experiments. The evaporator temperature is considered as response parameter which gives the proportionate changes of coefficient of performance. The effects of selected input parameters on evaporated temperature have been investigated. The capillary tube internal diameter, length of capillary tube and system operating time has been selected as input parameters. It was observed from literature survey that there was very few systematic experimentation and statistical analysis were only performed. Thus, L27 Taguchi’s design of experiment has been employed to conduct experiments and to identify the significant process parameters. The confirmation test has been conducted to validate the predicted result from the Taguchi method. It was observed that the evaporator temperature has been increased by increasing time of operation and coil diameter of capillary tube. However, the effect on inner diameter is directly proportionate to output response.

Pediatric tracheocutaneous fistula closure following tracheostomy decannulation

ObjectiveTo determine the frequency and risk factors that lead to the development of persistent TCF (tracheocutaneous fistula) formation in children following tracheostomy decannulation at our institution. MethodsA retrospective chart review of all pediatric patients at Children's Hospital Colorado who underwent tracheostomy decannulation and were being followed between January 1, 2007 and December 31, 2013. TCF was defined as a persistent fistula six months following decannulation. We determined patient demographics, age at tracheotomy, primary indication for tracheotomy, tracheostomy-tube size, medical comorbidities, age at decannulation, date of TCF closure, and method of TCF closure. ResultsOne hundred twenty-nine patients ranging from 51 days to 19 years of age underwent tracheostomy decannulation. 63 (49%) patients underwent surgical closure of TCF. Compared to those with spontaneous closure by multivariable analysis, those with surgical closure were younger at tracheostomy placement (p = 0.0002), had a tracheostomy for a longer duration (p = 0.0025), and were diagnosed with tracheobronchomalacia (p = 0.0051). The likelihood of spontaneous closure decreased over time. Tracheostomy tube internal diameter correlated with age (R = 0.64, p < 0.0001). ConclusionsApproximately 50% of pediatric tracheostomy stoma sites will close spontaneously. Development of a persistent TCF was associated with younger age at placement, longer duration of tracheostomy, and the presence of tracheobronchomalacia. These observations may help clinicians anticipate outcomes following tracheostomy decannulation in children.

The Influence of Technological Parameters on Drawing Force at Cold Drawing of Steel Tubes Using FEM Simulation

The process of cold die drawing of tubes is ranked among frequently used methods of production of seamless tubes and is performed in drawing tool which is characterized by simple design. Shape and dimensions of the drawing tool depend on tube reduction degree, i. e. on original diameter of initial tube and final internal diameter of the tube. Tube wall thickness is not determined by any tool. The technology of cold die drawing of tubes is influenced by various process parameters, i.e. geometry of the die itself, strain degree and strain rate, force conditions, conditions of friction, method of lubrication and the type of used lubricant. The contribution is concerned with evaluation of influence of the selected process parameters using FEM simulation. Designed graphs illustrate the impact of coefficient of friction and reduction cone of drawing tool on the size of drawing force.

Start-up in microgravity and local thermodynamic states of a hybrid loop thermosyphon/pulsating heat pipe

A wickless passive two phase closed loop heat transfer device especially designed for a future implementation on the heat transfer host module of the International Space Station is tested in relevant environment on board a parabolic flight. The tube internal diameter (3 mm) is larger than the static capillary threshold evaluated in normal gravity for this working fluid (FC-72), leading the device to work as a loop thermosyphon on ground and in hyper-gravity conditions, and as a Pulsating Heat Pipe when micro-gravity occurs. Novel start up tests, where the heat load has been provided after the occurrence of microgravity, show that the 20 s microgravity period is enough for the device activation and, most important, that the device activation is purely thermally induced and not affected by the previous acceleration field. Two miniaturized pressure transducers and direct fluid temperature measurement via two micro-thermocouples, allow to provide a detailed insight on the fluid local thermodynamics states both in the evaporator and in the condenser zone during microgravity. It is shown that the two-phase fluid close to the evaporator and the condenser is subjected to several degrees (up to 5 K) of superheating or subcooling. The level of subcooling seems to increase with the heat input level both in terms of temperature difference and in terms of percentage time with respect to the whole microgravity period.

Numerical Study on Oblique Hysteresis Performance of Composite-sectioned Square Concrete-filled Stainless Steel Tubular Columns

The composite-sectioned square concrete-filled stainless steel tubular column has the characteristics of high rigidity, strong integrity, reasonable force, beautiful structure and low maintenance cost. It has good performance in marine platform and cross-sea bridge structure and urban landmark buildings with high corrosion resistance. However, there are few studies on the performance and design methods of this kind of structure, which restricts its application. In this paper, Finite-element models (FEMs) for analyzing the tangential hysteresis behavior of the composite-sectioned square concrete-filled stainless steel tubular columns were established and verified. A parametric study was conducted on the influence of axial compression ratio, internal and external tube diameter ratio, and oblique angle. The calculated results showed that, the composite-sectioned square concrete-filled stainless steel tubular column has good oblique hysteresis ability, but the larger axial pressure ratio or larger oblique angle will weaken the capacity, while the pipe diameter has little effect on it.

Experimental Study on the Interfacial Evolution of Taylor Bubble at Inception of an Annulus

This present work reports results of an experimental campaign in a 20 mm internal diameter tube to comprehend the interfacial evolution of a fully developed Taylor bubble to an annular bubble at the inception of an annulus. The phenomenon has been observed by using a high speed photography camera and has been further analyzed by using image processing tools. Interfacial evolution is found to be a complex phenomenon with various physics rich processes occurring simultaneously in six stages, namely, retardation of fully developed Taylor bubble, plateau formation, doughnut shape formation and nucleation of lobes, preferential rise of leading lobe and retraction of lagging lobe, thread formation of lagging lobe, and finally, manifestation of an annular bubble. Effects of fluid viscosity and eccentricity on hydrodynamics features, such as annular bubble rise velocity, film thickness, nose shape, and reacceleration of the annular bubble are investigated in detail.

Experimental study on a hydrogen closed-loop pulsating heat pipe with two turns

A closed-loop pulsating heat pipe (PHP) with hydrogen as the working fluid has been tested at 10 different filling ratios (10–80%) and three condenser temperatures (19, 21, and 23 K) in vertical position. The PHP is made up of a capillary tube (internal and outer diameters of 2.3 and 3.3 mm, respectively) bended into a serpentine shape with 2 turns at each end. The lengths of the condenser, adiabatic and evaporator sections are 50, 500 and 50 mm, respectively. Experimental results show that the effective thermal conductivity of the PHP is between 30,000 and 70,000 W/(m·K), indicating that the PHP with 2 turns can run efficiently. The optimal filling ratio corresponding to the maximum effective thermal conductivity is different under different heat loads. Higher condenser temperatures are beneficial for the heat transfer, but do not affect the start-up.

Effects of Different Mixing Agents on the Stability of Sodium Tetradecyl Sulfate (STS) Foam: An Experimental Study.

To evaluate the effect of air, CO2 and contrast medium-air on the dwell time (DT) stability of sodium tetradecyl sulfate (STS) foam. Three types of foam sclerosants (air-foam, CO2-foam, contrast-air-foam) were injected eight times into an inclined straight plastic tube (internal diameters 4mm and 10mm) filled with a blood substitute. Injections were captured by CCD camera, and images were transferred for digital analysis and calculation of DT. Contrast-air-foam and air-foam in a 4-mm tube showed 5.6-/3.3-fold greater DT compared to CO2-foam, respectively (P = 0.001). Contrast-air-foam in a 10-mm tube showed 2.1-fold greater DT compared to CO2-foam (P = 0.0167). A mixture of air and iodinated contrast improves the stability of STS foam compared to mixtures using only air or CO2. Further, animal and clinical studies are needed to validate this in vitro result.

Using middle finger length to determine the internal diameter of uncuffed tracheal tubes in paediatrics.

The selection of an appropriately-sized tracheal tube is of critical importance in paediatric patients to reduce both the risk of subglottic stenosis from a tracheal tube that is too large, and inadequate ventilation or poor end-tidal gas monitoring from a tracheal tube that is too small. Age formulae are widely used, but known to be unreliable, often resulting in a need to change the tracheal tube. Previous work has shown that the length of the middle finger and the internal diameter can both be used to guide depth of tracheal tube insertion. Therefore, we hypothesised that middle finger length may also be related to tube internal diameter. We enrolled children aged up to 12 years presenting to our institution for elective anaesthesia and measured the length of the middle finger on the palmar aspect of the hand. Anaesthetists chose the airway device they felt most appropriate for the procedure, and were unaware of the middle finger measurement. Of 160 patients who were enrolled, 108 were included in the final analysis. We found a linear relationship between uncuffed tracheal tube internal diameter and median middle finger length for each size of tracheal tube. Relationship between middle finger length and cuffed tracheal tube internal diameter was less clear. We propose that the formula: 'middle finger length (cm) (round up to nearest 0.5) = internal diameter of uncuffed tracheal tube (mm)' may be an improvement compared with age formulae for selecting uncuffed tracheal tubes in children, although this requires formal testing.

Meta-heuristic and RSM approach for Multi-objective Optimization of Plain Flow Refrigerant Vapor Condensation inside Tubes

Condensers are extensively used heat exchangers in automobiles and air conditioning systems. Optimization of heat transfer and pressure drop inside condensers is an important area of concern for the designers. In the present study, condensation characteristics inside smooth horizontal tubes is optimized using teaching-learning based optimization (TLBO) algorithm and response surface methodology (RSM). Refrigerant mass velocity (G), vapor quality (x) and tube internal diameter (Di) are taken as design parameters. Heat transfer coefficient (h) and pressure drop (ΔP) values of refrigerants are calculated based on the mathematical models and served as objective functions for RSM. The same mathematical models are applied to formulate a multi-objective optimization problem with an aim to maximize heat transfer coefficient and minimize pressure drop and is solved using TLBO. Two different refrigerants have been considered to display the application of the approaches. Of the two methods applied, TLBO seems to give better optimum results.

Thermal performance of a meter-scale horizontal nitrogen Pulsating Heat Pipe

Cooling dry superconducting magnets using cryocoolers as a cold source is becoming a standard. Due to their simple operation, compact configuration, lightness, and thermal performance, Pulsating Heat Pipes (PHP) are good candidates, as two-phase thermal links, for these kind of systems. Initially developed to cool small electronic devices at ambient temperature, PHP have been also studied, in the cryogenic field, using N2, He, Ne and H2 as working fluids. In this paper, we present the thermal performances of a 1 m long horizontal PHP made of 36 stainless steel parallel tubes. The tube internal diameter is 1.5 mm, close to the critical diameter (∼1.7 mm) to maintain capillary forces necessary to the PHP operation. Both, the evaporator and condenser sections are copper made and are separated by an adiabatic section. This PHP has been studied using N2 as working fluid with the condenser temperature maintained at 75 K. Several pressure and temperature sensors placed in the three different sections allow monitoring the thermodynamic behavior of the PHP. Tests have been performed increasing and varying the input power as well as keeping it constant during long periods of time. The maximum equivalent thermal conductivity measured is 85 kW/m·K. This system can transfer a maximum heat power of 25 W before reaching its operation limit.

Experimental study on phase separation of refrigerant at horizontal T-junction

In this paper, the phase redistribution of refrigerant two-phase flow at a horizontal branch T-junction was investigated experimentally. The T-junction had equal-sized inlet and outlet tubes (internal diameter 8.0 mm). During the experiments, three refrigerants, namely R134a, R600a and R245fa were considered. The inlet mass flux and quality were varied from 200 to 500 kg m−2 s−1 and from 0.1 to 0.9, respectively. Meanwhile, the mass flux of the branch was regulated by keeping the mass flow ratios to 0.3, 0.5 and 0.7. Under these experimental conditions, intermittent and annular flows at the T-junction inlet were identified and predicted. After analyzing the experimental data, it was found that the vapor is preferred to flow into the branch. As the inlet quality increases, the fraction of vapor extracted into the branch decreases, whereas the mass flux has little influence on the phase redistribution of refrigerant under the same flow pattern. Furthermore, a higher vapor fraction can be obtained by a larger mass flow ratio. For the effect of refrigerant on the phase separation, the vapor faction of the branch satisfies the following order: R245fa > R600a > R134a. The product of momentum ratio and viscosity ratio between vapor and liquid is defined to characterize the phase separation degree of refrigerant qualitatively. In order to test the applicability of the published models in the literature, the present data are compared with the predicted values. The results show that the models for air-water are not appropriate to predict the phase redistribution of refrigerant two-phase flow at the T-junction. A separation model for refrigerant should be proposed by coupling with the pressure drop.

Characterisation of 40 mg/ml and 100 mg/ml tobramycin formulations for aerosol therapy with adult mechanical ventilation

BackgroundPreservative-free tobramycin is commonly used as aerosolized therapy for ventilator associated pneumonia. The comparative delivery profile of the formulations of two different concentrations (100 mg/ml and 40 mg/ml) is unknown. This study aims to evaluate the aerosol characteristics of these tobramycin formulations in a simulated adult mechanical ventilation model. MethodsSimulated adult mechanical ventilation set up and optimal settings were used in the study. Inhaled mass study was performed using bacterial/viral filters at the tip of the tracheal tube and in the expiratory limb of circuit. Laser diffractometer was used for characterising particle size distribution. The physicochemical characteristics of the formulations were described and nebulization characteristics compared using two airways, an endotracheal tube (ET) and a tracheostomy tube (TT). For each type of tube, three internal tube diameters were studied, 7 mm, 8 mm and 9 mm. ResultsThe lung dose was significantly higher for 100 mg/ml solution (mean 121.3 mg vs 41.3 mg). Viscosity was different (2.11cp vs 1.58cp) for 100 mg/ml vs 40 mg/ml respectively but surface tension was similar. For tobramycin 100 mg/ml vs 40 mg/ml, the volume median diameter (2.02 vs 1.9 μm) was comparable. The fine particle fraction (98.5 vs 85.4%) was higher and geometric standard deviation (1.36 vs 1.62 μm) was significantly lower for 100 mg/ml concentration. Nebulization duration was longer for 100 mg/ml solution (16.9 vs 10.1 min). The inhaled dose percent was similar (30%) but the exhaled dose was higher for 100 mg/ml solution (18.9 vs 10.4%). The differences in results were non-significant for type of tube or size except for a small but statistically significant reduction in inhaled mass with TT compared to ET (0.06%). ConclusionAerosolized tobramycin 100 mg/ml solution delivered higher lung dose compared to tobramycin 40 mg/ml solution. Tracheal tube type or size did not influence the aerosol characteristics and delivery parameters.

Numerical simulation of condensation inside an inclined smooth tube

In this study the condensation phenomena inside an inclined smooth tube were investigated. The tube internal diameter was 8.38 mm, and its length was 1488 mm. The condensing fluid was R134a at a saturation temperature of 40 °C. The Volume of Fluid (VOF) multiphase-flow formulation was utilized to solve the governing equations of continuity, momentum, energy and turbulence. The flow field was assumed to be unsteady, turbulent and three-dimensional. The fluid properties were considered to be constant as temperature changes were negligible. The effects on heat transfer coefficients of various parameters were investigated. These parameters included tube inclination angle, vapour quality, refrigerant mass flux, and flow regimes. Simulations were conducted at a heat flux of approximately 5 kW/m2, mass fluxes of 100–600 kg/m2·s, while the inclination angles of flow were varied between vertical downward, to vertical upward. The results of the simulations were compared to an experimental database and a good agreement was found with the experimental data. The numerical simulations gave new perspectives and complementary information that was not determined experimentally. The results showed that an optimum downward inclination angle of between −30° and −15° exists, for the heat transfer coefficients.

SOFTWARE SOLEEC PARA EL DISEÑO DE CONCENTRADORES SOLARES DE CANAL PARABÓLICO CON GENERACIÓN DIRECTA DE VAPOR

In recent years, the implementation of computational tools for analyzing, optimizing and designing thermal devices is an effort where several researches are focused and the application to concentrating solar collectors is not excluded of this tendency and this is the concern of the present work, which describes the application of software SOLEEC for parabolic trough solar collector (PTC) designing with direct steam generation systems (DSG). The software is a developed computational tool using MATLAB as programming language and can be used for designing a solar system for any longitude and any latitude (except for polar caps), and even it can be used for the evaluation of the solar resource availability. For designing DSG systems the absorber tube is divided into three sections: preheating, evaporation and overheating, so the adequate mathematical models for every section are introduced into the software’s codex and some graphical interfaces for designing and assessment are created. Some input data such as solar irradiance, absorber’s tube internal diameter, air temperature and velocity, working pressure, inlet water temperature and output steam temperature are necessary for executing the software. The user can choose among the most used construction materials as for the reflective surface, selective surface and coating tube. Finally, the software shows in tables the geometrical data for the collector such as: parabola aperture, total length, focal distance, coating tube diameter and thickness, also the thermal evaluation results as heat gain, heat losses, length for every section, necessary mass flux, thermal efficiency and the temperatures for the absorber and coating tubes respectively. A maximum error of 2% was found when the software is validated with other researches results.

4D Biofabrication Using Shape-Morphing Hydrogels.

Despite the tremendous potential of bioprinting techniques toward the fabrication of highly complex biological structures and the flourishing progress in 3D bioprinting, the most critical challenge of the current approaches is the printing of hollow tubular structures. In this work, an advanced 4D biofabrication approach, based on printing of shape-morphing biopolymer hydrogels, is developed for the fabrication of hollow self-folding tubes with unprecedented control over their diameters and architectures at high resolution. The versatility of the approach is demonstrated by employing two different biopolymers (alginate and hyaluronic acid) and mouse bone marrow stromal cells. Harnessing the printing and postprinting parameters allows attaining average internal tube diameters as low as 20 µm, which is not yet achievable by other existing bioprinting/biofabrication approaches and is comparable to the diameters of the smallest blood vessels. The proposed 4D biofabrication process does not pose any negative effect on the viability of the printed cells, and the self-folded hydrogel-based tubes support cell survival for at least 7 d without any decrease in cell viability. Consequently, the presented 4D biofabrication strategy allows the production of dynamically reconfigurable architectures with tunable functionality and responsiveness, governed by the selection of suitable materials and cells.

The role of ultrasound in appropriate endotracheal tube size selection in pediatric patients.

The aim of this prospective study was to investigate the success of ultrasound in pediatric patients in determining the appropriate sized cuffed endotracheal tube and to compare the results with conventional height-based (Broselow) tape and age-based formula tube size. One hundred and fifty-two children of 1-10 years of age, who received general anesthesia for adenotonsillectomy were enrolled to the study. In all participants, the transverse diameter of the subglottis was measured with ultrasound during apnea. An endotracheal tube was chosen with the outer diameter matched to the measured subglottic airway diameter. An age-based (Motoyama-Khine) and height-based (Broselow) endotracheal tube size was calculated. If there was resistance to passage of the tube into the trachea or an airway pressure >25 cmH2 0 was required to detect an audible leak, the endotracheal tube was replaced with internal diameter of 0.5 mm smaller. If there was an audible leak at airway pressure <10 cmH2 O, or peak pressure >25 cmH2 0 or a cuff pressure > 25 cmH2 O was required to seal, the tube was changed to the 0.5 mm larger internal diameter. Best-fit tube internal diameter was the resultant tube internal diameter that met the previously stated conditions. The need for endotracheal tube replacement and peak airway pressure were recorded. The internal diameter of ultrasound determined tube was the same as best-fit tube in 88% of children. Endotracheal tube was replaced in 15 patients with a one size larger, and in three patients with one size smaller tube. Using Bland-Altman analysis, a better agreement was observed with ultrasound measurement rather than height-based estimation and age-based formulas. Our findings show that subglottic diameter measured by ultrasound appears to be a reliable predictor for the assessment of the subglottic diameter of the airway in estimating appropriate size pediatric endotracheal tube.

Adherence to Evidence-Base Endotracheal Intubation Practice Patterns by Intensivists and Emergency Department Physicians.

Endotracheal intubation outside the operating room (OR) is mainly performed by intensive care (IC) physicians and emergency department (ED) physicians. We hypothesized that difference in practice patterns exists between these two groups of physicians. A retrospective chart review was performed on all endotracheal intubations that were performed out of OR over a fi ve year period at our health care facility. Practice patterns of IC and ED physicians were compared regarding use of (a) video laryngoscopy, (b) paralytic agents, (c) waveform capnography, and (d) use of larger size of endotracheal tube (internal diameter ≥ 8 mm). A total of 201 patients underwent out of OR intubations over a 5 year period. IC physicians used more often than ED physicians video laryngoscopy (67% vs. 49%; p = 0.008), waveform capnography (99% vs. 86%; p = 0.001) and larger size endotracheal tubes (95% vs. 60%; p < 0.001). Conversely, paralytic agents were used less frequently by IC than ED physicians (12% vs. 51%; p < 0.001). The success of fi rst intubation attempt was higher by IC than ED physicians (82% vs. 67%; p = 0.018). IC physicians more often adhered to currently considered preferable practices for endotracheal intubation than ED physicians in this single center retrospective study. Although larger scale studies are needed to unveil the effects of different practice patterns on short and long term outcomes, the present study identifi es opportunity to bridge practice gaps that could lead to improved outcomes.

Condensation heat transfer and pressure drop characteristics of R-600a in horizontal smooth and helically dimpled tubes

In the present study, condensation heat transfer and frictional pressure drops of refrigerant R-600a (iso-butane) inside a helically dimpled tube and a plain tube of internal diameter 8.3mm were measured and analyzed. All tests were performed at different vapor qualities up to 0.82 and average saturation temperatures ranging between 38 and 42°C. Refrigerant mass fluxes varied in the range of 114–368kg/m2s. The inner surface of the helically dimpled tube has been designed and reshaped through three-dimensional material surface modifications consists of both shallow and deep protrusions which are placed evenly in helical directions on the tube wall. The experimental results show that the heat transfer coefficients of the dimpled tube are 1.2–2 times of those in smooth tube with a pressure drop penalty just ranging between 58% and 195. The highest heat transfer coefficient is occurred at vapor quality of 0.53 and mass flow rate of 368kg/m2s. On the other hand, the maximum increase of pressure drop takes place at vapor quality of 0.55 and mass flow rate of 368kg/m2s.