Influence Of Thermal Conditions Research Articles

Mathematical modeling of drying kinetics of two varieties of cacao cultivated in the brazilian amazon region

Drying kinetics, along with mathematical modeling, provides means for simulations and predictions to achieve process optimizations. This study investigated the drying kinetics of Criollo and Forastero cocoa beans, varieties cultivated in the Amazon region, at three different temperatures (50 °C, 60 °C, and 70 °C). The results showed that the two varieties exhibited distinct behaviors during the drying process. The temperature of 60 °C was the most effective, as it provided seed water content closer to 8% for the Criollo (8.15% d.b.) and Forastero (8.89% d.b.) varieties. Mathematical models were fitted to the experimental data to analyze the drying kinetics. The Midili model (R² > 0.998, DQM < 0.02) provided the best fits for both varieties at all tested temperatures. The model parameters indicated that the drying rate increased with higher temperature and longer exposure time to drying air. Internal resistance to water transfer varied in some models, indicating a possible influence of thermal conditions. This study contributes to a better understanding of cocoa bean drying, providing important information for optimizing industrial drying processes. The results emphasize the importance of considering the specific characteristics of different cocoa varieties when developing efficient drying strategies.

The study of degradation and mechanical properties of poly(lactic) acid (PLA) based 3D printed filament

Additive manufacturing, commonly known as 3D printing technology, has become one of the mainstream processes in the manufacturing industry due to its advantages over conventional manufacturing, which have piqued the public’s interest. This study aims to focus on the influence of thermal conditions on crystallization towards mechanical properties of 3D printed poly(lactic) acid (PLA) degradation samples with 100% infill. As for the degradation profile, the highest weight loss recorded by the samples was 0.7%, observed in samples buried in soil with an abiotic medium for one month. The exposure of degraded samples to high temperature during drying affected their crystallinity, resulting in significant changes in strains, particularly between week 1 and week 2, where strains dropped significantly from 7.33% to 4.28%, respectively. In conclusion, it has been demonstrated that degradation for PLA material still can occur in an abiotic medium, albeit at a slower rate compared to a biotic medium due to the presence of additional microorganisms and bacteria. Besides, the post-heat treatment process on PLA degradation samples affects their crystalline structure, resulting in significant changes in mechanical properties, particularly especially strains. Therefore, it can be concluded that different materials exhibit distinct mechanical properties.

Cryogenic Deep Drawing Tool Design for Reduced Heat Transfer

Subject of this study is the usage of macro-structured tools for deep drawing of aluminum alloys at cryogenic temperatures in order to increase the drawing depth. The advantage of the macro-structure is the reduced contact area, which primarily leads to a reduction in frictional forces in the flange area and also minimizes the heat transfer from the tool to the cooled sheet metal. In addition to the geometry of the tools, the heat transfer is also influenced by the thermal properties of the tool materials. Therefore, the tool must be designed to reduce heat flux and thermal diffusivity. In this regard, substitute materials for the tools, specifically polymer, and steel-shielded polymer, were investigated. In this context, the heat transfer coefficients between the tool material and the aluminum blank are determined experimentally. The influence of thermal conditions on the cryogenic deep drawing process are investigated numerically and experimentally. The result of the study is an improved process understanding to ensure the blank temperature in a cryogenic range and increase the resistance against bottom cracks.

Nonlinear thermoelastic wave propagation in general FGM sandwich rectangular plates

The present work is dedicated to investigating the thermoelastic wave propagation behavior of sandwich rectangular plates (SRP) made of functionally graded material (FGM). The main contribution lies in the partial modification of basic theoretical expressions and solution methods to improve the accuracy of practical system models. An analytical model with three types of general configurations is established. The porosity distribution in FGM layers depends on the degree of mixture of the constituent materials, with the FGM layers without porosity taken as a reference model. The effect of porosity within FGMs is addressed through a refined analytical formulation of material properties, and the temperature-dependent material properties of FGM sandwich structures (FGMSS) maintain continuity through the thickness. This improved framework introduces a porosity function encompassing three distinct structural and geometrical functions: the core-to-thickness ratio (CTR), porosity volume fraction (PVF), and porosity distribution function (PDF). It is worth mentioning that the theoretical expressions maintain good continuity and reliability under the influence of thermal conditions and system parameters of the proposed structures. Furthermore, considering the generation of thermal strain energy (TSE) caused by thermal expansion of the structure in the normal direction, an improved analytical approach for determining TSE in rectangular plate structures is then investigated by introducing the Green's nonlinear strain (GNS). Hamilton's principle is applied to derive the wave motion equations and analytical solutions for the wave dispersion relations are derived. Furthermore, accurate numerical simulation is performed and the solution is verified with data available in published resources. In addition, we present a systematic parametric analysis to examine the effects of porosity, configuration, power-law exponent (PLE), PVF, CTR, temperature, and wave number on the thermoelastic wave propagation behavior of FGMSRP.

Vibration and flutter analysis of damaged composite plates under thermal environment and its passive control using piezoelectric patches

The internal flaws will largely affect the structural and aeroelastic characteristics of composite structures, especially at high thermal environments. The influence of thermal conditions on the passive control of vibration and flutter characteristics of damaged composite plates with piezoelectric patches is investigated in this work. The mathematical model is developed for the damaged composite plates with piezoelectric patches under thermal conditions by the finite element method. Internal flaws are incorporated in the composite plates based on the anisotropic damage modeling concept. Present finite element formulation is coded in the Matlab environment. The natural frequency, flutter velocity and flutter frequency values for damaged composite plates are obtained at different thermal conditions. Deterioration in the vibration and flutter characteristics are observed due to the presence of internal flaw in composite plates in the different thermal environments. PZT patches are bonded on the surface of the damaged composite plates subjected to the thermal environment and studies are carried out with different input voltages. Thus the improvement in the vibration and flutter characteristics of a damaged composite plate by employing PZT patches is presented for varying thermal conditions.

Nonlinear dynamic and stability of a small size moving beam under thermal conditions

Nonlinear transverse vibration of a micro‐size moving beam like structure under the influence of thermal conditions is studied. Hamilton principle is used to derive the nonlinear equation of motion. The derived equation of transverse motion is discretized using the Galerkin technique. The vibration attributes of the moving beam, such as frequencies of the transverse response, time response, and stability analysis, are investigated at different temperatures. For stability analysis, bifurcation diagrams are presented under the influence of temperature, length‐scale parameter, and excitation frequencies at various axial speeds of the beam.

Modelling of the Aluminium Electrolysis Process: Feeding and Dissolution of Alumina Particles

The present numerical study describes the feeding and dissolution behaviour of alumina particles in the electrolytic bath of industrial Hall-Héroult cells. The dissolution rate is controlled by thermal and chemical conditions as well as the transport and mixing of particles in the electrolyte. The model presented is implemented in the OpenFOAM® framework using the Lagrangian approach for the coupling of continuous (electrolyte and liquid aluminium) and dispersed phase (alumina particles). The model solves the particle motion, mass transfer from dispersed to continuous phase, the energy equation, and the transport of dissolved concentration. Moreover, the influence of thermal conditions and turbulent mixing due to gas bubbles arising under the anodes is considered by the model. The velocity field is adopted from a previously executed magnetohydrodynamic (MHD) simulation. With the help of the model developed, various studies are carried out. The focus corresponding to the increased flexibility of electric power consumption is on the thermal behaviour during cold operating conditions of the electrolysis cell. It is important to ensure that all the alumina feed is dissolved. The sinking of undissolved alumina to the bottom of the cell must be prevented as it impairs cell efficiency. The results show that the dissolution rate and total dissolution time depend on the bath temperature. A greater effect is observed for the bath superheat defined by the difference of bath temperature and liquidus temperature of the bath. Furthermore, the influence of process parameters like grain size and feeding masses are studied in detail.

Inhomogeneous Aging in Lithium‐Ion Batteries Caused by Temperature Effects

Lithium‐ion batteries (LIBs) are widely used as electrochemical energy storage devices due to their advantages in energy and power density as well as their reliability. One research focus is the cyclic lifetime of LIB, where the influence of thermal conditions during cycling is not yet completely understood. In previous publications, investigations on the cyclic aging behavior of LIB under various thermal boundary conditions are presented, including defined temperature gradients and temperature transients. Thereupon, herein, the results of cell openings and an extensive postmortem study with analyses of scanning electron micrographs, electrode thickness, X‐ray diffraction, and inductively coupled plasma optical emission spectroscopy are presented, evaluated, and correlated with the thermal conditions. The results reveal significant variations on the electrode and atomic scale for the different thermal boundary conditions during cycling. The electrodes exposed to a temperature gradient exhibit an inhomogeneous distribution of aging behavior that directly correlates with the local temperature. Cycling with superimposed transient temperatures reveals fundamentally different aging effects. With this knowledge, critical temperature conditions can be avoided in applications to prolong cyclic lifetime.

The influence of thermal conditions on potato yield in the administrative regions of the Republic of Belarus

The analysis of the dynamics of thermal conditions during 1961–1988 and 1989–2015, as well as the adjacent decade of the study period. Changes were estimated for the average temperatures of individual months of the year, high average and maximum daily temperatures, as well as for the duration of the active vegetation period and the sums of active temperatures. The established increase in average annual temperatures was 0.4 °С per decade. At the same time, in the first half of potato vegetation (May – June) the thermal trends are ambiguous, while in the second half (July – August) the increase of average air temperatures prevails. The increase in temperatures in the summer months is accompanied by an increase in the prevalence of negative thermal effects on potato yields, which is confirmed by negative correlation coefficients of potato yield deviations from trend lines and indicators such as the air temperature in July and the number of hot days (with an average temperature above 20 °С and a maximum temperature above 30 °С). Statistical reliability of correlation between potato yield deviations from trend lines and July temperatures is confirmed only in 1989 –2015 and covers 60 administrative districts. In these and most of the remaining areas, the correlation coefficients are negative. It is established that the proposed and justified critical value of the number of days with a maximum temperature above 30 °С (10 and more) determines more than a third of the negative deviations of potato yield in most of the country, and the probability of its negative impact in the modern period is 70 %. The decrease in average yield is 12.7 c/ha (8 %). It was found that the most unfavorable hot period occurs during the tuber formation and growth of potato tubers, in connection with which possible measures of adaptation of potatoes to temperature increase are proposed: the use of heat-resistant potato varieties, the shift of potato planting dates to earlier dates, irrigation (in the case of a combination of high temperatures with insufficient moisture).

Composite Casting and Characterization of Cu–Al Bilayer Compounds

In this study, an experimental die casting setup is designed and various composite casting experiments are performed to create Cu–Al bilayer compounds. The influence of thermal conditions and Al/Cu volume ratio on the growth of intermetallic phases and the mechanical and electrical properties is investigated. A distinctive correlation, especially with the thickness of eutectic phase, is detected that increases with higher process temperatures and volume ratios. An increased phase thickness leads to higher electrical resistance, but on the other hand, no clear influence on shear or bending strength could be determined. However, large layers of brittle and hard phases negatively influence a successive forming process.

Influence of Thermal Conditions on Particle Properties in Fluidized Bed Layering Granulation

Fluidized bed layering granulation is frequently used to formulate particles of high quality. From previous studies, it is well known that the dynamic behavior of the process, as well as the product properties depend on operating parameters. The process is characterized by heat and mass transfer between fluidized particles and the surrounding fluidization medium. To investigate the mutual influence between particle phase and fluidization medium, a dynamic model is introduced. The model comprises two parts: a population balance model to describe the evolution of the particle sizes and a system of ordinary differential equations to account for thermal conditions. For the first time, the dynamic model considers the bidirectional coupling of particles and fluidization medium in fluidized bed layering granulation. By means of simulations, it is shown that the derived model is capable of reproducing the experimental findings.

Influence of thermal conditions on the electrocaloric effect in a multilayer capacitor based on doped BaTiO3

We present the results of studies of thermal expansion, heat capacity, permittivity, polarization and the influence of different thermal conditions on the intensive electrocaloric effect (ECE), [Formula: see text], in a commercial multilayer capacitor based on doped BaTiO3. Investigations in a wide temperature range revealed one anomaly in the behavior of the physical properties at about 290[Formula: see text]K characteristic for the relaxors. Direct measurements showed a high reversibility of ECE under equilibrium thermal conditions. Good agreement was found between the values of [Formula: see text] determined by direct and indirect measurements at the electric field up to 15.4[Formula: see text]kV/cm. Quasi-isothermal conditions lead, firstly, to decrease of large [Formula: see text]0.94[Formula: see text]K obtained in adiabatic conditions under [Formula: see text][Formula: see text]kV/cm to 0.87[Formula: see text]K, and, secondly, the appearance of a difference between the values of [Formula: see text] and [Formula: see text] determined when the electric field is applied and removed. Using this phenomenon and changing the frequency of the periodic electric field, [Formula: see text][Formula: see text]kV/cm, the effect of cooling was obtained equal to [Formula: see text][Formula: see text]K. The results obtained are useful for further development of the electrocaloric refrigeration technique without thermal switches.

The Influence of Hydrocarbonate Ions on the Anodic Behavior of Aluminum at Different Temperatures

The influence of thermal conditions on the anodic behavior of aluminum in sodium hydrocarbonate solutions of various concentrations was studied. The concentration and temperature limits of local activation in the studied systems are established. The effect of the thermal activation of self-dissolving metal is found.

Disponibilidade térmica para diferentes culturas agrícolas em região de clima subtropical úmido obtida através da utilização de índice bioclimático

Existem vários sistemas de unidades bioclimáticas além dos graus-dia, embora sua utilização e limitação ainda sejam pouco conhecidas na agricultura contemporânea. Diante disso, este trabalho objetivou avaliar o desempenho do Índice Heliotérmico de Geslin (IHG) para diferentes culturas agrícolas difundidas em área de clima subtropical úmido, tendo como estudo de caso o município Guarapuava(PR). A comparação entre o IHG ideal em cada fase produtiva e o IHG efetivamente ocorrido durante as safras de 2008 a 2013 possibilitou identificar distintos níveis de influência da disponibilidade térmica para o cultivo agrícola na região. Os dados foram cedidos pelo Instituto Agronômico do Paraná – IAPAR e analisados através de estatística clássica, que serviu de base para a escolha do índice utilizado.

The rheological and crystallization behavior of polyoxymethylene

In the polymer melt processing, the solidification has a huge importance on the properties of the resulting part. For a semi-crystalline resin, this phenomenon involves a complex interplay between crystallization and the material rheology. In this work, an investigation is carried out on the influence of thermal conditions on crystallization kinetics and rheology of two commercial polyoxymethylene (POM) copolymers. In particular, isothermal crystallization experiments using differential scanning calorimetry (DSC) and rotational rheometry to measure the dynamic viscosity are performed. The evolution of the relative crystallinity and Normalized Rheological Function (NRF) are correlated by a recent technique which allows simultaneous analysis of several measurements, even if they are not carried out at same temperatures. On this basis, a relationship between the crystallinity and the hardening, i.e. the sharp increase in the viscosity, is obtained.

In English

A method has been developed of biomimetic hydroxyapatite (HA) biocompatible functional layer synthesis on the surface of the models of titanium articles of biomedical applications. Carboxyl-modified titanium surface acts as active nucleation site in biomineralization processes of HA synthesis which occurs in simulated body fluids (SBF) of different composition. A comparative study has been conducted on the influence of thermal conditions on the formation of HA in SBF of different chemical composition. The formation of hydroxyapatite coating on the surface of titanium has been confirmed by FTIR spectroscopy and XRD.

Additives and thermal treatment influence on microstructure of nonferrous alloys

Although Zn alloys are a very widely used material, there is a need for investigations concerning the influence of thermal conditions on its microstructure and its properties, which makes it useful for the specific tasks it has to fulfil for mass-produced items manufactured by the metalworking industry, in the automotive industry, as well as in countless electronic components. One of the possibilities is to create finer microstructures and enhance their properties, to change their chemical composition by adding alloying additives, and inoculation using modifiers. So in this paper, investigation results are presented concerning the influence of chosen alloying additives, such as Sr, Ce and Ti–B on the measured and calculated thermal characteristics and microstructure of zinc alloys with the addition of aluminium and copper. Based on the results on the phase and chemical composition of the cast Zn–Al–Cu alloys, inoculated with Sr and Ti–B, no differences were detected in the phase composition of the investigated alloys, owing to changes in cooling rates, which were chosen for the sample cooling process. A small amount of added cerium caused the occurrence of new phases present in the microstructure. Modification of the Zn–Al–Cu alloy precipitates changes in the thermomorphology of the phase and the ‘tweed’ type changes in the microstructure. Moreover, the addition of cerium causes a decrease in the temperature at the beginning (T L) and the end of the solidification, as well as the occurrence of a multicomponent eutectic, which can be detected on the derivative curve.

Hybrid Comopsites Shaped by Casting Methods

In the presented work two methods of casting: gravity casting and centrifugal casting have been described. The main aim of the study was development procedures for producing the AlSi / SiC+C hybrid composite. Composite suspensions with the same phase composition were cast into molds with different coefficients of thermal conductivity. This allowed to determine the influence of thermal conditions on the formation of the structure and distribution of particles in the matrix. In the paper the conditions of casting, macro-and microstructure and selected properties of the casts have been presented. The structure of components and cast composites was examined by light and electron microscope, applying properly made preparations.

Analysis of the Influence of Thermal Conditions on the Operation of Optoelectronic Devices

The optoelectronic device has been considered from the viewpoint of system analysis. It has been shown that thermal conditions influence the transfer function of this system and, as a consequence, the desired signal. Moreover, the self-radiation of the device′s elements, which also leads to a change in the output signal of the device, depends on the thermal conditions. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 86, No. 4, pp. 894–904, July–August, 2013.

Influence of thermal conditions on successful ide (Leuciscus idus L.) artificial reproduction during spawning season

Two forms of ide Leuciscus idus (L.) spawners: wild-coloured and ornamental: yellow-coloured were kept at three various temperature regimes shortly before spawning at optimal temperature regimes (group 1), under natural temperature conditions (group 2) and in rapidly increasing temperature (group 3). The quality and quantity of collected semen, ovulation rate and survival rate of embryos to the eyed-egg-stage were recorded. The quality of semen from group 3 (where the temperature increased over the thermal spawning optimum) was the worst (46 and 51% motility of spermatozoa for the wild-coloured and yellow form, respectively). The quantity of collected semen also was the lowest in the same groups (1.1 and 1.0 cm3 kg−1 for the wild-coloured and yellow form, respectively). Increasing the temperature to 16°C also caused a decreasing percentage of ovulated females (70% and 60% of ovulation for wild-coloured and yellow form, respectively) and biological quality of eggs (48.9 and 47.8% embryo survival for wild-coloured and yellow form, respectively). Fluctuations of temperature at a level of 8–14°C (group 2) did not negatively affect spawning results, except for a longer latency time (over 44 hrs). The results suggest that the temperature regime shortly before controlled reproduction of ide plays an important role influencing reproductive success.