Finite Element Heat Transfer Model Research Articles

Mesoscale modelling and three-dimensional experimental validation of heat transfer in shallow beds of polyamide powders for laser powder bed fusion

Abstract A good understanding of temperature-dependent material properties and the associated process parameters is required to successfully model the heat transfer in laser powder bed fusion (LPBF). To quantify the temperature distribution along the depth and top surface, a stationary laser sintering experimental set-up equipped with two infrared cameras is constructed in this study. A shallow bed of polymeric powder is spread on infrared-transparent Zinc Selenide (ZnSe) glass, so that one of the thermal cameras can see the heat transfer along the depth from the bottom. Two carbon black powders of treated polyamide (PA12 CB of 60 μm and PA6 CB of 80 μm) are used. A 3D finite-element heat transfer model is developed considering conductive, convective, radiative heat transfer, and phase change. Temperature-dependent material properties, such as thermal conductivity, density, specific heat, and emissivity, are estimated and considered. The model's accuracy is validated by comparing the temperature data along XYZ directions with the experimental values. The PA6 CB powder exhibits higher laser absorption and thermal conductivity than PA12 CB. This finding is evident from the rapid heating of PA6 CB due to higher laser absorption and faster cooling rate due to higher thermal conductivity. The emissivity of the powder bed is nearly uniform with the temperature for both powders and drastically increases at the melt pool. This change in emissivity is captured in the model.

Numerical heat transfer analysis considering thermal contact conductance between rough reciprocating sliding surfaces

The frictional heat generated leads to elevated surface temperatures, which markedly influence the reliability and service life of friction pairs. Considering the dynamic changes in the thermal contact conductance and friction coefficient, the heat transfer equations which consist of heat exchange due to temperature difference and frictional heat generation at the sliding interface have been established. A finite element heat transfer model is constructed between two rough reciprocating sliding surfaces. The influences of the reciprocating motion and the interface thermal contact conductance on the heat flow distribution coefficient and surface contact temperature are solved by numerical simulations respectively. Furthermore, a prediction model is developed based on the BP neural networks. The results indicate that the heat flow distribution coefficient and surface contact temperature increase with rising motion frequency or interface thermal contact conductance and eventually reach a steady state. Moreover, for a fixed motion frequency, both parameters increase linearly with motion amplitude under different interface thermal contact conductance. The prediction model for heat flow distribution coefficient and surface contact temperature shows average relative errors of 0.45% and 3.53%, respectively. This research provides a new efficient way to analyze heat transfer in reciprocating sliding contacts and predict the contact surface temperatures.

Evaluation of steel ladle refractories lining designs aiming energy savings using open‐source finite element tools

AbstractThis research aimed to implement a finite element heat transfer model to simulate the thermal cycle of steel ladles using an open‐source tool. FEniCS was selected, as it can solve partial derivative equations such as the heat transfer ones, which describes the thermal state of the steel ladle via finite element method. For this, each step of the steel ladle cycle (preheating, waiting steps, and holding) had its own model, comprising specific combinations of boundary conditions. An energy consumption analysis was carried out based on the calculation of the heat flux for each stage of the ladle cycle according to three selected configurations of the refractory lining chosen for the simulation. The results showed that the solutions obtained by both the open‐source method and by the commercial tool (Abaqus) were equivalent. The comparison of different lining configurations, especially using insulators, presented several advantages from the energy point of view. The attained conclusions can be of great interest to the refractory engineers who seek novel solutions to improve the insulating performance of the steel ladle. The present framework makes it possible to test a multitude of different designs and processing operation conditions, making the proposed tool a cost‐effective solution to aid the required improvements to reduce the carbon footprint of critical industrial processes such as steelmaking.

Thermal feedback in coaxial superconducting radio frequency cavities

The surface resistance of superconducting radio frequency (SRF) cavities depends on the strength of the applied rf field. This field dependence is caused by a combination of intrinsic losses and the extrinsic thermal feedback (TFB) effect. To test theories of intrinsic field dependence, the extrinsic part must be compensated for when analyzing experimental data from SRF cavity tests. Performing this compensation requires knowing thermal parameters that describe heat flow in the cavity walls. The relevant thermal parameters have been measured in the case of superfluid helium, below 2.177 K, but no detailed measurements have yet been reported for cooling of niobium surfaces in normal fluid helium baths. Because of this, the impact of TFB on the field dependence at temperatures near 4.2 K is unknown. In the present study, we report measurements of normal fluid helium boiling from niobium surfaces and its dependence on the orientation of the boiling surface and bath temperature. These measurements are used to create a finite-element model of heat transfer in cavities from TRIUMF’s coaxial test program. This tool is then used to compensate for TFB when analyzing a range of datasets from this program. Results are presented showing that TFB has a weak impact for the temperatures of 2.0 and 4.2 K, where SRF cavities are usually operated, but it is an important effect at intermediate temperatures. Published by the American Physical Society 2024

Structure and mechanism of directional heat induced asphalt pavement with thermal aggregation effect

Structure and mechanism of directional heat induced asphalt pavement with thermal aggregation effect

Modeling of laser-assisted micro-milling Inconel718

Modeling of laser-assisted micro-milling Inconel718

Designing umbrella-shaped heat-induced channels for oriented heat transfer in asphalt mixtures

In order to regulate the directional transfer and collection of heat in pavements, a novel solution has been proposed, named Umbrella-Shaped Heat-induced Channels (UHC). This UHC is composed of carbon fibers with high axial thermal conductivity and a heat-induced layer. A finite element heat transfer model is employed to analyze the heat transfer behaviors of asphalt mixtures. And an indoor irradiation experiment is conducted for feasibility verification. The results indicate that enhancing the thickness of the heat-induced layer or increasing the disparity in thermal conductivity between the heat-induced layer and asphalt mixtures can enhance the oriented heat transfer effect of UHC. The heat-induced layer boosts the horizontal heat flux of the UHC by 60.3% compared to the side without the heat-induced layer. This enhancement is attributed to the secondary thermal convergence effect of the heat-induced layer, which further amplifies the thermal induction and heat collection capabilities of UHC. This phenomenon is crucial for achieving directed heat conduction. The designed UHC can enhance the heat transfer efficiency of the asphalt pavement in the designated direction. Furthermore, it can alleviate the heat island effect, address permafrost thawing and high-temperature rutting issues, and enhance the efficiency of solar energy harvesting on pavements.

Temperature Profile Measurement From Radiofrequency Nasal Airway Reshaping Device.

Nasal airway obstruction (NAO) is caused by various disorders including nasal valve collapse (NVC). A bipolar radiofrequency (RF) device (VivAer®, Aerin Medical, Sunnyvale, CA) has been used to treat NAO through RF heat generation to the upper lateral cartilage (ULC). The purpose of this study is to measure temperature elevations in nasal tissue, using infrared (IR) radiometry to map the spatial and temporal evolution of temperature. Experimental and computational. Composite porcine nasal septum was harvested and sectioned (1 mm and 2 mm). The device was used to heat the cartilage in composite porcine septum. An IR camera (FLIR® ExaminIR, Teledyne, Wilsonville, OR) was used to image temperature on the back surface of the specimen. These data were incorporated into a heat transfer finite element model that also calculated tissue damage using Arrhenius rate process. IR temperature imaging showed peak back surface temperatures of 49.57°C and 42.21°C in 1 and 2 mm thick septums respectively. Temperature maps were generated demonstrating the temporal and spatial evolution of temperature. A finite element model generated temperature profiles with respect to time and depth. Rate process models using Arrhenius coefficients showed 30% chondrocyte death at 1 mm depth after 18 s of RF treatment. The use of this device creates a thermal profile that may result in thermal injury to cartilage. Computational modeling suggests chondrocyte death extending as deep as 1.4 mm below the treatment surface. Further studies should be performed to improve dosimetry and optimize the heating process to reduce potential injury. Laryngoscope, 134:1063-1070, 2024.

Heat transfer finite element model for laser powder-bed fusion on consolidated simulation geometry

Heat transfer finite element model for laser powder-bed fusion on consolidated simulation geometry

On the importance of heat source model determination for numerical modeling of selective laser melting of IN625

On the importance of heat source model determination for numerical modeling of selective laser melting of IN625

Thermal modeling of the convective heat transfer in the large air cavities of the 3D concrete printed walls

The cavity walls are a widely used construction system. They became popular in traditional masonry construction for their capacity to reduce the passage of moisture and improve the walls’ thermal performance. However, the latter only applied to narrow cavities with restricted internal air movement. Cavities are also present in emerging technologies, such as 3D concrete printed walls. However, the large cavities of the 3D printed concrete walls have high convective heat transfers that affect the envelope’s thermal performance. Therefore, the authors developed a conjugate heat transfer finite element model to study the large cavities in 3D printed concrete walls and determine the effect on the convective heat transfer of subdividing large cavities. The results show it is possible to reduce the heat flux four times, from 40.4 W/m2 to 9.1 W/m2, subdividing a large cavity into sixteen small ones. This reduction might be higher, increasing the number of cavity subdivisions. However, it is infeasible to restrict the air movements in unfilled air cavities over 25 mm wide for the Rayleigh numbers ≥ 105. Therefore, the practicality of minimizing heat transfer by subdividing large air cavities in 3D printed walls is limited.

Analytical investigation and parametric study on the fire behavior of glulam bolted beam-to-column connections based on the quasi-non-linear fracture mechanics model

Analytical investigation and parametric study on the fire behavior of glulam bolted beam-to-column connections based on the quasi-non-linear fracture mechanics model

Numerical modelling and fire testing of gypsum plasterboard sheathed cold-formed steel walls

Numerical modelling and fire testing of gypsum plasterboard sheathed cold-formed steel walls

Study of temperature-adjustment asphalt mixtures based on silica-based composite phase change material and its simulation

Study of temperature-adjustment asphalt mixtures based on silica-based composite phase change material and its simulation

Fast and accurate prediction of temperature evolutions in additive manufacturing process using deep learning

Typical computer-based parameter optimization and uncertainty quantification of the additive manufacturing process usually requires significant computational cost for performing high-fidelity heat transfer finite element (FE) models with different process settings. This work develops a simple surrogate model using a feedforward neural network (FFNN) for a fast and accurate prediction of the temperature evolutions and the melting pool sizes in a metal bulk sample (3D horizontal layers) manufactured by the DED process. Our surrogate model is trained using high-fidelity data obtained from the FE model, which was validated by experiments. The temperature evolutions and the melting pool sizes predicted by the FFNN model exhibit accuracy of $$99\%$$ and $$98\%$$ , respectively, compared with the FE model for unseen process settings in the studied range. Moreover, to evaluate the importance of the input features and explain the achieved accuracy of the FFNN model, a sensitivity analysis (SA) is carried out using the SHapley Additive exPlanation (SHAP) method. The SA shows that the most critical enriched features impacting the predictive capability of the FFNN model are the vertical distance from the laser head position to the material point and the laser head position.

Feasibility Analysis of Utilization of Shallow Geothermal Energy through LNG Tank Pile Foundation

Liquefied Natural Gas (LNG) needs an additional heat source to meet its heat demand in the process of gasification. Based on the background of using shallow geothermal energy, the feasibility of using LNG tank piles as heat exchangers for LNG gasification was studied. A two-dimensional finite element heat transfer model of energy piles was established, and the heat transfer capacity and long-term stability of different buried pipe options were analyzed. The results show that the LNG tank energy piles can meet part of the heat demand for LNG gasification to a certain extent.

Heat Insulation Performance of Lattice Thermal Protection Structure with Reinforced Plate

A lightweight lattice structure is proposed, which can be applied to the thermal protection system of high speed aircraft. The structure uses carbon fiber reinforced silicon carbide ceramic matrix composite as the framework, and the inner cavity can be filled with heat insulation materials with small thermal conductivity. In order to study the heat insulation performance of the structure, the three-dimensional finite element heat transfer model of the lattice structure with and without heat insulation material was established. Abaqus software was used to calculate the temperature distribution and change of the lattice structure under different temperature boundary conditions. The equivalent thermal conductivity of the lattice structures under different temperature boundary conditions is defined and calculated. The results show that the heat insulation effect of the lattice structure is improved obviously with the addition of heat insulation materials, but the time required to reach the stable state is increased. Without heat insulation materials, the strength of cavity radiation is greatly affected by the temperature boundary conditions on the top surface and positively correlated. Increasing heat insulation materials can effectively block the generation of cavity radiation, thus enhancing the heat insulation effect. The conclusion provides a foundation for further application of the lattice structure in thermal protection system of high speed aircraft.

Optimization of E. Coli Tip-Sonication for High-Yield Cell-Free Extract using Finite Element Modeling.

Optimal tip sonication settings, namely tip position, input power, and pulse durations, are necessary for temperature sensitive procedures like preparation of viable cell extract. In this paper, the optimum tip immersion depth (20-30% height below the liquid surface) is estimated which ensures maximum mixing thereby enhancing thermal dissipation of local cavitation hotspots. A finite element (FE) heat transfer model is presented, validated experimentally with (R2 > 97%) and used to observe the effect of temperature rise on cell extract performance of E. coli BL21 DE3 star strain and estimate the temperature threshold. Relative yields in the top 10% are observed for solution temperatures maintained below 32°C; this reduces below 50% relative yield at temperatures above 47°C. A generalized workflow for direct simulation using the COMSOL code as well as master plots for estimation of sonication parameters (power input and pulse settings) is also presented.

A three-dimensional thermal model of the human cochlea for magnetic cochlear implant surgery

A three-dimensional thermal model of the human cochlea for magnetic cochlear implant surgery

Numerical Investigation of Deposition Characteristics of PLA on an ABS Plate Using a Material Extrusion Process.

Three-dimensional prototypes and final products are commonly fabricated using the material extrusion (ME) process in additive manufacturing applications. However, these prototypes and products are limited to a single material using the ME process due to technical challenges. Deposition of plastic on another dissimilar plastic substrate requires proper control of printing temperature during an ME process due to differences in melting temperatures of dissimilar plastics. In this paper, deposition of PLA filament on an ABS substrate during an ME process is investigated using finite element analysis. A heat transfer finite element (FE) model for the extrusion process is proposed to estimate the parameters of the ME machine for the formulation of a heat flux model. The effects of printing temperature and the stand-off distance on temperature distributions are investigated using the proposed FE model for the extrusion process. The heat flux model is implemented in a proposed heat transfer FE model of single bead deposition of PLA on an ABS plate. From this FE model of deposition, temperature histories during the ME deposition process are estimated. The results of temperature histories are compared with experiments. Using the calibrated FE model, a proper heating temperature of ABS for deposition of PLA is evaluated.