Tube Internal Diameter Research Articles

Exchange rates of second generation Microcuff® pediatric endotracheal tubes in children weighing more than 3 kg : A retrospective audit.

Cuffed endotracheal tubes (cETT) pose the potential advantage of an infrequent need for reintubation in pediatric patients compared to uncuffed tubes. The aim of this study was to investigate tube exchange rates using second generation Microcuff® pediatric endotracheal tubes (PET) with an adapted sizing recommendation in alarge single institution cohort of children and to identify potential variables associated with an elevated risk of tube exchange. Patient data obtained from the electronic patient data management system of the Department of Anesthesia, University Children's Hospital Zurich, Switzerland, were retrospectively assessed for demographic and anthropometric information, size of the internal tube diameter used for positive pressure ventilation and divergence from the size recommendation chart. Data from 14,188 children younger than 16years (median 5.3years) and weighing at least 3 kg who underwent oral or nasal tracheal intubation using second generation Microcuff® PET between 2009 and 2015 were included. Of 13,219 oral tracheal intubations 12,049 (84.9%) were performed according to the manufacturer's size recommendation and 1170 with divergent endotracheal tubes. The odds ratio (OR) of oral reintubation was 0.13% (95% confidence interval 0.08-0.22%) for cases using the manufacture's size recommendation correctly and 22.74% (95% confidence interval 20.42-25.23%) for patients intubated with anot recommended tube (p < 0.0001). These findings indicate that the second generation Microcuff® PETs can be reliably used with low tube exchange rates across the entire pediatric age range when the tube size is selected according to the manufacturer's size recommendation chart. Adherence to the manufacturer's tube size recommendation is urgently advised.

Development and Assessment of the Performance of a Novel Parabolic Trough Solar Collector-Driven Three-Stage Cooling Cycle

Abstract A gaseous flow is employed as heat transfer fluid (HTF) in a parabolic trough solar collector (PTSC) for simultaneous production of cooling at three different levels of temperature to meet the demands of air conditioning, refrigeration, and ultra-low-temperature refrigeration required to ensure the efficacy of some special vaccines. The combined system consists of five subsystems including PTSC, Kalina cycle (KC), ejector refrigeration cycle (ERC), cascaded refrigeration cycle (CRC), and absorption refrigeration cycle (ARC). A simulation through an engineering equation solver (EES) is conducted to assess the impact of internal tube diameter of absorber and solar irradiation on rise of HTF temperature and mass flowrate of Kalina cycle fluid. It is determined that for given solar irradiation, the temperature of HTF goes down when internal diameter of absorber tube is enlarged. The influence of weather conditions; solar irradiation and ambient temperature, type of HTF, and concentration of ammonia–water basic solution on thermal and exergy efficiencies of three-stage cooling cycle (TSC) are examined. The TSC with helium-operated PTSC delivers better results than air and CO2. Exergy analysis shows that solar collector (30.26%) dissipates the highest exergy, followed by the ejector (12.5%) and vapor generator subsystem (7.61%). The type of CRC fluid pair affects TSC cycle refrigeration capacity and cooling exergy efficiency. The promotion of solar irradiation from 850 to 1200 W/m2 increases the cooling exergy efficiency of the three-stage cycle from 6.72% to 9.52% when the evaporator temperature is set at −45 °C and CRC employs NH3-propylene.

Advanced ultrasound techniques for studying liquid–liquid dispersions in confined impinging jets

Advanced ultrasound techniques were used to study liquid–liquid dispersed flows formed in impinging jets confined in small channels. Ultrasound speed and attenuation coefficient spectra of the propagated sound waves were used to obtain volume fraction and drop size distributions, respectively. The results were compared against drop size distributions obtained with high-speed imaging. Experiments were conducted in a 2 mm internal diameter tube for both kerosene oil continuous and glycerol/water continuous dispersions. The overall mixture flow rate was set at 60 ml/s, and the dispersed phase fractions were 0.02, 0.05, and 0.10. The measured volume fractions were found to be very close to the input ones, indicating a very small slip between the phases in the dispersed flows. From the ultrasound measurements, the drop size distributions were found to range from 32 to 695 μm under the different conditions used. The drop sizes at the two low input volume fractions were in reasonable agreement with the results from the imaging. Imaging, however, could not be used for the 0.10 input dispersed phase fraction. These results demonstrate the applicability of the ultrasound techniques to measurements in dispersed liquid–liquid flows in small channels.

Detailed visualization experiments on the start-up process and stable operation of pulsating heat pipes: Effects of dividing boards

To broaden the applicable orientation for the existing closed loop pulsating heat pipe (CLPHP) with a relatively large tube (internal diameter of 6 mm), this work fabricated a novel quartz CLPHP inserted with a dividing board in the straight section of each tube. The dividing board forms two semi-circles with an effective hydraulic diameter (Dh) of 3.09 mm. This method amplifies the surface tension effect with almost no change in the mass inventory of working fluid. Through a series of visualization experiments, the effect of filling ratio (FR) on the pulsation in the boarded model are first revealed by comparing with the original non-boarded CLPHP under the vertical and the horizontal orientations. The four longitudinal corners generated by dividing board are found not only accelerated the drain down of the liquid slugs but beneficial to the onset of nucleate boiling, prompting the threshold of pulsation motion for 10 - 20 W. Also, the visualization results for the vertical orientation show that the sealing between the dividing boards and the inner tube had a great impact on the performance and heat transfer behavior. The thermal resistance can be improved by 22 - 43 % without leakage between the semi-circles. Under the horizontal orientation, the boarded CLPHP with only three number of turns can be incited with pulsation motion successfully. The boarded design provides additional vapor channels and avoids the liquid slug trains being pushed away from the evaporator during the initial heating period. Also, the un-balanced capillary force due to the hydraulic diameter difference can sustain subsequent pulsation motion. However, the success under only FR = 50 % indicates that an appropriate FR was also necessary.

Ammonia single-phase and two-phase frictional pressure losses in horizontal smooth and straight inner-grooved tubes

The experimental study of single-phase and two-phase frictional pressure losses has been performed with ammonia flow in stainless steel smooth tubes (internal diameter of 5.5 mm and 8.5 mm) and six straight inner-grooved aluminium tubes with different nominal diameters (7.15 to 13.3 mm), length (0.45 to 2.0 mm) and thickness (0.35 to 0.8) of fins. Single-phase test boundary conditions correspond to Reynolds numbers of 1000 to 20,000. Two-phase tests have been carried out at saturation temperature of 45 to 65 °C, mass velocity of 50 to 210 kg·m−2s−1 and vapour quality of 0.1 to 0.9. Comparison of obtained test data with the existing frictional losses approaches shows that the Blasius model is appropriate to single-phase flows in smooth tubes, and Müller-Steinhagen and Heck's (1986) model is most accurate in predictions of two-phase frictional losses in smooth tubes. Existing approaches of single-phase frictional pressure loss predictions in the pipes and channels with longitudinal fins (Carnavos, 1980; Edwards and Jensen, 1994) are not adequately suited to the ammonia test points obtained in the considered straight inner-grooved tubes. A new semi-empirical model has been proposed, based on generalisation around the revealed geometric dimensionless factor, which accurately describes friction pressure losses in the considered inner-finned profiles. The simplest homogeneous model for defining two-phase friction pressure losses, using McAdams et al.'s (1942) recommendation for mixture dynamic viscosity definition and a new model of single-phase friction factor, best fit both quantitatively and qualitatively to ammonia two-phase test points in most of the considered straight inner-grooved tubes.

Transition to detonation in hydrogen-air mixtures due to shock focusing in a 3-wall 90-deg corner

This work presents an experimental investigation on the transition to detonation due to shock-wave focusing in a 3-wall 90-deg corner in hydrogen-air mixtures (17.5 – 60% H2) initially at 298 K and 1 bara. The reflector was placed at one side of 2 – m long, 0.14 m internal diameter tube. The other side of the tube was equipped with an ignition source and a flame acceleration section. The shock wave approached the reflector with a velocity in the range of 580 – 970 m/s. The reflector was placed symmetrically to the tube axis. The research proved that transition to detonation due to shock focusing highly depends on the shock wave strength and can be triggered in a stoichiometric mixture at shock speed VS = 605 m/s which corresponds to M = 1.485 or 59.9% of the speed of sound in combustion products. The ignition delay time recorded for transition to detonation was at the order of few microseconds. The detonability range observed with the 3-wall 90-deg reflector proved to be 15 - 70 % H2 in air compared to 18 - 59% H2 observed in work performed for a 90-deg wedge reflector configuration at the same initial conditions. Additionally, the scaling factor between critical shock velocity between both types of reflectors is almost constant and equal to 0.84 throughout the investigated mixtures. The high focusing ability of the 3-wall corner has also proved the minimum transition pressure recorded in the corner tip at the level of 8.95 MPa in a stoichiometric mixture. This value corresponds to a nearly 17-fold increase in pressure compared to normal shock post-reflection conditions. Considering the shock focusing as the major trigger for detonation the presented results may explain the differences between the detonability limits observed in obstacle-laden ducts and large-scale experimental setups.

The development of prediction model for cuffed tracheal tube size from the middle finger in pediatrics: a concise and feasible approach.

Selecting the optimal tracheal tube size is critically important for pediatric patients. Age-based formulas are often used, but still have limitations. The aim of this prospective study was to investigate whether middle finger measurements correlate with cuffed tracheal tube size and to further develop a prediction model based on these measurements. Patients under 12 years of age scheduled for elective surgery involving tracheal intubation were enrolled in the study. The length was determined from the tip of the distal metacarpal to the palm's root on the palm side, while the circumference was measured at the base of the palm using a soft tape measure. The appropriate cuffed tracheal tube size was determined based on specific criteria. If the tube encountered resistance during insertion or required an airway pressure >25 cmH2O to detect an audible leak, it was replaced with a tube 0.5 mm smaller. Conversely, if an audible leak occurred at an airway pressure <10 cmH2O, or peak pressure >25 cmH2O, or the cuff pressure >25 cmH2O to achieve a seal, the tube was exchanged for one with a 0.5 mm larger. Linear regression analysis was used to examine the association between middle finger circumference and length with the cuffed tracheal tube size. Subsequently, regression equations were constructed based on the results of the linear regression analysis and their predictive performance was compared to the conventional age-based formulas, including the Khine formula and Motoyama formula. The predictive performance was evaluated by mean absolute error (MAE), root mean square error (RMSE), and prediction accuracy. A total of 261 patients were analyzed in our study. The mean age of the patients was 46.19±35.83 months. The linear relationship was observed between the cuffed tracheal tube size and the middle finger circumference and middle finger length with R2 values of 0.77 and 0.73, respectively. In comparison to conventional age-based formulas, both middle finger circumference and middle finger length demonstrated superior predictive performance, characterized by lower MAE and RMSE, as well as higher prediction accuracy. Notably, the regression equation based on the middle finger circumference obtained the higher predictive accuracy of 0.590, with an MAE of 0.259 and an RMSE of 0.333 as opposed to the predictive accuracy of 0.391, MAE of 0.349, and RMSE of 0.473 derived from conventional age-based formulas. Based on the regression coefficients of linear regression, simplified formulas were proposed, with the middle finger circumference-based formula emerging as the most accurate and simple option. The appropriate cuffed tracheal tube size could be predicted by the middle finger circumference. Our proposed formula 'cuffed tracheal tube internal diameter (mm) = middle finger circumference (cm) - 0.2' has the potential to improve the selection of the cuffed tracheal tube size in pediatric patients.

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.

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

Optimization of low-NOx Burner Under the Combined Influence of Multiple Factors

ABSTRACT The influence degree of structural parameters and operating parameters on the low NOx performance of burners was studied by numerical simulation and orthogonal experiment. Excess air coefficient (factor A) and flue gas circulation rate (factor B) were used as operating factors, fuel nozzle diameter (factor C), cyclone blade end deflection angle (factor D), flame-stabilizer inclination angle (factor E), and internal circulation tube diameter (factor F) were used as structural factors, the average temperature (T av), maximum temperature (T max) of the combustion chamber, and NO emission value at the combustion chamber outlet (M NO) were used as indicators. Range analysis and variance analysis were used to analyze the specific influence of the above factors on the indicators. In the studied cases, the most significant factor affecting T av and M NO is the factor B, followed by the factor C. The more significant factor affecting T max is the factor A, followed by the factor C. The coupling of multiple parameters has a significant effect on the distribution of flow field in the combustion chamber. Vortices are produced in all the cases studied. The vortices are basically symmetrical, but the number of vortices varies from 2 to 6. The results show that the burner has good flame stability.

Development of Non-destructive Testing Method for Tube Inspection in Fin-Fan Coolers in Kazakhstan’s Oil/Gas, Chemical and Power Industries.

Many oil/gas fields in Kazakhstan contain high levels of highly corrosive H2S and CO2, sometimes at very high pressures. The management of corrosion is essential in maintaining plant safety and integrity of the processing facility. This paper describes the development of a non-destructive testing (NDT) method that improves the reliability of air-cooled heat exchangers by reducing down-time related to corrosive and erosive failure of fin-fan tubes. The project goal was to maximize the output of oil and gas plants and refineries while reducing the plant operating cost. The work first identified those NDT requirements for air-cooled heat exchangers damage assessment that would provide the greatest economic benefit for Kazakhstan industry. The main objective was to develop a state-of-an-art NDT method for air-cooled heat exchanger tubes, capable to: a) detect any damage mechanism while testing from tube internal diameter, b) accurately determine the damage in terms of wall loss, c) perform inspection quickly and expediently, d) requires minimum tube cleaning. Consequently, the method specially adapted for Kazakhstan conditions was developed based on a combination of Magnetic Flux Leakage (MFL) technique for flaw detection and with Hall effect measurement of wall thickness and gradual corrosion in tubes. The method has been tested in both laboratory and field conditions and the results were compared with accurate but slow ultrasonic IRIS method. High correlation was obtained, which proved that the developed technology is capable to deliver similar results at the speed almost 10 times faster and less than half the cost.

Accuracy of pilot balloon palpation for cuff pressure assessment in small versus large sized tubes: a prospective non-randomized observational study

Pilot balloon palpation is still a commonly used method to evaluate cuff pressure of the endotracheal tube after intubation. This study determined whether the size of the tracheal tube influenced the accuracy of pilot balloon palpation. A prospective observational analysis of 208 patients intubated with an endotracheal tube of internal diameter (ID) 6.0 or 8.0 was conducted. An anesthesiologist judged the cuff pressure by manual pilot balloon palpation, and then measured the cuff pressure with a pressure gauge. Cuff pressure exceeding 20–30 cmH2O was defined as false recognition. The intracuff pressure was significantly higher in ID 6.0 tube than in the ID 8.0 tube (41.9 ± 18.8 cmH2O vs. 30.3 ± 11.9 cmH2O, p < 0.001). The number of patients that were mistakenly perceived to have appropriate cuff pressure by pilot balloon palpation was significantly higher in the ID 6.0 group compared to the ID 8.0 group (85 (81.7%) vs. 64 (61.5%), p = 0.001). Therefore, a smaller tube size may further increase risk of inaccurate measurement by pilot balloon palpation and although pressure gauge is recommended for all sizes to maximize accuracy, groups with increased risk factors should be targeted for standardized use of the pressure gauge.

Enhanced internal condensation of R1233zd(E) on micro- and nanostructured copper and aluminum surfaces

In-tube condensation of refrigerants is an important process which affects thermal efficiency in many applications, ranging from refrigeration and air conditioning to electronics thermal management. In-tube heat transfer and pressure drop are important to heat exchanger sizing and design. In this work, micro- and nanostructured surfaces are applied to the internal wetted areas of copper and aluminum mini-channels to enhance the condensation heat transfer coefficient of hydrofluorocarbon R1233zd(E) refrigerant. To achieve scalable nanomanufacturing, surfaces were uniformly structured by relying on hydrochloric acid etching of aluminum and chemical oxidation of copper. The etched aluminum surfaces exhibited a 150% increase in heat transfer coefficient compared to smooth aluminum channels at specific qualities, with a 66% heat transfer coefficient improvement for complete phase change from saturated vapor to saturated liquid. Copper oxide structures showed no discernable difference in thermal-hydraulic performance when compared to smooth copper channels. Critical dimensionless parameters governing the heat transfer enhancement were identified by varying the tube internal diameter (2.3 mm to 4.7 mm), refrigerant mass flux (50 to 300 kg/(m2·s)), and refrigerant quality (0 to 1). The dimensionless parameters include the Bond number normalized to the condensate film thickness, and the Weber number modified by the vapor friction factor. The relatively small increase in pressure drop (< 10%) associated with these surface enhancements further supports the promise of this method. The scalable and cost-effective techniques used to create these aluminum microstructures may reduce manufacturing cost when compared with current enhancement approaches such as extrusion, drawing, and welding.

A Review on Pulsating Heat Pipe With Different Working Parameters Affecting The Performance

Every area of engineering is advancing, which is driving up demand for more compact and efficient heat transfer devices. Pulsating heat pipe development results from this (PHP). For managing moderate to high heat fluxes, PHP is a passive two-phase heat transfer device best suited for power electronics and related applications. A tiny diameter tube that is closed end to end to form a loop, is typically used. After being evacuated, the tube is partially filled with a working fluid. The applied heat flux determines the internal flow patterns in a PHP. The thermo-hydrodynamic properties of these devices are highlighted in this work. According to the state of the art, the device has to satisfy at least three thermo-mechanical boundary criteria in order to work as a pulsing heat pipe. Internal tube diameter, applied heat flux, and filling ratio are examples of this. The number of turns and thermo-physical characteristics of the working fluid also have a significant impact on the thermal behaviour. In addition, the report offers a review of previous studies on the use of pulsing heat pipes. Lastly, open questions regarding the process by which PHP operates with various working fluids, validation methods, and applications are explored.

Pulsation incitation and performance investigations for 3D Fin-and-Tube heat pipe heat exchanger by inserting dividing boards for various working fluids

In our previous study, we have shown that a heat pipe heat exchanger system modified from a commercial air-to-air heat exchanger operates without pulsations for working fluids of dielectric HFE-7000 or R134a, or under low heat loads for water, due to the large internal tube diameter of 5.6 mm. To incite pulsation and enhance the thermal performance, a straight dividing copper board is inserted into the straight section of each of the tube to form two semicircular compartments with an effective hydraulic diameter of 3.4 mm. The heat transfer characteristics and thermal performance against the hot air inlet temperature for the novel boarded model and the non-boarded model are experimentally explored with three working fluids (water, HFE-7000 and R134a) under six filling ratios (35%, 38.5%, 50%, 55%, 65%, 71.5%). Because water already works in a PHP mode in the non-boarded model under high heat loads, the thermal performance in the boarded model improved mildly by 2.7%–10.6%. Whereas, for HFE-7000 and R134a, the heat transfer mode is successfully incited from thermosyphon in the non-boarded model into PHP in the boarded model. The most significant thermal performance improvement was observed for HFE-7000 by 8.3%–24.5%. The improvement can be attributed to the switch of heat transfer mode, the generated corners for condensate accumulation, and the additional heat conduction via the copper board.

Performance Evaluation and Optimization of a Two Horse Power Concentric Tube Heat Exchanger

The aim of this research work was to improve the performance of a two horse power (2hp) shell and tube heat exchanger. The available area obtained from calculation is 3.77×10-³m2 and 383.75W/M²K. Overall heart transfer coefficient was obtained. The heat exchanger was satisfactory and consists of one pass copper tube of internal diameter 10mm and length 120mm. The shell length and internal diameter of the shell are 95mm and 60mm respectively. The concentric tube heat exchanger has a total length of 245mm and 136mm width. The hot fluid passes through the copper tube while the cold fluid move on the annulus made of mild steel. The results of the experiment shows that the heat was transferred from the hot fluid gradually move counter currently to the cold fluid in the same direction of flow. Mild steel was used for the construction of the shell while copper was used for the tube. The efficiency is 51.89% was obtained. This confirmed that the optimized equipment is more efficient than initial machine performance efficiency of 40.76%. Significantly, this equipment is of great need when vaporized liquid must be recovered back as liquid at specified conditions and also control the flow of thermal energy between two terminals.

Investigation of newly designed Alternate Perforated V-Notch (APVN) twisted tape with heat transfer characteristics

Swirl device is seen as a path to enhance the efficiency of a thermal switch. Swirl device with fabricated form of porosity and v-cuts twisted tape (tt) inner pipe insert helps to augment performance by improving the heat transfer (U) coefficient. This work is related to the thermal performance factor (TPF), friction factor (ff) and Nusselt (NNu) number in the inner tube inserted with a innovative design of Alternate Perforated V-Notch (APVN) tape having twisted ratio 6.25 incorporating porosity amount of Rp = 1.087% and width (w/W) ratio = 0.333, were investigated features to improve heat transfer rate. Enhancement in turbulent generation of the primary flow into the secondary flow with this design. Experiment test was performed on a pipe in pipe tubes of (d) internal diameter of 0.013 m with test section length of 0.9 m. Temperature of the warm water had kept constant at 60 °C within the Reynolds number range of 2246–16,224. The heat exchanger with empty tube (without tt) and the input of normal twisted tape (tt) has been checked. In addition to the investigated range, NNu, ff and TPF in the tube with APVN twisted tape insertion were observed (Rp - ratio) 1.833–2.276, 2.155–4.549 and 1.84–1.778 times more than the values of empty tube. The presented work is very useful in the field of energy conservation through maximum transfer of heat in the industrial process.

Compressive behavior of circular steel tubed high-strength concrete columns with embedded steel tubes

This paper presents an experimental study on circular steel tubed high-strength concrete columns embedded with steel tubes under axial compression. A total of 18 columns were tested in this study to investigate several parameters covering the continuity conditions for external steel tubes, diameters of internal steel tubes, thicknesses of external and internal tubes, and the number of CFRP layers. Test results show that the strength of specimens is improved to different levels due to the discontinuous external tubes and embedded internal tubes, and a significant enhancement can be achieved in terms of ductility and residual strength. Moreover, the concrete core as well as the sandwich concrete exhibits superior compressive behavior as the internal steel tube diameter increases under a constant steel ratio. Besides, when the external tubes are wrapped with CFRP jackets, more effective confinement can be provided for the inner concrete, while the effect of the position of internal steel tubes become less obvious. Finally, several existing models are selected to predict the axial stress-strain responses of the concrete in tubed columns. It is found that only two models can provide relatively reasonable predictions for the average axial stress-strain curves of concrete, but considerable overestimations of the ultimate stress are still observed for these two models, which indicates that further investigation is needed to develop a more accurate model.

Thermodynamic investigation of a novel cooling-power cogeneration system driven by solar energy

This communication develops a novel cooling-power cogeneration system consisting of a parabolic trough collector utilizes gasses as the medium for solar to heat conversion, and the Kalina cycle integrated series-flow double effect LiBr-H2O absorption chiller to generate electricity and large cooling, simultaneously. By developing a thermal model, a simulation through EES is conducted to investigate the influence of internal tube diameter of absorber and solar irradiation on the exit temperature of SHTF and flowing mass of the working fluid of Kalina cycle. It is determined that for the given inlet temperature and solar irradiation, the outlet temperature of SHTF is declined when the internal diameter of absorber tube is increased. The effect of change in SHTF, pressure at expander entry, and the concentration of ammonia-water basic solution on electrical power produced, refrigeration capacity, exergy of refrigeration, efficiencies of the cogeneration cycle are investigated. The cogeneration cycle with helium operated PTSC indicates better results than the use of air and CO2 as SHTF. Increase in the outlet temperature of SHTF (helium) leads to considerable increase in electrical power, refrigeration capacity, and exergy of refrigeration. The breaking down of solar exergy supplied to developed configuration reveals an exergy destruction of the order of 64.01% along with the exergy loss to environment of 1.92%, and exergy of refrigeration of 4.65% with generated power exergy of 29.42%, respectively. The computational results of present investigation are compared with the theoretically published data and a good agreement is found between these data.

Impacts on fish transported in tube fishways

Experimental data and numerical predictions of steady and unsteady flow in a 4 m high, 86 mm internal diameter tube fishway were compared quantitatively, and reflected expected uncertainties characteristic of the experiments and flow hydraulics. We then measured the response of a neutrally-buoyant fluid sensor and the behaviour of live fish transported vertically within the tube fishway. Ten repeat tests using the sensor and tests with seventy individual live fish demonstrated transport with 100% reliability. No ill effects were observed over a post-test monitoring period for two species of Australian native fish (Australian bass (Percalates novemaculeata) and Silver perch (Bidyanus bidyanus)) or as a function of size of the Silver perch that can be related to their passage through the fishway. There may have been temporary bruising of a few of the largest Silver perch tested. The largest Silver perch averaged 137 mm in length. The spatial distributions of the inert sensor and fish relative to the moving front during the transport process were quantified. Consequently, the volumes of water required during each operational cycle to ensure reliable delivery of fish over vertical distances less than 4 m were determined. The sensor measurements indicated negligible interactions with straight pipe walls but exposure to significant accelerations at sharp bends. Further experiments with live fish are required to quantify the possible adverse effects of alternative pipe transition designs on animals transported through them. Safe transport of fish up to a fish length/tube fishway delivery diameter ratio of 1.6 is demonstrated.