Symmetric Temperature Distribution Research Articles

Surface temperature distribution on dense 8YSZ ceramics during the steady stage in AC flash sintering

The exploration of temperature and its distribution within a sample is helpful for the understanding of the underlying mechanisms of flash sintering. In this work, surface temperature at steady stage of AC flash sintering of dense zirconia ceramics was measured using thermal imaging camera. The temperature of AC flash sintering samples was symmetrically distributed along the length of electric field, which was different from that of the asymmetrical distribution of DC flash sintering. Along the direction of electric field, the lowest and highest temperatures were respectively located at two ends and at midpoint of the sample. Steady stage temperature was shown to depend on current density and not on electric field strength. Steady stage temperature increased with current density. Possible mechanism of symmetrical temperature distribution on the surface of the sample during steady stage of AC flash sintering is discussed herein.

Thermal buckling of porous symmetric and non-symmetric sandwich plate with homogenous core and S-FGM face sheets resting on Pasternak foundation

The effect of porosity and thermal environment on buckling responses for the sandwich plates with different boundary conditions is analyzed and discussed in the present study. The author’s recently developed sandwich plate using a new modified sigmoid function based functionally graded material (S-FGM) plate of different symmetric and asymmetric configurations is considered. A new temperature distribution through the thickness based on modified sigmoid law is proposed in which temperature is assumed to be conducted in the thickness direction. Three different types of porosity are considered viz. even, uneven but symmetric and uneven but non-symmetric. A new uneven non-symmetric porosity model is used in which micro-voids are varied in accordance with material property variation in the thickness direction to capture the accurate distribution of voids on the plate. The principle of virtual work is employed to derive equilibrium equations. An exact solution is obtained using the assumed solution with shape functions satisfying the edge boundary conditions. This is implemented using Galerkin Vlasov’s method. The analysis has been performed to study the effect of porosity, geometric configurations, inhomogeneity parameter, and foundation parameter. It is observed that the elastic foundation parameters have the least effect on non-symmetric plate configuration subjected to nonlinear temperature distribution in comparison to other symmetric and non-symmetric plate configurations and temperature distribution. Besides, the non-symmetric plate configuration possesses maximum thermal buckling temperature in comparison to a symmetric configuration. The volume fraction exponent with value 2 is observed as a changeover point where the effect of porosity distribution is null and void for 2-1-1 plate configuration irrespective of boundary conditions. The calculated outcomes and interpretations can be useful as a validation study for the imminent investigation of sandwich S-FGM plates having porosities in the thermal environment.

Performance Assessment of Axial-Flux Permanent Magnet Motors from a Manual Manufacturing Process

Implementation of a new design for the process of assembling an axial-flux permanent magnet synchronous motor (AF PMSM) may lead to unstable motor parameters during operation at low and high speeds. In this paper, experimental data related to the AFPMSM used in an electric traction motor was monitored. The paper presents tracing of machine performance in order to find quality-related issues and to evaluate the assembly process. To assess the manual manufacturing process (low-volume production) and electrical machine performance, several motors, characterized by the same size and topology, were extensively tested. Useful AF PMSM parameters such as continuous torque and continuous current were measured. The winding temperature of the stators was also monitored and carefully examined. An attempt to assess motor performance, based on measurements and aimed at the identification of the weakest parts of the electric motor design is presented. In this paper it can be seen how the subcomponents of the machine and its detailed assembly process and tolerances play key roles in achievement of the designed continuous performance with symmetrical temperature distribution in the stator winding. Selected conclusions drawn from the obtained measurements were explained by a rotor/stator misalignment study using 3-D finite element analysis.

Temperature and Stress Evaluation during Three Different Phases of Friction Stir Welding of AA 7075-T651 Alloy

The current study performs an explicit nonlinear finite element simulation to predict temperature distribution and consequent stresses during the friction stir welding (FSW) of AA 7075-T651 alloy. The ABAQUS® finite element software was used to model and analyze the process steps that involve plunging, dwelling, and traverse stages. Techniques such as Arbitrary Lagrangian–Eulerian (ALE) formulation, adaptive meshing, and computational feature of mass scaling were utilized to simulate sequence events during the friction stir welding process. The contact between the welding tool and workpiece was modelled through applying Coulomb’s friction model with a nonlinear friction coefficient value. Also, the model considered the effect of nonlinear material properties as well as heat transfer conditions such as heat losses due to convection and thermal contact conductance between the workpiece and the backing plate interface on the thermal history. To validate the computational model results, an experimental procedure was carried out to measure temperature history on both sides of the specimen as well as the plunging force throughout the whole process time. The results obtained showed that symmetrical temperature distribution throughout the workpiece width was distinguished, implying that the tool rotation has a minor effect on the final temperature distribution. In addition, asymptotic V shape with high gradient temperature value in the weld nugget region after the full plunging was distinguished. Mechanical stresses and related plastic deformations generated, while achieving the FSW samples were evaluated in addition to the tool reaction force and heat generated to protect against tool failure.

Computer aided detection of diabetic foot ulcer using asymmetry analysis of texture and temperature features

Diabetic foot ulcer is a foremost complication of poorly controlled diabetes mellitus leading to lower extremity amputation. Early identification depends on repeated risk assessment, preferably on a day-to-day basis especially for high-risk patients. The temperature variations in the areas prone to ulcer are higher than non-ulcerous regions of the foot. The ultimate aim of this study was to develop an efficient algorithm for early detection of diabetic foot with infrared thermal images using asymmetry analysis. The left and right foot regions are segmented using region growing method. In normal plantar thermograms, symmetric temperature distributions are observed, whereas, in the case of the diabetic foot, asymmetry was observed between ipsilateral and contralateral regions of the foot. The texture and temperature features are extracted from the 11 regions of interest from the foot and asymmetric analysis was performed for the features extracted from the ipsilateral and contralateral regions of the foot. Support vector machine was used to classify the region of interest into normal and ulcer. The proposed method achieved maximum accuracy of 95.61%, sensitivity of 96.5% and specificity of 92.41%. The performance of the proposed technique shows that it is trustworthy and effective for early identification of pre-signs of ulceration and aids the clinicians in the treatment of the diabetic foot.

Eddy Activity Response to Global Warming–Like Temperature Changes

AbstractGlobal warming projections show an anomalous temperature increase both at the Arctic surface and at lower latitudes in the upper troposphere. The Arctic amplification decreases the meridional temperature gradient, and simultaneously decreases static stability. These changes in the meridional temperature gradient and in the static stability have opposing effects on baroclinicity. The temperature increase at the upper tropospheric lower latitudes tends to increase the meridional temperature gradient and simultaneously increase static stability, which have opposing effects on baroclinicity as well. In this study, a dry idealized general circulation model with a modified Newtonian cooling scheme, which allows any chosen zonally symmetric temperature distribution to be simulated, is used to study the effect of Arctic amplification and lower-latitude upper-level warming on eddy activity. Due to the interplay between the static stability and meridional temperature gradient on atmospheric baroclinicity changes, and their opposing effect on atmospheric baroclinicity, it is found that both the Arctic amplification and lower-latitude upper-level warming could potentially lead to both decreases and increases in eddy activity, depending on the exact prescribed temperature modifications. Therefore, to understand the effect of global warming–like temperature trends on eddy activity, the zonally symmetric global warming temperature projections from state-of-the-art models are simulated. It is found that the eddy kinetic energy changes are dominated by the lower-latitude upper-level warming, which tends to weaken the eddy kinetic energy due to increased static stability. On the other hand, the eddy heat flux changes are dominated by the Arctic amplification, which tends to weaken the eddy heat flux at the lower levels.

The Impact of the Gas Inlet Position, Flow Rate, and Strip Velocity on the Temperature Distribution of a Stainless-Steel Strips during the Hardening Process

A non-uniform temperature across the width of martensitic stainless-steel strips is considered to be one of the main reasons why the strip exhibits un-flatness defects during the hardening process. Therefore, the effect of the gas inlet position in this process, on the temperature distribution of the steel strip was investigated numerically. Furthermore, an infrared thermal imaging camera was used to compare the model predictions and the actual process data. The results showed that the temperature difference across the width of the strip decreased by 9% and 14% relative to the calculated temperature and measured values, respectively, when the gas inlet position was changed. This temperature investigation was performed at a position about 63 mm from the bath interface. Moreover, a more symmetrical temperature distribution was observed across the width of the strip. In addition, this study showed that by increasing the amount of the hydrogen flow rate by 2 Nm3/h, a 20% reduction of temperature difference across the width of strip was predicted. Meanwhile, the results show that the effect of the strip velocity on the strip temperature is very small.

One dimensional liner temperature prediction in a tubular combustor

Liner cooling can be optimized in the preliminary design phase by using one-dimensional heat transfer analysis in scope of the gas turbine combustor liner durability. So it is important to understand heat transfer process in the combustor liner for an effective prediction of liner wall temperatures. In this study, one –dimensional liner wall temperature predictions of an experimental tubular combustor have been performed for different operating conditions. Experimental tests have been obtained by the combustor atmospheric rig tests over a range of inlet temperature from 400 to 475 K and inlet mass flow rates of 0.035–0.050 kg/s at 6 different axial locations representing the primary zone, film cooled area, secondary zone and dilution zone. A tubular type combustor with air-blast fuel injections has been used for the experimental study. By the help of this architecture, it was possible to get more axially symmetrical temperature distribution compared to an annular combustor. Predictions shows that a maximum 85 K error in primary zone. It has been predicted more accurate results in the other zones.

Multiplicity of forced convective heat transfer of nanofluids in curved ducts

In the present work, a numerical study is made on the fully-developed forced convective heat transfer of nanofluids in a curved square duct using Eulerian-Lagrangian two-phase approach. The curvature ratio of the duct is 0.02 and its hydraulic diameter is 8 mm. The Al2O3-water nanofluids contain spherical nanoparticles with particle diameter of 30 nm and volume fraction of 0.5%. Three different flow structures of nanofluids are obtained through the small perturbations generated by three different computers at the same conditions. The flow has a structural 2-cell, 3-cell or 4-cell at different Dean numbers and on different solutions, which leads to multiple non-uniform nanoparticle concentration distributions and multiple temperature fields. Multiple flow fields are symmetric in a low Dean number region and asymmetric in a high Dean number region, which leads to multiple symmetric (asymmetric) nanoparticle concentration distribution and temperature distribution fields, multiple symmetric (asymmetric) local Nusselt number and local friction factor along the outer wall at low De values (high De values), and finally lead to multiple mean friction factor and multiple mean Nusselt number. A significant enhancement of heat transfer (e.g. 23.79% at De of 335.2) can be achieved at the expense of a slight increase of flow friction (e.g. 6.84% at De of 335.2) in curved square duct through switching the solutions. This study could provide an explanation, from a new respect, for the inconsistent results of convective heat transfer of nanofluid in the literature.

Eddy Sensitivity to Jet Characteristics

The atmosphere exhibits two distinct types of jets: the thermally driven subtropical jet and the more poleward eddy-driven jet. Depending on location and season, these jets are often merged or separated, and their position, structure, and intensity strongly influence the eddy fields. Here, the authors study the sensitivity of eddies to changes in the jets’ amplitudes and positions in an idealized general circulation model. A modified Newtonian relaxation scheme that has a very short relaxation time for the mean state and a long relaxation time for eddies is used. This scheme makes it possible to obtain any zonally symmetric temperature distribution and is used to systematically modify the jets’ amplitudes and locations. It is found that eddies are more sensitive to changes in the amplitude of the eddy-driven jet than to changes in the amplitude of the subtropical jet. Furthermore, when the eddy-driven jet is shifted poleward, eddies tend to intensify. These results are tested for robustness in two different reference simulations: one resembling a situation where the subtropical and eddy-driven jets are nearly merged and one when they are separated.

Far infrared cavity of a post C-rich AGB star under IRAS survey

In this paper, we discuss about the physical properties of the dusty environment around the mass losing carbon rich post AGB star located at R.A. (J2000) =06 h 53m 01s and Dec (J2000) =-02o 16’ 00”, in the far infrared IRAS maps. A cavity like structure (major diameter ∼ 103.3 pc & minor diameter ∼33.1 pc) is found to lie at R.A. (J2000)= 06 h 51 m 54.02 s and DEC (J2000) = -01o 35’ 43”, located at a distance ∼ 6.11 kpc from the star. We studied the distribution of flux density, dust color temperature, dust mass in the cavity. The dust color temperature is found to lie in the range 18.7 K to 20.5 K which shows the cavity is isolated and independently evolved. Such a low offset temperature variation shows that there is symmetric outflow or symmetric distribution of density and temperature. It further suggests that our structure is bigger in size and is far away from the far infrared loops(kk loops). The cavity may be in thermally pulsating phase. A possible explanation of the results will be discussed.BIBECHANA 90 (2018) 96

Comparison of numerical analysis on the downhole flow field for multi-orifice hydrothermal jet drilling technology for geothermal wells

Newly developed hydrothermal jet drilling technology has the potential of being economically advantageous over conventional drilling techniques for drilling deep wells in hard formations. By applying coiled tubing techniques and modulating fluid media in the bottomhole reaction chamber, there can be a high temperature and high velocity jet striking and conducting heat to break the rock. So far, there has been no specific study on the influence of nozzle structure on the flow field of multiple hydrothermal jets. This paper presents hydrothermal jet models with different numbers of orifices to investigate the features of flow field, carrying capacity, drilling ability and cooling effect. Results show that for two models in the absence of cooling water, the bottomhole center temperature and pressure are higher than the two sides under multiple hydrothermal jets conditions. This is similar to the flow pattern for a single jet. Additionally, for the five-orifice nozzle with cooling water injected, the entire high temperature region is cylindrical. Ambient cooling water envelops the inner hot water. By comparing different models, the five-orifice nozzle model without cooling water shows a circular symmetric distribution of the bottomhole temperature. With cooling water injected, the central high temperature region becomes rectangular, while the margin of the well bottom is cooled by the peripheral cooling water. The bottom rock average temperature in five-orifice model is lower than for the four-orifice model due to more drastic thermal and kinetic transfer between the hydrothermal jet and the cooling water. The five-orifice nozzle model is better than the four-orifice nozzle model in terms of bottomhole temperature, bottomhole pressure and carrying capacity. Therefore, the five-orifice nozzle should be adopted for hydrothermal jet drilling. It is also feasible to pump down relatively high temperature cooling water to guarantee the high temperature downhole environment. Meanwhile, the cooling water pressure should be controlled during the drilling process for better cooling efficiency. All results in this paper are relevant to the parameters design for multi-orifice hydrothermal jet drilling technology.

Influence of GDL Properties on Liquid Water Distribution and Temperature at CL Surface

Proper water management in proton exchange membrane fuel cell (PEMFC) is critical to achieve a high power density and durability of construction materials. The gas transport is blocked by liquid water remained in GDL, and it causes performance decrement with increase of concentration overpotential. The location of water accumulation is influenced by the temperature distribution inside GDL. At the same time, the temperature distribution is affected by the liquid water distribution, because the liquid water inside GDL decrease the effective thermal resistance. Then, the objective of this study was set to clear the mutual interaction between the liquid water distributions and temperature fields. For this purpose, temperature at the CL surface was measured using thin film thermocouple fabricated by MEMS based technology, and liquid water inside the GDL was visualized by X-ray CT.The experimental conditions were shown in the table. The GDL thermal property, especially the thickness, was changed intentionally to get symmetrical temperature distributions, and the influence of the GDL thermal property on the liquid water distributions and temperature have been examined.The thickness of the sensor was only about 9µm and the width is about 100µm. The electromotive force of the MEMS based sensor was confirmed to be proportional to the temperature difference. The MEMS sensor was inserted at the boundary between MPL and CL. The temperature rise from OCV was plotted in the bottom left figure. The temperature increased quadratically except for the high current density region of condition 4.The visualized liquid water distributions were shown in right hand side figures. The accumulated water was observed in cathode side GDLs in all conditions, however, the highest saturation of water was observed near the rib surface of condition 4. The accumulated water at the rib surface was supposed to reduce the contact thermal resistance and decrease the temperature at the CL surface. Figure 1

Influence of GDL Properties on Liquid Water Distribution and Temperature at CL Surface

Proper water management in proton exchange membrane fuel cell (PEMFC) is critical to achieve a high power density and durability of construction materials. The location of water accumulation is influenced by the temperature distribution inside GDL. At the same time, the temperature distribution is affected by the liquid water distribution, because the liquid water inside GDL decrease the effective thermal resistance. Then, the objective of this study was set to clear the mutual interaction between the liquid water distributions and temperature fields. For this purpose, temperature at the CL surface was measured using thin film thermocouple fabricated by MEMS based technology, and liquid water inside the GDL was visualized by X-ray CT. The GDL thermal property, especially the thickness, was changed intentionally to get symmetrical temperature distributions, and the influence of the GDL thermal property on the liquid water distributions and temperature have been examined.

Magneto-thermo-elastic response of a rotating functionally graded cylinder

In this paper, an analytical solution of displacement, strain and stress field for rotating thickwalled cylinder made of functionally graded material subjected to the uniform external magnetic field and thermal field in plane strain state has been studied. Stress, strain and displacement field as a function of radial coordinates considering magneto-thermo-elasticity are derived analytically. According to the Maxwell electro-dynamic equations, Lorentz force in term of displacement is obtained in cylindrical coordinates. Also, symmetric temperature distribution along the thickness of hollow cylinder is obtained by solving Fourier heat transfer equation in cylindrical coordinates. Using equation of equilibrium and thermomechanical constitutive equations associated with Lorentz force, a second-order inhomogeneous differential equation in term of displacement is obtained and will be solved analytically. Except Poisson\'s ratio, other mechanical properties such as elasticity modulus, density, magnetic permeability coefficient, heat conduction coefficient and thermal expansion coefficient are assumed to vary through the thickness according to a power law. In results analysis, non-homogeneity parameter has been chosen arbitrary and inner and outer surface of cylinder are assumed to be rich metal and rich ceramic, respectively. The effect of rotation, thermal, magnetic field and non-homogeneity parameter of functionally graded material which indicates percentages of cylinder\'s constituents are studied on displacement, Von Mises equivalent stress and Von Mises equivalent strain fields.

Geometric nonlinear thermoelasticity and the time evolution of thermal stresses *

In this paper we formulate a geometric theory of nonlinear thermoelasticity that can be used to calculate the time evolution of temperature and thermal stress fields in a nonlinear elastic body. In particular, this formulation can be used to calculate residual thermal stresses. In this theory the material manifold (natural stress-free configuration of the body) is a Riemannian manifold with a temperature-dependent metric. Evolution of the geometry of the material manifold is governed by a generalized heat equation. As examples, we consider an infinitely long circular cylindrical bar with a cylindrically symmetric temperature distribution and a spherical ball with a spherically-symmetric temperature distribution. In both cases we assume that the body is made of an arbitrary incompressible isotropic solid. We numerically solve for the evolution of thermal stress fields induced by thermal inclusions in both a cylindrical bar and a spherical ball, and compare the linear and nonlinear solutions for a generalized neo-Hookean material.

The Sensitivity of Tropical Cyclone Activity to Off-Equatorial Thermal Forcing in Aquaplanet Simulations

Abstract The sensitivity of global tropical cyclone (TC) activity to changes in a zonally symmetric sea surface temperature (SST) distribution and the associated large-scale atmospheric circulation are investigated. High-resolution (~50-km horizontal grid spacing) atmospheric general circulation model simulations with maximum SST away from the equator are presented. Simulations with both fixed-SST and slab ocean lower boundary conditions are compared. The simulated TCs that form on the poleward flank of the intertropical convergence zone (ITCZ) are tracked and changes in the frequency and intensity of those storms are analyzed between the different experiments. The total accumulated cyclone energy (ACE) increases as the location of the maximum SST shifts farther away from the equator. The location of the ITCZ also shifts in conjunction with changes to the SST profile, and this plays an important role in mediating the frequency and intensity of the TCs that form within this modeling framework.

Moisture Asymmetry and MJO Eastward Propagation in an Aquaplanet General Circulation Model*

Abstract The role of zonal moisture asymmetry in the eastward propagation of the Madden–Julian oscillation (MJO) is investigated through a set of aquaplanet atmospheric general circulation model (AGCM) experiments with a zonally symmetric sea surface temperature distribution. In the control experiment, the model produces eastward-propagating MJO-like perturbations with a dominant period of 30–90 days. The model MJO exhibits a clear zonal asymmetry in the lower-tropospheric specific humidity field, with a positive (negative) anomaly appearing to the east (west) of the MJO convection. A diagnosis of the lower-tropospheric moisture budget indicates that the asymmetry primarily arises from vertical moisture advection associated with boundary layer convergence, while horizontal moisture advection has the opposite effect. In a sensitivity experiment, the lower-tropospheric specific humidity field is relaxed toward a zonal-mean basic state derived from the control simulation. In this case, the model’s mean state remains the same, but its intraseasonal mode becomes quasi-stationary. The numerical model experiments clearly demonstrate the importance of the zonal moisture asymmetry in MJO eastward propagation.

Reliability-based design optimization of pin-fin heat sinks using a cell evolution method

Abstract This paper conveys the concept and idea of reliability-based design optimization (RBDO) to design a robust and reliable pin-fin heat sink for operating in an uncertain environment. In doing so, we formulate an RBDO heat sink design problem and incorporate a recently developed cell evolution method (CEM) to solve the formulated RBDO problem that aims to minimize entropy generation rate under the simultaneous variations caused by ambient temperature and the velocity of the air approaching the heat sink. From finite element analysis of the RBDO designed heat sinks, we found that the increment of the target reliability tends to create a more symmetric and uniform temperature distribution around the center of the heat sink and thereby presents a greater ability to resist the environmental variations. Besides, extensive simulation results reveal that the RBDO designed heat sink is superior to conventional deterministic ones in providing a much more robust and reliable heat dissipation performance when faced with environmental uncertainties. Furthermore, we report the visible findings about how the reliable solution varies depending upon the reliability indices for pin-fin heat sinks with inline and staggered arrangements.

Temperature and Stress Behavior During Close‐Edge Laser Welding

AbstractWelding aluminum in close edge position leads to non symmetric temperature distributions which strongly influence the resultant thermo‐mechanical loads. Therefore, a major challenge in this welding regime is the formation of hot cracks. A finite element model was established to predict the resultant stress and strain during welding, thus increasing the process knowledge, enabling flexible and cost‐effective process optimization.