Outer Surface Of Tube Research Articles

Prevention of microbial colonization of feeding tubes in the intensive care unit.

Various microorganisms which increase the mortality rate in the intensive care unit (ICU) cause microbial colonization of the nasogastric tube (NGT) and use the NGT as a reservoir. To detect the colonization on the NGT and to determine the effect that training regarding hand hygiene, NGT management, and enteral feeding (EF) provided to ICU nurses and auxiliary service staff (ASS) has on the level of NGT colonization. A quasi-experimental pre-test and post-test control design was used in this study. Microbial samples were taken from the outer and inner parts of NGT. The microorganisms were categorized as: group 1, no risk; group 2, low risk pathogenic; group 3, high-risk pathogenic group. The training was given to nurses (n=15) and ASS (n=7). Hand hygiene, NGT, and EF care training are provided to nurses and ASS by researchers. A total of three training sessions were scheduled to be held in 3 weeks so that all health care staff members were trained. Each session lasted 2 h in total. Patients were assigned to a group if one of the microorganisms presented on the outer surface of the patient's feeding tube and/or on the hub. The hand hygiene compliance was evaluated by direct observation according to the World Health Organization hand hygiene indications. The study was conducted with 46 patients. Evaluating the patients for the presence of microorganisms before education revealed that 4.3% were in group 1, 21.8% were in group 2, and 73.9% were in group 3. After the education, evaluating the samples for the presence of microorganisms revealed that 39.1% were in group 1, 13% were in group 2, and 47.8% were in group 3. A statistically significant difference was found between the number of samples included in the groups after the participants had received training (H=8.186; p=.017). An NGT could act as a reservoir of microbial colonization and high-risk microorganisms could be on the tube. Providing training not only to nurses but also to ASS will help reduce the risk of colonization. Eliminating such colonization with effective hand hygiene during NGT feeding is a cost-effective method. Providing training not only to nurses but also to ASS will help obtain the optimum benefit from patient care.

Experimental and numerical investigations on electromagnetic powder compaction of Aluminium 6061 alloy powder

The present research's objective is to investigate the electromagnetic radial powder compaction process and its effect on the densification, microstructure and mechanical properties of the Al 6061 alloy powder. Cylindrical product has been prepared from Al 6061 powder using the electromagnetic powder compaction method. In this method, electromagnetic force shrinks the packing tube and utilises the deformation of the tube to compact the Al 6061 powder. The electromagnetic forces were generated between the field shaper's inner cylindrical surface and the outer surface of the packing tube when a high voltage current is flowing through the solenoid coil. In this study, the Al 6061 powder is compacted at various discharge voltages such as 13 kV, 14 kV, 15 kV and 16 kV using a 20 kV and 40 kJ capacity electromagnetic forming machine. Sintering is performed on the compacted samples at 620 °C for 1 h in an N2 tubular furnace. The simulation was carried out using loosely coupled multi-physics software, and simulated results were validated with the experimental results. Ansys Maxwell is used to analyse the electromagnetic field, and Ls-Dyna is used for structural analysis. To describe the deformation behaviour of the packing tube, the Cowper –Symonds model was used. The deformation in the compact and stress-strain variation was analysed using simulation results and experimental results. The effect of field shaper on powder compaction is investigated using the magnetic field analysis of the Ansys Maxwell results. The velocity of the packing tube is analysed for various input discharge voltages. The Vickers micro-hardness of electromagnetic powder compacted samples increases with compaction voltage. Finally, the results predicted by numerical simulation were verified with experimental results and found in good agreement.

Combined compression-bending performance and design of CFST with localised pitting corrosion

This paper presents a comprehensive numerical study on the combined compression-bending performance of concrete-filled steel tubes (CFSTs) considering the commonly seen localised pitting corrosion damage in the marine environment. An advanced finite element modelling technique is utilised to simulate the localised corrosion pits on the outer surface of the steel tube considering its random nature. The differences between the load-moment interaction of CFSTs with uncorroded conditions, uniform corrosion simplification and pitting corrosion are discussed. The analytical results reveal the impact of localised pitting corrosion damage on the combined compression-bending performance of CFSTs can be grouped as the stress concentration around corrosion pits, premature local buckling of steel tubes and the reduction in effective confinement. An extended parametric study illustrates that the confinement factor and the mean pit depth have a considerable impact on the combined compression-bending behaviour of CFSTs with localised pitting corrosion. The feasibility of utilising existing design approaches calculates the load-moment interaction diagrams of locally pitted CFSTs following the DoV-based uniform corrosion simplification is evaluated. On this basis, simplified design methods accounting for the characteristic of pitting corrosion are proposed for estimating the post-corrosion load-bearing capacity of CFSTs under combined compression and bending, and reasonable accuracy is achieved.

Maximum benefits from the use of enhanced heat transfer surfaces

The paper presents a critical review of the performance evaluation criteria (PEC) developed by Webb (Webb, 1981). These criteria evaluate the benefits that could be obtained in heat exchangers if their surfaces and inserts are designed to enhance the heat transfer, particularly in two-fluid heat exchangers in single-phase flow. This study revealed that the imposed constraint for fixed pumping power in the comparison of the augmented channel with the reference one is a major obstacle to achieving greater benefit. Accordingly, the elimination of the constraint of fixed pumping power and the objective of reduced pumping power decreases substantially the criteria of Webb. A new constraint related to the fixed augmentation entropy generation number has been involved replacing the constraint of fixed pumping power. The pumping power can be left to increase until the augmentation entropy generation number is less than unity. The maximum benefit can be obtained when the augmentation entropy generation number reaches the value of unity. The use of greater in tube heat transfer enhancement (with the use of compound heat transfer enhancement techniques instead of simple ones), and with an enhanced outer tube surface of the augmented exchanger is a useful instrument to increase the benefits, only if the augmentation entropy generation number does not cross the frontier of unity.

Optimal operating strategy of ash deposit removal system to maximize boiler efficiency using CFD and a thermal transfer efficiency model

Ash deposits generated during the combustion process on the outer tube surface of a boiler reduces the boiler’s efficiency. In most boilers, ash deposits are physically removed with high-pressure steam using an ash deposit removal system, sootblower. However, most sootblowers spray steam with excessive pressure, without considering the characteristics of the ash deposit, resulting in problems such as waste of steam energy and damage to equipment. In addition, an optimal operation strategy based on the position of the sootblower and the injection angle of the steam nozzle are not considered, leading to a lowered efficiency of ash deposit removal and steam waste. Hence, this study proposes a novel method to determine the optimal operating conditions of a sootblower using computational fluid dynamics (CFD) and a thermal transfer efficiency model considering the properties of the ash deposits. This method was developed based on a commercial recovery boiler, and consists of (i) a sootblowing steam velocity model that considers the ash deposit characteristics, (ii) a three-dimensional CFD model considering the interior design of the boiler, and (iii) a thermal transfer efficiency model that calculates the thermal resistance depending on the amount of ash deposit removed.Case studies were performed to calculate the amount of ash deposit removed for various ash deposit thicknesses, and sootblower positions and angles using this methodology. The boiler heat transfer efficiency was calculated using the calculated ash deposit removal amount and thermal transfer efficiency model, and the optimum operating conditions for the sootblower with the optimum heat transfer efficiency were derived. This study presents a guideline for efficiently operating sootblowers according to the ash deposit characteristics, and can be applied not only to recovery boilers but also to other boilers in which ash deposits are generated.

Failure cause assessment of steam reformer radiant tube after long‐term service

AbstractThis study investigates the damage, microstructure, and mechanical evolution of service‐exposed HP40NbTi radiant tubes of a steam reformer furnace. Tube failure was reported after 6‐year of working at 525°C–830°C in the form of visible longitudinal and transverse cracks. The microstructure was evaluated using optical and scanning electron microscopy equipped with energy‐dispersive X‐ray spectrum analysis. The carbide phase transformation was determined by the method based on the matrix dissolution technique and X‐ray diffraction. The results of this study showed that the primary cause of the longitudinal crack formation is the local overheating and the oxidation of the dendritic grain boundaries. The M7C3 carbide transforms completely into the metastable M23C6 phase during high‐temperature service. Metallographic examinations revealed the shrinkage cavities and creep voids that are nucleated on both Cr‐ and Nb‐carbides. The continuous oxide layers of Cr2O3 and SiO2 formed near the inner and outer tube surfaces and the matrix's chemical composition near the outer tube surface was found to be depleted of Cr and C. Mechanical properties are irregular across the samples. A little margin of safety is noted, while the complete ductility dip is detected at room temperature. The root cause analysis of the failure under investigation showed that the tube failed due to the creep.

Novel halloysite nanotube-based ultrafine CoMn2O4 catalyst for efficient degradation of pharmaceuticals through peroxymonosulfate activation

In this study, a highly efficient catalyst was prepared by loading CoMn2O4 spinel oxide (CMO) on halloysite (HNT), a natural mineral nanotube, for the activation of peroxymonosulfate (PMS) towards the degradation of some frequently detected pharmaceuticals in water bodies. The CMO nanoparticles are evenly distributed on the outer surface of HNT tubes with little agglomeration and smaller grain size compared to bare CMO. A moderate loading of 40% CMO on HNT (i.e. 40-CMO/HNT) displayed an excellent catalytic ability, leading to the complete degradation of carbamazepine in 20 min. Carbamazepine was decomposed gradually by oxidation, hydrolysis and the cleavage of rings with 60% mineralization rate. The adhering of CMO on HNT contributed to better stability and durability than bare CMO and the recycling of 40-CMO/HNT was found feasible and efficient. A test of three-(3)-time-reuse showed that over 90% of carbamazepine was removed in each cycle, while the leaching of Co and Mn was reduced stepwise by 12.6% and 8.9%, respectively. The possible universal application of 40-CMO/HNT in removing common antibiotics was verified by targeting tetracycline, ofloxacin and sulfamethoxazole. The positive results promise the development of an effective treatment technology for the removal of common pharmaceuticals.

A practical Eulerian approach for predicting the deposition characteristics of fly ash particles on the outer surface of tubes

For the first time, this article proposes a practical Eulerian approach for simulating the deposition characteristics of fly ash particles in flue gas on the outer surface of tubes. In the present work, the deposition of fly ash particles includes both deposition and removal processes. The particle deposition process considers the effects of Brownian and eddy diffusion, gravity, thermophoretic, turbophoretic, and electrostatic forces. For validation purposes, the simulation results by the Eulerian approach are compared to two sets of representative experimental data from the literature. The average deviation in deposition height/mass between the first set of experiments in two different working conditions and simulations in this study is respectively 11.24 percent and 6.37 percent. In contrast, the second set of experiments and simulations has a deviation of 7.05 percent.

Acoustic Response of Reference Notches: Derivation of Acceptance Criteria for Automated Ultrasonic Testing Based on the Correlation Between Defect Quality and Effective Defect Size

This paper presents a detailed study of the acoustic response of artificially manufactured notches, which are established reference defects in common standards for ultrasonic testing (UT). Measurements were performed with standard tubes manufactured for the commissioning of automated UT machines. Included reference notches are at the inner and outer tube surface and have different lengths and orientations (longitudinal, oblique and transverse). From the acoustic reflection profile, i.e. the measured defect amplitude along the notch axis, the effective defect length and the defect homogeneity are introduced as measured quantities of the reference defect quality. The large data sample of 320 evaluated notch profiles gives insight to the statistics of the achieved reference defect quality. Key approach of the analysis is the correlation between both measured quantities. It reveals a universal behaviour, which can be described by a sigmoidal function converging for high quality defects towards the theoretical limits. Based on the obtained parametrization it is possible to define criterions for the required defect quality and the test speed as function of the specified repeatability. This solves the current dilemma how to distinguish between variations due to the reference quality from those related to the testing machine. Furthermore, the presented measurement procedure can be used for a reference certification, which complements existing standards for the ultrasonic system and the probes.

Novel composite phase change material of high heat storage and photothermal conversion ability

Using porous matrix as the supports for phase change materials (PCMs) can effectively eliminate the leakage problem of PCMs during the phase change process. In heat storage utilization, the as-prepared shape-stabilized phase change materials are highly desired to have high latent heat density, rapid heat transfer ability and less supercooling. Although mesoporous silica with large pore volume and specific surface area might be a promising matrix for PCMs, it would be more beneficial if its thermal conductivity and photo-thermal conversion capacity were further improved, especially for the utilization of solar thermal energy. Herein, a composite PCM, namely SA/CNTs@MS, was fabricated successfully using mesoporous silica coated carbon nanotubes (CNTs@MS) as the shape-stabilized matrix for the PCM stearic acid (SA). The results of characterizations showed that CNTs@MS had a core-shell structure with mesoporous silica of a thickness of about 30 nm coated on the outer surface of carbon tubes (CNTs) homogeneously. The melting enthalpy of the obtained SA/CNTs@MS composite was 125.6 J/g. Its thermal conductivity increased 64.7%, and the supercooling degree decreased 3.2 ℃ while compared with those of pure SA. The melting and solidification enthalpies of SA/CNTs@MS decreased 1.1% and 1.3%, respectively after 200 thermal cycles. Besides, it is also confirmed that SA/CNTs@MS had good photo-thermal conversion performance. These imply that the synthesized SA/CNTs@MS composite would be an ideal heat storage material, especially for solar energy utilization.

Low pressure DBD in He-Ne mixture. Spectroscopy of the Afterglow

The paper considers the possibility of using a low-pressure dielectric barrier discharge (DBD) as a plasma source for the active medium of a He-Ne-laser. The results of a spectroscopic study of the decay stage of a DBD plasma of a cylindrical configuration with a pronounced inverse population of the upper level of the 2p55s configuration, which makes the line of 632.8 nm one of the brightest in the visible region of the spectrum, are presented. Based on the analysis of data on the populations of the excited levels of the neon atom and the metastable levels of helium 21S0 and 23S1, it is shown that in the early stage of the DBD afterglow at helium pressures of a fraction of a Torr, the distribution of populations over the 2p55s and 2p54d levels of the neon atom, which is characteristic of the excitation transfer mechanism, is realized. In the late afterglow with the departure of helium atoms He21S0, emission in the visible region of the spectrum is formed mainly by transitions from levels of the 2p53p, configuration, the population of which is associated with He(23S1) atoms. At this stage, the population of the 2p55s and 2p54d states by electron-ion recombination processes is ineffective and does not lead to the formation of population inversion. As an optimal solution in terms of the 632.8 nm line brightness in the afterglow, it is proposed to use a discharge with electrodes along the outer surface of a cylindrical discharge tube, initiated at frequencies that exclude the recombination stage of the afterglow. Keywords: elementary processes, barrier discharge, inverse population, afterglow, helium-neon plasma, excitation transfer

Диэлектрический барьерный разряд в смеси He-Ne низкого давления. Спектроскопия послесвечения

The paper considers the possibility of using a low-pressure dielectric barrier discharge (DBD) as a plasma source for the active medium of a He-Ne laser. The results of a spectroscopic study of the decay stage of a DBD plasma of a cylindrical configuration with a pronounced inverse population of the upper level of the 2p55s configuration, which makes the line of 632.8 nm one of the brightest in the visible region of the spectrum, are presented. It is shown that in the early stage of the DBD afterglow, the distribution of the populations over the 2p55s and 2p54d levels of the neon atom is due to the excitation transfer mechanism Не(21S0) +Ne -- > He(11S0) + Ne*. In the late afterglow with the departure of helium atoms Не(21S0), emission in the visible region of the spectrum is formed mainly by transitions from levels of the 2p53p configuration, the population of which is associated with Не(23S1) atoms. At this stage, the population of the 2p55s and 2p54d states by electron-ion recombination processes is ineffective and does not lead to the formation of population inversion. As an optimal solution in terms of the 632.8 nm line brightness in the afterglow, it is proposed to use a discharge with electrodes along the outer surface of a cylindrical discharge tube, initiated at frequencies that exclude the recombination stage of the afterglow.

Mathematical modeling of relaxation of residual stresses in thin-walled pipelines in the delivery state and after bilateral surface hardening at creep

A mathematical model of reconstruction of the fields of residual stresses and plastic deformations in thin-walled cylindrical tubes in the delivery state and after bilateral surface plastic hardening was developed. It included a method for identification of the model parameters using the example of thin-walled mm tubes made of X18N10T steel based on experimental data for the axial and circumferential components of the residual stress tensor for samples in the delivery state and after bilateral mechanical ultrasonic hardening. The adequacy of the mathematical model for the reconstruction of residual stresses in the thin-walled tubes made of X18N10T steel was verified by the experimental data in the state of delivery and after bilateral surface plastic hardening, taking into account the anisotropy of the distribution of plastic deformation after hardening in the axial and circumferential directions. A method for calculating the two-way relaxation of residual stresses on the outer and inner surfaces of thin-walled tubes under creep conditions was developed based on the generalization of the corresponding method for unilateral hardening. The relaxation process in the thin-walled tubes made of 08X18N9 steel (an early analogue of X18N10T steel) under conditions of thermal exposure, axial tension, internal pressure and the combined action of axial tension and internal pressure was investigated on the basis of the constructed phenomenological creep theory for this steel. A detailed analysis of the kinetics of the fields of residual stresses during creep in the thin-walled samples in the delivery state and after bilateral hardening at different times was performed. It is shown that under these conditions, almost a complete relaxation of residual technological stresses occurs both in the samples in the delivery state and after bilateral surface plastic deformation within 50 hours.

Enhancement of the Rates of Liquid‐Solid Heat and Mass Transfer in Annular Ducts by Using Circular Fins

AbstractRates of solid‐liquid mass and heat transfer (by analogy) were measured at the outer surface of the inner tube of an annular duct under developing flow conditions using the electrochemical method that elaborates the measurement of the limiting current of the reduction of K3Fe(CN)6 at the tested model surface. Variables examined were physical features of the solution (density ρ, viscosity μ, and diffusivity D), solution superficial velocity, tube active length, and tube diameter. The experimental results were correlated by a dimensionless equation involving all affecting parameters. Due to the presence of the circular fins at the tube surface, the degree of mass transfer was enhanced by a factor ranging from two to six subject to the operative settings. Applications of the current findings in the design of catalytic reactors, membrane dialyzers, and double‐pipe heat exchangers were discussed.

Developing a Phototactic Electrostatic Insect Trap Targeting Whiteflies, Leafminers, and Thrips in Greenhouses.

Simple SummarySilverleaf whiteflies (Bemisia tabaci), vegetable leafminers (Liriomyza sativae), and western flower thrips (Frankliniella occidentalis) are very serious pests of greenhouse tomatoes. In Japan, growers of organic tomatoes currently use large numbers of yellow sticky traps to control insects, but these traps need replacing very regularly, as the sticky surface becomes clogged with insects. An electric field-generating apparatus, described herein, is a potential physical tool to control these pests that have entered greenhouses. The electric field was formed in the space between oppositely electrified insulated conductors arrayed in parallel with fixed separation. Although these conductors created a sufficiently strong force to capture insects entering the field, the force was insufficient to capture insects outside the field. The positive phototaxis of these insects was an inspiration to develop an improved electrostatic insect trap, which was constructed by introducing oppositely charged yellow-colored water into paired transparent insulator tubes to produce opposite poles. The finished apparatus exhibited coloration and insect attraction characteristics similar to commercial yellow sticky traps, but had the advantage that they could be cleaned easily and remain effective for long periods. The surfaces of the insulator tubes containing the charged yellow water were electrostatically active, but not excessively sticky, thus, the apparatus could be placed close to the plants. The close location of the devices enabled preferential attraction of flying or plant-settling insects to the trap. The present study provided an experimental basis for developing an electrostatic device to attract and capture insects that enter greenhouses.Our aim was to develop an electrostatic apparatus to lure and capture silverleaf whiteflies (Bemisia tabaci), vegetable leafminers (Liriomyza sativae), and western flower thrips (Frankliniella occidentalis) that invade tomato greenhouses. A double-charged dipolar electric field producer (DD-EFP) was constructed by filling water in two identical transparent soft polyvinyl chloride tubes arrayed in parallel with fixed separation, and then, inserting the probes of grounded negative and positive voltage generators into the water of the two tubes to generate negatively and positively charged waters, respectively. These charged waters electrified the outer surfaces of the opposite tubes via dielectric polarization. An electric field formed between the oppositely charged tubes. To lure these phototactic insects, the water was colored yellow using watercolor paste, then introduced into the transparent insulator tubes to construct the yellow-colored DD-EFP. This apparatus lured insects in a manner similar to commercially available yellow sticky traps. The yellow-colored DD-EFP was easily placed as a movable upright screen along the plants, such that invading pests were preferentially attracted to the trap before reaching the plants. Furthermore, pests settling on the plants were attracted to the apparatus, which used a plant-tapping method to drive them off the plants. Our study provided an experimental basis for developing an electrostatic device to attract and capture insects that enter greenhouses.

Nonlinear finite element analysis of circular stiffened FRP-concrete-steel double-skin tubular columns (DSTCs) and experimental compressive behavior of multiple DSTC shapes

A new variation of hybrid double-skin tubular column (DSTC) consisting of concrete sandwiched between outer fibre-reinforced polymer (FRP) and inner stiffened-steel tube shows better structural performance than its unstiffened conventional form. Vertical steel stiffeners placed on the outer surface of the steel tube can potentially reduce inner tubes’ local buckling and enhance composite interactions between column components, thus resulting in improved confined concrete behavior. The present study proposes an analysis-oriented confined concrete stress–strain model for nonlinear finite element (FE) simulation of circular stiffened DSTCs. Detailed FE analyses were performed using the proposed confined concrete model for validation against documented test results of circular DSTCs with parametric stiffener geometry variations. An excellent agreement was shown between numerical and test results (at most 5% errors at critical elastic, peak and ultimate axial loads). The numerical models captured well both the elastic and post-elastic behavior of stiffened DSTCs. Finally, 14-stiffened DSTC specimens of different cross-sectional shapes, i.e., circle-circle (CC), square-circle (SC) and square-square (SS) cross-sections were tested for investigating their behavior under axial compression. Stiffened DSTCs showed significantly increased axial load capacity (up to about 32% in this study) with enhanced ductility than unstiffened specimens. The SS-shape DSTCs provided with steel stiffeners at mid-flat sides of the inner steel tube manifested relatively better performance benefits than CC and SC shapes.

The Study on Collapse Behavior and Crashworthiness Capacity of AL/CFRP Tubes Focusing on Fiber Angles and Stacking Sequence

This study has been aimed to investigate the effect of fiber orientation angle and stacking sequence on the collapse behavior and impact absorption capacity of hybrid tube. The specimens have been AL/CFRP composite materials made of cylindrical aluminum tubes (6063 -T5). The outer surface of the aluminum tube has been reinforced by wrapping with 1, 2 and 3 layers of Carbon Epoxy Fiber. The specimens have been tested with a dropped hammer of 30 kg weight and an impact speed of 6.905 m/s. Failure mode, maximum load, and average load from the test have been recorded. The FEA models of specimens have been also developed and tested with the same condition of experiment. The results have revealed that the AL/CFRP hybrid tube could resist higher impact loads than naked aluminum tube. The values maximum load and mean load were likely to increase according to the number of fiber layers, especially for the 3 layers hybrid tubes. It has been found out that the fiber angle of 45 degree had slightly effect to the load whereas the 0 and 90 degree angles have been much more effective. It has been also found out that stacking sequence has affected the pattern of failure and impact capacity considerably. The specimens with 90 degree fiber in the outer layers i.e. [0/90/90] and [0/0/90/90] have been found to provide the most crashworthy. It could be concluded that the combination and the stacking sequence of the fiber angles of 0 and 90 degree have highly affected the collapse mode and the crashworthiness capacity of hybrid tube.

Heat transfer and friction factor correlations for double pipe heat exchanger with inner and outer corrugation

ABSTRACT The double pipe heat exchanger (DPHE) is one of the most widely applicable heat transfer devices in many industries. In this study, numerical simulation is carried out to investigate a corrugation effect on the outer and inner surface of the inner tube in the double pipe heat exchanger. The liquid water is used as working fluid. The operating Reynolds number (Re) ranged from 4000 to 20000 and the constant temperature condition was imposed on the tube wall. The two kinds of tube named as internally corrugated inner tube (ICIT) and externally corrugated inner tube (ECIT) are modeled and numerically studied at three different helix angles (α) 15°, 20°, and 25° using the k-ε turbulence model. These numerical simulation results in heat transfer coefficient, frictional loss, drop in pressure, and rate of heat transfer. The findings indicated that externally corrugated inner tube (ECIT) shows greater efficiency with those from internal corrugated tube. The PEC was obtained higher for ECIT at α = 15°. Additionally, this investigation also develops correlations for heat transfer (Nu) and friction factor (f) and indicated maximum divergence between calculated and numerical values for Nu and f is ±5% and ±10% respectively.

ПОВЫШЕНИЕ ЭФФЕКТИВНОСТИ ТЕПЛООТДАЧИ В ВОЗДУШНОМ КОНДЕНСАТОРЕ ПРОПАНА

A variant of reconstruction of the tube bundle of an air-cooling apparatus designed for propane con-densation is considered in order to increase the intensity of heat transfer from the outer surface of finned tubes to atmospheric air.

Dynamic response of a functionally graded cylindrical tube with power-law varying properties due to SH-waves

An analytical solution to the dynamic response of a functionally graded cylindrical tube embedded in a full homogeneous space subjected to elastic SH waves is presented using the wavefunction expansion method. The shear modulus of the functionally graded tube is assumed to have a power-law variation with radius. The wave fields in the tube and unbounded surrounding medium are derived in a form of wavefunction series with unknown coefficients. The wave field coefficients are obtained by satisfying the boundary conditions at the inner and outer tube surfaces. The influences of the inhomogeneity exponent, shear modulus and thickness of the functionally graded tube, and the frequency of the incident SH waves on the dynamic stress concentration factor (DSCF) of the tube are systematically discussed. It is concluded that the application of functionally graded materials (FGMs) with a positive inhomogeneity exponent tends to weaken the DSCF along the inner surface of the tube significantly but intensify that along the outer surface slightly, which is beneficial to the long-term use of the tube.