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To resolve the problem of ductile fracturing of beam flanges in traditional connections with concrete-filled steel tube columns using site-welded side plates, an alternative connection design requiring minimal site welding was designed and studied. An explicit analysis method, considering the fracture strain criterion developed by the stress triaxiality path, was adopted to study the seismic performance and fracture resistance of the proposed connection. The results of a verified finite-element model indicated that the steel beam flange in the connection never fractured. The connection exhibited a notably higher maximum bending moment and ductility than the traditional connection. The side plates in the proposed connection were tension-bending or compression-bending elements, unlike in the traditional connection. The failure modes, maximum bending moment, ductility and stress distribution of the side plates were compared and analysed parametrically. Based on the stress distribution of the side plates according to the finite-element results, a fitting formula related to the width and thickness of the side plates was obtained. A formula to calculate the flexural capacity was also developed according to the force model of the proposed connection. The calculations and finite-element results were in good agreement.

Horizontal buried heat exchangers cost less than vertical buried heat exchangers, but they need more land area. In order to reduce the required land area of horizontal buried tube heat exchanger, a finned strengthened heat exchanger pipe was designed to enhance the heat transfer performance, and a three-dimensional research model of shallow geothermal utilization system was established in Chengdu area . In this paper, the optimal shape and arrangement of fins are investigated, and the effects of inlet velocity, soil type, ambient temperature and intermittent operation on the enhanced heat transfer performance are studied. The results show that the enhanced heat transfer performance of rectangular fins is the best in the case of horizontal arrangement. The working fluid flow rate should not exceed 0.3m/s.Soil type has a great influence on heat transfer performance. The heat transfer of rock and soil is the largest, the heat transfer of clay is the smallest, but the strengthening effect of clay is the best. The longer the system runs, the obvious the influence of ambient temperature is, and the heat transfer efficiency increases by about 4% when the ambient temperature drops by 5K.

Palladium (Pd) membranes are a crucial device for separating hydrogen and are usually operated at normal pressure on the permeate side with a single outlet. Instead of these common operating conditions, the difference between using a double outlet and a single outlet is studied. Four different vacuum degrees (15–60 kPa) are applied on the permeate side, and the results are compared with the non-vacuum operations. Situations under the vacuum and the effects of temperatures (300–400 °C) on H2 permeation are discussed. Finally, the influences of different feed gas mixtures (H2/N2, H2/CO2, and H2/CO) on the Pd membrane performance are investigated. The results show that there is no difference in H2 permeation impact the single outlet and the double outlet on the permeate side. When a vacuum is imposed on the permeate side, the H2 permeation rate and H2 recovery are efficiently intensified, that is, when the pressure difference is 9 atm, they increase from 73.21 to 84.51% and from 0.0035378 to 0.0040808 mol∙s−1, respectively. Moreover, the H2 recovery can be improved to up to 68.44% under a vacuum degree of 60 kPa. At a given Reynolds number, an increase in temperature increases the H2 permeation rate but lowers its recovery, stemming from more H2 in the feed gas. This study also investigates the feed gas of H2/N2 under a vacuum to provide a useful insight into H2 production and separation from ammonia, and the results are compared with two different feed gases of H2/CO2 and H2/CO mixtures. The results suggest that the impurities (i.e., N2, CO2, and CO) have a negative influence on the Pd membrane, which causes the H2 permeation rate to decrease, and the effect of N2 is the least significant compared to the other two.

In this study, the tube surfaces generated by the curve defined in Galilean 3-space are examined and some certain results of describing the geodesics on the surfaces are also given. Furthermore, the conditions of being geodesic on the tubular surface are obtained with the help of Clairaut’s theorem, which allows us to constitute the specific energy. The physical meaning of the specific energy and the angular momentum is of course related with the physical meaning itself. Our results show that the specific energy and the angular momentum obtained on tubular surfaces can be expressed using arbitrary geodesic curve in Galilean space. In addition, some characterizations are given for these surfaces, with the obtained mean and Gaussian curvatures.

We all know that heat exchanger is one of the equipment to transfer the heat between the fluids. Heat will transfer from one side of fluid to another side of fluid. In this project we use counter flow heat exchanger. In this heat exchanger one kind of fluid will come from one side and another kind of fluid will come from another side. Both fluids will be sending inside to the tube in opposite direction. Here we are using two medium one is hot fluid and another one is APISN (American Petrol Institution of Super Natural) with B grade oil. Inside of apparatus we are using copper tube, to enhance the heat transfer. Because that copper is having higher thermal conductivity (385 W/m K). When we compared to the carbon steel (19 W/m K), copper is having more thermal conductivity. The reason for choosing copper tube is not only higher thermal conductivity; it's also having properties like corrosion resistance, max allows able stress and internal pressure. Hot fluid will be send through the way of inside of the copper tube. Over the copper tube will send APISN oil, both will be send in an opposite manner. In a setup of counter flow heat exchanger, we put two holes with some dimension. When the fluid goes inside of the tube we insert the digital thermo-meter to note down the temperature of both inlet and outlet. After taking all reading we will evaluate the counter flow heat exchanger with term of efficiency.

An experimental investigation was carried out on a novel type of concrete-filled tube column, which used geopolymer concrete and basalt-fibre-reinforced-polymer reinforcing bars and confinement tube. Geopolymer concrete was used in place of ordinary Portland cement concrete to counter the sustainability challenges of conventional cement manufacture. Longitudinal basalt-fibre-reinforced-polymer bars were used to replace steel reinforcement to avoid corrosion, while basalt-fibre-reinforced-polymer tube confinement was used to replace the conventionally used steel helix to enhance strength and ductility. Compressive load–deformation behaviour of 200 mm dia., 800 mm high specimens under concentric, 25 mm eccentric, 50 mm eccentric and four-point bending loads was experimentally investigated. Experimental axial load–bending moment diagrams were then produced. Although geopolymer concrete is normally considered to be more brittle than Portland cement concrete, the test results showed that the specimens with geopolymer concrete were more ductile compared to those with Portland cement concrete. It was also found that increased load eccentricity resulted in ductility enhancement in specimens with both types of concrete with basalt-fibre-reinforced-polymer bars and tubes, while steel-reinforced specimens suffered loss of ductility with increased load eccentricity.

Small tube irrigation is a new type of micro-irrigation that the emitters were replaced by small tubes. The small tubes of 4 mm diameter were connected to the laterals through the flow stabilizer or directly to the laterals. The discharge formulations and total heads of the system have been driven from the basic formulas of friction losses and other minor losses of the laterals. Based on hydraulic analysis of laterals, the cost function of lateral and pump, the operation cost and the objective function of lateral diameter optimization technique was established. In the study, a typical irrigation system of fruit tree was taken as an example, in which the length of lateral pipe was 100 m, and assuming that the small tube flow range is 10–40L/h, lateral diameter ranges 12–25 mm, and the field slope ranges −20%∼20%. The results showed that the minimum total cost was obtained with a lateral diameter of 13.6 mm at 10 L/h flow rate, for the flow rate of 20L/h, the minimum cost is obtained at the diameter of 13.6 mm for down-slopes and 17.2 for flat land and up-slopes, and for the flow rate of 30L/h and 40L/h the minimum cost is obtained at 17.2 mm diameter for any slopes.

During a severe accident, steam generator (SG) tubes undergo rapid changes in the pressure and temperature. Therefore, an appropriate creep model to predict a short term creep damage is essential. In this paper, a novel creep model for Alloy 690 SG tube material was proposed. It is based on the theta (θ) projection method that can represent all three stages of the creep process. The original θ projection method poses a limitation owing to its inability to represent experimental creep curves for SG tube materials for a large strain rate in the tertiary creep region. Therefore, a new modified θ projection method is proposed; subsequently, a master curve for Alloy 690 SG material is also proposed to optimize the creep model parameters, θi (i = 1–5). To adapt the implicit creep scheme to the finite element code, a partial derivative of incremental creep with respect to the stress is necessary. Accordingly, creep model parameters with a strictly linear relationship with the stress and temperature were proposed. The effectiveness of the model was validated using a commercial finite element analysis software. The creep model can be applied to evaluate the creep rupture behavior of SG tubes in nuclear power plants.

This paper presents a description of the modernized detonation driven shock tube DDST-M, in which conditions that simulate the entry of spacecraft into the Earth's atmosphere at the super orbital velocity (11.2 km/s) are achieved. The modernization consists in the inclusion of an additional element in the shock tube design - the prechamber, which separates the end wall of the tube with the igniter from the main volume by the perforated disc. The presence of the prechamber increases the energy efficiency of the facility, primarily due to a more complete combustion of the combustible mixture in the high-pressure chamber, which makes it possible to obtain higher shock wave velocities in the low-pressure chamber. A series of experiments was carried out to study the radiation characteristics of high temperature air in the range of shock wave velocities VSW = 4.2 ÷ 11.4 km/s and initial gas pressures p0 = 0.25 ÷ 10 Torr. Analysis of the obtained data made it possible to distinguish the features of the radiation in different parts of the spectrum depending on the shock wave velocity and the initial gas pressure. The measurement results are compared with the results of other studies.

This paper aims to numerically investigate the effects of turbulence-inducing elements with various geometries in a double pipe Heat Exchanger (HEX). The water is considered as a working fluid and the flow is turbulent. Also, CFD simulation has been carried out by finite volume method within commercial software. In the first section, the various geometries, including smooth tube, corrugated tube, tube with spherical elements, and a tube with axial fins, are evaluated. Subsequently, the heat transfer characteristics of two various hybrid nanoparticles comprise Ag-MoS2 and Fe3O4-SiO2, are compared. Ultimately, the optimized geometry has been selected for adding hybrid nanoparticles of Ag-MoS2 to enhancing heat transfer performance. The obtain results indicate that the double tube heat exchanger with the spherical elements has the best thermal performance. In addition, with changing the Reynolds number from 4000 to 13,000 in the optimized model with Ag-MoS2 1%, the convective heat transfer coefficient enhances 62.21%.

Electrochemical drilling (ECD) provides an alternative technique for drilling multiple small holes in difficult-to-machine materials in numerous industrial applications such as for aeroengines. The value and fluctuation of electrolyte flowrate can seriously affect the machining stability and hole quality in ECD. In particular, when drilling multiple holes, the distribution and fluctuations of the electrolyte flowrate in each channel could influence the uniformity of the electrolyte flowrate among multiple tube electrodes, thereby affecting the machining stability and the maximum feed rate. Thus, an eight-channel flow control system was developed to measure and regulate in real time the electrolyte flowrate supplied into each individual tube electrode. This paper proposes ECD of small holes with real-time flowrate control to improve the uniformity of electrolyte flowrate in each tube electrode and reduce the fluctuations in the electrolyte flowrate. In single-hole drilling, when the electrolyte flowrate was regulated in real time, the hole quality and machining stability were considerably better than without regulation. This is because the electrolyte flowrate remains basically constant, which stabilizes the flow field. Moreover, by considering the hole profile, it was found that an electrolyte flowrate of 200.0 mL/min can be acceptable for ECD of small holes. When the eight-channel flow control system was used in multiple-hole drilling, the uniformity of the electrolyte flowrate in each tube electrode was obviously improved, which led to a more stable process. Additionally, the maximum feed rate can attain 2.40 mm/min in multiple-hole drilling. Based on these findings, a matrix (5 × 32) of multiple small holes was successfully fabricated with a satisfactory diameter consistency, as the machining stability and machining efficiency had been enhanced.

In the present study, the effect of conical obstacles on heat transfer and flow characteristics in a circular tube was investigated. In most previous studies, stationary obstacles were used to stim...

This chapter deals with the mechanics of inelastic bending in the presence of tension. Bending a circular tube ovalizes its cross sections and leads to a limit-load instability. Bending in the presence of tension can aggravate the growth of ovalization. Two types of combined bending-tension loading have been identified. The first is encountered in a suspended line, where the tension is used to control the shape of the suspended section. In this case, the tension is reacted by a distributed force normal to the axis of the tube that occurs because of the weight of the pipe and the buoyancy force. The transverse force acts at the axis of the tube and thus does not influence ovality. In this type of loading, the tension interacts with the bending (and possibly pressure) through an inelastic action by aggravating the state of stress. In the second type of combined bending-tension loading, the pipe is bent over a rigid surface, in which case the tension is reacted by a distributed force acting on the surface of the bent tube. This type of loading is encountered, for example, by a pipeline passing over a curved stinger and when winding or unwinding a line on a reel.

The nose is not a tube, nor can it be regarded as two pipelines transporting air to the lung.

Low fuel regression rate is one of the major drawbacks of hybrid rocket motors. In this study, a novel injector concept is proposed to provide a substantial enhancement in the fuel regression rate....

Background: The aim of this study was to investigate the clinical effectiveness of an indwelling transanal tube for the prevention of anastomotic leakage (AL) after a radical operation for Hirschsp...

An experimental study has been conducted to investigate the heat transfer characteristics of supercritical carbon dioxide (sCO2) uniformly heated in the horizontal circular smooth tube. The results illustrated that there was a significant difference in heat transfer between the top wall and bottom wall due to the buoyancy. Bulk flow acceleration cannot be negligible in the high heat flux region, which leads to heat transfer deterioration. A new heat transfer correlation is proposed, in which the buoyancy parameter and bulk flow acceleration have been taken into account. The new correlation and six classic correlations for sCO2 are examined in horizontal tubes. The comparison indicates that the new correlation has a better performance for sCO2 flowing through a horizontal heating tube under natural circulation conditions. For example, 94.9% of the calculated results using the new heat transfer correlation were within ±30% of the experimental results while only 87.9% of that using the Jackson correlation (the best of the six) were within the same error bands.

In the present study, an experimental study and a numerical method are used to simulate the effect of utilizing finned helical coil heat exchanger horizontally oriented with and without internal hollow core inside the shell and monitoring the heat transfer intensification behavior and performance enhancement, by using ANSYS FLUENT 2019R3 package. The working fluid in the inlet side of the coil will be superheated vapor refrigerant (R410a) after the compression stage of the air conditioner (1TR) split type, the working fluid in the shell side is water with various flow rates (1,2 and 3) LPM. Found that when using a heat exchanger with internal hollow core reduces the time needed to reach the steady-state outlet temperature and directly proportional to the size of the core by 20% and slightly increasing the water outlet temperature by 5%.

In this paper, the challenge is to increasing of the heat exchanger performance by placing different size balls inside the tubes. the development of previous studies to enhance relatively bad case of heat transfer where the inserting (a large ball and then a small ball) to collide the water molecules in the ball and generate turbulent flow (Reynolds number range from 50,000 to 350,000) and thus increase the thermal performance due to collision of particles with the inner casing of the tube and reduce the stagnation near the wall. The usefulness of small ball, after the big ball, is Reduce of gets wake flow. A simulation was made when changing the diameter ratio of big to small ball (Dr = 3, 4, 5). Also, the distance between the big ball and the small ball was changed (X = 2, 3, 5) mm. It was concluded that the best ball diameter ratio and best Distance is (Dr= D_b/D_sb = 5), (X = 3 mm), respectively. The pressure drop acts as a side effect of enhancement. Therefore, the method of equal pumping was adopted. The average thermal performance factor (TPF=1.178) of tube with insert the balls enhanced by 17.8% at (x=3mm) and (Dr=5) when compared with smooth tube.

Ag–C composite coating exhibits excellent electrical and thermal conductivities, good arc mobility, and low contact resistance, making it has a good prospect in switch contact of high voltage isolators. At present, the electro-deposition method is mainly used to prepare Ag/C composite coatings. However, the production efficiency of the electro-deposition method is low and the obtained coatings are thin. The electrical explosion spraying, due to its simplicity and high efficiency, has attracted significant attention in coating preparation. In this study, a new method that confines Ag and graphite powders in a tube for electrical explosion spraying was proposed. Powder electrical explosion spraying was used for preparing an Ag/C composite coating by employing a self-designed device. The heating behavior of the powder during exploding, macroscopic morphology, micromorphology, deposition efficiency, and thickness of the coatings, as well as the deposition behavior of the sprayed particles, were investigated. After a single spraying, a dense and uniform Ag/C composite coating was obtained at the charging voltage of 13 kV and a spray distance of 18 mm. The results show that the coating area is approximately 39.25 mm2, the coating thickness was 50 μm, and the deposition efficiency was 35%. the coatings have good adhesion with the substrate. the interface between the coating and the substrate appeared as an inter-diffusion of elements, which was typical of a metallurgical bonding interface. Graphite is evenly distributed in the coating. Furthermore, the underlying deposition behavior of the coating was carefully characterized.

BACKGROUND: Lowering kVp affects the image contrast and computed tomography (CT) attenuation values of low kVp CT is different from those of conventional 120-kVp scans. The purpose of this study is to determine the diagnostic performance and to establish the reference range of low-kVp unenhanced CT for the assessment of hepatic steatosis in liver transplantation donors using magnetic resonance (MR) spectroscopy as a reference standard. METHODS: This retrospective study included 165 potential donors (male:female =114:51, 36.5±12.0 years old) who underwent 100-kVp single-slice unenhanced CT scan and MR spectroscopy. The difference between hepatic and splenic attenuation (CT(L-S)) and liver-to-spleen attenuation ratio (CT(L/S)) were calculated. Reference standard was the fat signal fraction measured by MR spectroscopy. Limits of agreement between CT measurements and the reference standard were calculated. Areas under receiver operating characteristic curves (AUROCs) of CT(L-S) and CT(L/S) were compared for the diagnosis of moderate to severe steatosis. Cut-off values of CT(L-S) and CT(L/S) that provided a balance between sensitivity and specificity and the highest specificity using the lower limit of the reference range were calculated. RESULTS: Eighty-seven subjects had a non-steatotic liver. Sixty-one subjects had mild steatosis and 17 subjects had moderate to severe steatosis based on MR spectroscopy. CT(L-S) and CT(L/S) values were negatively correlated with the fat signal fraction (P

For two kinds of specially made enhanced tubes with outer diameters of 19mm and 25mm, the falling film evaporation experiment was carried out by using environmental refrigerant R1234ze (E) under the experimental condition that the water velocity in the tube was controlled from 1 to 3.5 ms−1. "The Wilson-Gnielinski Separation Method" and "The Wilson-Gnielinski-Heat Flux Correction Method" were used to process the experimental data. The comparative analysis showed that when the heat fluxes of all the test points outside the tube were constant, the results of two calculation methods were almost the same. When the heat fluxes of all the test points outside the tube were fluctuant, the results of two calculation methods were different and the heat flux correction method should be applied to reduce the error. The enhanced tube with outer diameter of 19mm was used to investigate the heat transfer performance of falling film evaporation, with spray density ranging from 0.03 to 0.1kgm−1s−1, heat flux ranging from 15 to 45 kWm−2 and evaporation temperature ranging from 0 to 25°C. And the enhancement rate inside the tube was obtained by using the heat flux correction method. Finally, the variation trends of the overall heat transfer coefficient and the outside tube heat transfer coefficient under different working conditions were both obtained experimentally and analyzed theoretically.

This paper presents two-dimensional heat transfer results for the first time in an expansion tube, using infrared thermography at a Mars entry condition. Experiments were performed in the X2 expans...

Pulse tube is one of the main parts of the pulse tube cryocooler. Ideally, the pulse tube works under adiabatic environment without heat transfer loss. But in real case, entropy is generated in the pulse tube itself from heat exchanged with the walls, turbulent mixing of the hot and cold gas segments, circulation of the gas within the tube, and end effect losses from the adiabatic to isothermal transition in the cycle. All these processes reduce the enthalpy flow in the pulse tube from the ideal acoustic power. However, no 1D model can sufficiently simulate these effects in the past. Also, most of the 1D models about the pulse tube part with a heat transfer coefficient is far from accurate, especially for micro pulse tube in which the heat transfer is more obvious. This work revealed that the basic heat transfer changes instantaneously and shows different tendencies in different time of one cycle, and no suitable law or explanation could fare well the phenomenon eventually. The phase angle changes from negative to positive that results in the relatively heat flux along the pulse tube becomes smaller, that could help the pulse tube to make a good performance.

The tube indirect evaporative cooler is energy-saving and environmentally friendly, and its heat transfer mechanism still needs to be fully indicated, for which the numerical method is more suitable than the experiment. Because many numerical researches focusing on the tube indirect evaporative cooler are usually based on the simplified models, such as single tube model, single side model, one-dimensional and two-dimensional model, the further improvement is still needed. Meanwhile, the tube indirect evaporative cooler is always expected to supply more cooling air with lower temperature at lower cost of energy, but many present studies are focusing on the improvement of heat transfer only and ignoring the energy cost. This paper proposed a three-dimensional full-scale numerical model and method verified by the experimental data, by which, the energy output (primary air-cooling capacity) and quality (temperature of primary air outlet) at the resistance loss(resistance) of the tube indirect evaporative cooler are analyzed with the help of Fluent software.

A numerical calculation model of multihead twisted spiral tube was established. In the range of Reynolds number from 5000 to 35000, the influence of different twisted structure on the flow and heat transfer characteristics of the multihead twisted spiral tube was studied by numerical calculation. Numerical calculation results indicate that the Nusselt number and friction coefficient increase with the increase in the ratio of outside and inside diameter of the cross-section, the increase in the number of twisted nodes, and the increase in the number of twisted spiral tube heads. Under the condition of the same spiral structure and the same hydraulic diameter, the heat transfer performance of the multihead twisted spiral tube is better than that of the spiral smooth tube. In addition, through artificial neural network analysis, the ratio of outside and inside diameter of the cross-section, number of twisted nodes, and the number of twisted spiral tube heads were optimized to promote the comprehensive heat transfer performance. The performance evaluation criterion is the highest when the ratio of outside and in-side diameter of the cross-section is 25/22.5, the number of twisted nodes is 3, and the number of twisted spiral tube heads is 3, which is 1.849 of the spiral smooth tube.

The main objective of this research paper is to evaluate the performance of triple concentric tube heat exchangers experimentally under steady-state conditions. Water is considered as the working fluid and is circulated through the inner tube, inner annulus, and outer annulus at different temperatures. For this purpose hot water, normal water, and intermediate temperature water are considered. The experiment has been performed in the laboratory of the Mechanical Engineering Department at BIT Sindri Dhanbad in India. The arrangement of a triple concentric tube is installed by using three tubes of different materials. Aluminium, Copper, and galvanized iron (G.I) are used to make an inner tube, inner annulus, and outer annulus respectively. The variation of fluid temperature along the length of the heat exchanger has been measured. Also, the variation of friction factor and Nusselt number with Reynolds number has been studied for different conditions. The best result of this experimental study has been found in counter-current arrangement (A2) and the value of the overall coefficient is 0.42.

Heat transfer enhancement is the essential region to protect energy, and furthermore, to accommodate a financial perspective is a concern. Heat transfer enhancement techniques are utilized into different mechanical applications as into heat exchanger, air conditioners, solar tubes, chemical reaction tube and refrigerating devices. The few passive types of equipment as twisted tapes, irregular components, wires inserts etc. are an efficacious technique to upgrade into heat transfer. Amongst the transcendent techniques utilizing in heat transfer for passive type is twisted tape inserts. The present research paper reviews the heat transfer enhancement region with twisted tapes into recent years. Past examinations on various kinds of twisted tapes (basis of review) were shown. Also, the paper unveiled the research for future on twisted tapes will more noteworthy improvement in heat exchanger device additionally gives scope for various altered methods for the new advancement of heat transfer improvement. [copyright information to be updated in production process]

To enhance the temperature uniformity and NOx reduction performance of the gas-fired radiant tubes, we proposed a new multi-stage dispersed burner based on fuel-staging combustion technology in this study. The effect of fuel nozzle structural parameters, including secondary fuel nozzle distance D (30, 50, 70 mm), secondary fuel nozzle diameter ds (2, 3, 4, 5, 6 mm) and tertiary fuel nozzle diameter dt (2.5, 5, 7.5, 10 mm) on the flow field, temperature distribution, NOx generation and thermal efficiency were analyzed by numerical simulations. The results show that the multi-stage dispersed fuel nozzle could slow down the combustion rate and form a low-oxygen dilution zone in the reaction process, reducing the maximum combustion temperature and NOx emission. With the increase of the secondary fuel nozzle distance, the NOx concentration at the outlet decreased from 69.0 ppm to 54.6 ppm, and a decrease of 20.9%. When the secondary fuel nozzle diameter increased from 2 mm to 6 mm, the maximum wall temperature difference gradually increased 72.8 K to 76.3 K. NOx emission at the outlet first decreased, then increased, and was as low as 45.6 ppm at a 5 mm diameter. Furthermore, increasing the tertiary fuel nozzle diameter could reduce the maximum wall temperature difference and NOx emission, and improve thermal efficiency. When dt = 7.5 mm, the overall performance of the radiant tube was the best, and the outlet NOx concentration, wall temperature difference and thermal efficiency were 46.1 ppm, 73.0 K, 63.7%, respectively.

Layup temperature is a vital factor that affects the production quality of automated fiber placement for thermoset composites. For high quality production, this paper proposes a new prediction model of layup temperature by considering the structure of infrared heater of automatic fiber placement equipment. The model was first verified by comparing with the temperature results of layup experiments. Then a prediction on the effects of heater structure arrangement on layup temperature was conducted in the model. The research shows that the length of infrared tube and the radian of reflective-film have significant influences, rather than other parameters. According to this investigation, a heater structure-based heating strategy was presented in the paper to efficiently achieve constant temperature control in variable speed layup process.

The effect of the design on the heat transfer is numerically investigated by using the wavy inner tube in a double-pipe heat exchanger. A wavy inner tube was used in the design to give a turbulent effect to the fluid along the inner tube of a double tube heat exchanger. In numerical study, ANSYS 12.0 Fluent code program was used, and the basic protection equations were solved for steady-state, 3-D and turbulent flow conditions. The study was examined at Reynolds numbers ranging from 2700-5300. The obtained results were compared with the experimental data performed under the same conditions. As a result of this comparison, after it was seen that the results obtained from the numerical analysis and the experimental results were compatible with each other, the wave number of the inner tube was increased and analyzed with the ANSYS fluent code program. When the data obtained as a result of the analyzes were evaluated, it was seen that the highest heat transfer was obtained from the 16 wave tube heat exchanger, which has the highest number of waves and under counter flow conditions. The increase in heat transfer increased by 270% compared to the straight tube.

This paper aims to experimentally investigate the heat transfer characteristics of pool boiling on horizontal U-shaped tubes in a large-scale confined space. The saturation temperature ranges from 20 to 40°C and the heat flux varies from 2.5 to 10.5 kWm−2. Two types of tubes with an outside diameter of 19.05 mm are tested: a smooth tube and a fin-enhanced tube with 0.4 mm fin height, 1220 fpm (fins per meter) and a 0.12 mm fin gap. The tubes are made of titanium with a length of 1165 mm. In case of pool boiling, the heat transfer coefficient for the tested tubes increases with increasing saturation temperature and heat flux. The fin-enhanced tube facilitates the bubble nucleation with the heat transfer coefficient enhancement factor varying in the range of 1.25∼2.28. Furthermore, the experimental heat transfer coefficients are compared with four correlations obtained in the open literature. R-J correlation and Copper correlation are found to be the optimum correlation for the smooth tube and the enhanced tube with the mean relative error of 10.93% and 11.48%, respectively. Findings from this study can supply a fundamental basis for validation and improvement propane heat transfer performances for the intermediate fluid vaporizer (IFV) engineering design.

In recent decades, the application of concrete-filled single and double skin steel tube columns in moderate and high rise structures has expanded rapidly hence understanding the influence of various parameters on the axial load characteristics of composite columns has become a top priority. A parametric investigation of the action of concrete-filled single skin and double skin tube columns under the influence of axial load is presented in this research. A numerical finite element analysis with the help of ABAQUS/CAE 6.14 software is carried out considering the various parameters such as varying grade of steel tube and concrete core, steel tube thickness, ratio of diameter-to-thickness of columns and slenderness ratio of column specimens. All of the variables studied have a significant impact on the CFST (single skin and double skin) columns' axial compressive strength, and these factors are addressed in detail in this work. The study revealed that growing ratio of diameter to thickness reduces the ultimate load capacity of both type of composite columns. It is also observed that when there is an increase in the steel and concrete grade, the loading capacity of the columns gets enhanced. Also, reduced length-to-diameter ratio is found to improve the axial loading capacity of columns. The axial strength of concrete filled single skin tube columns (CFST) is found to get highly influenced with the variations of all the different parameters as compared to concrete filled double skin tube columns.

The Magnetically Impelled Arc Butt (MIAB) welding process uses a rotating arc as its heat source and is known as an efficient method for tube welding. Interaction of external magnetic field and induced magnetic flux results in the creation of Lorentz force along peripheral edges of tubes. The circumferential arc rotation helps in the uniform heating of faying surfaces. After sufficient melting, faying surfaces are pressed against each other for weld formation. This paper aims at studying the notch tensile properties of T11 tubes welded by MIAB welding. In MIAB welded T11 steel tubes various Thermo-Mechanically Affected Zones (TMAZ) are formed as an effect of heat and pressure during welding. Tensile properties of all these TMAZs are different due to varying microstructures. Therefore notched tension testing was carried out to compare the properties of various zones in welded T11 tubes. All TMAZs show higher notch ductility with Notch Strength Ratio (NSR) greater than one. In comparison to the base metal, all TMAZs except TMAZ III display no loss in notch strength. The presence of granular bainite in TMAZ III causes lower notch strength with a Normalized Notch strength (NTSN) ratio less than unity.

The inclusion of baffles in a double pipe heat exchanger is becoming increasingly important as it improves the heat exchanger's performance. CFD analysis is used in this paper to investigate the performance of double pipe heat exchangers with and without helical baffles on both shell tube sides. The 3D Computation Fluid Dynamics (CFD) model was created in Solid Works, and the FloEFD software was used to analyze the conjugate Heat Transfer between the heat exchanger's tube and shell sides. Heat transfer characteristic like Outlet temperature of shell and tube are investigated along with pressure drop on shell and tube side. Based on CFD results of Double Pipe Heat exchanger with helical baffle on both shell side and tube side (Type 4) gives the better results than the other type of heat exchangers with an increased pressure drop than the others, results reveals that type 4 outlet temperature of shell side is 8% higher and on tube side it is 5.5% higher, also pressure drop on shell side is 12% higher and on tube side it is 42% higher than the other types.

Retinal microsurgery requires precise manipulation of delicate tissue in the interior of the eye. Force sensing instruments can provide surgeons the imperceptible force information, thereby improving the safety of retinal microsurgery. Previous force sensing microneedles have demonstrated robust performance in transverse force measurement. However, in some surgical operations such as puncturing the vessel, the axial force sensing function is critical. In this article, we present a three degrees of freedom force sensing microneedle based on fiber Bragg grating (FBG) sensors. A novel configuration of the FBG sensors is arranged to detect the transverse and axial forces. Three optical fibers with dual FBGs are longitudinally attached along the outside surface of a Nitinol tube. Benefiting from the novel configuration of the FBG sensors, a hollow channel can be used to pass through injection catheter. A new force calculation algorithm was developed to decouple the transverse forces and axial forces. Experimental results demonstrate the proposed force calculation algorithm can achieve a resolution of 0.124 and 0.74 mN for transverse forces and axial forces, respectively. Validation and temperature compensation experiments show the force sensor can provide consistent and accurate measurement of 3-D forces within 35–37 °C temperature variation.

Based on a new type of elastic scroll tube bundle (ESTB) heat exchanger, the influence of shell-side fluid inlet velocity and tube bundle constraint condition on the enhanced heat transfer performa...

We analyzed mitigation strategies for steam generator tube rupture (SGTR) accidents using MARS code under both full-power and low-power and shutdown (LPSD) conditions. In general, there are two approaches to mitigating SGTR accidents: supplementing the reactor coolant inventory using safety injection systems and depressurizing the reactor coolant system (RCS) by cooling it down using the intact steam generator. These mitigation strategies were compared from the viewpoint of break flow from the ruptured steam generator tube, the core integrity, and the possibility of the main steam safety valves opening, which is associated with the potential release of radiation. The “cooldown strategy” is recommended for break flow control, whereas the “RCS make-up strategy” is better for RCS inventory control. Under full power, neither mitigation strategy made a significant difference except for on the break flow while, in LPSD modes, the RCS cooldown strategy resulted in lower break and discharge flows, and thus less radiation release. As a result, using the cooldown strategy for an SGTR under LPSD conditions is recommended. These results can be used as a fundamental guide for mitigation strategies for SGTR accidents according to the operational mode.

Energy saving is the major challenge for people now these days because of the depleting fossils fuels day by day. Shell & tube heat exchanger is used in many industrial applications such as renewable energy, aviation industry, automobile industry, oil, and gas industry and many more for energy conversion at reduced cost without any environmental effects. This is accomplished by utilizing a fluid that has higher thermal conductivity. The utilization of nanofluid in such equipment increases heat transfer rate very rapidly because of its higher thermophysical properties relative to other fluids. The principal goal of this paper is to give an extensive review of the utilization of nanofluids in shell & tube heat exchangers to reduce the pressure drop, increase energy saving and ultimately increase the effectiveness of the system without any environmental effects.

This article aspires to evaluate the effect of dynamic control on the stream’s nature in an abruptly expanded conduit of a diameter ratio of 2.2. The investigation was done for Mach 1.6, 1.8, 2.0, and 2.5. Results are shown when control renders any change in the flow field. It is found that at Mach 1.6 for NPR = 7 and the tube size of L = 10D, the jets’ noise is considered in the control mechanism’s nonappearance and existence. The results show that there is a significant decrease in the noise level, and jets become quiet. It is also observed that the base pressure is also minimal whenever the jet’s noise is low due to the microjets. At Mach 1.6, 1.8, and 2.5, the control findings decrease the duct’s pressure value for most cases. However, in Mach 2.0, when the control is activated, it increases the duct’s static pressure. The microjets do not interrupt the flow field in the pipe adversely.