Effect Of Non-uniform Temperature Research Articles

Universal time-dependent Ginzburg-Landau theory

We study the hydrodynamics of superconductors within the framework of Schwinger-Keldysh effective field theory (EFT). We show that in the vicinity of the superconducting phase transition the most general leading-order EFT satisfying the local Kubo-Martin-Schwinger condition is described by a version of the time-dependent Ginzburg-Landau (TDGL) equations augmented with stochastic terms. This version of TDGL is applicable in the gapless regime independent of any microscopic details. Within this approach, it is possible to include systematically the effects of nonuniform temperature and heat conductivity, as well as explicit or spontaneous breaking of time reversal. We also introduce a thermal version of the Josephson relation and use it to construct an exotic hydrodynamics describing a phase of matter where heat can flow without dissipation.

Experimental and simulation analysis of thermal behavior of large‐span roof system under solar radiation

SummaryThe large‐span metal roof systems can produce a significant nonuniform temperature effect under solar radiation, leading to potential safety hazards. An experiment is conducted to study the nonuniform thermal behavior of a small‐scale continuous welded stainless steel roof (CWSSR) system under solar radiation. The small‐scale CWSSR system considered different roof slopes and sunward side and nightside. The efficiency of the numerical analysis of the thermal behavior of the roof slab is verified in comparison with the experimental results. Based on the numerical and experimental results, the thermal effect of a full‐scale CWSSR system is studied under different orientations, wind speeds, and atmospheric temperature. Through the analysis of research results, the nonuniform thermal features of the CWSSR system are significant and cannot be overlooked. The temperature difference between the sunward side and nightside roof slab is positively correlated with the roof slope. The thermal behavior of the CWSSR system is greatly influenced by wind speeds but is less affected by orientations and atmospheric temperature.

A new pin-resolved ultra-fine-group method based on global–local resonance treatment framework

In order to accurately consider intra-pin effects such as the spatial self-shielding effect and non-uniform temperature effect, several pin-resolved resonance self-shielding methods have been developed recently. The basic strategy of these pin-resolved resonance self-shielding methods is to divide resonance calculation into the whole domain calculation (global) and the 1-D fuel pin calculation (local), which we call the global–local resonance treatment framework. The spatial self-shielding effect, non-uniform temperature effect and resonance interference can be considered accurately by the 1-D fuel pin calculation with the ultra-fine-group method. Due to the simplified geometry, the computation time is short. In addition, the 1-D fuel pin calculation can be performed in parallel. This paper reviews pin-resolved resonance self-shielding methods that have been proposed and proposes a new pin-resolved ultra-fine-group method. These methods are implemented in the numerical nuclear reactor neutronics code SHARK developed by Nuclear Power Institute of China. Numerical results show good accuracy in the pressurized water reactor analysis.

Fire performance of functionally-graded-material sheathed load bearing thin-walled structural framing

This paper presents the fire rating performance of load-bearing thin-walled system sheathed with Functionally Graded Material (FGM) board under standard ISO834 fire through numerical simulation. FGMs are one of the new classes of advanced composite materials that possess continuous variation of material properties within a given direction. The composition of the FGM sheathing is defined by the volume fractions of the constituents’ materials (metal/ceramic) based on the power-law (P-FGM) material function. The general rule of mixtures is then used to predict the thermo-mechanical properties of the FGM sheathing. Fire rating analyses for the Cold-Formed Steel (CFS) wall system were conducted under steady-state conditions where the elastic buckling load from bifurcation analysis under fire conditions was first obtained. Then using the RIKS ON algorithm, collapse analysis was performed in a time frame until failure deformation occurred. The effect of non-uniform temperature on mechanical and thermal properties of the wall stud was included at each time frame in both elastic and collapse analysis.From the FE analysis using ABAQUS, it was observed that the use of FGM as a sheathing material for fire protection increases the failure time for all load ratios compared with the traditional gypsum board. The increase in failure time has a significant implication for improving the safety of occupants during fire scenarios. The study also shows that the novel composite material (FGM board), if properly designed, can lead to an alternative fire protection material in the thin-walled system.

Nonuniform-temperature effects on the phase transition in an Ising-like model

In this study, we investigate the spatially nonuniform-temperature effects on the QCD chiral phase transition in the heavy-ion collisions. Since the QCD effective theory and the Ising model belong to the same universality class, we start our discussion by mimicking the QCD effective potential with an Ising-like effective potential. In contrast to the dynamical slowing down effects which delays the phase transition from quark-gluon-plasma to hadron gas, the spatially nonuniform-temperature effects show a possibility to lift the phase transition temperature. Besides, both the fluctuations and the correlation length are enhanced in the phase transition region. Furthermore, the critical phenomena is strongly suppressed like as the critical slowing down effects. The underlying mechanism is the nonzero-momentum mode fluctuations of the order parameter induced by the nonuniform temperature. Our study provides a method to evaluate the nonuniform-temperature effects, and illustrate its potential influence on analyzing the QCD phase transition signals at RHIC.

Effect of non-uniform temperature & humidity distribution in the frontal airflow on evaporator frosting performance of a frost-free refrigerator

Abstract The frost-free refrigerator typically has three compartments, i.e. refrigerating, variable-temperature and freezing ones. The temperature and humidity (T&H) inside each compartment vary dramatically, leading to non-uniform T&H distribution in the overall return air. Therefore, frost maldistribution occurs on the evaporator and further induces airflow redistribution. In this article, the quasi-static 3–2–1–1 frosting model is built considering 3D evaporator, 2D T&H of frontal airflow, 1D frost growth and 1D non-uniform fin spacing. The model is verified by the experiment data in the open literature. Results show that frost mass is similar with non-uniform and uniform T&H distribution in frontal airflow, but frost distribution is much different. The evaporator capacity for non-uniform airflow is lower at the early stage of frosting process than that for uniform airflow, but higher later due to the airflow transverse redistribution when the airflow transfers transversally from higher to lower T&H areas owing to frost maldistribution. The transverse redistribution results in the air velocity increment and heat transfer compensation effect. Moreover, the fan stall for non-uniform airflow arises later and results in the larger airflow rate and evaporator capacity at later frosting process.

Non-uniform temperature field and effects of large-span spatial truss structure under construction: Field monitoring and numerical analysis

The large-span spatial truss structure under construction can produce significant non-uniform temperature effect due to strong solar radiation, and it directly affects the quality of structural closure and even leads to potential safety hazards. In order to study the non-uniform temperature field, the steel roof of Xi'an Silk Road International Convention and Exhibition Center under construction was selected as the studied structure, the real-time temperatures of test points and thermal boundary conditions were monitored for 30 days. The numerical simulation method of temperature field of spatial truss structure was established considering real-time shadow effect, which can be effectively analyzed by the proposed shadow analysis algorithm. During monitoring period, the structural temperature field under strong solar radiation is significantly non-uniform with maximum temperature difference between test points of 15.6℃, and the maximum temperature rise of test point compared with atmospheric temperature is 16.9℃. By comparison with test results, the accuracy of numerical method is verified, and the daily root mean square of error rates for all monitored members is lower than 6.5% during the monitoring period. Through the analysis of test and simulation results, the non-uniform features of temperature field of large-span spatial truss structure was studied. In addition, the temperature effect was calculated for different healing times considering non-uniform temperature field of large-span spatial truss structure under construction. Then some construction suggestions for healing time were also given. The research method and conclusions of this paper can provide valuable references for thermal design, monitoring and control of large-span spatial truss structure.

Effects of non-uniform temperature of the ice nucleus on heterogeneous ice nucleation

In this paper, effects of non-uniform temperature in the ice nucleus on heterogeneous ice nucleation are investigated via two approaches: changes in Gibbs free energy function and availability function. Analytical expressions for non-uniform temperature distribution inside the ice nucleus and heat transfer from the nucleus to the supercooled wall are obtained in terms of the contact angle and supercooled wall temperature based on the consideration that thermal conductivity resistance of the nucleus, interfacial resistance and thermal resistance due to curvature of ice/water interface are in series. With non-uniform temperature in the nucleus taken into consideration, it is found that the critical radius of the ice nucleation obtained based on availability analysis is slightly larger than those obtained based on Gibbs free energy analysis. Both heterogeneous critical radius and nucleation energy barrier are found to be increasing with surface contact angle. On an ice-phobic surface at small supercooling degrees, the critical radius and the nucleation energy barrier obtained with or without heat transfer taken into consideration differ greatly with the increase of the contact angle. However, at large supercooling degrees and small contact angles, differences in the critical radius and nucleation energy barrier by availability analysis are negligible with or without heat transfer effects. Thus, heterogeneous nucleation behaviors on ice-philic surfaces can be estimated based on the assumption of uniform temperature in the ice nucleus when degree of wall supercooling is large.

The effect of non-uniform temperature on the sorption-enhanced steam methane reforming in a tubular fixed-bed reactor

The effect of non-uniform temperature on the sorption-enhanced steam methane reforming (SE-SMR) in a tubular fixed-bed reactor with a constant wall temperature of 600 °C is investigated numerically by an experimentally verified unsteady two-dimensional model. The reactor uses Ni/Al2O3 as the reforming catalyst and CaO as the sorbent. The reaction of SMR is enhanced by removing the CO2 through the reaction of CaO + CO2 → CaCO3 based on the Le Chatelier's principle. A non-uniform temperature distribution instead of a uniform temperature in the reactor appears due to the rapid endothermic reaction of SMR followed by an exothermic reaction of CO2 sorption. For a small weight hourly space velocity (WHSV) of 0.67 h−1 before the CO2 breakthrough, both a low and a high temperature regions exist simultaneously in the catalyst/sorbent bed, and their sizes are enlarged and the temperature distribution is more non-uniform for a larger tube diameter (D). Both the CH4 conversion and the H2 molar fraction are slightly increased with the increase of D. Based on the parameters adopted in this work, the CH4 conversion, the H2 and CO molar fractions at D = 60 mm are 84.6%, 94.4%, and 0.63%, respectively. After CO2 breakthrough, the reaction of SMR dominates, and the reactor performance is remarkably reduced due to low reactor temperature.For a higher value of WHSV (4.03 h−1) before CO2 breakthrough, both the reaction times for SMR and CO2 sorption become much shorter. The size of low temperature region becomes larger, and the high temperature region inside the catalyst/sorbent bed doesn't exist for D ≥ 30 mm. The maximum temperature difference inside the catalyst/sorbent bed is greater than 67 °C. Both the CH4 conversion and H2 molar fraction are slightly decreased with the increase of D. However, this phenomenon is qualitatively opposite to that for small WHSV of 0.67 h−1. The CH4 conversion and H2 molar fraction at D = 60 mm are 52.6% and 78.7%, respectively, which are much lower than those for WHSV = 0.67 h−1.

Effects of non-uniform temperature on closure construction of spatial truss structure

Due to exposure to the natural environment, the non-uniform temperature effect of a spatial truss structure that is under construction is the main factor that causes difficulties in closure construction; thus, the construction quality and efficiency will be directly affected. The standard hall roof of the Xi'an Silk Road International Convention and Exhibition Center is selected here as the research object to study the structural non-uniform temperature effect on closure construction. The structural temperature field and effect during construction are simulated by finite element methods based on the on-site monitoring of thermal boundary parameters. During the closure construction period, the temperature distribution is significantly non-uniform. Furthermore, the non-uniform temperature effect causes the alignment deviation of welded joints, the value of which can be up to 14.3 mm. The assembly quality of members and the structural connection accuracy have difficulty meeting the requirements at most times. After forming, the structural residual stress may reach 68 MPa, and nearly 6% of members experience residual stress of over 50 MPa. Construction suggestions for the welding time and sequence are proposed according to analysis of one-month's simulation results. The research method and conclusions of this paper can provide valuable references for the closure construction of a spatial trusses or similar structures.

The on-the-fly subgroup method capable of treating spatial self-shielding, resonance interference and temperature distribution effects

The pseudo-resonant-nuclide subgroup method (PRNSM) based global-local self-shielding calculation scheme was recently developed to resolve the spatial self-shielding and resonance interference effects for large-scale problems. But the PRNSM is not able to treat non-uniform temperature distribution. The reason is that the PRNSM generates physical probability tables at different temperatures with inconsistent subgroup probabilities. To overcome this defect, the on-the-fly subgroup method (OSM), which is an improvement of the PRNSM, is proposed. The new method generates the physical probability tables for different temperatures with shared subgroup probabilities and is able to treat non-uniform temperature distribution. This method replaces the PRNSM in the global-local self-shielding calculation scheme and is implemented in the high-fidelity neutronics code NECP-X. The numerical results show that the OSM can treat the spatial self-shielding effect, the resonance interference effect and the non-uniform temperature effect simultaneously. Besides, NECP-X is able to predict fuel temperature coefficients with high accuracy.

Effects of Non-Uniform Temperature of the Walls on the Soret Experiment

We present a numerical study of a Soret experiment, which is conducted in a cell filled with a binary mixture and placed between differently heated horizontal walls. In real experiments, in the corner regions of the cell, where glass is in contact with metal, the uniformity of temperature can be perturbed. We study the effect of the temperature non-uniformity on the Soret separation considering two variable parameters: the local deviation of temperature from the value on the rest of the wall, and the length of the interval on which temperature perturbations occur. The cases of symmetric and non-symmetric perturbations are examined. Our non-linear numerical simulations reveal two distinct regimes of mass transfer in a mixture with Soret effect: diffusive and convective. The diffusive regime is sustained until temperature non-uniformity less than 3-5% of the applied temperature difference and occupies 5% of the wall length at each corner. In the convective regime, the emerging flow prohibits component separation by mixing of liquid components. It is noted a strong flow appears at the earliest moment of the experiment which rapidly attenuates.

Effects of Non-Uniform Temperature on In-Situ Current Distribution and Non-Uniform State of Charge Measurements for LiFePO4 and LiNiMnCoO2 Cells

Understanding internal state non-uniformity occurring across the electrodes in large-format Lithium-ion batteries, and among parallel-connected cells, is a critical part of the cell and battery module design process. Two five-cell parallel groups were tested using LiFePO4/C6 (LFP), and LiNiMnCoO2/C6 (NMC) chemistries. Pulse and full-capacity discharges were performed at various States of Charge (SOC), C-rates, average temperatures, and levels of temperature non-uniformity. In pulse testing, the current non-uniformity was lower for the LFP group compared to the NMC group. The hottest cell in the LFP group produced up to 40% more current than average, while this was up to 80% for NMC. Conversely, under charge depleting conditions the NMC group experienced less current non-uniformity, and in certain cases provided a nearly uniform current distribution in the presence of non-uniform temperature. Higher temperature sensitivity in the impedance causes larger current non-uniformity under pulse conditions. However, due to the presence of non-uniform SOC in charge depletion conditions, the Open Circuit Voltage (OCV) versus SOC gradient plays a significant role in controlling the current distribution, where steeper OCV versus SOC minimizes the effect of the non-uniform impedance.

An interband cascade laser-based in situ absorption sensor for nitric oxide in combustion exhaust gases

A direct absorption nitric oxide sensor for combustion exhaust gas measurements, based on an interband cascade laser operating at 5.2 µm, is presented. The sensor was applied to the hot air co-flow of an auto-ignition test rig (800–1300 K), which contains nitric oxide mole fractions of the order of 1 mol%, due to prior microwave plasma heating. The effect of non-uniform temperature along the beam path, on both absorption line strength and gas density, was included in mole fraction measurements at various co-flow temperatures and velocities. At an absorption length of only 82 mm, a noise-limited detection limit of 30 ppm with a 10 ms observation time was achieved at 800 K. The results were compared in detail to previously measured mole fractions, using a sampling gas analyzer.

Effects of Non-Uniform Temperature on in-Situ Current Distribution and Non-Uniform State of Charge Measurements for LiFePO4 and LiNiMnCoO2 Cells

Understanding internal state non-uniformity that occurs across the electrodes in large-format Lithium-ion batteries (LIBs), and among parallel-connected cells, is a critical part of the cell/module design process [1]. The reduction of non-uniform current distributions is critical as this leads to non-uniform utilization, which effectively reduces energy density, and can eventually cause non-uniform degradation, leading to earlier cell/module failure. Several studies, performed particularly at high charge/discharge rates (i.e., above 1C-rate), show single cell temperature differences greater than 20°C, for large-format Lithium-ion cells [2]. As engineers maximize the energy density of Lithium-ion cells, and push them to extreme limits (e.g., Tesla Supercharging), the problems of non-uniform currents and temperatures will continue to be exacerbated. Therefore, high-rate battery systems generally require the integration of a battery thermal management system (BTMS). Coupling the optimization of cell/module, and BTMS designs, to efficiently minimize thermal non-uniformity and packaging requirements, requires spatially-resolved coupled thermal-electrical-electrochemical models. However, little published research exists regarding the measurement of spatially distributed effects in Lithium-ion batteries and the experimental validation of spatially distributed models. Under uniform thermal conditions, the in-situ internal current/State of Charge (SOC) distributions within a segmented-cathode (LiFePO4) cell have been measured by Zhang et al. [3]. Yang et al. studied the non-uniform SOC buildup between two 18650 LiFePO4 cells connected in parallel, where each cell was held at a different temperature [4]. Klein et. al. studied the non-uniform temperature effects on the bulk cell resistance under constant current pulses and dynamic current charge-depleting cases for a LiNiMnCo pouch cell [5]. This study presents the non-uniform temperature effects on in-situ current/SOC distributions among modules of five parallel-connected cells. Two commercially available 18650 cell chemistries were used; LiFePO4/Graphite (LFP) and LiNiMnCo/Graphite (NMC). For each chemistry, the five cells were connected in parallel with a current measuring shunt in series with each cell. The test system is illustrated in Figure 1a, and the module is in Figure 1b. Average module temperatures of 15, 25, and 35°C were used with temperature differences across the module being controlled to 0, 5, 10, and 20°C. Direct-current pulse tests were performed at 20, 50, and 80% SOC using 10sec pulses at constant C/5, C/2, 1C, and 2C-rates. Additionally, C/5, C/2, and 1C-rate constant current full-capacity discharges were performed under the same thermal conditions to observe the effects of non-uniform SOC among the cells. The pulse results indicate that the LFP cell resistance has a lower temperature sensitivity than the NMC, and therefore experiences less current non-uniformity for the same amount of temperature non-uniformity. Larger current non-uniformity is observed at lower average temperatures, where the resistance is more temperature sensitive. The current distribution develops quickly (i.e., <2sec) and remains fairly constant during the 10sec pulse. However, the constant current full discharge results are quite different. Figure 1c-e plots the measured normalized current for the left/middle/right (cold/mean/hot) LFP cells for the average module temperature case of 25°C and the C/5, C/2, and 1C-rates, respectively. The instantaneous current distributions measured at the same average module SOC as the pulse tests are more uniform in the full capacity discharge tests. Therefore, the amount of maximum non-uniform SOC is lower than would be expected from extrapolating the pulse test current distribution results. Additionally, the NMC unit, which had a larger current distribution in the pulse testing compared to LFP, has a substantially lower current-distribution than the LFP unit for the full-capacity discharges. Finally, using the measured SOC profiles for each cell, a tolerable amount of temperature uniformity for each chemistry is interpolated from the results. Figures 1f and 1g present these results for two maximum tolerable SOC non-uniformities of 2% and 5%. The NMC chemistry provides a higher tolerance to temperature non-uniformity for a given SOC non-uniformity tolerance, as compared to the LFP chemistry. The results of this study are aimed at aiding both the validation of spatially resolved models, and to quantify the thermal non-uniformity targets for these common commercially available Lithium-ion cell chemistries. [1] T. Waldmann, G.Bisle, B.-I. Hogg, S. Stumpp, M.A. Danzer, M. Kasper, P. Axmann, M. Wohlfarht-Mehrens, Jounal of The Electrochemical Society 162 (6) (2015) A921-A927 [2] C. Veth, D. Dragicevic, C. Merten, Journal of Power Sources 267 (2014) 760-769 [3] G.Zhang, C.E. Shaffer, C.-Y. Wang, C.D. Rahn, Journal of The Electrochemical Society 160 (4) (2013) A610-A615. [4] N. Yang, X. Zhang, B. Shang, G. Li, Journal of Power Sources 306 (2016) 733-741. [5] M. Klein, S. Tong, J. Park, Applied Energy 165 (2016) 639-647. Figure 1

The Effect of Non-Uniform Temperature and Velocity Fields on Long Range Ultrasonic Measurement Systems in MYRRHA

The Effect of Non-Uniform Temperature and Velocity Fields on Long Range Ultrasonic Measurement Systems in MYRRHA

Efficient Three Dimensional Nonlinear Thermo-Mechanical Analysis of Structures Subjected to Fire

Abstract In this paper, a computationally efficient integrated frame-work is developed for coupled thermo-mechanical analysis of 3D frames. It can account for physical phenomena like large deformations, temperature dependent material degradation, permanent plastic deformations and fire induced spalling which are prevalent at elevated temperatures. The developed frame-work utilizes three way sequential coupling between thermal, mass transport and structural analysis. A two level discretization scheme is incorporated where 1D beam column elements are utilized for structural analysis, the cross-section of these beam-column elements are further discretized into matrix of segments. Aforementioned strategy entails sequential coupling of effects of non-uniform temperature and pore pressure across the cross-section into structural analysis. Subsequently structural analysis is performed with an updated Lagrangean based formulation with force deformation relationships deduced form classical Euler-Bernoulli beam column theory. Critical physical phenomena like cracking, crushing, spalling and transient states of strain in case of concrete and yielding in case of steel are duly accounted. Cross-sectional reduction due to spalling are accounted for by replacing the spalled segments with void segments in the subsequent time steps. Numerical examples of steel and concrete structures subjected to various fire scenarios are presented to demonstrate the accuracy of developed framework. Furthermore, progressive collapse analysis is carried out for concrete and steel 3D subjected to fire.

Investigations on the effect of non-uniform temperature on fluid flow and heat transfer in a trapezoidal cavity filled with porous media

Simulations were carried out for natural convection in a trapezoidal cavity filled with porous media to investigate the effect of uniformly and non-uniformly heated bottom wall using finite element computational procedure. The enclosure used for flow and heat transfer analysis has hot bottom wall, constant temperature cold top wall and adiabatic side walls. The bottom wall is subjected to uniform/linear/sinusoidally varying temperatures. Results are presented in the form of stream lines, isotherms, heatline plots, local and average Nusselt numbers. Heatline visualization technique is a useful method that gives information on heat transport from the heated to cold region inside the porous trapezoidal enclosure with varying temperature boundary conditions. Nusselt numbers are computed for Darcy-modified Rayleigh numbers or Rayleigh number (Ra) ranging from 100 to 2000 for an aspect ratio (H/L) of 0.5. It is observed from this study that the uniform temperature at the bottom wall of the enclosure gives higher Nusselt number as compared to the linear and sinusoidally varying temperature cases. The average Nusselt numbers increases monotonically with Rayleigh number for bottom wall and top walls. The power law correlations between average Nusselt number and Rayleigh numbers are presented for convection dominated regions.

In-plane nonuniform temperature effects on the performance of a large-format lithium-ion pouch cell

Due to the temperature sensitive behavior of lithium-ion batteries a thermal management system (TMS) is typically integrated into the battery pack design. This system plays a crucial role in the total battery pack performance. During operation the TMS will induce nonuniform temperature distributions within the cells of the pack, due to relatively low cell thermal conductivity. However, limited research has been published regarding the effects of thermal nonuniformity throughout a cell, module, or pack. Understanding these effects will be beneficial to heat exchanger design and TMS control strategy optimization. Here, an experimental investigation is performed where fixed one-dimensional temperature distributions, emulating the effects of edge-based heat transfer, are applied across the face of a 10Ah NiCoMn Li-ion pouch cell. Average cell temperature conditions of 15, 25, and 35°C with edge-to-edge temperature differences (ΔT) of 0, 5, 10, and 20°C are applied. At each thermal treatment the effects on: (1) the pulse resistance at 50% state of charge, (2) the bulk resistance on a Charge-Depleting US06 power profile, and (3) the overpotential during Constant-Current charge are investigated. Pulse resistance is decreased with increased ΔT. However, the discharge resistance on the Charge-Depleting cycle was increased with increased ΔT. The Constant-Current charging overpotential (and therefore resistance) was also increased with increased ΔT. All effects are largest at 15°C, and negligible at 35°C.

Effect of Non-Uniform Temperature Distribution over the Cross-Section in Steel Frame Structure

The paper deals with the effect of non-uniform temperature over the cross-section in the steel frame structure under fire loading. The unequal temperature distribution causes additional bending moments in statically indeterminate structures. Numerical results of thermal and structural analysis from the commercial computer software ANSYS are compared with the experimental measurements on the steel frame exposed to high temperature.