Non-constant Temperature Research Articles

Effect of shell-induced stresses on the magnetic properties of Fe-based glass-coated microwires: Accounting of initial technical parameters

The study focuses on examining the impact of shell-induced stresses on the magnetic characteristics of Fe-based microwires encased in glass, with particular attention given to the critical fabrication parameters employed in the microwire production process utilizing the Taylor-Ulitovsky method. We systematically investigate how internal stresses affect magnetization reversal behaviors in both glass-coated and uncoated Fe77.5Si7.5B15 microwires through experimental analysis and compare these effects with those resulting from stress-annealing procedures. The simulation of stress distribution caused by the solidification process is based on thermo viscoelasticity theory considering a non-constant glass transition temperature. The analysis also includes the knowledge of the initial parameters of the microwires during the manufacturing.

Indirect prediction of remaining discharge energy of lithium-ion batteries: Looking into future complex non-constant temperature operating conditions

Remaining discharge energy (RDE) is the basis for estimating the remaining driving mileage of electric vehicles. The prediction of RDE is affected by various factors, such as the future discharge current and temperature of the battery. The simplified indirect method predicts the RDE by piecewise averaging the future current under ideal conditions at a constant temperature. Based on the simplified indirect method, this study considers the influence of temperature and proposes an indirect method with a wider range of applications. The proposed indirect method predicts the RDE based on the difference between the remaining chemical energy and future heat loss using both the future current and future environment temperatures as inputs. The battery RDE under no isothermal conditions can be predicted without calculating the terminal voltage across the full state-of-charge range. The proposed indirect method predicts the RDE values under various working conditions with a maximum prediction error and root-mean-square error of ±0.4 Wh and 0.3 Wh, respectively. This suggests that the proposed method exhibits good accuracy and robustness, and demonstrates the potential for practical applications.

Simulation of the laminar thermal boundary layer problem over a flat plate by exploring the local non-similarity technique

ABSTRACT The classical problem of boundary layer problem over a flat plate is considered by employing a local non-similarity approach of the momentum and energy equations provided with the non-constant heat flux condition. Several similarity solutions are seen in literature that have not captured the complete solutions of the physical phenomenon. This paper demonstrates that the solution obtained using the local non-similar technique is preferred to the solution obtained using the similarity transformation technique, especially if the non-constant temperature (surface) with the hot fluid is considered. By exploiting the local non-similarity technique, the mathematical model presented in two-variable differential system is transformed into a coupled non-dimensional ODEs system of equations that is evaluated at a certain streamwise value using a Runge–Kutta–Fehlberg fourth-fifth numerical method. Upon validation of the method, the profile distributions of respective boundary layers with respect to the Biot and temperature ratio parameters are analysed and discussed. Table and graphs are used to illustrate the improvements in the local non-similarity solution and the necessity of adopting this method for non-similar problems. For Biot parameter , the thermal boundary layer is supported positively and downsizes the thermal boundary layer.

A theoretical and applied convective heat transfer model for deep-buried underground tunnels with non-constant wall temperature

Underground tunnel ventilating has been used in many hydropower stations to reduce the building energy consumption of the underground space by precooling or preheating air. The tunnel wall temperature has an important influence on the cooling or preheating performance of the deeply buried underground tunnels. To solve the problem that the heat balance equation is difficult to solve due to the wall temperature variation along the tunnel, a simple heat transfer model under the non-constant wall temperature condition was developed. The developed model is validated against field tests which showed good agreement between the model results and test data. Field tests of underground traffic tunnels in 5 hydropower stations show that the maximum and minimum attenuations reach 13.0 °C and 2.2 °C, respectively. The comparison results show that the relative deviation of the prediction value of the developed model is 3.72% lower than that of the existing constant wall temperature model. Furthermore, the developed model is used for performance simulation of tunnel ventilation for real great hydropower stations, and the conclusions show that the maximum deviations between the calculated model and tested values range from 0.34 °C to 2.76 °C, and the maximum relative deviations range from 1.89% to 9.69%. In addition, the average relative deviations range from 1.13% to 2.40%. Data comparison verifies that the developed model established in this paper has accurate prediction performance, which is conducive to the design optimization of air conditioning and utilization of natural thermal for underground hydropower stations.

Metamodelling the hot deformation behaviour of titanium alloys using a mean-field approach

During the thermomechanical processing of titanium alloys in the β-domain, the β-phase undergoes restoration phenomena. This work describes them by a mean-field physical model that correlates the flow stress with the microstructural evolution. To reduce the computational time of process simulations, metamodels are developed for specific outputs of the mean-field physical model using Artificial Neural Network (ANN) and Decision Tree Regression (DTR). The performance of the obtained metamodels is evaluated in terms of the coefficient of determination (R²), the root-mean-square error (RMSE), and the mean relative error (MRE). No significant difference was observed between R2training and R2testing, meaning that all the metamodels correctly generalise the overall behaviour of the outputs for a wide range of inputs. The evolution of the metamodel outputs is compared with the model predictions in two different situations: 1) at a constant strain rate and temperature, and 2) during Finite Element (FE) simulations of the hot deformation of a hat-shaped sample, where temperature and effective strain rate vary at each element during deformation. The evolution of the outputs at constant and non-constant strain rates and temperature demonstrated the robustness of the metamodels in predicting the heterogeneous deformation within a workpiece. The computational time required by the metamodels to calculate selected outputs can be more than 100 times less than that of the model itself at a constant strain rate using MATLAB® and up to 19% less when coupled with FE simulations. The simulation results combined with microstructural analysis are used to visualise the different restoration mechanisms occurring in different regions of the hat-shaped sample as a function of the local thermomechanical history. The changes in strain rate and temperature during deformation influence the evolution of the wall dislocation density and the immobilisation rate of mobile dislocations at subgrain boundaries, leading to different kinetics of microstructure evolution.

Asymptotic derivation of multicomponent compressible flows with heat conduction and mass diffusion

A Type-I model of a multicomponent system of fluids with non-constant temperature is derived as the high-friction limit of a Type-II model via a Chapman-Enskog expansion. The asymptotic model is shown to fit into the general theory of hyperbolic-parabolic systems, by exploiting the entropy structure inherited through the asymptotic procedure. Finally, by deriving the relative entropy identity for the Type-I model, two convergence results for smooth solutions are presented, from the system with mass-diffusion and heat conduction to the corresponding system without mass-diffusion but including heat conduction and to its hyperbolic counterpart.

Improving prediction of temperature profiles of packaged food during retort processing

A one-dimensional (1D) apparent position (AP) numerical solution (APNS) method was previously proposed to predict the evolution of temperature at the slowest heating point (SHP) of canned food in any shaped container during retort processing. In this study, the APNS method was implemented in a two-dimensional (2D) computational domain in a conductive cylinder that provides a contour of AP for the SHP instead of a single AP in the existing 1D method, enabling the selection of the optimal AP that could substantially improve the prediction accuracy of the APNS method. The 2D method was implemented in a web-based software tool. This tool provided a perfect prediction of a simulated product temperature profile of a conductive canned food in a truncated cone-shaped container, and reasonably good predictions of experimentally measured product temperature profiles of canned food in different shaped containers subjected to natural convection or mixed convection/conduction at non-constant heating temperature. • A 1D APNS method has been used to predict temperature profiles of canned food. • A 2D APNS method was developed in this study to improve the prediction accuracy. • The 2D method was validated using data for conductive and convective canned food. • The 2D method was implemented in a web-based software tool.

Effect of temperature gradient on quantum transport.

The recently introduced multisite tensor network path integral (MS-TNPI) method [Bose and Walters, J. Chem. Phys., 2022, 156, 24101] for simulating quantum dynamics of extended systems has been shown to be effective in studying one-dimensional systems coupled with local baths. Quantum transport in these systems is typically studied at a constant temperature. However, temperature seems to be a very obvious parameter that can be spatially changed to control this transport. Here, MS-TNPI is used to study the "non-equilibrium" effects of an externally imposed temperature profile on the excitonic transport in one-dimensional Frenkel chains coupled with local vibrations. We show that in addition to being important for incorporating heating effects of excitation by lasers, temperature can also be an interesting parameter for quantum control.

Thermo-chemo-mechanical characterization, modeling, and analysis of hydration of calcium-sulfoaluminate cement paste

The reaction kinetic of a commercial calcium sulfoaluminate (CSA) cement was characterized by heat flow calorimetry. Distinct behavior is observed whether tartaric acid is added as retarding agent or not. Employing the so-obtained calorimetric data, heat of hydration and chemical affinity of the investigated binder mixture was determined. Furthermore, continuous ultrasonic propagation velocity measurement gave access to the stiffness gain of paste samples. However, the ultrasonic test setup is characterized by a non-constant temperature history (temperature rise and fall). Modeling the temperature history and the history of the degree of hydration with a thermo-chemical analysis scheme, the intrinsic material function of the stiffness evolution of the investigated hydrating CSA paste was obtained. Furthermore, the robustness of the thermo-chemical analysis scheme was demonstrated by the comparison of the measured with the simulated temperature evolution. The versatility of the approach may contribute to a systematic assessment and optimization of the heat/mechanical evolution of CSA binder systems under various geometric, temporal, and thermal boundary condition.

Preparation of LiNi0.5Mn1.5O4 cathode materials by non-constant temperature calcination and research on its performance

Preparation of LiNi0.5Mn1.5O4 cathode materials by non-constant temperature calcination and research on its performance

Heat transfer efficiency of energy tunnel influenced by inlet temperature, flow rate and pipe spacing

Energy geostructures can be used in urban Heating Ventilating and Air Conditioning (HVAC) system to save energy and reduce emissions. Energy tunnel can extract shallow geothermal energy economically and efficiently without pollution. Based on the utility tunnel in Nanjing, China, heat transfer pipes are buried in the utility tunnel on the non-constant temperature zone to be an energy tunnel. Field test and numerical simulation on the heat exchange efficiency of energy tunnel are carried out. The inlet/outlet temperature and thermal induced stresses are measured and discussed. The results show that the unit heat area transfer efficiency of the energy tunnel is about 63W/m2, the heat transfer efficiency is positively correlated with the inlet temperature and flow rate, and negatively correlated with the pipe spacing.

A novel approach for health management online-monitoring of lithium-ion batteries based on model-data fusion

In order to ensure the safe and stable operation of electric vehicles and energy storage systems, online monitoring of the state of health and the remaining useful life of lithium-ion batteries is the key to the health management of lithium-ion batteries. A novel approach for health management online monitoring of lithium-ion batteries based on mechanism modeling and data-driven fusion is proposed in this paper. An improved semi-empirical capacity degradation model of the lithium-ion batteries fully considering internal resistance and temperature is established. After the data sets of the lithium-ion batteries are de-noised by the wavelet packet, the parameters of the model are identified according to the genetic algorithm and a particle filter framework is designed to online update the parameters of the model. Through the fusion of the two, the remaining useful life and state of health of the lithium-ion batteries can be predicted accurately. The proposed method is verified by the battery cycle test data from the Advanced Life Cycle Engineering Center of University of Maryland and the NASA Ames Prognostics Center of Excellence, the mean absolute error and root mean square error of the remaining useful life for the lithium-ion batteries are respectively less than 20 and 25 cycles at constant temperature condition, and respectively less than 3.30 and 3.60 cycles at non-constant temperature condition. Compared with the existing methods, the proposed method has higher prediction accuracy and better fitting performance, which can provide a certain theoretical basis for the safe operation of lithium-ion batteries.

Temperature Acquisition System for Real Time Application of First Velocity Correction by EDM (Electronic Distance Measurement)

The first velocity correction is used to correct the measured distance affected by the velocity variation of the electromagnetic wave propagation in a medium. This correction depends on the refractive index of the propagation medium and reference refractive index. The influence of the temperature in the medium refractive index is critical; some estimates establish that variation 1°C causes 1ppm of error in distances. In the measuring processes with total stations, the temperature is usually collected at only one point, for example, in the position where the measuring instrument is setup. However, the wave propagates in a medium of non-constant temperature, where the extremes of the line can present variations and thus this measurement in only one point could be non-representative. In this context, it was developed a low-cost real-time temperature acquisition system. This system provides the temperature values in different locations allowing their monitoring through the time. Experiments realized during the geodetic monitoring of a dam, show variations up to 8°C among geodetic points on the dam and around it. An analysis was development to evaluate the influence of temperature variations on monitoring distances and geodetic coordinate of a 2d network with different approaches (temperature modeling). The results shows different values for distances (1.0 mm) and coordinates (0.5 mm) depending of the approach choose.

Compressibility and variable inertia effects on heat transfer in turbulent impinging jets

This article shows the importance of flow compressibility on the heat transfer in confined impinging jets, and how it is driven by both the Mach number and the wall heat flux. Hence, we present a collection of cases at several Mach numbers with different heat-flux values applied at the impingement wall. The wall temperature scales linearly with the imposed heat flux and the adiabatic wall temperature is found to be purely governed by the flow compression. Especially for high heat-flux values, the non-constant wall temperature induces considerable differences in the thermal conductivity of the fluid. This phenomenon has to date not been discussed and it strongly modulates the Nusselt number. In contrast, the heat transfer coefficient is independent of the varying thermal properties of the fluid and the wall heat flux. Furthermore, we introduce the impingement efficiency, which highlights the areas of the wall where the temperature is influenced by compressibility effects. This parameter shows how the contribution of the flow compression to raising the wall temperature becomes more dominant as the heat flux decreases. Thus, knowing the adiabatic wall temperature is indispensable for obtaining the correct heat transfer coefficient when low heat-flux values are used, even at low Mach numbers. Lastly, a detailed analysis of the dilatation field also shows how the compressibility effects only affect the heat transfer in the vicinity of the stagnation point. These compressibility effects decay rapidly further away from the flow impingement, and the density changes along the developing boundary layer are caused instead by variable inertia effects.

Gıdalarda polifenol oksidaz enzimi inaktivasyonunun modellenmesi ve simülasyonu

The aim of this study was to realize more realistic models for the inhibition of browning reactions and nutritional losses and for keeping the fruit vegetables fresh, by inactivating of polyphenol oxidase (PPO) enzyme in real temperature and pressure scenarios. High pressure and heat treatment applications are dynamic methods and modeling should be done by taking into consideration the heating-cooling times and temperature changes, pressurization-expansion times and pressure changes as applied in the industry, not at constant pressure and temperature values. For this purpose, the studies on inactivation of polyphenol oxidase (PPO) enzyme in pineapple puree and apple juice samples under constant pressure and temperature conditions were modeled and the inactivation profile in non-constant temperature and pressure values were predicted. It was observed that the highest PPO inactivation was achieved with a rate of 98.8% in the scenario where three repetitive pressure cycles were applied. By adapting these simulation models to different enzymes in different fruits and vegetables, it would be possible to benefit from the methods applied for enzyme inactivation in the food industry.

Numerical Solution of Bioheat Transfer Problems with Transient Blood Temperature

In the heat treatment process, blood perfusion starts up a negative feedback mechanism. The blood temperature undergoes a transient process before onset of equilibrium and then changes the situation of temperature distribution. In substance, the blood temperature undergoes a transient process for heat exchange between blood and tissue. For more fully exploring the heat transfer behavior of biological tissue, this paper analyzes the bioheat transfer problems with the nonconstant blood temperature based on the Pennes bioheat equation. A numerical scheme based on the Laplace transform is proposed for solving the present problems.

Simulation of boil-off losses during transfer at a LH2 based hydrogen refueling station

Losses along the LH2 pathway are intrinsic to the utilization of a cryogenic fluid. They occur when the fluid is transferred between 2 vessels (liquefaction plant to trailer, trailer to station storage, station storage to pump or compressor, then possibly onto fuel cell electric vehicles …) and when it is warmed up due to heat transfer with the environment. Those losses can be estimated with good accuracy using thermodynamic models based on the conservation of mass and energy, provided that the thermodynamic states are correctly described. Indeed, the fluid undergoes various changes as it moves along the entire pathway (2 phase transition, sub-cooled liquid phase, super-heated warming, non-uniform temperature distributions across the saturation film) and accurate equations of state and 2 phase behavior implementations are essential. The balances of mass and energy during the various dynamics processes then enable to quantify the boil-off losses. In this work, a MATLAB code previously developed by NASA to simulate rocket loading is used as the basis for a LH2 transfer model. This code implements complex physical phenomena such as the competition between condensation and evaporation and the convection vs. conduction heat transfer as a function of the relative temperatures on both sides of the saturated film. The original code was modified to consider real gas equations of state, and some semi-empirical relationships, such as between the heat of vaporization and the critical temperature, were replaced by a REFPROP equivalent expression, assumed to be more accurate. Non-constant liquid temperature equations were added to simulate sub-cooled conditions. The model shows that under environmental heat transfer only the liquid phase of a LH2 vessel would experience cooling, while the boil-off is mainly a result of evaporation from the saturation film onto the vapor phase. Under the conditions assumed for this work, it was also concluded that the actual LH2 density was lower than the corresponding saturation density given by the working pressure of the vessel. During a bottom fill transfer, for example from a LH2 trailer to an on-site stationary vessel, it is shown that the boil-off losses are due to the compression of the vapor phase (“pdV” force). The model indicates that the magnitude of those losses is not dependent on the regulated pressure in the receiving vessel but is rather a function of the initial pressure in the vessel, amounting to more than 12% of losses for a vessel initially at 100 psia. At last, the model is used to estimate the amount of vapor H2 vented when depressurizing a LH2 trailer following a LH2 delivery.

Comparisons of photovoltaic modules for their performances based on different substrates

Performance of photovoltaic (PV) module is investigated on different substrates, TPT, glass and aluminum. Theoretical simulations are made to calculate temperature field for those modules using a simple heat transfer model based on the finite element method (FEM). Theoretical results are obtained by keeping 3.2 mm of substrates thicknesses, and the average temperatures of PV modules are 62.78 °C, 64.38 °C and 68.71 °C for TPT, glass and aluminum substrates, respectively. Furthermore, the temperature distribution is studied with the specific substrate thickness, and interestingly only the temperature with aluminum substrate is decreased by increasing the substrate thickness. In addition, experiments are designed for the three modules, which are encapsulated and measured under non-constant and constant temperature conditions. Both theoretical and experimental results along with the temperature have a good agreement with each other. Power decays of three PV modules are also estimated, and found that their electrical efficiencies are close to 11%.

Analysis of behavior of solutions’ support for nonlinear partial equations

An actual problem is the study of thermal processes in a fairly large range of temperature changes. This, in turn, leads to the study of nonlinear heat equations. In addition, note that in the study of the heat distribution process in space (when we are dealing with a non-constant temperature), as is well known, there are heat flows which are directed from places with higher temperature to places with the lowest temperature. As a result, the equation contains absorption. An adequate mathematical model in this case is a semilinear second-order parabolic equation, which includes the absorption. For such equations, it is very difficult (often impossible) to write the solution explicitly. Therefore, the study of the properties of solutions is an important and urgent problem. The paper analyzes the behavior of the solutions’ support of the Cauchy problem for the above-mentioned above partial differential equation. The result of the research is a theorem, which was proved in the work. It states that under certain conditions on the parameters of the problem, shrinking property of support holds.

Numerical homogenization of elastic and thermal material properties for metal matrix composites (MMC)

A two-scale material modeling approach is adopted in order to determine macroscopic thermal and elastic constitutive laws and the respective parameters for metal matrix composite (MMC). Since the common homogenization framework violates the thermodynamical consistency for non-constant temperature fields, i.e., the dissipation is not conserved through the scale transition, the respective error is calculated numerically in order to prove the applicability of the homogenization method. The thermomechanical homogenization is applied to compute the macroscopic mass density, thermal expansion, elasticity, heat capacity and thermal conductivity for two specific MMCs, i.e., aluminum alloy Al2024 reinforced with 17 or 30 % silicon carbide particles. The temperature dependency of the material properties has been considered in the range from 0 to $$500{\,}^\circ \mathrm {C}$$ , the melting temperature of the alloy. The numerically determined material properties are validated with experimental data from the literature as far as possible.