Analysis Of Conduction Heat Transfer Research Articles

Heat Transfer Analysis of Cryogenic EXLO Specimen Handling.

A conduction heat transfer analysis of ex situ lift-out specimen handling under cryogenic conditions (cryo-EXLO) is performed and compared with experimentally determined temperature values using a type K thermocouple. Using a finite-volume solver for heat conduction, the analysis confirms that manipulation of a specimen by a probe above a working surface cooled at liquid nitrogen (LN2) temperatures can remain below the critical vitreous temperature up to several hundreds of micrometers above the working surface, allowing for ample distance for lift out and specimen manipulation. In addition, the temperature above the cryogenic shuttle sample holder working surface remains below the vitreous temperature for several tens of minutes without adding cryogen, yielding sufficient time to complete multiple manipulations. Periodically topping off the cryogen level may allow for unlimited cryo-EXLO manipulations with this hardware and geometry.

Bernoulli Distillation System (BDS) for Bioethanol Sorghum Stalk Purification

Sorghum is a plant that produces syrup, forage and animal feed silage. The utilization of sorghum stalk as fuel oil (bioethanol) is an energy increasingly needed by the depletion of deposits of fossil fuel oil. Thus, tools and methods are needed to produce sorghum stem bioethanol, which has a certain purity level. This study aims to increase the purity of bioethanol from sorghum stems using the Bernoulli Distillation System (BDS) by experimentally testing the purification of sorghum stem bioethanol. In the bioethanol purification stage, heat transfer in the reactor and condenser was analyzed, and the performance of the ejector was analyzed with a vacuum pressure (-55 cmHg), temperature 71°C, test time of 1800, 3600, 5400 and 7200 seconds with a test material of 28% capacity 20 liters. The results of the analysis of the highest conduction heat transfer on the water jacket wall are 14757.72 Joules, the reactor tank is 962.1 Joules, the bottom of the reactor tank is 765.05 Joules and convection in the reactor fluid is 2.09 Joules. The highest heat transfer energy in the condenser is 72683.1 Joules. While the efficiency of the water jet ejector is 65.4%, the highest increase in bioethanol content is 51% in 3600 seconds, as much as 745 ml. The characteristics of the bioethanol obtained included a calorific value test of 1389.48 cal/gram, a viscosity of 1.02044, a flash point of 32.5°C, and a density of 0.934 g/cm3. Thus, the Bernoulli Distillation System’s purification process can increase bioethanol levels effectively and efficiently.

Analysis of conductive filament heat transfer in TiO2-based RRAM device

Abstract Resistive random access memory (RRAM) has developed into a new type of non-volatile memory that has attracted much attention for its high density and low power; TiO2 has been studied to make RRAM because of its high conductivity. Based on the COMSOL Multiphysics finite element method and domain decomposition method, an electrically-thermally coupled model of TiO2-based RRAM with oxygen vacancy (Vo) conduction mechanism is constructed, the formation and cutting process of RESET and SET conductive filament (CF) under different voltages is simulated. Moreover, the characteristics of the internal temperature distribution of the CF are explored. The results show that the RESET process is more sensitive to heat changes, the transverse direction thermal value of the CF is more obvious than the longitudinal direction, and the rate of change is faster. Additionally, the electric field induces the migration of the Vo in filament, which affects the enthalpy change of the device’s heat transfer and resistive properties. This is an important reference for a deeper understanding of the switching behavior of RRAM devices and the control mechanisms for thermal studies.

Impact of various heat sources on the transient heat transfer rate in a 3D cylinder consisting of parts with different thermal conductivity coefficients

Impact of various heat sources on the transient heat transfer rate in a 3D cylinder consisting of parts with different thermal conductivity coefficients

FEM-Based Conductive Heat Transfer Analytical Description of Solidification Rate and Temperature Gradient during Lateral Laser Beam Oscillation Welding of Aluminum Alloy.

This study investigates the feasibility of utilizing the finite element method (FEM)-based conductive heat transfer (CHT) analysis simulation to determine temperature gradients and solidification rates at the solid-liquid interface during laser beam oscillation welding. By comparing experimental observations with FEM-based CHT analysis, the underlying microstructural evolution and grain formation during welding were examined. FEM-based CHT enables the calculation of temperature gradients (G) and solidification rates (R), offering insights into the formation of equiaxed structures, which are crucial for suppressing hot cracking. Columnar-to-equiaxed structure transition thresholds, such as G/R and G3/R, accurately predict the emergence of fully equiaxed grain structures, validated by electron backscatter diffraction. This research provides valuable insights into temperature gradients and solidification rates in oscillation welding, guiding process design for achieving refined equiaxed structures and minimizing hot cracks.

Hybrid Trefftz finite element method for heat conduction in cylindrical composite laminates

Laminated composites are made of continuous fibers and matrix which can provide required engineering properties. This paper proposed a hybrid Trefftz finite element method for the analysis of conductive heat transfer in cylindrical composite laminates by assuming two independent temperature fields. The non-conforming intra-element field which is approximated by a linear combination of T-complete solutions satisfying the governing equation and undetermined coefficients is defined within the element domain, while the auxiliary conforming frame field which is interpolated by standard one-dimensional shape functions is defined on the element boundary. Due to the fabrication characteristics of laminates, each layer can be treated as an orthotropic medium for which the hybrid functional is employed to enforce the continuity of temperature and heat flux across the interface of adjacent elements. The proposed method is tested on three numerical examples and compared with exact or ABAQUS solutions. It was found that the proposed method exhibits low sensitivity to mesh distortion and achieves more acceptable results compared with ABAQUS.

Second-Law Considerations in Monte Carlo Ray-Trace and Discrete Green’s Function Analysis of Coupled Radiation and Conduction Heat Transfer

Abstract A generic Monte Carlo ray-trace (MCRT) engine for computing radiation distribution factors (RDFs), working in tandem with an efficient finite volume formulation based on discrete Green’s functions (DGFs), has been used to solve a massive (2636 nodes) coupled radiation/conduction problem. Distribution factors computed using the MCRT method are known to produce unconditionally stable solutions to pure radiation problems even though the RDFs themselves do not conform exactly to the reciprocity principle. However, when these same RFDs are introduced into time-dependent finite volume conduction formulations based on DGFs, the resulting model is found to be fundamentally unstable due to inherent violations of the second law of thermodynamics. A novel approach to addressing this instability is presented and demonstrated for the case of a telescope typical of those employed to monitor the planetary energy budget from low Earth orbit.

Comprehensive Molten Salt Storage Shell and Supporting Structure Design and Analysis—Part II: A Conductive and Convective Numerical Finite Element Heat Transfer Analysis for Molten Salt Cylindrical Shells at 700 °C, and Comparison with Theoretical Analysis

Comprehensive Molten Salt Storage Shell and Supporting Structure Design and Analysis—Part II: A Conductive and Convective Numerical Finite Element Heat Transfer Analysis for Molten Salt Cylindrical Shells at 700 °C, and Comparison with Theoretical Analysis

Comprehensive Molten Salt Storage Shell and Supporting Structure Design and Analysis—Part I: A Conductive and Convective Theoretical Heat Transfer Analysis for Molten Salt Cylindrical Shells at 565 °C and 700 °C

Comprehensive Molten Salt Storage Shell and Supporting Structure Design and Analysis—Part I: A Conductive and Convective Theoretical Heat Transfer Analysis for Molten Salt Cylindrical Shells at 565 °C and 700 °C

Computational analysis of conductive heat transfer in a rectangular slab of stable boundary using Monte Carlo method

Heat transfer is of immense importance in many engineering studies. Monte Carlo technique are broadly utilized in the operation research fields and atomic physics in which difficult problems above the existing tools of theoretical mathematics were resolved. The target of this study is to confirm the short duration in which heat transfer occurs in a quadrilateral slab where the temperature is provided throughout the borderline. An effort was made towards providing appropriate condition for the explanation of the heat transfer in a substance. The Shrinking Periphery Monte Carlo technique was utilized to obtain heat transfer in a helical pattern, upward and downward movement, which was compared with the standard Monte Carlo technique. The result of the study showed that the dimension of the quadrilateral slab determines the duration to calculate temperature dissemination in the system. The study revealed that the helical pattern is the shortest route in computing run time for temperature dispersal in a slab. The helical pattern is paramount in determining temperature distribution in a quadrilateral slab of stable state. The application of this technique to examine the conduction of heat in quadrilateral slabs produced good outcomes.

Analysis of thickness and interfacial thermal resistance of Au microheater on glass or polyimide substrate

The 3ω method is widely used for measuring the thermal properties of a substrate or thin film on which a microheater is deposited. Recently, samples with non-formal shapes and has a thermal conductivity of 1 W/mK or below have been analyzed using the bidirectional 3ω method. In measuring the thermal conductivity of such samples, the measurement sensitivity and accuracy can be increased using a 3ω sensor fabricated on a low thermal conductivity substrate such as glass or polyimide. In this study, thermal characterization is conducted on a microheater deposited on glass and polyimide substrates for a 3ω sensor. The effects of the microheater thickness and the interfacial thermal resistance between the substrate and microheater, on the temperature amplitude and phase lag are analyzed. Results from analytic solutions considering the microheater thickness and the interfacial thermal resistance are compared with results from numerical analysis of two-dimensional conduction heat transfer and experiment.

Coupled heat transfer analysis and experiments to evaluate the radiative cooling potential of concrete and green roofs for buildings

Improving building energy efficiency is one of the most important challenges towards the mitigation of climate change concerns. Buildings use significant amount of energy for cooling loads. Development of new night-time and day-time radiative cooling modalities by roofs is essential for reducing the energy consumption during the summer months. If a surface is desired to be kept cool while exposed to the sun, it should have (i) the maximum reflection of solar energy at visible wavelength range, and (ii) the maximum radiative emission from the surface at atmospheric radiation bands (8–13 μm wavelength range). In this study, reinforced concrete panels and three different types of plant-covered roof layers were investigated for their potential use for passive cooling applications, including moss, cactus and green leaves. Fourier transform infrared spectroscopy (FTIR) measurements were conducted to determine the absorbance of different samples at infrared wavelengths. In addition, reverse heat leak method was used to determine the effective conductivity values (R-values). The power of cooling parameter of each sample was determined first, and after that a coupled radiation and conduction heat transfer analysis was carried out to evaluate their insulation potential. It was demonstrated that moss is a better candidate to be used as a radiative cooling material, and it is a better insulator than the other tested materials.

Analysis of Conductive, Convective and Radiative Heat Transfer in Longitudinal Fins of Variable Profiles

The heat transfer enhancement by conduction, convection and radiation is still a topic of considerable attention in a number of areas and applications such as fin design despite the fact that numerous studies already exist in literature. In this study, the non-linear steady state heat equation is numerically solved for various fin surface profiles using the combined convection and the radiation modeling approach. The numerical solution is obtained using the Matlab® bvp4c package that is based on the shooting method. The results of this study indicate that the energy transfer by radiation is generally small compared to the transfers by conduction and convection but in situations where the fin base temperature is high, the radiation contribution can be significant and should be included when modeling the extended surface problems. However, it is acceptable to exclude the radiation energy transfer in some applications particularly when the fin thickness is small. The concept of Diminished Radiation Length (DRL) is introduced in this paper, which determines the length of the fin from the base at which the heat dissipation by radiation drops down to 0.4 Watts or less. The results presented in this paper can help the fin designers to select the appropriate fin parameters and decide whether the radiative heat loss is small enough to be neglected from the analysis.

Direct Simulation of Volumetric Solar Receiver with Highly Concentrated Radiation

The volumetric solar receiver is a promised technology for high-temperature solar absorption in the concentrated solar power, industrial solar thermal usage and solar fuel production. Existing numerical simulation separated computations of light and convective flow and two-way coupling was not perfectly integrated between radiation and convective transport. This paper describes conjugate analysis of radiation, convection and conduction heat transfer in the volumetric receiver for perfect three-way coupling between three mechanisms of heat transfer. The numerical scheme was used for the volumetric receiver with plane surface and that with cut-back inlets for optimization of the geometry. The simulation was made for single cell of honeycomb with 2.4 mm pitch and 0.5 mm wall thickness. Two cases of surface geometry was computed: plane surface; cut-back inlet with 10 mm depth. Basic equations are momentum and energy equations with radiation transport equation. The discrete ordinates method was applied for solving the radiation intensity to consider perfect interaction between radiation, convection and conduction. The material of the receivers are assumed as stainless steel. The numerical simulation demonstrated the superiority of the cut-back receiver which increased the exit temperature by 30 K and decreased 2 Pa for the smallest beam angle of 10°. The contour plot of total heat flux on the wall revealed that the shadow effect was attenuated by the cut-back inlet leading to heat transfer enhancement. The novelties of this work are to treat perfect interaction between radiation and convection in volumetric receiver and to demonstrate the excellence of cut-back inlet receivers.

Finite Volume Monte Carlo (FVMC) method for the analysis of conduction heat transfer

The numerical solution of the heat equation is a particularly challenging subject in complex, practical applications such as functionally graded materials for which analytical solution is not available or hardly attainable. The Monte Carlo method is a powerful technique with some advantages compared to the conventional methods and is often used when all else fail. In this paper, we introduce the Finite Volume Monte Carlo (FVMC) method for solving 3D steady-state heat equation where, instead of using the usual finite difference scheme for discretization of the heat equation, the finite volume scheme is used. The FVMC method is tested for three problems to assess the robustness of the method, first one in a simple geometry for validation and evaluation of the predictive performance, the second one in a complex geometry with unstructured mesh and the last one in a problem with a variable heat source and different kinds of boundary conditions. Comparisons were made to the analytical solution in the first test case, whereas for the remaining test cases, the CFD methods were utilized in the absence of the analytical solutions. It was observed that the FVMC temperature distribution agrees perfectly with analytical and CFD solutions in all problems. Despite expecting computational accuracy to improve by increasing total number of particles in the FVMC method, a very good accuracy was obtained for all considered problems after a small number of walks, and the calculated relative root-mean-square errors were below 1%.

Coupling Computation between Weld Mechanics and Arc Plasma Process for Residual Stress Analysis

Abstract This article presents an advanced computational framework to accurately simulate weld residual stress, which is generated as a result of thermomechanical behavior during welding. The basis of the framework is coupled process–mechanics modeling and analysis of gas tungsten arc welding (GTAW). In the developed modeling and analysis, a heat source model dependent on the welding heat input condition was constructed by considering the physics of the welding arc. Formation of the weld pool and temperature field was calculated through a combined conductive and convective heat transfer analysis with the constructed heat source model. Transient temperature fields obtained were used for large-deformation thermal elastic–plastic analysis of residual stress induced by welding. The modeling and analysis were applied to calculate the welding thermomechanical problems of low-carbon austenitic stainless steel. The calculated weld penetration, temperature profiles, and distribution of residual stress in the welds were compared with the experimental measurements to validate the accuracy of the modeling and analysis. The effect of convective heat transfer on weld pool formation was further investigated in relation to a parameter derived from welding thermal conduction theory for a moving point heat source. The dimensions of weld penetration and the convective heat transfer effect were estimated by the parameter. Thus, it was concluded that the developed modeling and analysis techniques successfully achieved an accurate weld residual stress analysis and provided a more detailed understanding of the convective heat transfer effect on weld pool formation.

Numerical prediction of effective thermal conductivity of ceramic fiber board using lattice Boltzmann method

Application of the lattice Boltzmann method has been extended for the analysis of combined transient conduction and radiation heat transfer through highly porous fibrous insulation media. Firstly, LBM has been employed for the analysis of combined mode of transient conduction radiation heat transfer in a 2 D rectangular enclosure containing an absorbing, emitting and scattering medium and results are compared with already published ones. The results have been found in good accord for different values of radiation-conduction parameter, scattering albedo and south (hot) wall emissivity. Furthermore, the proposed LBM for the calculation of effective thermal conductivity of ceramic fiber board has been employed. A random-generation growth method for generating micro morphology of natural ceramic fiber board has been selected. The conductive, radiative and effective thermal conductivity has been numerically estimated using the present LBM. It is found that the predicted effective thermal conductivity for different values of fibrous bulk density is in good agreement with the experimental data.

Analysis of Sustainable Materials for Radiative Cooling Potential of Building Surfaces

The main goal of this paper is to explore the radiative cooling and solar heating potential of several materials for the built environment, based on their spectrally-selective properties. A material for solar heating, should have high spectral emissivity/absorptivity in the solar radiation band (within the wavelength range of 0.2–2 μm), and low emissivity/absorptivity at longer wavelengths. Radiative cooling applications require high spectral emissivity/absorptivity, within the atmospheric window band (8–13 μm), and a low emissivity/absorptivity in other bands. UV-Vis spectrophotometer and FTIR spectroscopy, are used to measure, the spectral absorption/emission spectra of six different types of materials. To evaluate the radiative cooling potential of the samples, the power of cooling is calculated. Heat transfer through most materials is not just a surface phenomenon, but it also needs a volumetric analysis. Therefore, a coupled radiation and conduction heat transfer analysis is used. Results are discussed for the selection of the best materials, for different applications on building surfaces.

Numerical Investigation of Heat Transfer Behaviour During TIG Welding of Stainless Steel Pipes for Various Welding Heat Input Conditions

In the present work, tungsten inert gas (TIG) welding was carried out on stainless steel pipe joints and the heat transfer behaviour for various welding heat input was analysed. In this work austenitic stainless steel of grade 304L was used and the experiment was carried out on bead on plate and weld profile was analysed. The bead profile was obtained from the experiment and microstructure was characterized. The bead profile dimensions from the experiment were used in the calibration of heat source model during finite element heat transfer analysis. Based on the calibrated heat source model, TIG welding of stainless steel pipes was analysed. Numerical simulation was considered as conduction heat transfer analysis and weld pool convection was neglected in the model. The non-linear transient heat transfer analysis was carried out on pipes and thermal cycles at various locations were analysed.

Comparative Study of Optimization in Pultrusion with Pre-Heating and Die-Cooler Temperature for Improved Cure

Pultrusion is a composite manufacturing technique for processing continuous composite profiles with a constant cross section. In such system, energy and mass balances are used to model the thermal and kinetic behavior of the material during processing. This work aims to compare the results obtained in the recent literature, regarding thermal optimization of pultrusion. In the present analysis, an alternative thermal configuration has been suggested, with the objective of maximizing the mean degree of cure. A general-purpose FE software, ANSYS-CFX®, has been used to perform a three-dimensional (3D) conductive heat transfer analysis. Several case studies were conducted where the degree of cure was analyzed for varying heating scenarios. Results have shown that it is possible to get a higher cure in less process time if the die is isolated from the environment.