Tube Side Research Articles

Heat Transfer and Fluid Flow Behavior of a Carbon-Based Hybrid Nanofluid in a Microchannel Heat Sink

In this article, detailed work on the heat transfer and fluid flow behavior of carbon-based hybrid nanofluid (multi-walled carbon nanotubes + graphene nanoplatelets/H2O) was studied numerically. The carbon-based hybrid nanofluids have been prepared experimentally and their measured properties were used for this study. The numerical study was carried out by passing the nanofluids under laminar flow through the tube side of the microchannel heat sink (MCHS). A constant heat flux on the heat sink base was applied and a single-phase model approach was used for analyzing the heat transfer. The nanofluid volume concentration varied from 0.01% to 0.2%. The improvement in the heat transfer coefficient is observed to be a maximum of 73%, with a maximum of 18% pressure drop variation across the MCHS for 0.2 vol%. The pressure drop variation across the MCHS is minimal for all the considered volume fractions of the nanomaterials. The results confirmed that the hybrid nanofluid possesses a remarkable heat transfer characteristic for transporting heat effectively.

Equivalent stress-strain models of components in high-strength concrete-filled circular steel tube columns

Nine circular concrete-filled steel tube (CFST) columns with 109 MPa concrete were tested under eccentric axial loading to derive the equivalent axial stress-strain models of the steel tube and concrete. Based on the measured strain data and the theory of elasticity and plasticity, the progressions of the axial and hoop stresses at different locations of the steel tube section were obtained. For the compression side of the steel tube, the hoop stress was developed at or after yielding; then, the ratio of the axial stress to the effective stress, σsa/fe, gradually decreased to a value of around 0.77. For the tension side of the steel tube, σsa/fe continued to increase after yielding and kept constant when σsa/fe reached a value of approximately 1.15. Using the developed axial stress-strain model of the steel tube, the equivalent axial stress-strain relationship of concrete was determined by matching the axial load-vertical displacement curve obtained from the fiber model analysis to that from the test. The confinement index, ξ, mainly influences the peak compressive stress and strain of concrete, whereas the eccentricity ratio has some influence on the descending branch of the stress-strain curve. The fiber model with the proposed stress-train models of steel and concrete can well simulate the behavior of circular CFST columns with high-strength concrete under compression-flexural loading when 0.35 ≤ ξ ≤ 0.85, 0.14 ≤ e/D ≤ 0.68, and 3.8 ≤ Le/D (Le is the effective length of a column) ≤ 10.6.

Thermo-hydraulic design of a horizontal shell and tube heat exchanger for ethanol condensation

Horizontal shell and tube condensers are widely used in several industrial applications due to its versatility and heat transfer efficacy. In the present work, the thermo-hydraulic design of a horizontal shell and tube heat exchanger intended to condense 25,000 kg/h of a pure ethanol stream was carried out. Several key design parameters were calculated such as the number of tubes, heat transfer area, overall heat transfer coefficient, shell internal diameter, baffle spacing, as well as the pressure drop for both streams. The heat exchanger type is of pull-through floating head, and will present a number of tubes of 731, a heat transfer area of 223.68 m2, an overall heat transfer coefficient of 499.36 W/m2.ºC, a shell internal diameter of 1.684 m and a baffle spacing of 0.674 m. Around 157 kg/s of chilled water will be required for this heat transfer service. The values of both the shell side (10,069.25 Pa) and tube side (42,192.63 Pa) pressure drop are below the maximum values set by the process.

Stakeholder Model for Standard Operating Procedure of Radiation Safety Practice in Radiopharmaceutical Therapy

Using Xofigo procedure as an example of radiopharmaceutical therapy, to provide a quantitative analysis methodology for standard operating procedure development with binary stakeholder model. A Xofigo procedure was selected for this study. After nurse places the intravenous (IV) pole and start delivery of the saline liquid into the patients for required temporal period, calibrated Xofigo syringe will be transported into the treatment room by medical physicist and authorized radiation oncologist starts injecting the Xofigo liquid into the patient through the 3-way stopcock. During this process, the status of liquid path is from the syringe with Xofigo liquid to patient, and the saline liquid tube is shutoff. After about 1 minutes of injection, which most of the Xofigo radioactive liquid is injected into patient side, the 3-way stopcock will shut off the connection between the patient and syringe. The saline liquid then is abstracted into in the syringe from the saline bag hung on the IV pole, the liquid amount will be used for diluting the residual Xofigo liquid inside the syringe. Then the 3-way stopcock switch is switched off the connection between the saline bag and the syringe, and syringe is connected to the patient side again, then the saline liquid inside the syringe is injected into patient, and this process dilutes the residual Xofigo radioactive liquid at the inside surface of the syringe and the path to the patient. This dilution process could repeat a few times, depends on the estimation of residual amount. Then the syringe will be unscrewed from the 3-way stopcock by opening the path from the saline bag to the patient. At this moment, the saline is switched off from outside by cutting the tube with a scissor or unscrewed from the 3-way stopcock. A binary stakeholder quantitative model was used to evaluate the last step with a computational simulation program the tube cut-off process. Based on the numerical results from the simulation program, at the best situation, if the residual isotope liquid had been diluted completely, the radiative dose to both procedures would not be different, and the only difference is the tool used and workload dispatch to both medical physicist and radiation oncologist. And at the worst scenario, there were some radioactive residuals had gone into the IV-saline tube, then the radioactive contamination could be in the scissor, both side of cut off tube, and potential contacting point will increase to two stakeholders, one more tool(scissor), which could be treated as a stakeholder. The optimization principle could be simplified as to decrease the contacting point and contacting stakeholders by a computational simulation of a stakeholder model for a Xofigo radiopharmaceutical procedure. The analysis methodology could expand to all the steps in radiopharmaceutical therapy in developing a standard operating procedure and other complex radiation safety practice simulation system.

GRAIL gravity gradients evidence for a potential lava tube at Marius Hills on the moon

Lunar lava tubes are underground channels formed by volcanic eruptions and lava flow during the Moon's volcanic period. Intact lunar lava tubes have the potential to serve as secure shelters for humans and facilities, as they provide a safe and pristine environment with a constant temperature. In this study, the lunar gravity field model derived from NASA's GRAIL mission data is analyzed for detecting of an empty lava tube in the Marius Hills region. Compared to the classical Hessian matrix, the gravitational gradient method used in this study is capable of detecting anomaly signals both in the north-south and east-west directions. Using this method, we detect a north-south anomaly signal in the Marius Hills region, located at 57.5°W and 14.3°N, indicating a negative density anomaly near the known lunar sinuous rilles and the Marius Hills Hole skylight. This suggests the presence of a potential lava tube, which is confirmed by the results of the forward method and lunar radar echo data. The extent of the lava tube is estimated with the forward method to be ∼60 km in length, ∼9 km in width, ∼605 m in depth, and ∼55 m in height. Furthermore, the gradient features indicate that the skylight located on the eastern side of the lava tube could serve as an entry to the main part of the lava tube.

Surfactant amplifies yield-stress effects in the capillary instability of a film coating a tube.

To assess how the presence of surfactant in lung airways alters the flow of mucus that leads to plug formation and airway closure, we investigate the effect of insoluble surfactant on the instability of a viscoplastic liquid coating the interior of a cylindrical tube. Evolution equations for the layer thickness using thin-film and long-wave approximations are derived that incorporate yield-stress effects and capillary and Marangoni forces. Using numerical simulations and asymptotic analysis of the thin-film system, we quantify how the presence of surfactant slows growth of the Rayleigh-Plateau instability, increases the size of initial perturbation required to trigger instability and decreases the final peak height of the layer. When the surfactant strength is large, the thin-film dynamics coincide with the dynamics of a surfactant-free layer but with time slowed by a factor of four and the capillary Bingham number, a parameter proportional to the yield stress, exactly doubled. By solving the long-wave equations numerically, we quantify how increasing surfactant strength can increase the critical layer thickness for plug formation to occur and delay plugging. The previously established effect of the yield stress in suppressing plug formation [Shemilt et al., J. Fluid Mech., 2022, vol. 944, A22] is shown to be amplified by introducing surfactant. We discuss the implications of these results for understanding the impact of surfactant deficiency and increased mucus yield stress in obstructive lung diseases.

Thermal coupling of methanol steam reforming and hydrogen combustion to produce fuel cell hydrogen: A comparative theoretical study between membrane and hydrogen-recycled shell-and-tube reactors

Methanol steam reforming (MSR) is one the most interesting routes for production of fuel cell grade hydrogen. As this reaction is endothermic, its energy supply is one of the most important problems. In this line, recycling and burning the unconverted hydrogen exits from the exhaust of the fuel cells on the shell side of a shell-and-tube reactor (HR) has been suggested in the literature as one the energy supply solutions. In this work, the performance of a membrane-assisted shell-and-tube reactor (MR-HCO), in which part of the hydrogen produced by the MSR is continuously transferred to the shell side through the membrane layer and burned to supply energy, is investigated and compared with HR reactor. To this end, a set of heterogeneous 1D and 2D models are employed to model the shell and the tube sides of the reactors, respectively. The influence of air and steam-methanol feed hourly space velocities on maximum combustion temperature and methanol conversion are examined. It is observed that the MR-HCO has higher methanol conversion, hydrogen flow, and thermal efficiency, while lower CO concentration compared with the HR reactor. Furthermore, the MR-HCO showed a good potential to control the shell temperature rise and prevent hot spots.

Enhancement of heat transfer in a vertical shell and tube heat exchanger using air injection and new baffles: Experimental and numerical approach

Vertical shell and tube heat exchangers play a critical role in many industrial processes, and their importance lies in their high heat transfer efficiency, versatility, compact size, easy maintenance, and longevity. To improve the hydrothermal performance, this research investigates the influences of air bubbles injection inside the shell with disc and ring baffles with circular holes, which is the first time to be addressed. The experiments used a fixed oil mass flow rate with 0.23 kg/s inside the tube sides and various cold water flow rates on the shell side within the 0.15–0.23 kg/s range. Three baffles’ configurations, such as single segmental (SSB), disc and ring (DRB), and disc and ring with circular holes (DRCHB), were investigated with different volume flow rates of air bubbles injection in the shell experimentally. A numerical model is performed and validated for the three baffles shapes. The performance parameters such as number of transfer units, effectiveness, heat transfer coefficient, pressure drop, and performance evaluation criterion are studied. The experimental findings showed that efficacy improved with the increase of the cold-water mass flow rates, whereas the DRCHB baffle shape with air injection)10 × 10−5 m3/s(achieved the highest effectiveness with an enhancement rate of 202% to 231%. The DRCHB configuration with maximum air injection has the highest values of the number of transfer units, heat transfer coefficient, and performance evaluation criterion compared to the other baffles configurations moreover, the pressure drop is the smallest in this case DRCHB without air injection. The numerical results showed that both novel configurations (DRB and DRCHB) have more uniform velocity and temperature distributions compared to the segmental baffles, which may effectively increase the hydrothermal performance.

Experimental investigation on heat transfer performance of the grooved spiral wound heat exchanger

To enhance the heat transfer efficiency of the spiral wound heat exchanger, a grooved spiral wound heat exchanger (GSWHE) was proposed. A test platform was accomplished to experimentally investigate the heat transfer performance with the comparison of a spiral wound heat exchanger (SWHE). The uncertainty analysis of the experiment was conducted, with the maximum relative error being not more than ±5%. The comprehensive heat transfer coefficient of the GSWHE is higher than that of the SWHE when the cooling water flow rate is low. To determine the heat transfer coefficient of both sides, the Wilson plot method was applied. The tube side heat transfer coefficient in the SWHE is found to have an error of about ±30% compared to the empirical correlations. The results also clearly suggest that grooves enhance the heat transfer of the shell side in the GSWHE. By employing effectiveness as a criterion, the comprehensive performance of the GSWHE was found to be 1.23 times higher than that of the SWHE.

I‐beam to RHS‐column joints with welded studs under cyclic loading

AbstractThe design of removable beam‐column joints between open structural steel beams and rectangular hollow section (RHS) columns is not easy because of the inaccessibility to the tube interior from outside. I‐beam to RHS‐column joints with threaded welded studs are of great interest due to their low‐cost assembling technique and easy on‐site execution. This study examines the cyclic performance of these joints with welded studs. A quasi‐static experimental study on the cyclic response of eight joint specimens is described. The strength of the joint and the failure modes were revealed. The ductility of the joints was also evaluated according to the rotation capacity after yielding, classifying all of them as having intermediate ductility and, therefore, implying some capacity to withstand limited plastic deformations when subjected to seismic forces. Some equations were also used to classify the joints according to the components that mainly govern the deformation of the full joint. In addition, the energy dissipation rate was assessed for all the specimens, finding the highest energy dissipation rates in the most rigid joints.

Flow Characteristics and Heat Transfer Performances of Quadrant Helical Baffle Heat Exchanger with Grooved Joint

Helical baffle heat exchanger has a wide application in many industrial fields because of its high efficiency and low resistance. A new structure of the grooved helical baffle is proposed to strengthen the stability between the overlapped baffles during the spiral flow of fluid. Based on this structure, the liquid water was selected as the working medium in the tube side and shell side, the flow field characteristics and heat transfer performances of the quadrant helical baffle heat exchanger are numerically analyzed using software FLUENT 2017. The results show that when the helical angle is large (50°) and the overlapped amount is small (0.5), the comprehensive performance of the heat exchanger is the best. Therefore, the heat exchanger performance can be improved by choosing the appropriate combination of helical angle and overlapped amount. The correlation formula of the shell side heat transfer coefficient with helical angle, overlapped amount and mass flow rate is obtained by means of regression analysis, which can provide a reference for engineering application and optimal design of grooved helical baffle heat exchanger.

A new subspecies of Spermacoce bequaertii (Rubiaceae: Spermacoceae)

A new subspecies of the African species Spermacoce bequaertii is described and illustrated. This new subspecies (subsp. brevituba is restricted to the Kasai district in the Democratic Republic of Congo, and differs from the typical subspecies in having smaller mature flowers with a glabrous corolla tube inside.

A Comparison of Proximal and Tracheal Airway Pressures During Pressure Controlled Ventilation.

Airway pressure is usually measured by sensors placed in the ventilator or on the ventilator side of the endotracheal tube (ETT), at the Y-piece. These remote measurements serve as a surrogate for the tracheal or alveolar pressure. Tracheal pressure can only be predicted correctly by using a model that incorporates the pressure at the remote location, the flow through the ETT, and the resistance of the ETT if the latter is a predictable function of Y-piece flow. However, this is not consistently appropriate, and accuracy of prediction is hampered. This in vitro study systematically examined the ventilator pressure in dependence of compliance of the respiratory system (CRS), inspiratory time, and expiratory time during pressure-controlled ventilation by using a small intratracheal pressure sensor and a mechanical lung simulator. Pressures were measured simultaneously at the ventilator outlet, at the Y-piece, and in the trachea during pressure-controlled ventilation with a peak inspiratory pressure of 20 cm H2O and a PEEP of 5 cm H2O while changing CRS (10, 30, 60, 90, and 100 mL/cm H2O) and varying inspiratory time and expiratory time. Tracheal pressures were always lower (maximum 8 cm H2O during inspiration) or higher (maximum 4 cm H2O during expiration) than the pressures measured proximal to the ETT if zero-flow conditions were not achieved at the end of the breathing cycles. Dependent on CRS and the breathing cycle, tracheal pressures deviated from those measured proximal to the ETT under non-zero-flow conditions. Intratracheal pressure and pressure curve dynamics can differ greatly from the ventilator pressure, depending on the ventilator setting and the CRS. The small pressure sensor may be used as a measurement method of tracheal pressure via integration onto an ETT.

Pengaruh Penambahan Natural Rubber Pada Ban Dalam Dengan Metode Presure

The inner tube determines the effectiveness and efficiency of a commercial transportation vehicle, where the inner tube is expected to have high durability against friction with the outer tire and to have high tensile stress when holding a heavy load. To answer this condition, the process of adding natural rubber material to the inner tube was carried out using the pressure method with 2 variables, namely one layer of inner tube and one layer of natural rubber which was affixed to the outer side of the inner tube, as well as one inner tube with two layers of natural rubber located on the side outside and inside on the inner tube. Then the testing process is carried out, namely tensile brake and hardness to obtain data to determine the effect of adding natural rubber to the inner tube using the pressure method as one of the references for producing better inner tubes. After the research process was carried out, the results of the tensile brake test were 20.4 Kgf on the first specimen, 23.8 Kgf on the second specimen, 31.05 on the third specimen. Furthermore, from the hardness test, a result was obtained, namely 52° on the first specimen, 48° on the second specimen, 44° on the third specimen.

Iron Control in Liquid Effluents: Pseudo-Emulsion Based Hollow Fiber Membrane with Strip Dispersion Technology with Pseudo-Protic Ionic Liquid (RNH3+HSO4-) as Mobile Carrier.

The transport of iron(III) from aqueous solutions through pseudo-emulsion-based hollow fiber with strip dispersion (PEHFSD) was investigated using a microporous hydrophobic hollow fiber membrane module. The pseudo-protic ionic liquid RNH3HSO4- dissolved in Solvesso 100 was used as the carrier phase. This pseudo-protic ionic liquid was generated by the reaction of the primary amine Primene JMT (RNH2) with sulphuric acid. The aqueous feed phase (3000 cm3) containing iron(III) was passed through the tube side of the fiber, and the pseudo-emulsion phase of the carrier phase (400 cm3) and sulphuric acid (400 cm3) were circulated through the shell side in counter-current operational mode, using a single hollow fiber module for non-dispersive extraction and stripping. In the operation, the stripping solution (sulphuric acid) was dispersed into the organic membrane phase in a tank with a mixing arrangement (a four-blade impeller stirrer) designed to provide strip dispersion. This dispersed phase was continuously circulated from the tank to the membrane module in order to provide a constant supply of the organic solution to the fiber pores. Different hydrodynamic and chemical parameters, such as feed (75-400 cm3/min) and pseudo-emulsion phases (50-100 cm3/min) flows, sulphuric acid concentration in the feed and stripping phases (0.01-0.5 M and 0.5-3 M, respectively), metal concentration (0.01-1 g/L) in the feed phase, and PPILL concentration (0.027-0.81 M) in the carrier phase, were investigated. From the experimental data, different diffusional parameters were estimated, concluding that the resistance due to the feed phase was not the rate-controlling step of the overall iron(III) transport process. It was possible to concentrate iron(III) in the strip phase using this smart PEHFSD technology.

Exploration of transient flow perturbations in a bulb turbine diffuser using proper orthogonal decomposition

Hydraulic turbines with high efficiency over a wide range of operating conditions offer a much sought-after flexibility to electricity producers. However, some low-head turbines exhibit sharp losses of efficiency close to their peak efficiency discharge that are linked to draft tube flow separations whose causes remain misunderstood. This paper presents the latest results obtained in the scope of the BulbT project that focused on the flow dynamics related to the efficiency drop. The main objectives are to document the transient characteristics of the flow in the hub-wake region and investigate interactions between the core flow and wall separations to identify potential mechanisms explaining the efficiency drop. Using proper orthogonal decompositions of synchronized time-resolved velocity and pressure measurements, highly energetic modes representing stochastic perturbations across BulbT's draft tube are identified. These perturbations occur only for the discharges affected by the efficiency drop, past the best efficiency point. Despite the absence of near-wall velocity measurements, the modal decompositions provide evidence that the onset of the efficiency drop is the result of two independent types of flow separation that occur on opposite sides of the draft tube. Upstream separations are found to happen simultaneously with an asymmetric acceleration of the flow in a region surrounding the turbine's axis and the tip of the runner hub and become the most important contributor to the efficiency drop at the highest measured flow rate. Furthermore, the likeliness of observing one kind of flow separation increases after it has already occurred, pointing to a strong history effect.

A transcriptional and regulatory map of mouse somite maturation

The mammalian body plan is shaped by rhythmic segmentation of mesoderm into somites, which are transient embryonic structures that form down each side of the neural tube. We have analyzed the genome-wide transcriptional and chromatin dynamics occurring within nascent somites, from early inception of somitogenesis to the latest stages of body plan establishment. We created matched gene expression andopen chromatin maps for the three leading pairs of somites at six time points during mouse embryonic development. We show that the rate of somite differentiation accelerates as development progresses. We identified a conserved maturation program followed by all somites, but somites from more developed embryos concomitantly switch on differentiation programs from derivative cell lineages soon after segmentation. Integrated analysis of the somitic transcriptional and chromatin activities identified opposing regulatory modules controlling the onset of differentiation. Our results provide a powerful, high-resolution view of the molecular genetics underlying somitic development in mammals.

Analysis of Flow and Pressure Drop on Tube Side of Spiral Tube Heat Exchanger under Sloshing Conditions

The utilization of the spiral tube heat exchanger (SHE) has become increasingly prevalent in large-scale liquefaction processes. However, the flow pattern and frictional pressure drop of two-phase flow in the spiral tube have been scarcely studied, particularly under offshore sloshing conditions. An experimental system had been developed to explore the flow pattern and frictional pressure drop characteristics of mixed hydrocarbon fluid in a spiral tube. Moreover, these have been developed in order to examine the effects of sloshing style (roll, pitch, heave), sloshing period (5–15 s), sloshing amplitude (5–15° or 50–150 mm), mass flux (200–800 kg/(m2·s)), vapor quality (0–1), and saturation pressure (2–4 MPa) on the frictional pressure drop of methane/ethane mixture in the spiral tube. The results indicated that sloshing conditions reduce the frictional pressure drop, thereby enhancing fluid flow. A correlation was established to predict the sloshing factor of frictional pressure drop, and the MARD under verification conditions was 6.04%. Furthermore, three flow pattern boundaries were proposed based on We* as an indicator.

Dynamic response of concrete-filled square steel tubular columns under lateral impact load at flat or corner zone

The dynamic response of columns under lateral impact is of great significance for guiding structural design under accidental loads. The present study aims to investigate the effect of different impact directions on the dynamic response of square concrete-filled steel tubular (CFST) columns by conducting drop hammer tests at flat or corner zones. The main experimental parameters included hammer mass, drop height, indenter radius, built-in steel bars, shear span ratio, width-thickness ratio, and column sizes. The experimental results showed that the impact zone has a significant effect on the dynamic response of CFST specimens. Under higher impact energies, specimens impacted at corner zones were more likely to fracture on the tensile side of the steel tube than specimens impacted at flat zones. And the specimens impacted at the corner zone were more sensitive to the change of indenter radius. Smaller shear span ratios, built-in steel bar, and larger column sizes improved the impact resistance of tested specimens. The 3D finite element models were developed and analyzed by ABAQUS/Explicit to explore dynamic behavior further.

A Modified Correlative Model for Condensation Heat Transfer in Horizontal Enhanced Tubes with R32 and R410A Refrigerants

An experimental study was performed that compared tube side condensation heat transfer characteristics of enhanced tubes (hydrophobic surface tubes (HYD), herringbone micro fin tube (HB), and a composite hydrophobic/herringbone (micro fin) tube (HYD/HB)) to the performance of a smooth tube (ST). The condensation heat transfer coefficient (HTC) was calculated from data that were recorded for smooth and enhanced tubes that had an outer diameter (OD) of 12.7 mm. Data were collected (as a function of mass flow rate) using a couple of refrigerants (R410A and R32), for saturated temperatures of 35 °C and 45 °C, with vapor qualities that ranged from 0.8 to 0.2. Several previously reported smooth tube HTC models were used to calculate values that could be compared to experimentally obtained HTC values. The correlation model that demonstrated the best accuracy (for the conditions considered) was then modified for use with the enhanced tubes from this study. Results from the modified correlation show differences with experimental values that ranged from −10% to +17%; the new modified correlation demonstrates high prediction accuracy. An accurate correlation allows the evaluation of enhanced heat transfer tubes for use in high-efficiency heat exchanger systems. The development of this new model is significant in the study of enhanced heat transfer.