Finite Element Analysis Of Heat Transfer Research Articles

Numerical investigation of laser powder bed fusion of glass

AbstractAdditive manufacturing of glass using laser powder bed fusion has been recently developed, demonstrating its potential to be applied in small scale applications such as flow reactors for the chemical engineering and pharmaceutical manufacturing industries. While previous research demonstrated that complex 3-dimensional shapes can be manufactured, built parts are often brittle, exhibit high porosity and lack transparency. This study employs a transient, heat transfer finite element analysis to shed light on the thermal response of laser—glass powder bed interaction and the impact of processing parameters. Through this understanding, the research seeks to identify practical strategies that can be employed to improve the quality and properties of the built parts. Bulk solid and powder soda lime silica glass properties are used as input in the model, while the laser heat flux and scan strategy, conversion of powder feedstock to bulk solid glass and heat losses from convection and radiation effects are introduced in the model through Fortran coding. The study showed that effective powder consolidation, resulting in well-defined geometrical features, is achieved for temperatures near the glass melting point. Additionally, uniform consolidation depths and widths can be achieved by increasing laser power, elevating substrate temperature and reducing scan speed within certain limits, whilst ensuring hatch spacing is below the corresponding single scan track width for unidirectional adjacent laser trajectories.

Finite element heat transfer analysis in selective laser melting of AlSi10Mg alloy using bi-directional scan strategy: Enhanced thermal conductivity considerations

In the present work, a 3D finite element model was created using the commercial ABAQUS software to analyze the selective laser melting process of AlSi10Mg powder in a bidirectional multi-track, multi-layer configuration. The focus of this investigation was to examine distribution of temperature, melt pool geometry, thermal history, and the temperature change rate. To improve the accuracy of the results, the enhanced thermal conductivity was utilized to incorporate the Marangoni convection effect. The results revealed that, in the initial track, the maximum temperature and dimensions of the melt pool increased, ultimately reaching a plateau as the deposited path extended. However, using a bidirectional scan strategy, the maximum temperature at the second track reached its peak and then stabilized. While the maximum heating and cooling rates in the first track showed a nearly identical trend, both parameters decreased at the beginning of the second track and then began to rise again. It can be attributed to the overlapping of the molten zone between the first and second tracks. With an increase in the number of tracks, the maximum temperature, melt pool width, and depth increased until they reached a steady state, with specific values of 2093 K, 258 μm, and 150 μm, respectively. Introducing more layers initially caused an increase in the maximum temperature and dimensions of the melt pool, which eventually reached a steady-state condition. Finally, temperature distribution of the steady-state simulated melt pool was found to match with thermal behavior and eutectic Si features of the experimental sample.

An Improved Method for Deriving the Heat Source Model for FCAW of 9% Nickel Steel for Cryogenic Tanks.

The International Maritime Organization (IMO) is tightening regulations on air pollutants. Consequently, more LNG-powered ships are being used to adhere to the sulfur oxide regulations. Among the tank materials for storing LNG, 9% nickel steel is widely used for cryogenic tanks and containers due to its high cryogenic impact toughness and high yield strength. Hence, numerous studies have sought to predict 9% nickel steel welding distortion. Previously, a methodology to derive the optimal parameters constituting the Goldak welding heat source for arc welding was developed. This was achieved by integrating heat transfer finite element analysis and optimization algorithms. However, this process is time-consuming, and the resulting shape of the weld differs by ~15% from its actual size. Therefore, this study proposes a simplified model to reduce the analysis time required for the arc welding process. Moreover, a new objective function and temperature constraints are presented to derive a more sophisticated heat source model for arc welding. As a result, the analysis time was reduced by ~70% compared to that previously reported, and the error rates of the weld geometry and HAZ size were within 10% and 15% of the actual weld, respectively. The findings of this study provide a strategy to rapidly predict welding distortion in the field, which can inform the revision of welding guidelines and overall welded structure designs.

Experimental and numerical study on the validity of the energy-based time equivalent method for evaluating the fire resistance of timber components exposed to travelling fires

An energy-based time equivalent method that is capable of converting the fire resistance design of timber components exposed to the realistic fire to that of the standard fire was proposed. To verify the effectiveness of the method applied to the improved Travelling Fires Methodology (iTFM) fires, a series of iTFM fires and their corresponding equivalent standard fire tests were implemented on six glued laminated timber columns. The effectiveness of the method was fully confirmed by comparing the fire effects, the temperature distribution of the pyrolysis layer, and the remaining load-bearing capacity after fire for the timber columns under the iTFM fires and their equivalent standard fires. Meanwhile, it was well illustrated that the adhesive layer was almost no effect on the fire resistance of the timber columns by comparing the cross-sectional temperature distribution, charring depth and charring rate in two directions of the timber columns. To simplify the application of the energy equivalence method, the thermal properties relationships applied to the finite element heat transfer analysis of timber were modified. The accuracy of the modified thermal property relationships was demonstrated by comparing the surface temperature, charring depth, and charring rate obtained from finite element simulations with those measured by the experiment. The simplified energy equivalence method based on the finite element was not only easy for designers to apply, but also helped to promote the development of performance-based fire protection design for timber structures.

A case study on the water-cooling pipe scheme in concrete early curing stage

Modelling of early curing stage of a bridge pier foundation pile cap of 4.5m thick, to be constructed at Betong division, Sarawak was carried out to verify scheme of water-cooling pipe can meet temperature specifications in which concrete must not reach a peak temperature of 70°C, and differential temperature at core and surface of concrete must not exceed 25°C. Modelling was carried out using transient heat transfer finite element analysis programme and by treating the pile cap as a concrete solid body, assuming no heat generation nor thermal conductivity of reinforcement bars. The result shows that the cooling scheme is feasible to meet temperature limitations of the specifications.

Numerical Investigation on Fire Performance of LSF and Steel Modular Floor Panels

The steel Modular Building Systems (MBSs) that have been influenced by the Light-gauge Steel Frame (LSF) techniques have become a prominent culture in the industry. However, the detrimental behaviour of steel structural components at high temperatures has elevated the risk of fatal accidents in the event of a fire. Although several research investigations have addressed the fire performance of steel modular wall systems, the behaviour of modular floor systems has not been adequately addressed in the state of the art. Hence, to promote the fire safety and optimum design techniques in the modular construction industry by addressing the aforementioned research gap, this study investigated 48 conventional LSF and MBS floors for their structural and insulation Fire Resistance Levels using Finite Element Modelling (FEM) and Heat Transfer Analyses (HTA) techniques. Initially, full-scale experimental fire tests were modelled using FEM methods, and the validity of the techniques was verified prior to the analyses of parametric floor systems. Furthermore, the structural behaviour of the channel section joists in the elevated temperatures was studied, and hence a correlation was established to determine the critical steel temperature at the structural fire failure with respect to the applied Load Ratio (LR). An additional 12.5 mm thick plasterboard sheathing on single plasterboard sheathed floors resulted a 30 min improvement in structural and insulation FRLs. In addition, the modular floor systems demonstrated enhanced structural and insulation Fire Resistance Levels (FRLs) against the corresponding conventional LSF floor designs due to double LSF skin build-up. The incorporation of rockwool insulation and the increase in the insulation volume implied increased structural and fire performances. However, insulation material in the modular designs was more effective. The fire-rated conventional and modular LSF floor systems are expected to be practised in the construction industry to achieve required fire resistances with optimum material usage.

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

Ablative Thermal Response Numerical Modeling Under Arcjet Test Conditions

The finite element Heat Transfer and Erosion Analysis Program (Hero) provides solutions for multidimensional ablation, internal heat conduction, thermal decomposition, and pyrolysis gas flow problems. As part of a code validation study, two-dimensional axisymmetric results from Hero are compared with thermal response data obtained from arcjet tests. The results are also compared with two other two-dimensional axisymmetric computational methods (Fully Implicit Ablation and Thermal (FIAT) and Finite Element Ablation and thermal Response (FEAR)). Hero model predictions compare favorably with the arcjet test data for all conditions and other computational methods where there is not significant pyrolysis. Where pyrolysis occurs, the Hero model more accurately predicts surface recession than the FIAT and FEAR codes. This serves to validate the methodology used in the Hero code.

Analytical calculation of temperature‐induced strain of supertall structures

Estimating temperature-induced strain is of critical importance for structural safety assessment. Most previous studies estimated the temperature-induced strain by statistical analysis, resulting in the unexplainable physical meaning of the obtained model coefficients. In this paper, an analytical formula for the temperature-induced strain of supertall structures is derived based on the simulated temperature field. First, a supertall structure is simplified as a cantilever column, and the theoretical relationship between the sectional two-dimensional temperature field and strain is derived. Afterwards, the structure is extended to a generalised cantilever column bounded by springs at the top end, and the theoretical relationship of temperature and strain is derived as well. The formula shows that the sectional strain is composed of the sectional average temperature-induced strain and the gradient temperature-induced strain along two horizontal directions. A finite element (FE) model is established to verify the derived strain formula. Finally, the formula is applied to a real supertall structure, the Wuhan Yangtze River Navigation Centre, on which a long-term structural health monitoring system has been installed. The temperature field of the whole structure is obtained by the FE heat transfer analysis, and the temperature-induced strain is calculated according to the derived formula. The average difference between the theoretically derived and measured strains is less than 7 με. This study provides a simple theoretical formula for calculating the temperature-induced strain of supertall structures, avoiding the complicated FE structural analysis.

The Use of Machine Learning for the Prediction of fire Resistance of Composite Shallow Floor Systems

This paper is proposing an machine learning based expert system for preliminary prediction of the insulation fire resisting performance of shallow floor systems when subject to exposure to the ISO 834 Standard Fire Curve. The proposed system is a digital tool which incorporates a machine learning algorithm trained on the outcomes of pre-run two-dimensional finite element heat transfer analyses of shallow floor system details. The algorithm predicts the insulation performance of similar details with a measurable accuracy of 96% (i.e the insulation rating band was predicted correctly in 96% of the cases) without the requirement for an explicit deterministic analysis. The paper presents the challenges and prerequisites to build such an expert system and acts as a proof of concept for the use of machine learning for the assessment of the insulation performance of shallow floor system under the guidance of BS EN 1363-1:2012. A Support Vector Machine machine learning algorithm is adopted in this work. The required processes that were needed for the development of the expert system include the stages of data acquisition, exploratory data analysis, choice of machine learning algorithm, model training, tuning, and validation. This expert system is useful for practitioners to rapidly assess the feasibility of different construction details at early stages of the design process.

Finite element heat transfer analysis of the aluminum-composite solid state cooling device using latent heat storage effect of nickel titanium shape memory alloy

Finite element heat transfer analysis of the aluminum-composite solid state cooling device using latent heat storage effect of nickel titanium shape memory alloy

Experimental and simulation investigations of CPV/TEG hybrid system

Concentrator photovoltaic (CPV) technology is a leading approach for increasing the utilization and deployment of PV systems. A major disadvantage is the need for cooling to maintain the performance of the solar cell. Active cooling is power-consuming and complex. A proposed passive cooling subsystem, uses a thermoelectric generator (TEG), besides cooling the solar cell, it generates power from waste heat. Three TEG modules with different sizes and numbers of junctions were tested. The performance of the TEGs was simulated using the finite element method and heat transfer analysis. The simulated model was validated for each TEG against the manufacturer datasheet and demonstrated good agreement between the simulated and measured performances. A CPV/TEG hybrid system was investigated experimentally and compared with the obtained simulation results. The proposed system was proven to deliver a net electrical power higher than obtained using the CPV system only. Compared to only a CPV cell on top of a heat sink, the generated power of the CPV/TEG hybrid system increased by 7.4%, 5.8%, and 3% corresponding to using the 30×30mm2, 40×40mm2 and the 62×62mm2 TEG modules, for which the number of junctions are 31, 127 and 49, respectively.

Estimation Method of Interpass Time for the Control of Temperature during a Directed Energy Deposition Process of a Ti-6Al-4V Planar Layer.

Directed energy deposition (DED) provides a promising additive manufacturing method to fabricate and repair large metallic parts. However, it may suffer from excessive heat accumulation due to a high build rate, particularly during a wire feeding-type DED process. The implementation of interpass time in between two depositions of beads plays an important process role to passively control the interpass temperature. In this study, a method to estimate the proper interpass time using regression analysis from heat transfer finite element analysis is proposed for maintaining the interpass temperature during a wire feeding-type DED deposition of a planar layer. The overlapping beads of a planar layer are estimated using a polygonal-shaped bead profile in the finite element model. From the estimated proper interpass time, a selected proper interpass time scheme (PITS) is suggested for practical implementation. The selected PITS is applied in a thermo-mechanical finite element model to evaluate the temperature distribution and its effects on the depth of the melt pool, the depth of the heat-affected zone (HAZ), displacement, and residual stresses. By comparing the predicted results with those using a constant interpass time scheme (CITS), the selected PITS shows better control in reducing the depths of the melt pool and HAZ without severely inducing large displacement and residual stresses.

Heat transfer in the tank-inflorescence of Nidularium innocentii (Bromeliaceae): Experimental and finite element analysis based on X-ray microtomography

In Bromeliaceae, various traits have evolved for the uptake and storage of water; however, their roles in bromeliad inflorescences remain unresolved. This study investigates the role of water in the flowers and inflorescences of Nidularium innocentii, and describes water as a protection mechanism. Individuals were divided into groups with and without water provision in inflorescences. Both groups were maintained with water in soil and leaves under the same environmental conditions. During anthesis, individuals were collected, and inflorescences were measured. Another specimen was prepared and scanned using X-ray microtomography (μCT), generating a high-resolution 3D model that was converted into a discretized geometry. Heat transfer finite element analysis (FEA) of the μCT-based geometry was then performed to simulate external temperature dissipation with the presence and absence of water in 3D. Flower size in the control group was significantly larger, and many injuries were observed in the drought group. FEA data indicated that the water environment led to lower temperature variation when compared to the air environment by significantly alleviating thermal amplitude. Water acted as a temperature stabilizer for the inflorescence, while its absence initiated physiological stress responses.

A Study on Activation Algorithm of Finite Elements for Three-Dimensional Transient Heat Transfer Analysis of Directed Energy Deposition Process

Heat transfer finite element analysis (FEA) for directed energy deposition (DED) process is crucial to properly estimate the residual stress in the additive manufactured part. The material deposition of the DED process is generally simulated by activation of finite elements. However, the activation algorithm of inactive finite elements is complicated. Besides, existing element activation algorithm is not suitable for highly focused energy source. In order to overcome these discrepancies, an inactive element activation algorithm with two-element cross section has been proposed for simulating a DED process using a high intensity laser heat flux. The nodal temperature during the element activation has been evaluated. The proposed algorithm has been implemented into the heat transfer FEAs for multilayer and planar depositions to investigate the applicability of the proposed algorithm. Finally, the results of FEAs using the proposed algorithm have been compared to those of commercial software SYSWELD.

Optimal Thickness Design of Thermal Protective Clothing

Under the premise of ensuring the protective effect, it is of great significance to design the optimal protective suit. In this paper, under the premise of analyzing the basic temperature distribution, the optimal thickness of the protective clothing is optimized. First, a temperature distribution model based on the heat transfer equation. The partial differential equations of temperature, time and spatial position are written for fabric layers I, II, III and air layer IV respectively. The initial and boundary conditions are given according to the measured external temperature and thermodynamic laws of skin. The finite difference method is used to numerically solve the partial differential equations to obtain the temperature distribution at different time and space. It was found that the human skin temperature increased with time and reached a steady state at time t=1645s. Then the optimal thickness is solved. Under the condition of meeting the basic safety requirements, the constraint optimization model with the optimal II layer thickness (ie the thinnest and the lowest cost) as the objective function is established. Then use the particle swarm optimization algorithm based on dynamic target method to solve. The optimum layer thickness was found to be 6.2 mm. Finally, the model was tested. Using the finite element heat transfer analysis of ANSYS workbanch to simulate the temperature distribution in the actual material, the similarity is high, which proves that the temperature distribution model is more accurate. This model can be extended to other heat transfer related clothing and container optimal thickness design.

Effects of muscle protein denaturation and water distribution on the quality of false abalone (Volutharpa ampullacea perryi) during wet heating

AbstractThe effects of wet heating at 95–100 °C on the degree of myosin and actin denaturation in false abalone (Volutharpa ampullacea perryi) were predicted by a heat transfer model. The contributions of water mobility and tenderness to sensory acceptability were assessed after 5, 10, 15, 30, and 60 min heating treatments. 3D finite element heat transfer analysis and reaction kinetics demonstrated that the muscle proteins were completely denatured in 60–80 s during wet heating. In the low field 1H nuclear magnetic resonance (LF‐NMR) and magnetic resonance imaging (MRI) analyses, the content of immobilized water was reduced with extended cooking time, and the shear force also decreased. Sensory acceptability was reduced with the increase of cooking time. Partial least squares (PLS) analysis indicated a high correlation among immobilized water, color, taste, and sensory acceptability. Our results may help in understanding the mechanisms of quality assessment and control during seafood cooking.Practical applicationsFalse abalone (Volutharpa ampullacea perryi) has been widely consumed as it can provide a high quality of nutrition with a relatively inexpensive cost. Wet heating is the most conventional processing procedure, then the effects of heating on the sensory and textual properties of false abalone meat should be carefully controlled. Since most researches are concerning the changes of collagen, the present study provided quantitative characterizations of muscle protein denaturation and water distribution on the quality of false abalone using 3D finite element heat transfer analysis, LF‐NMR, MRI techniques, and PLS analysis. The results would be useful to simulate actin and myosin denaturation as well as the protons distribution under different thermal schedules of food cooking, and they could be applied for the food quality control in the industry.

Finite-Element Analysis of Heat Transfer of Horizontal Ground-Freezing Method in Shield-Driven Tunneling

When applying the artificial ground-freezing method in a shield-driven tunnel, the design of the freezing zone and freezing time is of practical interest. Therefore, the distribution and evolution of heat transfer in a frozen soil wall are key issues in the examination of the freezing effect. In this study, the horizontal ground-freezing method for soil reinforcement in shield-driven tunneling was considered. A cup-shaped freezing scheme was adopted at the launching shaft of the shield-driven tunnel. Three-dimensional (3D) finite-element analysis was used to examine the heat transfer within the cup-shaped frozen soil wall. By this method, the feasibility of the artificial ground-freezing method in the shield tunneling of Nanjing Subway Line 10 was demonstrated. Four types of soil were considered as the in situ soils surrounding the shield machine: sandy, cement-admixed sandy, soft clay, and cement-admixed soft clay. The simulation results indicate that the cement-admixed sandy soil was the most favorable material in terms of ground freezing; it had the highest decreasing rate of temperature in the process of ground freezing. In contrast, the soft clay was the most unfavorable material in terms of ground freezing. The results imply that the closure time of the cup-shaped frozen soil wall was sensitive to the thermal physical properties of soils in addition to the in situ water content.

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.

SU-F-207-05: Excess Heat Corrections in a Prototype Calorimeter for Direct Realization of CT Absorbed Dose to Phantom

Purpose: To reconcile air kerma and calorimetry measurements in a prototype calorimeter for obtaining absorbed dose in diagnostic CT beams. While corrections for thermal artifacts are routine and generally small in calorimetry of radiotherapy beams, large differences in relative stopping powers of calorimeter materials at the lower energies typical of CT beams greatly magnify their effects. Work-to-date on the problem attempts to reconcile laboratory measurements with modeling output from Monte Carlo and finite-element analysis of heat transfer. Methods: Small thermistor beads were embedded in a polystyrene (PS) core element of 1 cm diameter, which was inserted into a cylindrical HDPE phantom of 30 cm diameter and subjected to radiation in a diagnostic CT x-ray imaging system. Resistance changes in the thermistors due to radiation heating were monitored via lock-in amplifier. Multiple 3-second exposures were recorded at 8 different dose-rates from the CT system, and least-squares fits to experimental data were compared to an expected thermal response obtained by finite-element analysis incorporating source terms based on semi-empirical modeling and Monte Carlo simulation. Results: Experimental waveforms exhibited large thermal artifacts with fast time constants, associated with excess heat in wires and glass, and smaller steps attributable to radiation heating of the core material. Preliminary finite-element analysis follows the transient component of the signal qualitatively, but predicts a slower decay of temperature spikes. This was supplemented by non-linear least-squares fits incorporating semi-empirical formulae for heat transfer, which were used to obtain dose-to-PS in reasonable agreement with the output of Monte Carlo calculations that converts air kerma to absorbed dose. Conclusion: Discrepancies between the finite-element analysis and our experimental data testify to the very significant heat transfer correction required for absorbed dose calorimetry of diagnostic CT beams. The results obtained here are being used to refine both simulations and design of calorimeter core components.