Simulation Of Temperature Distribution Research Articles

Computer Simulation of Temperature Distribution during Cooling of the Thermally Insulated Room

This paper is devoted to modelling of temperature distribution and its time evolution in rooms with specific thermal insulation and heat transfer for different external conditions. The simulation results should help to design the room architecture and wall materials to reduce energy losses due to heating or cooling, and to increase the inside thermal comfort. For this purpose, a methodological procedure using real data processing in the COMSOL Multiphysics modelling environment and spatial visualization of temperature evolution is proposed. This paper describes a mathematical model for simulation of the temperature evolution inside a space with thermally insulated walls under selected outside conditions. Computer simulations are then used to assess the temperature distribution inside the room and the heat flow through the room walls. Results of the simulations are used for subsequent determination of the time needed for the desired decrease of air temperature inside the tested room during its cooling due to the low ambient temperature, which is related to the thermal stability of the building, specific heat capacity, and thickness of the thermal insulation. Under the studied conditions, the time to reach the temperature drops by 20 percent in a room with windows was from 1.4 to 1.8 times lower than that in the room without windows. The proposed methodology shows the flexibility of computer modelling in the design of insulated building systems. The mesh density testing was performed by comparing the air temperature evolution in the model of the selected mesh density and the model with its maximum value enabled by the size of computer memory. The maximum temperature deviation calculated for the mesh of the presented model was 0.57%.

Simulation and Optimization of Temperature Distribution in Induction Heating Reactor

Simulation and Optimization of Temperature Distribution in Induction Heating Reactor

A Finite Element Modeling Prediction in High Precision Milling Process of Aluminum 6082-T6

This study investigates micro-end-milling machining prediction using three-dimensional finite element modeling method. The FE model was developed for contouring up-milling operation for prediction of chip flow, burr formation, cutting temperature and cutting forces in an integrated model. The flow stress behavior of the workpiece was modeled by the Johnson–Cook material constitutive model. Different cutting conditions were simulated to consider the effect of the process variables that might be difficult or impossible to follow in the physical experiments at this scale. The tool was precisely 3D modeled to describe the detailed geometry of the tool which is one of the critical aspects of the model and is characteristic of the cutter tool micro-geometry design. Furthermore, the tool deflection was studied using a FE model under the experimental cutting forces measured in the different cutting conditions in order to consider the micro-end-mill deviation from the nominal position. 3D simulations of chip flow and temperature distribution are compared in various cutting conditions. The results of the burr formation, temperature distribution and cutting forces in three directions predictions are compared against the experiments. Simulations were able to predict the burr height with an accuracy between 1 and 4 µm depending on cutting parameters settings. The results of this study are beneficial to comprehend the micro-end-milling chip and burr formation to increase the machinability of the workpiece and to understand the influence of cutting parameter in order to prevent several experimental tests prior to the final machining.

Simulation of temperature distribution in the oriented silicon steel coil in the heating stage of annealing process

Annular furnace is widely used for high temperature annealing of oriented silicon steel coils. The coils are placed under a cover in a protective atmosphere. The heating rate of the process must be strictly controlled to prevent magnetic property variations of the products. In this work, temperature distribution in the coil at the heating stage is simulated using finite method. Effects of fuel flux at burners on temperature distribution in the furnace are also analysed. Experiments are carried out to measure the parameters needed in simulations and to verify the simulation results. For a coil of 510 mm inside and 1710 mm outside diameters, the largest temperature difference in the coil is found to be as high as 438 °C, which occurs at about 8 h of heating. A total of 72 h is needed for the temperatures across the coil to reach a target level of 1170 °C. The temperature difference in the coil can be greatly reduced if N2 is replaced by H2 as protective atmosphere and the gap between sheet layers in the coil is reduced. Temperature distribution on the cover during heating is found to be rather uniform with the largest difference being within 30 °C.

Application of a lattice Boltzmann method combined with a Smagorinsky turbulence model to spatially resolved heat flux inside a refrigerated vehicle

In this work the simulation of velocity and temperature distributions inside a refrigerated vehicle is evaluated. For this purpose a 3D double distribution lattice Boltzmann method (LBM) with the Bhatnagar–Gross–Krook (BGK) collision operator is coupled by the buoyancy force calculated with the Boussinesq approximation. This LBM is extended by a Smagorinsky subgrid method, which numerically stabilizes the BGK scheme for low resolutions and high Reynolds and Rayleigh numbers. Besides validation against the two benchmark cases porous plate and natural convection in a square cavity evaluated at resolutions of y+≈2 for Ra numbers between 103 and 1010, the method and its implementation are tested via comparison with experimental data for a refrigerated vehicle at Re≈53000.The aim of the investigation is to provide a deeper understanding of the refrigerated vehicle’s insulation processes including its thermal performance under turbulent flow conditions. Therefore, we extend this method by the half lattice division scheme for conjugate heat transfer to simulate in the geometry of a refrigerated vehicle including its insulation walls. This newly developed method combination enables us to accurately predict velocity and temperature distributions inside the cooled loading area, while spatially resolving the heat flux through the insulation walls. We simulate the time dependent heating process of the open door test and validate against measurements at four characteristic velocity and 13 temperature positions in the truck.

Highly Improved Switching Properties in Flexible Aluminum Oxide Resistive Memories Based on a Multilayer Device Structure

AbstractMultilayer aluminum oxide (Al2O3) resistive memory devices, exhibiting robust switching properties fabricated on a flexible polyethylene naphthalate substrate using only physical vapor deposition methods at room temperature, are reported here. Improved reliability and robust switching properties of the multilayer Al2O3 memory devices are observed compared to those of the single‐layer devices, with the assistance of a guide filament formed in the bottom Al2O3 resistive layer. The multilayer Al2O3 resistive memory devices exhibit nonvolatile and bipolar resistive switching properties with high ON/OFF ratio (>104), DC sweep endurance cycles (>700), statistical uniformity, and retention times (2 × 104 s). The role of the guide filament in the multilayer structure is identified in the non‐rewritable properties of the bottom layer device, increased reset current values, and spatial temperature distribution simulation. Thus, the formation sites of the switchable filament in the top Al2O3 layer can be specified by the guide filament, resulting in remarkable improvement of reproducibility with more robust metallic percolation paths. The reliable resistive switching properties in flexible conditions is also evaluated in a bent radius of 10 mm, and the suggested flexible multilayer memory devices can provide promising strategies to be utilized in future practical storage media.

Estimation of Credibility of the Results of Measuring Temperature within Specimens of Wood Columns Obtained During Fire Tests

Analysis of the results of experimental studies of wood columns mode of behaviour both having fire retardant coating based on OSB slabs and without any coating under standard time – temperature curve fire conditions was realized. An assumption was made that thermocouple wires could be positioned along isotherm at a distance of at least50 mmfrom measuring thermojunctions (otherwise disturbance of the structure of isotherm itself possible). Due to specific features of thermocouples positioning within the specimen, this assumption calls in question of credibility of the obtained results of temperature indices measuring. Bearing this in mind we prepared calculation scheme of the specimen of wood column under study. We have composed finite elements scheme of specimen under study for heat engineering calculations. We simulated temperature distributions within the wood column specimen section at various moments of time and substantiated the obtained results. It was revealed in the course of the study conducted that the obtained results were adequate for relative error was as small as ca. 4.5% and Fisher test did not exceed appropriate tabulated value. Thus, assumption made does not affect in general credibility of the results of measuring thermal values within the layers of specimens obtained during fire tests.

Simulation of Coal and Biomass Cofiring with Different Particle Density and Diameter in Bubbling Fluidized Bed under O2/CO2 Atmospheres

A 2D dynamic model for a bubbling fluidized bed (BFB) combustor has been developed for simulating the coal and biomass cofiring process under 21% O2/79% CO2 atmosphere in a 6 kWth bubbling fluidized bed, coupled with the Euler-Euler two-phase flow model. The kinetic theory of binary granular mixtures is employed for the solid phase in order to map the effect of particle size and density. The distribution of temperature, volume fraction, velocity, gas species concentration, and reaction rates are studied with numerical calculations. The simulated temperature distribution along the height of the combustor and outlet gas concentrations show good agreement with experimental data, validating the accuracy and reliability of the developed cofiring simulation model. As indicated in the results, there are two high temperature zones in the combustor, which separately exist at the fuel inlet and dilute phase. The reaction rates are related to the species concentration and temperature. The higher concentration and temperature lead to the larger reaction rates. It can be seen that all of the homogeneous reaction rates are larger at the fuel inlet region because of rich O2 and volatiles. High mass fraction of volatile gas is found at the fuel inlet, and the main reburning gas at the dilute phase is CH4. The mass fraction distribution of CO is related to the volume fraction of fuel which is due to the fact that the source of CO is not only from the devolatilization but also from the gasification. On the basis of this theoretical study, a better understanding of flow and combustion characteristics in biomass and coal cofiring under oxy-fuel atmospheres could be achieved.

Channel temperature analysis of AlGaN/GaN HEMTs in quasi-static and pulse operation mode

Abstract GaN-based HEMTs’ high potential is deteriorated by self-heating during the operation, this has influence on the electrical properties as well as device reliability. This work is focused on an average channel temperature determination of power AlGaN/GaN HEMT prepared on SiC substrate using quasi-static and pulsed I-V characterization. There was analyzed the drain current change relation to temperature dependent electrical HEMT parameters such as source resistance, threshold voltage, saturation velocity, resp. leakage current which allows to calculate an average channel temperature versus dissipated power for various ambient temperature. Differential temperature of investigated device with and without heatsink was determined. Obtained results were discussed using simulated spatial temperature distribution.

Validation of mathematical model of electrothermal calculation of DC catenary on the basis of scale model

The article compares the results of calculation of the finite element simulation of current and temperature distribution in the scale model of the DC catenary with the data of laboratory tests. Researches were carried on various versions of the structural design of catenary model, reflecting the topological features of the wire connection, characteristic of the DC contact network. The proportions of the cross-sectional area of the scaled model wires are comparable to each other with the corresponding values for real DC catenary. The article deals with the operating conditions of the catenary model in the modes of transit and current collection. When studying the operation of the scale catenary model in the transit mode, the effect of the structural elements on the current distribution and heating of the wires was obtained. Within the framework of the scale model, theoretical assumptions about the current overload of the supporting cable near the middle anchoring have been confirmed. In the current collection mode, the experimental dependences of the current in the transverse wires of the scale model are obtained from the coordinate of the current collection point. Using the model it was experimentally confirmed that in the section of the contact wire with local wear, not only the temperature rise occurs but also the current redistribution due to the smaller cross section. Thus, the current share in other longitudinal wires of the scale model increases and their temperature rises. Scale and mathematical models are constructed with allowance for laboratory clamps and supporting elements that participate in the removal of heat from the investigated wires. Obtained study results of the scale model allow to draw a conclusion about the adequacy of the mathematical model and its correspondence to the real physical process. These conclusions indicate the possibility of applying mathematical model for calculating real catenary, taking into account the uneven contact wear wire and the armature of the contact network.

A new strategy for the numerical modeling of a weld pool

Welding processes involve high temperatures and metallurgical and mechanical consequences that must be controlled. For this purpose, numerical simulations have been developed to study the effects of the process on the final structure. During the welding process, the material undergoes thermal cycles that can generate different physical phenomena, like phase changes, microstructure changes and residual stresses and distortions. But the accurate simulation of transient temperature distributions in the part needs to carefully take account of the fluid flow in the weld pool. The aim of this paper is thus to propose a new approach for such a simulation taking account of surface tension effects (including both the “curvature effect” and the “Marangoni effect”), buoyancy forces and free surface motion.The proposed approach is validated by two numerical tests from the literature: a sloshing test and a plate subjected to a static heat source. Then, the effects of the fluid flow on temperature distributions are discussed in a hybrid laser/arc welding example.

Interfacial thermal resistance between porous layers: Impact on thermal conductivity of a multilayered porous structure

Features of thermal transport in multilayered porous silicon nanostructures are considered. Such nanostructures were fabricated by electrochemical etching of monocrystalline Si substrates by applying periodically changed current density. Hereby, the multilayered structures with specific phononic properties were formed. Photoacoustic (PA) technique in gas-microphone configuration was applied for thermal conductivity evaluation. Experimental amplitude-frequency dependencies were adjusted by temperature distribution simulation with thermal conductivity of the multilayered porous structure as a fitting parameter. The experimentally determined values of thermal conductivity were found to be significantly lower than theoretically calculated ones. Such difference was associated with the presence of thermal resistance at the interfaces between porous layers with different porosities arising because of elastic parameters mismatch (acoustical mismatch). Accordingly, the magnitude of this interfacial thermal resistance was experimentally evaluated for the first time. Furthermore, crucial impact of the resistance on thermal transport perturbation in a multilayered porous silicon structure was revealed.

Shear Strength of Reactive Resistance Welded Ti6Al4V Parts with the Use of Ni(V)/Al Multilayers

The Ti6Al4V/(Ni/Al)/Ti6Al4V joints were obtained through reactive resistance welding which takes advantage of electric current heating to initiate the rapid exothermic reaction of Ni(V)/Al multilayers and activate diffusion of elements across the Ni/Al-Ti6Al4V interfaces. Simulations of temperature distribution, carried out using COMSOL® software, showed temperature gradient in the joint being a result of differences in resistivity of the Ti6Al4V alloy and the (Ni/Al)/Ti6Al4V interface. Shear tests revealed that extending duration of the process from 2 to 6 minutes helped to improve the shear strength from ~ 240 to ~ 335 MPa. The microstructure observations of the samples after those tests showed that de-cohesion of the joint occurred along the filler material/base material interface. A microcrack network characteristic for reacted Ni/Al foil with small ridges was found on the flat surfaces of fractured samples.

Numerical simulation of temperature distribution in a planar solid oxide fuel cell using lattice Boltzmann method

The present paper deals with a numerical simulation of heat sources effects on temperature field inside a solid oxide fuel cell component. The temperature distribution is investigated using a co-flow planar SOFC comprising the air and fuel channel and two-ceramic electrodes, separated by an electrolyte. The Lattice Boltzmann Method is used for the numerical simulation of the physical problem. Once the numerical code is validated against published works, the effects of different geometrical and operating parameters such as, SOFC configuration, porosity, anode thermal conductivity, operating temperature and current density, on temperature distribution are discussed. It was found that temperature distribution is very sensitive to the inlet temperature, the current density and the thermal conductivity. Moreover, the electrode porosity has a smaller effect on cell temperature. Comparisons between three different cases of cell configuration indicate that the anode-supported is the best SOFC design.

Fabrication of a Cell Culture Plate With a Three-Dimensional Printed Mold and Thermal Analysis of PDMS-Based Casting Process

Abstract Polydimethylsiloxane (PDMS)-based casting method was used to fabricate PDMS cell culture platforms with molds printed by a fused deposition modeling (FDM) printer. Cell viability study indicated that the produced plates have the suitable biocompatibility, surface properties, and transparency for cell culture purposes. The molds printed from acrylonitrile-butadiene-syrene (ABS) were reusable after curing at 65 °C, but were damaged at 75 °C. To understand thermal damage to the mold at elevated temperatures, the temperature distribution in an ABS mold during the curing process was predicted using a model that considers conduction, convection, and radiation in the oven. The simulated temperature distribution was consistent with the observed mold deformation. As the maximum temperature difference in the mold did not change appreciably with the curing temperature, we consider that the thermal damage is due to the porous structure that increases the thermal expansion coefficient of the printed material. Our study demonstrated that FDM, an affordable and accessible three-dimensional (3D) printer, has great potential for rapid prototyping of custom-designed cell culture devices for biomedical research.

THE EFFECT OF WHOLE BODY GAS CRYOTHERAPY ON THE HUMAN THERMAL STATE

The therapeutic effect of the whole body gas cryotherapy (WBGC) procedure is achieved when the average temperature of the human’s (patient’s) skin surface during the procedure is in a certain temperature range, and the rate of reduction of this temperature exceeds a certain threshold value. The paper presents the results of a theoretical analysis of the patient’s thermal state at the stage of the therapeutic effect of WBGC. The analysis was based on the results of the numerical simulation of temperature distribution in different parts of patients (mеn) of different body constitution (height, cm × mass, kg) 160 × 60, 175 × 75, 190 × 90. Particular attention was paid to the relationship between the amount of heat flow removed from the skin surface and the rate of cooling of the skin of a patient. The results of numerical modeling are presented graphically and are summarized as the ratio between the dimensionless average temperature of the skin at the treatment stage of the WBGC procedure and the time of the patient’s stay in the procedural chamber, referred to the time of the beginning of this stage. With regard to WBGC within the temperatures range of –160 to –110 °C the following regularities were found: 1) approximate constancy (descripancy less than 1 %) at the stage of therapeutic modality of the coefficient of heat transfer from the skin surface to the gas medium in the treatment chamber; 2) the exponential dependence of the value of cutaneous blood flow rate (blood perfusion) on the mean temperature of cooled cutaneous coverings; 3) linear dependence of the logarithm of the ratio of the rate of skin temperature reduction to the value of heat flux density removed by convection and radiation on the logarithm time.

High temperature rheological behavior and sintering kinetics of CF/PEEK composites during selective laser sintering

As a kind of high performance polymer with excellent mechanical strength, high temperature property and chemical resistance, the polyether-ether-ketone (PEEK) and its composites are the promising candidates that can satisfy the demands for high stiff and lightweight in aerospace industry. So it is very attractive to fabricate PEEK and its composites parts with additive manufacturing technology, especially the selective laser sintering (SLS), due to its advantage on the fabrication of the parts with complex geometries. However, the strengths of the PEEK and its composites prepared by SLS are obviously lower than their injection molded parts and the laser sintering kinetics of the PEEK composites is seldom studied. In this paper, to fabricate the carbon fibers (CF) reinforced PEEK composites with high strength by SLS, the sintering kinetics of CF/PEEK composites was thoroughly studied based on the high temperature rheological behavior. A novel effective melting zone was defined by combining the simulated temperature distribution with the viscosity-temperature relationship and used to predict the process planning. Finally, the calculation results were validated by employing the simulation parameters in experiments and the tensile strength of CF/PEEK composites reached 109 ± 1 MPa with an elasticity modulus of 7365 ± 468 MPa, which is 85% higher than injection molded pure PEEK. Therefore, methods in this work could be considered as a complement to the numerical analysis of SLS process and the reinforced CF/PEEK composites may be used in aerospace industry for the structure optimization and lightweight design with complex geometries.

Thermal aspects in friction stir process of AISI 316L: Numerical and experimental investigation

ABSTRACTFriction stir processing (FSP) is an innovative surface engineering method, considered as a green processing technique. A good physical understanding of the process can be reached by the combined efforts of experimental examination and numerical modeling. In this paper, numerical and experimental investigations of heat generation during FSP of AISI 316L were performed. A 3D nonlinear thermal model was developed to simulate the thermal history. The simulated temperature distributions were compared with experimental values.

Effect of Temperature Distribution in Ultrasonically Welded Joints of Copper Wire and Sheet Used for Electrical Contacts.

The temperature distribution occurring at the interface while joining a simple electrical contact comprising of a copper wire and a copper sheet using ultrasonic metal welding was analyzed using finite element method. Heat flux due to plastic deformation and friction was calculated and provided as input load for simulation of temperature distribution. The results of temperature obtained from simulation are found to be in good agreement with the results of temperature from experiments measured using thermocouple. Special focus was given to how the heat generated at the wire–sheet interface affect the strength of the joint in tension. With the knowledge of heat generated at the interface while welding, it is possible to control the strength of the joint and produce defect free joints. Based on the results from finite element analysis and experiments, it is observed that the influence of heat developed due to friction and plastic deformation of metallic specimens has a significant effect on the progress of welding and strength of the joint.

The Effect of Different Heights and Angles of Energy Director on Interface Temperature for Ultrasonic Welding of Thermoplastics

Besides technological parameters in the ultrasonic welding process, height and angle of energy director (ED) also affect the quality of the joint strength owing to its energy transfer and melting. This paper deals with evaluating the effect of distinct ED heights and angles of butt-joint on temperature distribution at the weld interface. Experiments were simulated using transient thermal analysis of Ansys 18 for 3D-samples made of acrylonitrile butadiene styrene (ABS) and high-density polyethylene (HDPE). The results obtained from simulation of temperature distribution in various ED heights and angles and welding amplitudes are presented and compared with each other.