Academic literature on the topic 'Maximum channel wall temperature'
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Journal articles on the topic "Maximum channel wall temperature"
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Hall, D. A., G. C. Vliet, and T. L. Bergman. "Natural Convection Cooling of Vertical Rectangular Channels in Air Considering Radiation and Wall Conduction." Journal of Electronic Packaging 121, no. 2 (1999): 75–84. http://dx.doi.org/10.1115/1.2792671.
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Temperature distributions on the surfaces of vertical channels formed by parallel plates heated uniformly and symmetrically and cooled by conduction, radiation, and natural convection in air are determined numerically and experimentally. Effects of wall separation, thickness, thermal conductivity, and emissivity on the wall temperature distribution are determined. Both cases of controlled and uncontrolled channel edge leading and exit edge temperatures are examined. Optimum channel widths and correlations for the maximum wall temperature rise are offered for both the controlled and uncontrolled edge temperature conditions.
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Alharbi, Ali Y., Deborah V. Pence, and Rebecca N. Cullion. "Thermal Characteristics of Microscale Fractal-Like Branching Channels." Journal of Heat Transfer 126, no. 5 (2004): 744–52. http://dx.doi.org/10.1115/1.1795236.
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Heat transfer through a fractal-like branching flow network is investigated using a three-dimensional computational fluid dynamics approach. Results are used for the purpose of assessing the validity of, and providing insight for improving, assumptions imposed in a previously developed one-dimensional model for predicting wall temperature distributions through fractal-like flow networks. As currently modeled, the one-dimensional code fairly well predicts the general wall temperature trend simulated by the three-dimensional model; hence, demonstrating its suitability as a tool for design of fractal-like flow networks. Due to the asymmetry in the branching flow network, wall temperature distributions for the proposed branching flow network are found to vary with flow path and between the various walls forming the channel network. Three-dimensional temperature distributions along the various walls in the branching channel network are compared to those along a straight channel. Surface temperature distributions on a heat sink with a branching flow network and a heat sink with a series of straight, parallel channels are also analyzed and compared. For the same observed maximum surface temperature on these two heat sinks, a lower temperature variation is noted for the fractal-like heat sink.
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Kim, S. H., N. K. Anand, and L. S. Fletcher. "Free Convection Between Series of Vertical Parallel Plates With Embedded Line Heat Sources." Journal of Heat Transfer 113, no. 1 (1991): 108–15. http://dx.doi.org/10.1115/1.2910512.
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Laminar free convective heat transfer in channels formed between series of vertical parallel plates with an embedded line heat source was studied numerically. These channels resemble cooling passages in electronic equipment. The effect of a repeated boundary condition and wall conduction on mass flow rate (M), maximum surface temperature (θh,max and θc,max), and average surface Nusselt number (Nuh and Nuc) is discussed. Calculations were made for Gr*=10 to 106, K=0.1, 1, 10, and 100, and t/B=0.1 and 0.3. The effect of a repeated boundary condition decreases the maximum hot surface temperature and increases the maximum cold surface temperature. The effect of a repeated boundary condition with wall conduction increases the mass flow rate. The maximum increase in mass flow rate due to wall conduction is found to be 155 percent. The maximum decrease in average hot surface Nusselt number due to wall conduction (t/B and K) occurs at Gr*=106 and is 18 percent. Channels subjected to a repeated boundary condition approach that of a symmetrically heated channel subjected to uniform wall temperature conditions at K≥100.
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Vasnev, I. R., and N. N. Fedorova. "Numerical modeling of heating a heat flux gauge in a supersonic flow." Journal of Physics: Conference Series 2389, no. 1 (2022): 012010. http://dx.doi.org/10.1088/1742-6596/2389/1/012010.
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Abstract This paper has developed a mathematical model for calculating the conjugate heat transfer between a supersonic airflow at the freestream Mach numbers M ∞ = 3, 4, 5, and a copper plate simulating the sensitive thermocouple element. The calculation results are compared with the experiment. The calculations show the effect of turbulence intensity, temperature boundary condition, and flow rate on sensor heating. The results of the sensor's initial heat fluxes, maximum temperatures, and heating times in different flow regimes are presented. Also, the flow regimes with an adiabatic wall are considered. As a result of calculations, it is shown that for the given freestream Mach numbers under "cold" wall temperature conditions, the sensor warms up to the maximum temperature in 1.5-3 seconds and reaches temperatures from 789 to 1076 K. If the adiabatic conditions are assumed at the channel walls, depending on the Mach number at the channel entrance, the sensor is heated from 1600 to 2250 K.
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Webb, B. W., and D. P. Hill. "High Rayleigh Number Laminar Natural Convection in an Asymmetrically Heated Vertical Channel." Journal of Heat Transfer 111, no. 3 (1989): 649–56. http://dx.doi.org/10.1115/1.3250732.
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Experiments have been performed to determine local heat transfer data for the natural convective flow of air between vertical parallel plates heated asymmetrically. A uniform heat flux was imposed along one heated wall, with the opposing wall of the channel being thermally insulated. Local temperature data along both walls were collected for a wide range of heating rates and channel wall spacings corresponding to the high modified Rayleigh number natural convection regime. Laminar flow prevailed in all experiments. Correlations are presented for the local Nusselt number as a function of local Grashof number along the channel. The dependence of both average Nusselt number and the maximum heated wall temperature on the modified Rayleigh number is also explored. Results are compared to previous analytical and experimental work with good agreement.
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Manca, Oronzio, Marilena Musto, and Vincenzo Naso. "Experimental Investigation of Natural Convection in an Asymmetrically Heated Vertical Channel with an Asymmetric Chimney." Journal of Heat Transfer 127, no. 8 (2005): 888–96. http://dx.doi.org/10.1115/1.1928909.
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An experimental investigation on air natural convection, in a vertical channel asymmetrically heated at uniform heat flux, with downstream unheated parallel extensions, is carried out. One extension is coplanar to the unheated channel wall and the distance between the extensions is equal to or greater than the channel gap (geometrically asymmetric chimney). Experiments are performed with different values of the wall heat flux, aspect ratio (Lh∕b), extension ratio (L∕Lh) and expansion ratio (B∕b). For the largest value of the aspect ratio (Lh∕b=10), the adiabatic extensions improve the thermal performance in terms of lower maximum wall temperature of the channel. Optimal configurations of the system with asymmetrical chimney are detected. Flow visualization shows a cold inflow in the channel-chimney system that penetrates down below the channel exit section. Maximum wall temperatures and channel Nusselt numbers are correlated to the channel Rayleigh number, Ra*, and to the geometrical parameters, in the ranges 3.0×102⩽Ra*B∕b⩽1.0105, 1.0⩽B∕b⩽3.0 and 1.0⩽L∕Lh⩽4.0 with Lh∕b=5.0 and 10.0.
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Lv, Junjie, Guanquan Du, Ping Jin, and Ruizhi Li. "Heat Transfer Analysis and Structural Optimization for Spiral Channel Regenerative Cooling Thrust Chamber." International Journal of Aerospace Engineering 2023 (June 14, 2023): 1–17. http://dx.doi.org/10.1155/2023/8628107.
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There is currently a lack of efficient heat transfer analysis methodologies for spiral channel regenerative cooling that has been increasingly applied in liquid rocket engines. To figure out the heat transfer characteristics of the spiral channel regenerative cooling thrust chamber, a simple 1D method based on the traditional semi-empirical formula after correcting the flow velocity is proposed. The accuracy of this approach is verified by the 3D numerical simulation. The verified method is further used to analyze the distribution of inner wall temperature in the test case and optimize the channel’s parameters. The research shows that the maximum inner wall temperature cooled by the spiral channel is 8.5% lower than that of the straight channel under the same channel size and boundary condition, indicating that the application of the spiral channel significantly improves the cooling effect. In addition, the 1D model combined with the second-order response surface model is employed to optimize the channel width, channel height, pitch, and inner wall thickness aiming for the best cooling effect. The calculated maximum temperature of the inner wall after the structure optimization is 586.6 K, which is 29.8% lower than the initial structure before optimization.
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Liu, Chun-Ho. "Turbulent Plane Couette Flow and Scalar Transport at Low Reynolds Number." Journal of Heat Transfer 125, no. 6 (2003): 988–98. http://dx.doi.org/10.1115/1.1571084.
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The turbulence structure and passive scalar (heat) transport in plane Couette flow at Reynolds number equal to 3000 (based on the relative speed and distance between the walls) are studied using direct numerical simulation (DNS). The numerical model is a three-dimensional trilinear Galerkin finite element code. It is found that the structures of the mean velocity and temperature in plane Couette flow are similar to those in forced channel flow, but the empirical coefficients are different. The total (turbulent and viscous) shear stress and total (turbulent and conductive) heat flux are constant throughout the channel. The locations of maximum root-mean-square streamwise velocity and temperature fluctuations are close to the walls, while the location of maximum root-mean-square spanwise and vertical velocity fluctuations are at the channel center. The correlation coefficients between velocities and temperature are fairly constant in the center core of the channel. In particular, the streamwise velocity is highly correlated with temperature (correlation coefficient ≈−0.9). At the channel center, the turbulence production is unable to counterbalance the dissipation, in which the diffusion terms (both turbulent and viscous) bring turbulent kinetic energy from the near-wall regions toward the channel center. The snapshots of the DNS database help explain the nature of the correlation coefficients. The elongated wall streaks for both streamwise velocity and temperature in the viscous sublayer are well simulated. Moreover, the current DNS shows organized large-scale eddies (secondary rotations) perpendicular to the direction of mean flow at the channel center.
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Trenc, F., and R. Pavleticˇ. "Combined Air-Oil Cooling on a Supercharged TC & IC TAM Diesel Engine." Journal of Engineering for Gas Turbines and Power 115, no. 4 (1993): 742–46. http://dx.doi.org/10.1115/1.2906768.
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In order to reduce the maximum cylinder wall temperatures of an air-cooled TC&IC diesel engine with large longitudinal and circumferential temperature gradients, a curved, squared cross-sectional channel supplied with engine lubrication oil was introduced into the upper part of the cylinder wall. Numerical analyses of the heat transfer within the baseline air-cooled cylinder and intensive experimental work helped to understand the temperature situation in the cylinder at diverse engine running conditions. The results of the combined cooling were greatly affected by the design, dimensions, position of the channel, and the distribution of the cooling oil flow, and are presented in the paper.
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Lotfian, Ali, and Ehsan Roohi. "Radiometric flow in periodically patterned channels: fluid physics and improved configurations." Journal of Fluid Mechanics 860 (December 7, 2018): 544–76. http://dx.doi.org/10.1017/jfm.2018.880.
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With the aid of direct simulation Monte Carlo (DSMC), we conduct a detailed investigation pertaining to the fluid and thermal characteristics of rarefied gas flow with regard to various arrangements for radiometric pumps featuring vane and ratchet structures. For the same, we consider three categories of radiometric pumps consisting of channels with their bottom or top surfaces periodically patterned with different structures. The structures in the design of the first category are assumed to be on the bottom wall and consist of either a simple vane, a right-angled triangular fin or an isosceles triangular fin. The arrangements on the second category of radiometric pumps consist of an alternating diffuse–specular right-angled fin and an alternating diffuse–specular isosceles fin on the bottom wall. The third category contains either a channel with double isosceles triangular fins on its lowermost surface or a zigzag channel with double isosceles triangular fins on both walls. In the first and the third categories, the surfaces of the channel and its structures are considered as diffuse reflectors. The temperature is kept steady on the horizontal walls of the channel; thus, radiometric flow is created by subjecting the adjacent sides of the vane/ratchet to constant but unequal temperatures. On the other hand, for the second category, radiometric flow is introduced by specifying different top/bottom channel wall temperatures. The DSMC simulations are performed at a Knudsen number based on the vane/ratchet height of approximately one. The dominant mechanism in the radiometric force production is clarified for the examined configurations. Our results demonstrate that, at the investigated Knudsen number, the zigzag channel experiences maximum induced velocity with a parabolic velocity profile, whereas its net radiometric force vanishes. In the case of all other configurations, the flow pattern resembles a Couette flow in the open section of the channel situated above the vane/ratchet. To further enhance the simulations, the predictions of the finite volume discretization of the Boltzmann Bhatnagar–Gross–Krook (BGK)–Shakhov equation for the mass flux dependence on temperature difference and Knudsen number are also reported for typical test cases.
Dissertations / Theses on the topic "Maximum channel wall temperature"
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Krishnamurthy, Nagendra. "Investigation of Fouling in Wavy-Fin Exhaust Gas Recirculators." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/32012.
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This dissertation presents a detailed account of the study undertaken on the subject of fouling of Exhaust Gas Recirculator (EGR) coolers. The fouling process in EGR coolers is identified to be due to two primary reasons â deposition of fine soot particles and condensation of hydrocarbons known as dry soot and wet soot fouling, respectively. Several numerical simulations are performed to study the fouling process. Preliminary analysis of the particle forces for representative conditions reveal that drag, thermophoresis and Brownian forces are the significant transport mechanisms and among them, the deposition process is dominated by thermophoresis. Soot deposition in a representative turbulent plain channel shows a direct relationship of the amount of deposition with the near-wall temperature gradient. Subsequently, periodic and developing flow simulations are performed on a wavy channel geometry, a common EGR design for various Reynolds numbers and thermal boundary conditions. Constant heat flux boundary condition is used in the periodic fully-developed calculations, which assist in establishing various deposition trends. The wavy nature of the walls is noted to affect the fouling process, resulting in specific deposition patterns. For the lower Reynolds number flows, significantly higher deposition is observed due to the higher particle residence times. On the other hand, the developing flow calculations facilitate the use of wall temperature distributions that typically exist in EGR coolers. The linear dependence of the amount of deposition on the near-wall temperature gradient or in other words, the heat flux, is ascertained. It is also observed in all the calculations, that for the sub-micron soot particles considered, the deposition process is almost independent of the particle size. In addition, the nature of the flow and heat transfer characteristics and the transition to turbulence in a developing wavy channel are studied in considerable detail. Finally, a study on the condensation of heavy hydrocarbons is undertaken as a post-processing step, which facilitates the prediction of the spatial distribution and time-growth of the combined fouling layer. From the calculations, the maximum thickness of the dry soot layer is observed to be near the entrance, whereas for the wet soot layer, the peak is found to be towards the exit of the EGR cooler. Further, parametric studies are carried out to investigate the effect of various physical properties and inlet conditions on the process of fouling.<br>Master of Science
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Kesawan, Sivakumar. "Fire performance and design of light gauge steel frame wall systems made of hollow flange sections." Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/120153/1/Kesawan_Sivakumar_Thesis.pdf.
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Load bearing Light Gauge Steel Frame (LSF) wall system is a cold-formed steel structure made of cold-formed steel studs and lined on both sides by gypsum plasterboards. In recent times its use and demand in the building industry has significantly increased due to their advantages such as light weight, acoustic performance, aesthetic quality of finished wall, ease of fabrication and rapid constructability. Fire Resistant Rating (FRR) of these walls is given more attention due to the increasing number and severity of fire related accidents in residential buildings that have caused significant loss of lives and properties.
LSF walls are commonly made of conventional lipped channel section studs lined with fire resistant gypsum plasterboards on both sides. Recently, greater attention has been given to innovative cold-formed steel sections such as hollow flange sections due to their improved structural efficiency. The reliance on expensive and time consuming full scale fire tests, and the complexity involved in predicting the fire performance of LSF wall studs due to their thin-walled nature and their exposure to non-uniform temperature distributions in fire on one side, have been the main barriers in using different cold-formed steel stud sections in LSF wall systems. This research overcomes this and proposes the new hollow flange section studs as vertical load bearing elements in LSF wall systems based on a thorough investigation into their fire (structural and thermal) performance using full scale fire tests and extensive numerical studies.
Test wall frames made of hollow flange section studs were lined with fire resistant gypsum plasterboards on both sides, and were subjected to increasing temperatures as given by the standard fire curve in AS 1530.4 (SA, 2005) on one side. Both uninsulated and cavity insulated walls were tested with varying load ratios from 0.2 to 0.6. LiteSteel Beam (LSB), a welded hollow flange section, which was available in the industry was used to fabricate the test wall panels. Axial deformations and lateral displacements along with the time-temperature profiles of the steel stud and plasterboard surfaces were measured. Five full scale tests were performed, and the test results were compared with those of LSF walls made of lipped channel section studs, which proved the superior fire performance of LSF walls made of hollow flange section studs. The reasons for the superior fire performance are presented in this thesis. The effects of load ratio and plasterboard joint on the fire performance of LSF walls and temperature distribution across the stud cross-sections were identified.
Improved plasterboard joints were also proposed.
The elevated temperature mechanical properties of cold-formed steels appear to vary significantly as shown by past research. LSBs were manufactured using a combined cold-forming and electric resistance welding process. Elevated temperature mechanical properties of LSB plate elements are unknown. Therefore an experimental study was undertaken to determine the elevated temperature mechanical properties of LSB plate elements. Based on the test results and previous researchers' proposed values, suitable predictive equations were proposed for the elastic modulus and yield strength reduction factors and stress-strain models of LSB web and flange elements.
Uninsulated and insulated 2D finite element models of LSF walls were developed in SAFIR using GiD as a pre- and post processor to predict the thermal performance under fire conditions. A new set of apparent thermal conductivity values was proposed for gypsum plasterboards for this purpose. These models were then validated by comparing the time-temperature profiles of stud and plasterboard surfaces with corresponding experimental results. The developed models were then used to conduct an extensive parametric study. Uninsulated and insulated LSF walls with superior fire performances were also proposed.
Finite element models of tested walls were also developed and analysed under both transient and steady state conditions to predict the structural performance under fire conditions using ABAQUS. In these analyses, the measured elevated temperature properties of LSB plate elements were used to improve their accuracy. Finite element analysis results were compared with fire test results to validate the developed models. Following this, a detailed finite element analysis based study was conducted to investigate the effects of stud dimensions such as web depths and thicknesses, elevated temperature mechanical properties, types of wall configurations, stud section profiles, plasterboards to stud connections and realistic design fire curves on the fire performance of LSF walls. It was also shown that the commonly used critical temperature method is not appropriate in determining the FRR of LSF walls.
Gunalan and Mahendran's (2013) design rules based on AS/NZS 4600 (SA, 2005), and Eurocode 3 Part 1.3 (ECS, 2006) were further improved to predict the structural capacity of hollow flange section studs subjected to non-uniform temperature distributions caused by fire on one side. Two improved methods were proposed and they predicted the FRRs with a reasonable accuracy. Direct Strength Method (DSM) based design rules were then established and they also predicted the FRR of LSF walls made of hollow flange section studs accurately. Finally, spread sheet based design tools were developed based on the proposed design rules.
Overall, this research has developed comprehensive fire performance data of LSF walls made of hollow flange section studs, accurate design rules to predict their fire rating and associated design tools. Thus it has enabled the use of innovative hollow flange sections as studs in LSF wall systems. Structural and fire engineers can now use these tools to undertake complex calculations of determining the structural capacities and fire rating of hollow flange section studs subjected to non-uniform temperature distributions, and successfully design them for safe and efficient use in LSF walls of residential and office buildings.
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Gunalan, Shanmuganathan. "Structural behaviour and design of cold-formed steel wall systems under fire conditions." Thesis, Queensland University of Technology, 2011. https://eprints.qut.edu.au/49799/1/Shanmuganathan_Gunalan_Thesis.pdf.
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In recent times, light gauge steel framed (LSF) structures, such as cold-formed steel wall systems, are increasingly used, but without a full understanding of their fire performance. Traditionally the fire resistance rating of these load-bearing LSF wall systems is based on approximate prescriptive methods developed based on limited fire tests. Very often they are limited to standard wall configurations used by the industry. Increased fire rating is provided simply by adding more plasterboards to these walls. This is not an acceptable situation as it not only inhibits innovation and structural and cost efficiencies but also casts doubt over the fire safety of these wall systems. Hence a detailed fire research study into the performance of LSF wall systems was undertaken using full scale fire tests and extensive numerical studies. A new composite wall panel developed at QUT was also considered in this study, where the insulation was used externally between the plasterboards on both sides of the steel wall frame instead of locating it in the cavity. Three full scale fire tests of LSF wall systems built using the new composite panel system were undertaken at a higher load ratio using a gas furnace designed to deliver heat in accordance with the standard time temperature curve in AS 1530.4 (SA, 2005). Fire tests included the measurements of load-deformation characteristics of LSF walls until failure as well as associated time-temperature measurements across the thickness and along the length of all the specimens. Tests of LSF walls under axial compression load have shown the improvement to their fire performance and fire resistance rating when the new composite panel was used. Hence this research recommends the use of the new composite panel system for cold-formed LSF walls. The numerical study was undertaken using a finite element program ABAQUS. The finite element analyses were conducted under both steady state and transient state conditions using the measured hot and cold flange temperature distributions from the fire tests. The elevated temperature reduction factors for mechanical properties were based on the equations proposed by Dolamune Kankanamge and Mahendran (2011). These finite element models were first validated by comparing their results with experimental test results from this study and Kolarkar (2010). The developed finite element models were able to predict the failure times within 5 minutes. The validated model was then used in a detailed numerical study into the strength of cold-formed thin-walled steel channels used in both the conventional and the new composite panel systems to increase the understanding of their behaviour under nonuniform elevated temperature conditions and to develop fire design rules. The measured time-temperature distributions obtained from the fire tests were used. Since the fire tests showed that the plasterboards provided sufficient lateral restraint until the failure of LSF wall panels, this assumption was also used in the analyses and was further validated by comparison with experimental results. Hence in this study of LSF wall studs, only the flexural buckling about the major axis and local buckling were considered. A new fire design method was proposed using AS/NZS 4600 (SA, 2005), NAS (AISI, 2007) and Eurocode 3 Part 1.3 (ECS, 2006). The importance of considering thermal bowing, magnified thermal bowing and neutral axis shift in the fire design was also investigated. A spread sheet based design tool was developed based on the above design codes to predict the failure load ratio versus time and temperature for varying LSF wall configurations including insulations. Idealised time-temperature profiles were developed based on the measured temperature values of the studs. This was used in a detailed numerical study to fully understand the structural behaviour of LSF wall panels. Appropriate equations were proposed to find the critical temperatures for different composite panels, varying in steel thickness, steel grade and screw spacing for any load ratio. Hence useful and simple design rules were proposed based on the current cold-formed steel structures and fire design standards, and their accuracy and advantages were discussed. The results were also used to validate the fire design rules developed based on AS/NZS 4600 (SA, 2005) and Eurocode Part 1.3 (ECS, 2006). This demonstrated the significant improvements to the design method when compared to the currently used prescriptive design methods for LSF wall systems under fire conditions. In summary, this research has developed comprehensive experimental and numerical thermal and structural performance data for both the conventional and the proposed new load bearing LSF wall systems under standard fire conditions. Finite element models were developed to predict the failure times of LSF walls accurately. Idealized hot flange temperature profiles were developed for non-insulated, cavity and externally insulated load bearing wall systems. Suitable fire design rules and spread sheet based design tools were developed based on the existing standards to predict the ultimate failure load, failure times and failure temperatures of LSF wall studs. Simplified equations were proposed to find the critical temperatures for varying wall panel configurations and load ratios. The results from this research are useful to both structural and fire engineers and researchers. Most importantly, this research has significantly improved the knowledge and understanding of cold-formed LSF loadbearing walls under standard fire conditions.
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Tortuel, Damien. "Vers la compréhension du rôle de SigX dans la réponse au stress de l'enveloppe chez Pseudomonas aeruginosa Pf4 phage infection induces SOS and cell envelope stress responses in Pseudomonas aeruginosa Pf4 phage infection reduced virulence-associated phenotypes in Pseudomonas aeruginosa The temperature-regulation of Pseudomonas aeruginosa cmaX-cfrX-cmpX operon reveals an intriguing molecular network involving the sigma factors AlgU and SigX." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMR002.
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Pseudomonas aeruginosa est un pathogène opportuniste très résistant, pour lequel il est critique de trouver de nouvelles thérapies. Cette bactérie s’adapte facilement à son environnement grâce à son grand génome et à sa grande proportion de régulateurs permettant une régulation très fine de ses gènes. L’enveloppe est la première barrière au contact direct de l’environnement, et est un lieu d’échanges très important entre ce dernier et la bactérie. L’enveloppe représente donc une cible thérapeutique potentielle intéressante. SigX est un facteur sigma à fonction extracytoplasmique, permettant de répondre à des situations de stress d’enveloppe détectées par la bactérie, mais dont le stimulus exact reste à déterminer. Ce facteur sigma pourrait faire partie d’un nouveau système de transduction atypique du signal, qui pourrait coupler SigX à un canal mécanosensible. Ces travaux ont mené à la découverte de trois nouvelles conditions activatrices de SigX, l’infection par des phages Pf4, la perte du canal mécanosensible CmpX, et le choc froid. Ces dernières semblent provoquer de fortes perturbations et une augmentation de la rigidité membranaire qui pourrait être le stimulus activateur de SigX. Ces travaux ont permis d’étoffer les connaissances et de se rapprocher de la condition activatrice de SigX, et de préciser les fonctions cellulaires et régulatrices des membres du système SigX-CfrX-CmpX, mettant en exergue l’implication d’un canal mécanosensible dans la physiologie de Pseudomonas aeruginosa<br>Pseudomonas aeruginosa is a very resistant opportunistic pathogen, for which it is critical to find new therapies. This bacterium easily adapts to its environment, through its large genome and proportion of regulators allowing a very fine regulation of its genes. The cell wall is the first barrier in contact with environment, and therefore represents a very important place ofexchange. The cell wall thus represents an interesting potential therapeutic target. SigX is an extracytoplasmic function sigma factor, responding to cell wall stresses detected by the bacterium, but the precise stimulus remains to discover. This sigma factor could be part of a new atypical signal transduction system that could couple SigX with a mechanosensitive channel. This work has led to the discovery of three new sigX activating conditions, which are Pf4 phage infection, loss of the CmpX mechanosensitive channel, and cold shock. These conditions seem to cause strong perturbations and an increase in membrane stiffness that could be the activating stimulus of SigX. This work has led to a better understanding of the activating condition of SigX, and to the clarification of the cellular and regulatory functions of the SigXCfrX-CmpX system members, highlighting the involvement of a mechanosensitive channel in the physiology of Pseudomonas aeruginosa
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Bellec, Morgane. "Études du couplage entre turbulence et gradient de température pour l'intensification des transferts de chaleur dans les récepteurs solaires à haute température." Thesis, Perpignan, 2017. http://www.theses.fr/2017PERP0005/document.
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Une voie prometteuse pour améliorer le rendement des centrales solaires à tour consiste à chauffer de l'air pressurisé à haute température afin d'alimenter un cycle thermodynamique de Brayton. Pour cela, il est indispensable de concevoir des récepteurs solaires performants,permettant de forts transferts de chaleur vers le fluide. Le développement de tels récepteurs passe par une compréhension fine de leurs écoulements internes. Il s'agit d'écoulements complexes, combinant de hauts niveaux de turbulence et un fort gradient de température entre la paroi irradiée par le flux solaire concentré et la paroi arrière isolée. On se propose dans ce travail de réaliser une étude amont numérique et expérimentale de ce type d'écoulements.D'une part, des mesures de vitesse par SPIV (vélocimétrie par images de particules stéréoscopique) sont effectuées dans une soufflerie de canal plan turbulent lisse dont la cellule de mesure est représentative d'un récepteur solaire surfacique. On observe en particulier l'influence d'un chauffage asymétrique sur les statistiques de la turbulence. Ces mesures sont d'autre part complétées par des simulations fines LES (simulation des grandes échelles)menées dans les conditions de la soufflerie. Pour finir, une simulation LES d'un canal plan texturé sur une paroi par une géométrie innovante est conduite. Cette architecture interne du récepteur combine des générateurs de tourbillon et des riblets afin d'intensifier les échanges de chaleur vers le fluide<br>A promising line of research to increase the efficiency of solar tower power plants consists in heating pressurized air to high temperatures in order to fuel a Brayton thermodynamic cycle. This requires to design effective solar receivers that allow for intense heat transfers toward the fluid. To develop such receivers, an in-depth understanding of their internal flows is needed. These are complex flows, combining strong turbulence and strong temperature gradient between the concentrated sun irradiated wall and the back insulated wall.The aim of this work is to investigate numerically and experimentally such flows.On one hand, velocities are measured by SPIV (Stereoscopic Particle Image Velocimetry) in a turbulent channel flow wind tunnel whom measurement cell is similar to a surface solar receiver. The influence of an asymmetric heating on the turbulence statistics are especially investigated. These measurements are supplemented by Large Eddy Simulations run under the same conditions as the wind tunnel. Finally, a Large Eddy Simulation is run in a channel flow textured on one wall by an innovative geometry. This internal receiver design combines vortex generators and riblets in order to enhance the heat transfers
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Kishore, Siripurapu Yada. "Design of Micro-Channel Heat Sink for Wall Temperature Uniformity." Thesis, 2017. http://ethesis.nitrkl.ac.in/8990/1/2017_MT_SYKishore.pdf.
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Micro-channel heats sinks are gradually replacing conventional fan heat sinks for electronic chip cooling as the heat flux removal rates required for their cooling needs are increasing day by day due to the increase in complexity and miniaturization of electronic devices. Because of higher surface to volume ratio of the micro-channels, makes them suitable to use in high heat flux removal applications. The research concentrated on this novel high heat flux removal method from last two decades. Most of the early research mostly concentrated on the optimization of geometrical parameters, flow conditions etc., to minimize the thermal resistance and pumping power. But present trends in research shifted to address the main drawback of the micro channel heat sinks i.e., wall temperature uniformity. Present research work is aimed to design a high performance heatsink for wall temperature uniformity by optimising the various parameters influencing it. All the different configurations proposed in the literature was studied carefully and based on those configurations and along with necessary modifications, performance of proposed micro channel heat sink is analysed computationally in commercially available CFD software Ansys15.0 Fluid Flow (FLUENT).
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Chiang, Fu-lung, and 江富隆. "Analysis of the mixed convection in the convergent channel at uniform wall temperature." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/24207805236784717806.
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碩士<br>國立交通大學<br>工學院碩士在職專班精密與自動化工程組<br>98<br>Abstract
The numerical study is carried out to investigate fluid flow and heat transfer characteristics in vertical channel with convergent wall at uniform temperature. The numerical results can be able to divide into two parts. As far as the first part was concerned, we changed the convergence angles, and observed the varying trend between two different zones in the flow field. As for the second part, we fixed the convergence angles, changed the Reynolds number and observed the varying trend in the flow field.
The parameters studied included the convergence angle and the Reynolds number.
The convergence angles and the Reynolds number were demonstrated significantly affected by the fluid flow, temperature distribution, and heat transfer rate. Increasing the convergence angles could be made the corner zone narrow down, and last disappeared. Increasing the Reynolds number leads to the fluid flow more heat transfer rate. Not only the maximum value of nusselt number, but the total average value of nusselt number was increased as well. The entrance length in the convergence section has been shortened. However, increasing of Reynolds number has no significant impact on corner zone.
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Willie, Robert H. "Fully developed laminar natural convection in a vertical parallel plate channel with symmetric uniform wall temperature." Thesis, 1996. http://hdl.handle.net/1957/34268.
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Described in this thesis is an investigation of the fully developed natural convection
heat transfer in a vertical channel formed by two infinitely wide parallel plates
maintained at a uniform wall temperature. Closed-form solutions for the velocity
and temperature profiles are developed along with local and averaged Nusselt
numbers. The local Nusselt number based on bulk temperature is found to be 3.77.
This result is an analog corresponding to 7.60 for fully developed laminar forced
convection in a parallel plate channel with uniform wall temperature boundary
condition. The local Nusselt number based on the ambient temperature is deduced
as a function of flowwise location. Results are compared with existing numerical
and experimental data to find good agreement.<br>Graduation date: 1997
Books on the topic "Maximum channel wall temperature"
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Willie, Robert H. Fully developed laminar natural convection in a vertical parallel plate channel with symmetric uniform wall temperature. 1996.
Find full textBook chapters on the topic "Maximum channel wall temperature"
1
Fan, Xianguang, Hailing Mao, Chengxiang Zhu, Juntao Wu, Yingjie Xu, and Xin Wang. "Design of Multi-channel Pressure Data Acquisition System Based on Resonant Pressure Sensor for FADS." In Proceeding of 2021 International Conference on Wireless Communications, Networking and Applications. Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-2456-9_46.
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AbstractResonant pressure sensors have high accuracy and are widely used in meteorological data acquisition, aerospace and other fields. The design and experiment of multi-channel pressure data acquisition system based on resonant pressure sensor, which used for the flush air data sensing(FADS) system, are described. The hardware architecture of DSP and FPGA is applied to the data acquisition system. The digital cymometer and 16-bit analog-to-digital converter are used to measure the output signal of the sensor. It is shown the data acquisition system has favourable performance within the operating temperature range. The maximum experimental error is less than 0.02%FS over the range 2–350 kPa. The period of sampling and fitting is less than 8 ms. The frequency and voltage measurements meet accuracy requirements. The calculated pressure and standard pressure result appears excellent linearity, which reach up to 0.9999.
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Li, Yunxiang, Lu Meng, Song Li, et al. "Study on the Effects from Spacer Wires on Coolant Flow Within a Fuel Assembly Used in the CiADS Core." In Springer Proceedings in Physics. Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-1023-6_4.
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AbstractSpacer wires are frequently applied as the positioning components of fuel bundles in lead-based fast reactor fuel assemblies. It is extremely important to carry out the research of the impacts from spacer wires on coolant flow within fuel assemblies, and therefore the safety performances of reactor core. In this paper, the open source CFD calculation software OpenFOAM was adopted to perform the refined numerical simulation on the multi-pitch assembly model of 61 bundles and analyze the distribution of flow characteristics such as pressure, velocity, and temperature. The results show that: there is a pressure difference on both sides of the wires, which may cause the coolant to mix laterally; the mixing effect incurred by the wires may cause the uneven distribution of coolant velocity. There are obvious high-speed and low-speed zones, and the high-speed zone is located at the same position as the low-pressure zone. Due to the high flow rate in the peripheral sub-channel, the coolant temperature is lower. The maximum temperature difference at the outlet of the fuel assembly can reach 20K, which may cause local overheating and therefore cladding rupture under accidental conditions. The simulation can provide a reference for the correction of the calculation results of the 1D single-channel program and lay the foundation for the development of the subsequent two-phase flow model for fuel assemblies containing wire spacers.
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Yang, Mingrui, Chixu Luo, Dan Wang, Tianxiong Wang, Xiaojing Liu, and Tengfei Zhang. "Development and Preliminary Verification of a Neutronics-Thermal Hydraulics Coupling Code for Research Reactors with Unstructured Meshes." In Springer Proceedings in Physics. Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-1023-6_58.
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AbstractTo maximize their adaptability and versatility, research reactors are designed to adapt to various operational conditions. These requirements result in more complex configurations and irregular geometries for research reactors. Besides, there is usually a strong coupling of neutronics-thermal hydraulics (N-TH) fields inside the reactor. A three-dimensional N-TH coupling code has been developed named CENTUM (CodE for N-Th coupling with Unstructured Mesh). Steady-state and transient neutronic analyses are performed using a 3D triangular-z nodal transport solver with the stiffness confinement method (SCM). Meanwhile, thermal-hydraulics calculations adopt a multi-channel model. For a preliminary verification of the code, we examine CENTUM with benchmark problems including TWIGL, 3D-LMW, and NEACRP. CENTUM produces maximum power errors of −1.27% and −0.45% for the TWIGL A1 and A2 cases, respectively. For the 3D-LMW benchmark, the largest relative power error of 3.84% is observed at 10 s compared with the reference SPANDEX code. For the NEACRP N-TH coupling benchmark, CENTUM results in a 0.35 ppm error in critical boron concentration, a 2.16 °C discrepancy in the fuel average Doppler temperature, and a 0.63% overestimation in the maximum axial power. Moreover, transient results considering thermal-hydraulics feedback are in good agreement with the PARCS reference solutions, with the maximum relative power deviation being only 0.055%.
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Chen, Jun, Zhenjie Zhang, Xiaofei Ding, Haitao Ma, and Haoran Ma. "Microstructure Evolution and Element Redistribution in Carburizing Process of Ethylene Cracking Furnace Tube." In Advances in Transdisciplinary Engineering. IOS Press, 2022. http://dx.doi.org/10.3233/atde220415.
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Carburizing is the main damage form of ethylene cracking furnace tubes. In this process, the microstructure of the furnace tube would change and the element diffuses and redistributes. After serving for about 41000h, the radiation section of a plum blossom tube of SC-1 tubular cracking furnace from a petrochemical company was tested and analyzed in this article. Results show that the higher the service temperature, the more serious the carburizing of the furnace tube. In the inner-wall carburized zone of the middle temperature section of the furnace tube with an initial C content of 0.1wt%, the maximum C content reaches 1.83wt% and the number of carbides increases obviously as well as its organizational morphology changes from fine granular to coarse block or chain like and its organizational type changes from single M23C6 to the coexistence of M23C6, M7C3 and MC type carbides. The Cr and C elements in the carburized zone are mainly concentrated in the grain boundary area in the form of carbides. At the same time, the diffusion of alloy elements causes Cr deficiency in the matrix, and the carbide deficiency zone appears in the subsurface of the inner wall.
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Vishnu, S. B., and Biju T. Kuzhiveli. "Effect of Roughness Elements on the Evolution of Thermal Stratification in a Cryogenic Propellant Tank." In Low-Temperature Technologies [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.98404.
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The cryogenic propulsion era started with the use of liquid rockets. These rocket engines use propellants in liquid form with reasonably high density, allowing reduced tank size with a high mass ratio. Cryogenic engines are designed for liquid fuels that have to be held in liquid form at cryogenic temperature and gas at normal temperatures. Since propellants are stored at their boiling temperature or subcooled condition, minimal heat infiltration itself causes thermal stratification and self-pressurization. Due to stratification, the state of propellant inside the tank varies, and it is essential to keep the propellant properties in a predefined state for restarting the cryogenic engine after the coast phase. The propellant’s condition at the inlet of the propellant feed system or turbo pump must fall within a narrow range. If the inlet temperature is above the cavitation value, cavitation will likely to happen to result in the probable destruction of the flight vehicle. The present work aims to find an effective method to reduce the stratification phenomenon in a cryogenic storage tank. From previous studies, it is observed that the shape of the inner wall surface of the storage tank plays an essential role in the development of the stratified layer. A CFD model is established to predict the rate of self-pressurization in a liquid hydrogen container. The Volume of Fluid (VOF) method is used to predict the liquid–vapor interface movement, and the Lee phase change model is adopted for evaporation and condensation calculations. A detailed study has been conducted on a cylindrical storage tank with an iso grid and rib structure. The development of the stratified layer in the presence of iso grid and ribs are entirely different. The buoyancy-driven free convection flow over iso grid structure result in velocity and temperature profile that differs significantly from a smooth wall case. The thermal boundary layer was always more significant for iso grid type obstruction, and these obstructions induces streamline deflection and recirculation zones, which enhances heat transfer to bulk liquid. A larger self-pressurization rate is observed for tanks with an iso grid structure. The presence of ribs results in the reduction of upward buoyancy flow near the tank surface, whereas streamline deflection and recirculation zones were also perceptible. As the number of ribs increases, it nullifies the effect of the formation of recirculation zones. Finally, a maximum reduction of 32.89% in the self-pressurization rate is achieved with the incorporation of the rib structure in the tank wall.
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Bai, Xiaohui, Cunliang Liu, and Akira Nakayama. "Flow and heat transfer in graded porous media and its application in aeroengine cooling." In Transport Perspectives for Porous Medium Applications [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.1003282.
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In recent decades, many studies on flow and heat transfer in porous media have been conducted by researchers to take advantage of its high specific surface area and good heat transfer performance. What is more, the graded porous media have also drawn great attention since the graded arrangement enhances local heat transfer coefficient, so as to improve the overall heat transfer performance and temperature uniformity. The new forms of structure provide a new design of cooling system for some high-power heat sources, such as electronic components, compact heat exchangers, and hot components in aeroengine. In this chapter, the problems of channels filled with vertically graded porous media and axially graded porous media have been introduced, respectively. The flow and heat transfer characteristics of graded porous media have been studied based on porous media theory, considering the parameters of porosity, permeability, pore diameter, etc. The profiles of velocity and temperature vary with different porosity arrangements present. The maximum heat transfer coefficient was obtained for the case of high porosity at the center and low porosity near the wall. Furthermore, the possibility of application in the aeroengine cooling has been discussed.
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Yuan, Wenjun, Dongming Chen, and Haifeng Zhang. "On drag reduction by spanwise wall oscillation in compressible turbulent channel flow." In Boundary Layer Flows - Advances in Modelling and Simulation [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.1002209.
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In this chapter, we summarize our progress in the investigation of drag reduction (DR) by spanwise wall oscillation (SWO). Reliable direct numerical simulation (DNS) models have been established for compressible turbulent channel flow. A large amount of 39.3% drag reduction has been achieved for supersonic compressible flows. It is found that the compressible effect is modest with respect to the turbulent effect for the skin-fiction in compressible turbulent channel flows. The reduced DR is mainly because of the decreasing turbulent contribution, and the related small compressible term also slightly decreases with the increase Wm+. More DNS cases with different maximum wall velocities, oscillation periods, and flow Reynold numbers for compressible cases should be analyzed. The optimal combination with the highest drag reduction efficiency has significant importance on real applications, which deserves to be studied in detail to characterize the underlying mechanisms.
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Suman Bal Mukund. "Thermal characterization of heat reflective coating for building application." In Construction Materials and Structures. IOS Press, 2014. https://doi.org/10.3233/978-1-61499-466-4-1461.
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The paper describes the measurement of thermal conductance and resistance of a reflective coating in the laboratory by guarded hot plate apparatus. Thermal resistance (R) of the coating and white wash was found 0.0012 m2K/W and zero respectively and reflectivity of heat reflective coating and white washing is 0.85 and 0.70. The maximum temperature difference of ceiling and the west wall surface between heat reflective coated room and the room treated with white wash were recorded as 6.0&deg;C and 3.8&deg;C respectively. The cooling load was reduced by 5.75% and 12.7% for heat reflective coated room on wall and for both the roof and walls respectively when compared to white wash application on wall and on roof and wall both when air-conditioner of 18000 Btu/hr capacity was used in each of the identical rooms maintaining indoor temperature at 23&deg;C.
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Duan, Y. H., H. M. Yang, J. P. Yuan, L. Su, and W. T. Li. "Estimation of Internal Maximum Thermal Stress of Tunnel Side Wall Lining Concrete During Construction Period." In Advances in Transdisciplinary Engineering. IOS Press, 2021. http://dx.doi.org/10.3233/atde210197.
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Thermal cracks in lining concrete of large section hydraulic tunnel usually occur in side walls during construction, and most of them are harmful penetrating cracks. In order to meet the needs of real-time rapid control for engineering design in construction period, nine influencing factors of maximum tensile of side wall lining concrete σmax during construction period are determined on the basis of comprehensive analysis of temperature stress effects and finite element simulations, and their influencing regularities are analyzed. Then the estimation formula of σmax and real-time control method of thermal crack are put forward. Through the application of real-time temperature control and crack prevention control of lining concrete in flood discharge tunnel, the estimation formula of σmax and the real-time thermal crack control method are proved to be correct and applicable.
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Whalley, P. B. "Critical Heat Flux in Flow Boiling." In Boiling, Condensation, and Gas-Liquid Flow. Oxford University PressOxford, 1990. http://dx.doi.org/10.1093/oso/9780198562344.003.0017.
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Abstract In Chapter 16 (see, for example, Fig. 16.2) it was seen that the heat transfer coefficient in flow boiling could fall rapidly and the wall temperature increase rapidly at some point along the heated channel. This phenomenon is known by many names, none of them entirely satisfactory.
Conference papers on the topic "Maximum channel wall temperature"
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Halvorsen, Anne Marie K., and Terje Søntvedt. "CO2 Corrosion Model for Carbon Steel Including a Wall Shear Stress Model for Multiphase Flow and Limits for Production Rate to Avoid Mesa Attack." In CORROSION 1999. NACE International, 1999. https://doi.org/10.5006/c1999-99042.
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Abstract A corrosion rate model is developed for carbon steel in water containing CO2 at different temperatures, pH’s, CO2 fugacities and wall shear stresses. The model is based on loop experiments at temperatures from 20-160°C. The data are taken from a database containing more than 2400 data points at various temperatures, CO2 fugacities, pH’s and wall shear stresses. To find the best fit of the data, data for each temperature present in the data base was evaluated separately to find typical trends for the change in corrosion rate versus CO2 fugacity, wall shear stress and pH. To facilitate use of the corrosion model a simplified method for calculating wall shear stress in multiphase flow is included. This model includes a viscosity model for dispersions and is developed for oil wet and water wet flow. Criteria for the maximum production rate to avoid mesa attach in straight sections and behind welds is also included.
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Blumer, David, Sudha Yellapantula, Randy Barnes, et al. "Application of Temperature Compensated, Fixed Mount, Multichannel UT Device to Examine Erosion in a Bend and High-Precision Corrosion Rates of Pit Inhibition." In CORROSION 2014. NACE International, 2014. https://doi.org/10.5006/c2014-4134.
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Abstract A fixed mount, multichannel UT device with improved temperature compensation has been developed. Utilizing a fixed mount approach and the improved temperature compensation help improve the accuracy and the resolution of the wall thickness measurements. When equipped with sixteen transducers, it allows for the generation of a wall thickness loss (erosion and/or corrosion) contour map, ensuring that an area of localized wall loss is not missed. Extensive laboratory testing using an outdoor flow loop and a field trial have been performed with the device. The laboratory flow loop testing investigated the magnitude and location of erosion for a variety of operating conditions. Gas and liquid flow rates were varied examining, gas only, low liquid loading, annular, and slug flows. The need for multiple transducers is demonstrated as the location of maximum erosion changes significantly from gas dominant low liquid flows to slug flow. The field trial on a large scale water injection system at Kuparuk, Alaska tested the performance of different corrosion inhibitors and various doses on the corrosion rate of known, existing pits in sea water and produced water pipelines using direct wall thickness measurements by the UT device. The high precision of the measurements allowed for the validation of the inhibitor performance on the pipe wall itself, not just corrosion monitoring probes and coupons.
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Simonetti, F., P. B. Nagy, A. Brath, C. L. Willey, G. Instanes, and A. O. Pedersen. "Ultrasonic Computerized Tomography for Continuous Monitoring of Corrosion and Erosion Damage in Pipelines." In CORROSION 2015. NACE International, 2015. https://doi.org/10.5006/c2015-05750.
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Abstract Throughout the oil and gas industry corrosion and erosion damage monitoring plays a central role in managing asset integrity. This paper introduces a novel technology for continuous monitoring of wall-loss rates in pipelines. A pair of permanently installed ring arrays of ultrasonic transducers encircles the pipe and delimits the section to be monitored. The arrays excite and receive guided ultrasonic waves that travel inside the pipe wall and insonify the entire pipe section. The received signals are then processed by advanced tomographic algorithms to produce a point-by-point map of wall thickness loss between the arrays. The algorithms are designed to detect changes between two material states of the pipe and use differential measurements to eliminate time-independent experimental uncertainties. As a result, wall loss can be estimated with accuracy beyond the pipe manufacturing tolerances. Moreover, a strategy that combines a robust temperature compensation scheme with the intrinsic thermal stability of electromagnetic acoustic transducers (EMATs) is used to address signal instabilities caused by typical thermal fluctuations experienced in field applications. Full-scale experiments are presented demonstrating maximum-depth estimation accuracy better that 0.5% of wall thickness with excellent thermal stability up to 175 °C.
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Manca, Oronzio, Sergio Nardini, and Vincenzo Naso. "Effect of Wall Conduction on Natural Convection in Symmetrically Heated Vertical Parallel Plates With Discrete Heat Sources." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-33649.
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The effect of heat conduction on air natural convection in a vertical channel, symmetrically heated, with flush-mounted strips at the walls, was numerically analyzed. Reference was made to laminar two-dimensional steady-state flow and to full elliptic Navier-Stokes equations on a I-shaped computational domain. Solutions were carried out by means of the FLUENT code. Results are presented in terms of wall temperature profiles, air velocity and temperature profiles in the channel. The wall temperature is affected by the location of the strip on the channel wall and maximum wall temperature is far larger when the heater is located in the upper region of the channel. Heat conduction in the channel wall lowers maximum wall temperature below the heater and the thicker the wall the larger the temperature reduction.
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Bianco, Nicola, Oronzio Manca, Sergio Nardini, and Vincenzo Naso. "Radiation Effects on Natural Convection in Air in a Divergent Channel With Uniformly Heated Plates." In ASME 2003 Heat Transfer Summer Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/ht2003-47135.
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Nowadays trends in natural convection heat transfer are oriented toward either the seeking of new configurations to enhance the heat transfer parameters or the optimization of standard configurations. An experimental investigation on air natural convection in divergent channels with uniform heat flux at both the principal walls is presented in this paper to analyze the effect of radiative heat transfer. Results in terms of wall temperature profiles as a function of the walls diverging angle, the interwall spacing, the heat flux are given for two value of the wall emissivity. Flow visualization is carried out in order to show the peculiar pattern of the flow between the plates in several configurations. Nusselt numbers are then evaluated and correlated to the Rayleigh number. The investigated Rayleigh number ranges from 7.0 × 102 to 4.5 × 108. The maximum wall temperature decreases at increasing divergence angles. This effect is more evident when the minimum channel spacing decrease. A significant decrease in the maximum wall temperature occurs passing from ε = 0.10 to ε = 0.90, except in the inlet region. Flow visualization shows a separation of the fluid flow for bmin = 40 mm and θ = 10°. Correlations between Nusselt and Rayleigh numbers show that data are better correlated when the maximum channel spacing is chosen as the characteristic length.
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Andreozzi, Assunta, Nicola Bianco, Giovanni Lacasa, and Vincenzo Naso. "Mixed Convection Heat Transfer in a Convergent Vertical Channel With a Moving Plate." In ASME 8th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2006. http://dx.doi.org/10.1115/esda2006-95502.
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A numerical investigation of mixed convection in air in a convergent vertical channel, due to the interaction between a buoyancy flow and a moving plate induced flow, is presented. The plate moves at a constant velocity along the buoyancy force direction and the principal inclined walls of the channel are heated at uniform heat flux. The numerical analysis is carried out by means of the finite volume method, using the commercial code Fluent. The effects of the channel spacing, wall heat flux, moving plate velocity and converging angle are investigated. Heated wall temperature increases at increasing converging angle, except for natural convection in a 10 mm minimum channel gap. The effect of the converging angle on the wall temperatures is less marked at the larger channel spacing. Maximum temperature of the moving plate is attained in the parallel wall channel for a 30 W m−2 wall heat flux, both in the 10 mm and 40 mm channel, whereas for a 220 W m−2 wall heat flux in the 40 mm channel in mixed convection, maximum wall temperatures are exhibited for a 10° angle. Nusselt, Reynolds and Richardson numbers are correlated by a monomial equation for each converging angle and a unique monomial correlation for all investigated angles in the 2.1·10−2 – 5.1·105 Richardson number range is presented.
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Nie, Jianhu, Steve Cohen, Yitung Chen, Blake Carter, and Robert F. Boehm. "Velocity and Temperature Distributions in Bipolar Plate of PEM Electrolysis Cell." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-42622.
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Numerical simulations of three-dimensional water flow were performed for the purpose of examining velocity and temperature distributions in the bipolar plate of a simplified PEM electrolysis cell. The flow range in the present study is assumed to be hydrodynamically stable and steady with uniform inlet temperature. All solid wall surfaces are maintained as being adiabatically insulated except that the walls adjacent to the active area of the MEA are supplied with constant heat flux. A minimum of the peak values of mainstream velocity component in the channels develops in the middle of the plate. The maximum of these peak values appears in the channel near the exit tube. The maximum temperature develops in the channels in the center of the plate and near the exit header section. The maximum temperature decreases with increasing flowrate.
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Lin, Qin, and Stephen J. Harrison. "Experimental Study on Natural Convection in an Asymmetrically Heated Inclined Channel With Radiation Exchange." In ASME 2003 Heat Transfer Summer Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/ht2003-47202.
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Heat transfer in an asymmetrically heated, inclined channel by natural convection and radiation exchange was experimentally investigated. Experiments were conducted on channels with small inclination angle (to horizontal) ranging from 18° to 30° and a wall surface emissivity of 0.29 to 0.95. The channel length/space ratio was between 44 and 220. In each test, a uniform heat flux was applied along the top wall of the channel, while the bottom wall was thermally insulated. Temperature profiles along both the top and bottom walls of the channel were recorded under different heat flux and channel length/space ratios. The dependency of maximum wall temperature and heat transfer on the channel spacing and surface emissivity was explored. As a result of this work, correlations of local and average Nusselt number, with modified channel Rayleigh number, were determined and proposed for channels at inclination angle of around 18° and surface emissivities of around 0.95. The proposed correlation will be valid for modified-Rayleigh number in the range of 10 < Ra” < 5.6 × 104 at asymmetric heat flux boundary conditions.
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Alharbi, Ali Y., Deborah V. Pence, and Rebecca N. Cullion. "Temperature Distributions in Microscale Fractal-Like Branching Channel Networks." In ASME 2003 Heat Transfer Summer Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/ht2003-47501.
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Heat transfer to liquid flow through fractal-like branching flow networks is investigated using a three-dimensional computational fluid dynamics approach. Results are used to assess the validity of, and provide insight for improving, assumptions imposed in a previously developed one-dimensional model to predict wall temperature distributions along a fractal-like flow network. Assumptions in the one-dimensional model include (1) reinitiating thermal and hydrodynamic boundary layers following each bifurcation, (2) negligible minor losses at the bifurcations, and (3) constant thermo-physical fluid properties. It is concluded that temperature varying fluid properties and minor losses should be incorporated in the one-dimensional model to improve its predictive capabilities. No changes to the redevelopment of the boundary layers at each wall following a bifurcation are recommended. Surface temperature distributions along heat sinks with parallel and fractal-like branching flow networks are also investigated and compared. For the same observed maximum surface temperature between the two heat sinks, considerably lower temperature variations and pressure drops, greater than 50 percent, are noted for the fractal-like heat sink.
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Xi, Lei, Liang Xu, Jianmin Gao, and Zhen Zhao. "Study on Conjugate Thermal Performance of a Steam-Cooled Ribbed Channel with Thick Metallic Walls." In ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-58386.
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Abstract In this work, a conjugate heat transfer model was established to numerically investigate the conjugate thermal performance of a steam-cooled ribbed channel with thick metallic walls. By employing the software of ANSYS CFX, the flow field in the channel and the temperature field in the solid channel were calculated. The flow behavior, heat transfer performance and temperature gradient distributions of ribbed channels with wall thickness (δ) of 1–5 mm, rib height-to-hydraulic diameter (e/D) of 0.047–0.188, rib pitch-to-height ratio (P/e) of 5–15 and rib angle-of-attack (α) of 30°–90° were compared and analyzed. The optimum structure parameters of thick-wall ribbed channel with higher heat transfer performance and lower maximum temperature gradient were obtained. The results show that the SST k-ω turbulence model is more suitable for the conjugate heat transfer problem of steam in the thick-wall ribbed channels. The friction factor reduces gradually with the increase of Re, increases greatly with the increase of e/D and α, and first increases then decreases with the increase of P/e. The average Nusselt number increases up to 8.81 times, while the maximum temperature gradient decreases about 45.35% when Reynolds number varies from 10,000 to 70,000. The rib angle of about 45°–60°, e/D of 0.188, and P/e of 10 are suitable to obtain the optimum thermal performance of steam flow in the ribbed channel. The influence of δ on the flow and heat transfer characteristics is non-significant.
Reports on the topic "Maximum channel wall temperature"
1
Parkins, R. N., and R. R. Fessler. NG-18-85-R01 Line Pipe Stress Corrosion Cracking Mechanisms and Remedies. Pipeline Research Council International, Inc. (PRCI), 1986. http://dx.doi.org/10.55274/r0012143.
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Stress corrosion cracking of line pipe from the soil side involves slow crack growth at stresses which may be as low as half the yield strength, this slow crack growth continuing until the crack penetrates the wall to produce a leak or until the stress intensity on the uncracked ligament reaches the value for a fast fracture to penetrate the wall thickness. The controlling parameters that contribute to the mechanism of failure, essentially involving growth by dissolution in the grain boundary regions, are, as with other systems displaying such failure, electrochemical, mechanical, and metallurgical, acting conjointly. Electrochemical influences relate to environment composition, potential, and its variation under disbonded coatings and temperature, whilst mechanical factors of significance include pressure variations, and their time dependence, as well as maximum pressure. Metallurgical parameters, whilst not yet fully understood, including those aspects of steel composition and structure that influence grain boundary composition and the microplasticity associated with load changes, as well as surface condition, e.g. the presence or otherwise of mill scale. These controlling parameters indicate the remedial measures available for control of the problem, although some, for practical or economic reasons, are not invariably applicable. Thus, control by metallurgical approaches or through coatings or manipulation of the surface conditions is only applicable to future lines, but for those already in existence lowering the temperature, limiting pressure fluctuations and more precise control of cathodic protection should help alleviate the problem.
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Krauss, T., and L. Meyer. Characteristics of turbulent velocity and temperature in a wall channel of a heated rod bundle. Office of Scientific and Technical Information (OSTI), 1995. http://dx.doi.org/10.2172/107015.
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Badrinarayanan and Olsen. PR-179-11201-R01 Performance Evaluation of Multiple Oxidation Catalysts on a Lean Burn Natural Gas Engine. Pipeline Research Council International, Inc. (PRCI), 2012. http://dx.doi.org/10.55274/r0010772.
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Two-way catalysts or oxidation catalysts are the common after-treatment systems used on lean burn natural gas engines to reduce CO, VOCs and formaldehyde emissions. The study evaluates the performance of oxidation catalysts from commercial vendors for varying catalyst temperature and space velocity. For this study, a part of the exhaust from a Waukesha VGF-18 GL lean burn natural gas engine was flowed through a catalyst slipstream system to assess the performance of the oxidation catalysts. The slipstream is used to reduce the size of the catalysts and to allow precise control of temperature and space velocity. Analyzers used include Rosemount 5-gas emissions bench, Nicolet Fourier Transform Infra-Red spectrometer and HP 5890 Series II Gas Chromatograph. The oxidation catalysts were degreened at 1200oF (650oC) for 24 hours prior to performance testing. The reduction efficencies for the emission species varied among the oxidation catalysts tested from different vendors. Most oxidation catalysts showed over 90% maximum reduction efficiencies on CO, VOCs and formaldehyde. VOC reduction efficiency was limited by poor propane emission reduction efficiency at the catalyst temperatures tested. Saturated hydrocarbons such as propane showed low reduction efficiencies on all oxidation catalysts due to high activation energy. Variation in space velocity showed very little effect on the conversion efficiencies. Most species showed over 90% conversion efficiency during the space velocity sweep. Adding more catalyst volume may not increase the reduction efficiency of emission species. Varying cell density showed very little effect on performance of the oxidation catalysts. The friction factor correlation showed the friction factor for flow through a single channel is inversely proportional to cell density.
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Ruschau. L51771 Alternative Acceptance Criteria of Girth Weld Defects. Pipeline Research Council International, Inc. (PRCI), 1997. http://dx.doi.org/10.55274/r0010187.
Full textAbstract:
The girth weld defect acceptance standards based on good workmanship reflect quality levels that can be reasonably expected from a qualified welder. Workmanship (WM) or weld quality standards specify a maximum allowable length whilst the percentage loss of cross-sectional area is used for porosities. This approach to defect acceptance philosophy has arisen from the use of radiography as the NDE technique for detecting and quantifyingweld discontinuities. The first WM standard for inspection and acceptance of finished girth welds was implemented by API in 1953. The specific requirements of the 1953-standard were largely based on the Unfired Pressure Vessel Code which was first adopted by ASME in 1931. Since then, a number of slightly revised standards were issued to reflect what should be attainable with normal good welding practices. The failure behaviour of defective girth welds in large diameter pipe lines was assessed using radiographic and mechanized ultrasonic inspection, small scale (tensile, hardness, Charpy and CTOD) and wide plate tests. The specimens were taken from girth welds in API 5LX70 pipe of 1219 mm (48 inches) in diameter by 8,0 mm (0,323 inch) and 13,3 mm (0,524 inch) wall. The test welds were made with the SMAW (8 welds) and GMAW (9 welds) welding processes. Upon completion of the non-destructive tests, 96 curved wide plate specimens were tested to destruction under tensile load. Testing was performed at low temperature (-50�C/-58�F). Defect type, defect position and size were determined from photographs of the fracture face and macro sections (defect characterization and sizing). In total, 290 typical surface breaking and embedded defects in SMAW or GMAW girth welds have been evaluated.