Finite Element Heat Transfer Model Research Articles

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

Efficiently and actively dissipating accumulated heat within asphalt pavement is crucial for reducing pavement distress and improving subgrade stability. This paper proposed a novel inverted “T” shaped heat induced structure (IT-HIS) that facilitates the rapid transfer of heat from the pavement to the subgrade and shoulders. The IT-HIS consists of two components: a vertical gradient thermal conductivity structure utilizing steel slag, and a horizontal oriented carbon fiber heat induced structure. The heat transfer behavior of the IT-HIS was analyzed using a finite element heat transfer model created in ABAQUS, and the results were validated through indoor irradiation experiments. The findings demonstrated that the IT-HIS enhanced heat flow and promoted secondary aggregation in the vertical direction, while facilitated lateral heat dissipation. Compared to the ordinary group (OG), the heat flux of IT-HIS at depths of 5 cm and 6.5 cm increased by 19.8 % and 64.6 %, respectively. The indoor irradiation experiment results indicated that during the heat absorption period, the IT-HIS reduced temperatures at depths of 0 cm, 2 cm, and 5 cm by 1.5 ℃, 1.7 ℃, and 1.1 ℃, respectively. During the heat dissipation period, the IT-HIS reduced temperatures at depths of 0 cm, 5 cm, and 10 cm by 0.9 ℃, 0.7 ℃, and 1.8 ℃, respectively. The IT-HIS enhanced the cooling effect during daytime and inhibited heat upward during nighttime based on the gradient thermal conductivity structure. The proposal and validation of this structure provide a fundamental approach to forming large-scale high-speed microchannel heat dissipation within asphalt pavements, and is expected to provide experimental and theoretical foundations for the development of directional active cooling technologies.

Modeling of laser-assisted micro-milling Inconel718

Nickel-based superalloy Inconel718 is a typical difficult-to-machine material with the characteristic of high strength and hardness. Demands for micro parts of nickel-based superalloy Inconel718 are growing in aerospace, biomedical and other fields. Laser-assisted micro-milling (LAMM) can realize precision machining of the workpiece because of its lower cutting force. However, the machining mechanism and the change law of cutting force during LAMM of nickel-based superalloy Inconel718 are still unclear. There is a crucial need for modeling of LAMM Inconel718. This paper explores LAMM of nickel-based superalloy Inconel718 and realizes the simulation of LAMM process. A three-dimensional transient heat transfer finite element (FE) model is established to predict the temperature distribution of a Gaussian heat source in LAMM. Multiple sets of simulations of laser pre-heating with various laser power are conducted to analyze the temperature fields of workpiece and determine the appropriate laser parameters. A novel 3D model of the full machining process of LAMM Inconel 718 is constructed by ABAQUS with multi-subroutine, a fully coupled thermal-mechanical process is achieved. A modified Johnson-Cook constitutive model is used to reflect the size effect and flow stress of LAMM Inconel 718. Finally, the validity of the models is verified by experiments. Based on the verified model, the appropriate laser pre-heating parameters are obtained, and the prediction of cutting forces of LAMM Inconel718 is achieved.

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

Accurate prediction of temperature distribution and melt pool geometry in metal additive manufacturing is highly dependent on the appropriate selection of heat source models. In the present study, a three-dimensional (3D) finite element (FE) heat transfer model is developed utilizing Abaqus by integrating different heat source models focusing on the surface heat source model and volumetric heat source model for selective laser melting (SLM) of Inconel 625 (IN625). All of the predicted peak temperatures, molten pool width, and depth are evaluated and compared with the experimental results cited from open literature. The relative error in simulated peak temperature and melt pool geometry from the surface heat source model is much higher in comparison to the volumetric heat transfer model. Further, a hybrid heat source model incorporating surface and volumetric heat models is developed to fulfill the numerical modeling of SLM of IN625 with high accuracy, which is highly recommended for the in-depth simulation study.

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

In this study, an analytical approach is developed to estimate the fire resistance of glulam bolted connections under coupled shear force and bending moment. This approach includes the combined finite-element heat-transfer model and load-carrying capacity theoretical model. Considering embedment failure and splitting failure as observed in fire tests, a combination of Johansen's model and quasi-non-linear fracture mechanics model is further developed in the proposed approach. The model is validated by experiments, and the comparison between theoretical results and experimental data shows good agreement. Parametric analysis is conducted to investigate different design parameters (e.g., the wood member thickness, the edge distance of the bolts and the load distance) that influence the load-carrying capacity of the connection in fire. Results show that increasing the thickness of wood member is an effective way to obtain better fire performance. The bolt edge distance has little influence on the resistance ratio (Rfire/R20°C) at the beginning of the fire process (Time ≤15 min) as long as the connection satisfies the minimum requirement of the edge distance of 4d in Chinese code (GB/T50708-2012). The influence of edge distance becomes evident with the time in fire increases (Time >15 min).

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

Gypsum plasterboards are used in Light-gauged Steel Framed (LSF) walls as the primary fire-resistant material. In addition to thermal protection, they provide restraints to the cold-formed steel studs at the screw locations and improve the load-bearing capacity. In this study, three full-scale standard fire tests were conducted first to investigate the thermal and structural behaviour of LSF walls in fire. Close examination of the plasterboard joint opening up and plasterboard fall-off phenomena showed that most of the plasterboard joint compound fell-off after 17 min of fire exposure and the joint gap gradually widened afterwards. A multi-step heat transfer finite element (FE) model was developed incorporating the physical changes observed during the fire tests and validated using the test results. The important time–temperature profiles obtained from this study and past literature were compared, and idealised time–temperature profiles of wall studs were developed for use in structural FE models. Past studies involving elevated temperature structural FE models considered mainly the in-plane restraints provided by plasterboard sheathing. Hence the effects of their out-of-plane restraints were investigated using structural FE models and fire tests, and suitable out-of-plane restraint values were proposed for numerical analysis. This study has shown that out-of-plane restraints significantly reduced the lateral deflections of LSF walls and improved their fire resistance levels (FRL) when double layers of plasterboards were used. However, excessive out-of-plane restraints could adversely affect the FRL. Overall, this research has used the fire test results to enhance the understanding of the thermal and structural behaviour of LSF walls and provided useful data and recommendations for more accurate thermal and structural modelling of LSF walls.

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

In recent years, extreme temperatures have occurred frequently in summer, which is a challenge to asphalt pavement and its surrounding environment. Phase change materials (PCMs) have unique energy storage characteristics, which provide a new idea for alleviating the high-temperature damage of pavement and reducing the environment temperature. In this paper, the silica composite phase change materials (SiO2-PCMs) were prepared by the sol–gel method, and SiO2-PCMs with better performance was applied to the asphalt mixture. The finite element heat transfer model was established by measuring the boundary conditions, and the temperature adjustment effect was predicted and analyzed. SiO2-PCMs meet the mixing temperature requirements of asphalt mixtures and have excellent compatibility, thermal cycle stability and anti-leakage ability. Asphalt mixture with PEG/SiO2 has an excellent temperature adjustment effect, and it can reduce the upper surface temperature of the asphalt mixture by about 9 °C. The high unity of theory and experiment is implemented by establishing the heat transfer model. PCMs reduce the temperature of asphalt pavement by storing and transforming energy, which provides reference and theoretical support for improving the near-surface thermal environment and prolonging the service life of asphalt pavement.

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

In traditional cochlear implant surgery, physical trauma may occur during electrode array insertion. Magnetic guidance of the electrode array has been proposed to mitigate this medical complication. After insertion, the guiding magnet attached to the tip of the electrode array must be detached via a heating process and removed. This heating process may, however, cause thermal trauma within the cochlea. In this study, a validated three-dimensional finite element heat transfer model of the human cochlea is applied to perform an intracochlear thermal analysis necessary to ensure the safety of the magnet removal phase. Specifically, the maximum safe input power density to detach the magnet is determined as a function of the boundary conditions, heating duration, cochlea size, implant electrode array radius and insertion depth, magnet size, and cochlear fluid. A dimensional analysis and numerical simulations reveal that the maximum safe input power density increases with increasing cochlea size and the radius of the electrode array, whereas it decreases with increasing electrode array insertion depth and magnet size. The best cochlear fluids from the thermal perspective are perilymph and a soap solution. Even for the worst case scenario in which the cochlear walls are assumed to be adiabatic except at the round window, the maximum safe input power density is larger than that required to melt 1 mm3 of paraffin bonding the magnet to the implant electrode array. By combining the outcome of this work with other aspects of the design of the magnetic insertion process, namely the magnetic guidance procedure and medical requirements, it will be possible to implement a thermally safe patient-specific surgical procedure.

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.

Fire performance of innovative 3D printed concrete composite wall panels – A Numerical Study

The 3-Dimensional (3D) printing technology in the construction sector has seen an accelerating growth owing to its potential advantages. For this layer-based construction, a detailed investigation on fire performance is necessary. However, there are limited research studies for 3D Printed Concrete (3DPC) walls exposed to fire. Therefore, this paper investigates the fire performance of different types of 3D printed concrete walls using validated Finite Element Models (FEMs). Validated heat transfer FEMs were extended to investigate the fire performance of a range of 3DPC wall configurations (solid, cavity, and composite) under standard fire conditions. The results show that 3DPC non-load bearing cavity walls underperform when subjected to standard fire compared to solid 3DPC walls. The novel composite 3DPC walls with the use of Rockwool as cavity insulation offers superior fire resistance.

Study of an optimal heating command law for structures with non-negligible thermal inertia in varying outdoor conditions

In this numerical study, an optimal energetic control model applied to local heating sources to prevent black-ice occurrence at transport infrastructure surface is addressed. The heat transfer Finite Element Model developed and boundary conditions hypothesis considered are firstly presented. Several heat powering strategies, in time and space, are then introduced. Secondly, control laws are presented with the objective of preventing ice formation while avoiding excessive energy consumption by taking also into account weather forecast information. In particular, the adjoint state method is adapted for the case of an operation without some continuous properties (discontinuous time heat sources). In such case, a projection from the space of continuous time functions to a piecewise constant one is proposed. To perform optimal control, the adjoint state method is addressed and discussed for the different powering solutions. To preserve some specific technical components and maintain their lifetime, operational constraints are considered and different formulations for the control law are proposed. Time dependent convecto-radiative boundary conditions are introduced in the model by extracting information from existing weather databases. Extension to updated inline weather forecast services is also presented and discussed. The final minimization problem considered has to act on both energy consumption and non-freezing surface temperature by integrating these specific constraints. As a consequence, the final optimal solution is estimated by an algorithm relying on the combination of adjoint state method and gradient descent that fits mathematical constraints. Results obtained by numerical simulations for different operative conditions with various weather conditions are presented and discussed. Finally, conclusion and perspectives are proposed.

Coupled heat transfer and phase transformations of dual-phase steel in coil cooling

Dual-phase steels are generally used in the car industry due to high tensile strength and good formability, which are obtained by a mixture of bainite and ferrite phases. This microstructure is achieved through slow rate coil cooling. However, the manufacturing of dual-phase steels introduces various challenges such as the instability of the cold rolling process. An important factor affecting this is the non-uniform coil cooling of a hot rolled strip. In coil cooling the cooling rates are not controlled and there are different thermal contacts during coil conveyance causing unequal cooling of the steel coil. Unequal cooling rates lead to non-uniform coil cooling, producing irregular phase transformations on different sides of the coil, which causes periodical variations of the phase fractions in the steel strip. Varying phase fractions cause thickness deviations in the strip during the cold rolling process. A three-dimensional transient heat transfer finite element model was developed and used for modeling the complete coil conveyance chain and coil field cooling of the coil on an industrial scale. A coupled phase transformation model is implemented as a subroutine into the finite element model for calculating the resulting phase fractions. It was found that the different thermal contacts during the coil conveyance produce uneven cooling rates causing length- and widthwise variations in the phase fractions. The heat transfer model is validated by comparing temperature profiles between the simulated and measured coil edges. The phase transformation model is fitted into experimental data and verification is carried out in industrial conditions by comparing the modeled phase fractions and test samples from a cooled and unwound steel coil.