Non-uniform Temperature Research Articles

Numerical Investigations on Heat and Mass Transport in Passive Solar Evaporators with Non-Uniform Surface Temperature

Passive solar desalination with no discharge promises great potential for sustainable desalination. Herein, we provide a comprehensive modelling scheme for the investigation of coupled heat and mass transport in passive desalination devices. Our modelling approach integrates mass, momentum, species, and energy transport models to study the coupled phenomena of wicking, solar-driven evaporation, and salt precipitation. Our numerical model can predict the impact of spatiotemporal variation in temperature, salt concentration, and wicking velocity on the evaporation flux and thermal efficiency of solar evaporators. The impact of the evaporator’s shape, solar flux, salt concentration, and light reflection by salt crystals has been studied on the evaporator’s performance. We observed a two-fold increase in evaporation flux when solar irradiance increases from 1000 W/m2 to 2500 W/m2. A reduction in the thermal efficiency of the evaporators is predicted at higher solar fluxes. The modelled evaporator can achieve an evaporation flux of over 0.5 kg/m2h under 1000 W/m2 for 3.5 wt.% saline water. The salt concentration along the z-position of the evaporator exhibited a double arch-shaped profile, which influences its evaporation performance. These findings provide vital guidelines for the design of high-throughput solar desalination systems.

Inverse analysis on non-uniform temperature and emissivity fields based on multispectral infrared thermal image data

Inverse analysis on non-uniform temperature and emissivity fields based on multispectral infrared thermal image data

Post-earthquake fire resistance of completely overlapped thin-walled joints at non-uniform elevated temperatures

Post-earthquake fire resistance of completely overlapped thin-walled joints at non-uniform elevated temperatures

Effect of non-uniform temperature on the thermal behavior of large-span spatial steel structures under construction

Effect of non-uniform temperature on the thermal behavior of large-span spatial steel structures under construction

A novel hybrid thermoelectric generator configuration with blocking diodes to reduce power loss by preventing reverse current effects under non-uniform temperature distribution

A novel hybrid thermoelectric generator configuration with blocking diodes to reduce power loss by preventing reverse current effects under non-uniform temperature distribution

Three-Dimensional Cellular Automaton Modeling of Annealed Silicon Thin Film Surface Morphology.

Controlling the surface morphology of polycrystalline silicon (Si) thin films is essential for enhancing the performance of thin-film transistor (TFT) devices. This study introduces a novel three-dimensional cellular automaton (CA) algorithm for simulating the surface morphology evolution of Si thin films during crystallization. Unlike conventional CA models, this algorithm enforces strict mass conservation and dynamically adjusts the liquid surface to accurately account for density variations between the liquid and crystalline silicon phases. The model's accuracy was validated through comparisons with experimental data, and molecular dynamics simulations were used to investigate the atomic-scale mechanisms driving surface protrusion formation. Key parameters affecting surface morphology were examined, including seed crystal distribution, shape, and initial orientation, nonuniform linear temperature fields, and liquid-to-solid density ratios. Protrusion height was significantly affected by the solid-liquid interface orientation (increasing with near-perpendicular alignment), growth site spacing (following a logarithmic relationship), and hydrogen (H) doping (which reduced the protrusion via density modulation). These findings provide insights for controlling surface morphology and offer a pathway to optimize the fabrication process of TFT devices.

Revisiting gas temperature in dielectric barrier discharge (DBD): an unsolved problem of plasma catalysis

Abstract Gas temperature is an essential parameter in terms of thermodynamics and kinetics of a plasma chemical reaction, but the gas temperature in dielectric barrier discharge (DBD) plasma is difficult to be measured and often misunderstood as near room temperature. In this work, the axial distributions of center (Tc) and wall (Tw) temperatures in a bare, water-cooled, heat-insulated and furnace-heated DBD reactors are measured. It is found that Tc is significantly higher than Tw and hasasymmetric bow-likeprofile of axial distribution, which indicates axial and radial nonuniformity of gas temperature in DBD plasma. Based upon radial distribution of the gas temperature in the DBD plasma by simulation, a radial-averaged gas temperature (TgRA) is obtained, which confirms that the Tc is a reliable representative of gas temperature in DBD plasma. Finally, the effects of flow rate, discharge power,specific energy input, alternating-current (AC) frequency and pulse modulation on the gas temperature are investigated.

Transient modeling and analysis of a stepped-configuration thermoelectric generator considering non-uniform temperature distribution

Transient modeling and analysis of a stepped-configuration thermoelectric generator considering non-uniform temperature distribution

Experimental investigation on thermal instability in high current-carrying glow plasmas at high pressure

In this paper, the thermal instability of uniform large-volume DC glow plasma at high pressure is investigated by using discharge pulse modulation and two-color laser interferometry. It is found that the number density of neutral particles changes periodically with the pulse modulation. The number density of neutral particles decreases with time during the power-on duration, which is related to the thermal instability developed in the radial non-uniform temperature field, while the backflow of neutral particles during the power-off duration terminates the development of thermal instability. The alternation of these two processes gives rise to the periodic change in the number density of neutral particles. As the average discharge current continues to increase, it is found that there appears an abnormal fluctuation in the number density of neutral particles with time during the power-on duration. It is believed that this fluctuation is related to the thermal instability depending on the enhanced axial temperature gradient. Both axial and radial temperature gradients have an impact on the development of thermal instability, but the thermal instability dependent on the axial temperature field occurs only at a large axial temperature gradient.

Performance and aging of a lithium-ion battery in a non-uniform temperature distribution condition

Performance and aging of a lithium-ion battery in a non-uniform temperature distribution condition

THEORETICAL STUDIES OF THERMAL PROCESSES IN ELECTROLYTIC-PLASMA HARDENING

This article examines the theoretical aspects of thermal processes occurring during electrolytic-plasma hardening (EPH), including the analysis of temperature fields and heating rates. The finite difference method was used for numerical modeling, allowing for a more precise determination of the temperature distribution in the treated material. The heat transfer problem in a flat plate with a thickness of 15 mm was considered, where the boundary conditions were as follows: on one boundary, heating was carried out by a surface thermal flux from the electrolyte plasma, while on the opposite side, heat was dissipated through convection in an air medium. The calculations revealed non-uniform temperature distribution over time and depth, confirming the formation of three distinct structural zones: the hardened zone, the heat-affected zone, and the base matrix. The temperature of the samples during the experiment was measured using a thermocouple positioned 2 mm from the heated surface. Experimental data obtained from the treatment of 45 steel samples confirmed the accuracy of the numerical modeling. The research results demonstrate the effectiveness of numerical modeling, including the finite difference method, in optimizing EPH parameters, thereby reducing the volume of experimental work and lowering technology development costs. The obtained data can be used to improve surface hardening technologies for structural steel components used in agricultural machinery, mechanical engineering, and other industries. The study confirms the potential of EPH for enhancing the operational characteristics of steel products.

Density-driven flow in chamfered enclosures with obstacles under regular and irregular inner temperature distributions: A hybrid finite element method and neural network approach

ABSTRACT Non-uniform temperature distributions on the outer boundaries of engineering systems have been extensively studied, whereas fewer investigations have addressed cases involving non-uniform isothermal distributions on inner boundaries. This study examines flow structures within chamfered enclosures containing obstacles with uniform and non-uniform temperature distributions. Three cases are analyzed: sinusoidal temperature distributions on the inner boundaries with various phase angles, linear isothermal distributions, and uniform isothermal distributions. The chamfered domain is filled with a heat-generating, thermally non-equilibrium permeable medium, and two formulations are proposed to study the system’s irreversibility. The governing equations are solved numerically using an effective finite element (FE) technique based on the Characteristic Based Split (CBS)-pressure algorithm, and the data are analyzed and predicted using an artificial neural network (ANN) approach. The results show that velocity components are significantly influenced by inner heating, particularly in the sinusoidal heating case at higher Rayleigh numbers. The hybrid nanofluid flow exhibits non-uniform structures in the sinusoidal heating case, while symmetrical flow patterns are observed in the other cases. Furthermore, the phase angle ( ξ = 270 0 ) produces the maximum temperature values compared to other configurations. Furthermore, in Case 1, decreasing the Darcy number (Da) from 10 − 2 to 10 − 5 reduces the flow activity by up to 98.4%.

Impact of Channel Geometry and Operating Temperature on the Performance of Solid Oxide Electrolyzer Cells: A Study of Uniform and Non-Uniform Temperature Effects

This study investigates the effects of channel geometry and operating temperature on the performance of Solid Oxide Electrolyzer Cells (SOECs), a promising technology for efficient hydrogen production. Through computational simulations and experimental analysis, we explore the impact of different channel designs—rectangular, triangular, and semicircular—on system efficiency. Among the geometries, rectangular channels deliver the highest performance, with a 10% efficiency improvement over the others. Additionally, increasing the operating temperature from 1073 K to 1273 K accelerates reaction kinetics, yielding a 15% efficiency gain. The study identifies the optimization of both channel design and temperature as crucial for maximizing hydrogen production. Furthermore, the research finds that non-uniform temperature distribution has minimal impact on performance for the small-scale fuel cell configuration used. These findings emphasize the importance of understanding the interplay between geometry and operating conditions in SOEC design and contribute to the advancement of sustainable hydrogen production technologies.

Junction Temperature Estimation Model of Power MOSFET Device Based on Photovoltaic Power Enhancer

In a photovoltaic power enhancer system, when it is operated in current-control mode, significant nonuniform temperature distribution occurs in the converter due to thermal coupling effects, dissipative boundary conditions, and differences in device losses within the in-phase bridge. Accurate on-site estimation of the power device’s junction temperature is critical in the system design. To address this problem, a novel thermal behavior estimation model based on electro-thermal analysis is proposed in this paper, which can be used for asymmetric power MOSFETs in a photovoltaic power enhancer system. Thermal coupling effects and dissipative boundary conditions are, firstly, analyzed in a three-dimensional finite element model. A coupling impedance matrix is constructed through step power response extraction to describe the significant thermal coupling effects among devices. The complete heat sink is decoupled into several sub-parts representing different dissipative boundary conditions. A compact RC network model for estimating junction temperature is established based on the combination of the coupling impedance and the sub-heat-sink impedance. The proposed model is verified by finite element simulation and experimental measurement.

Temperature-dependent interface and creep modelling of steel piles in frozen ground

ABSTRACT Performance of pile foundations is significantly influenced by the micromechanical behaviour of the pile–soil interface. In frozen ground, the interface behaviour is temperature-dependent and viscous. This study examines the pullout behaviour of a single pile embedded in frozen soil using a two-dimensional axisymmetric finite element model developed with Abaqus software. A cohesive zone model (CZM) is employed along with a penalty type contact interaction to represent the interface behaviour while a time-hardening power-law creep model is used to simulate the viscous response of the interaction. The model is coupled with temperature and verified by data from temperature-controlled laboratory pullout and creep tests of model pile in frozen sand. The findings demonstrated that CZM effectively describes the behaviour of the frozen interface. Conceptual models that account for non-uniform temperature profiles and variable temperature time-series, showcase the significant influence of temperature on the overall performance of pile foundations in cold regions.

Impact of Non-Uniform Surface Temperature on the Apparent Radiative Properties of Cavity Receivers

Abstract Radiative surface properties play a critical role in the design, analysis and optimization of solar–thermal systems. Cavity receivers increase the efficiency of solar–thermal energy systems through the cavity effect. The cavity effect refers to increased absorption of radiation due to multiple reflections within a cavity. Apparent radiative surface properties of a cavity characterize the effective interactions of radiation passing through an imaginary surface covering the cavity aperture. In this study, we investigate the extent to which the apparent emissivity of a cavity with a non-uniform surface temperature profile may be estimated using an isothermal enclosure model. A cylindrical cavity was assumed to have a linearly increasing, linearly decreasing or parabolic temperature profile. The cavity's apparent emissivity and absorptivity were calculated for various length-to-diameter ratios (L/D) and intrinsic emissivity (ε). This work shows that a spatially varying surface temperature can significantly affect the apparent emissivity and absorptivity, especially for shallow cavities with low intrinsic emissivity. Moreover, under non-isothermal conditions, changes in the cavity's geometry result in larger changes in the apparent radiative properties than observed for isothermal cases. For a cavity with an intrinsic emissivity of 0.3, the percent difference between non-isothermal and isothermal conditions reaches ∼25% for L/D ratios of 4 and 8 for cavities with linearly increasing or parabolic temperature profiles. Similarly, for ε=0.9 and ΔTw/T0=0.1, this difference is <1% across all three wall temperature cases when L/D=4.

Experimental and theoretical investigating on measurement of dynamic response characteristics of the semi-infinite pressure tube with non-uniform temperature

Experimental and theoretical investigating on measurement of dynamic response characteristics of the semi-infinite pressure tube with non-uniform temperature

Analysis of internal and external factors affecting thermal contact resistance from the perspective of entransy dissipation

Analysis of internal and external factors affecting thermal contact resistance from the perspective of entransy dissipation

Efficiency limit of photovoltaic/thermal (PV/T) and thermodynamic enhancement methods based on non-uniform temperature fields

Efficiency limit of photovoltaic/thermal (PV/T) and thermodynamic enhancement methods based on non-uniform temperature fields

Study on temperature field and residual stress in T welding joint of stainless steel

The stainless steel used more and more popularity in the construction and transport sector because they combine favorable aesthetic aspects, good mechanical properties and corrosion resistance. Hence, the stainless steel structures have a high long-life with low maintenance costs. The local heating and cooling during welding produce a non-uniform temperature distribution. Uneven shrinkage of the welded joint creates residual stress in welded structures. This paper studies the temperature field during welding and the residual stresses after welding in T welding joint of stainless steel by the imaginary force method and the finite element analysis. The thickness of SUS316L stainless steel plate in T-joint is 10 mm. Two welds on both sides of the T-joint are welded simultaneously by the MIG welding process. In this study, ESI SYSWELD finite element software is applied for thermo-mechanical analysis of stainless steel T welding joint. The residual stresses of this welding joint are calculated by the theory based on the imaginary force method. The results of temperature field and residual stresses in the T-joint are presented and discussed. The results of residual stresses by finite element method are compared with the results of residual stresses by the imaginary force method. The residual stress results that are determined by the finite element method are compared with the residual stress results that are calculated by the imaginary force method.