Three-dimensional Heat Transfer Analysis Research Articles

Three-dimensional heat and moisture transfer analysis for thermal protection of firefighters’ gloves with phase change materials

Transient three-dimensional (3D) heat and moisture transfer simulations were conducted to analyze the thermal performances of the entire phase change material (PCM) integrated into firefighters’ gloves. PCM was broken down into several segments to cover the back and palm of the hand but to avoid finger joints to keep hand functions. Parametric studies were performed to explore the effects of PCM melting temperatures, PCM locations in the glove and PCM layer thicknesses on the overall thermal performance improvement of firefighters’ gloves. The study found that PCM segments could extend the time for hand skin surfaces (areas covered or not covered by PCM) to reach second-degree burn injury (60 °C) by 1.5–2 times compared to conventional firefighters’ gloves without PCM. Moreover, PCM segments could help mitigate the temperature increase on hand skin and glove surface after fire exposure.

Investigation of thermal performance at forced convection in plate-fin heat sink

Interest in studies on more effective and faster heat dissipation in microelectronic equipment has increased in recent years due to the cooling area and equipment size limitations. This study attempts to focus on the effect of different fin geometry parameters on pure forced convection heat transfer. Total surface areas of plate-fin heat sinks were kept constant and were carried out for ten different heat sinks in these analyses. The Ansys-Fluent 2023 R1 commercial package program was used to perform the thermal and hydrodynamic performance analyses. Three-dimensional turbulent forced convection heat transfer analyses at heat sinks were subjected to fluid flow (500≤Re≤3000). The effects of gap between fins, fin thickness, fin height, fin number, and air velocity on the heat transfer and the friction factor were obtained and discussed for heat sinks. It was observed that there was a maximum difference of 0.27 % between the maximum temperatures obtained as a result of this analysis and the experimental study results in the literature. Among the ten cases examined (from Case 1 to Case 10), the highest heat transfer coefficient was obtained in Case 2 (number of fins 6, gap between fins 4 mm, fin height 17 mm and fin thickness 2 mm) at Re = 3000. The heat transfer coefficient of Case 2 was 41.29 % higher than the heat transfer coefficient of Case 4 at Re = 3000; though, the friction factor of Case 2 is 55.93 % higher than Case 4. Also, a useful correlation for the heat transfer coefficient was generated for the fin geometric parameters and Reynolds number.

Three-dimensional heat transfer analysis of Hot Gas Torch (HGT)-assisted Automated Fiber Placement (AFP) for thermoplastic composites

Automated Fiber Placement (AFP) is a key additive manufacturing process for the production of complex composite structures. This study focuses on the in-situ AFP process for thermoplastic composites with Hot Gas Torch (HGT), which includes heating, consolidation, and solidification steps. Temperature control is critical to achieving high quality parts as it affects bond quality, crystallization, and solidification. However, previous studies have oversimplified convective heat transfer by assuming a constant coefficient, resulting in discrepancies between simulations and experiments. This paper introduces a novel distribution function to model the convective heat transfer coefficient, thereby improving temperature predictions. An optimization loop is used to determine the parameters of the function, which ensures agreement with experimental data. The proposed approach accurately predicts the temperature distribution, which is validated against unseen experimental results. By incorporating the distribution of the convective heat transfer coefficient, this study improves the understanding of heat transfer mechanisms in AFP for thermoplastic composites, leading to improved manufacturing processes and part quality.

Numerical Modeling and Analysis of Transient and Three-Dimensional Heat Transfer in 3D Printing via Fused-Deposition Modeling (FDM)

Fused-Deposition Modeling (FDM) is a commonly used 3D printing method for rapid prototyping and the fabrication of plastic components. The history of temperature variation during the FDM process plays a crucial role in the degree of bonding between layers. This study presents research on the thermal analysis of the 3D printing process using a developed simulation code. The code employs numerical discretization methods with an implicit scheme and an effective heat transfer coefficient for cooling. The computational model is validated by comparing the results with analytical solutions, demonstrating an agreement of more than 99%. The code is then utilized to perform thermal analyses for the 3D printing process. Interlayer and intralayer reheating effects, sensitivity to printing parameters, and realistic printing patterns are investigated. It is shown that concentric and zigzag paths yield similar peaks at different time intervals. Nodal temperatures can fall below the glass transition temperature (Tg) during the printing process, especially at the outer nodes of the domain and under conditions where the cooling period is longer and the printed volume per unit time is smaller. The article suggests future work to calculate welding time at different conditions and locations for the estimation of the degree of bonding.

Aircraft engine nozzle guide vane surface temperature optimization

An optimization method based on the sensitivity of global and local geometric parameters is proposed to improve the cooling efficiency of E3 engine nozzle guide vane. For 29 geometric parameters that affect the vane maximum temperature in the cooling design, the sensitivity ranking of them is firstly obtained by the DOE method. Then the most influential parameters including the diameter or location of the film cooling hole are selected as the optimization variables to decrease the maximum surface temperature of the nozzle guide vane. On this basis, to further reduce the local temperature downstream the pressure side, a new duck-paw type film cooling hole is applied. The duck-paw type film cooling hole was produced with the adjoint method through identifying the sensitivity of the geometric boundary parameters of the film cooling holes. Compared to the cylindrical holes, the duck-paw shaped film cooling hole can greatly improve the cooling efficiency under the same conditions. The duck-paw type film cooling holes are applied to the last two rows of film cooling holes located on the pressure side of nozzle guide vane. Three-dimensional conjugate flow and heat transfer analysis results show that the maximum temperature of the optimized cooling structure vane is reduced by 39K, and the average temperature decreases by nearly 20K.

Enhanced heat transfer in a microchannel with pseudo-roughness induced by Onsager-Wien effect

A three-dimensional numerical analysis of flow and conjugate heat transfer in a microchannel in the presence of the electric-field-induced Onsager–Wien effect is performed. A novel design is proposed to induce a pseudo-roughness effect in the microchannel and thereby increasing the heat transfer. A series of thin plate electrode pairs are flushed along the bottom wall of the microchannel. The electric-field-enhanced dissociation of ions induces the Onsager–Wien effect, and generates small flow vortices near the bottom wall of the channel. These flow vortices with sharp local velocity gradients effectively disrupt the viscous and thermal boundary layers, and thus, introduce a pseudo-roughness effect. This disruption of the boundary layers improves the heat transfer between the channel wall and the working fluid. The thermal and hydraulic performances in the microchannel are quantified as a function of the flow Reynolds number Re and electric Reynolds number ReEL. In general, the performance factor PF is higher when the flow and electric Reynolds numbers are higher. However, the associated pressure drop penalty reduces the PFPF<1 in viscous-effect-dominated flows at Re=250. By contrast, the Onsager–Wien effect increases the PF to a maximum value of 1.26 in inertia-dominated flows at Re=1000 and ReEL=15. A significant heat transfer enhancement is realized, even at a low applied voltage of ∼1 kV. The results of this study indicate that the pseudo-roughness produced by the electric-field-induced Onsager–Wien effect can substantially enhance the heat transfer in a microchannel with a trivial amount of additional power consumption. Results presented in this study will serve as a benchmark to design microchannels with enhanced heat transfer by using active vortex generation based on Onsager-Wien effect.

Performance improvement of a heat sink with triangular slotted and interrupted fins: A computational study

The present study reports a three-dimensional computational analysis of free convection heat transfer from heat sinks with vertical fins mounted on a vertical base. The difference in the base and ambient temperature varies from 10 °C to 60 °C. This work proposes four novel geometrical modifications on the continuous rectangular fins intending to augment the heat transfer rate. These modifications include (a) providing triangular slots, (b) changing the value of minimum thickness at the neck of the slotted fin, (c) offsetting the position of the neck, and (d) interrupting the slotted fins. Thus, the work investigates the thermal performances of six different heat sink configurations concerning heat dissipation rate (Q), specific heat transfer rate (Q/m), average Nusselt number (Nu), the weight of the heat sink, and effectiveness. In all these cases, the heat sink volume remains the same. The current analysis shows that the heat sink with a single slot, with the neck at the base (ε=0) and having interruptions, dissipates the maximum heat (14.89% higher than the conventional continuous fin heat sink) with a weight reduction of 24.1%. The present study also proposes a correlation for the average Nusselt number in terms of relevant parameters, which has an accuracy of 6 %.

Physics-informed deep learning for three-dimensional transient heat transfer analysis of functionally graded materials

We present a physics-informed deep learning model for the transient heat transfer analysis of three-dimensional functionally graded materials (FGMs) employing a Runge–Kutta discrete time scheme. Firstly, the governing equation, associated boundary conditions and the initial condition for transient heat transfer analysis of FGMs with exponential material variations are presented. Then, the deep collocation method with the Runge–Kutta integration scheme for transient analysis is introduced. The prior physics that helps to generalize the physics-informed deep learning model is introduced by constraining the temperature variable with discrete time schemes and initial/boundary conditions. Further the fitted activation functions suitable for dynamic analysis are presented. Finally, we validate our approach through several numerical examples on FGMs with irregular shapes and a variety of boundary conditions. From numerical experiments, the predicted results with PIDL demonstrate well agreement with analytical solutions and other numerical methods in predicting of both temperature and flux distributions and can be adaptive to transient analysis of FGMs with different shapes, which can be the promising surrogate model in transient dynamic analysis.

Data-Driven Conjugate Heat Transfer Analysis of a Gas Turbine Vane

Cooling structures of gas turbine blades have become more complex to achieve a better cooling effect. Therefore, heat transfer analysis tools with higher accuracy and efficiency are required to verify the effectiveness of cooling designs and continuously improve the design. In this work, a data-driven method is combined with a decoupled conjugate heat transfer analysis. The analysis object is a typical air-cooled gas turbine first-stage vane with film cooling, impingement cooling, and pin-fin cooling. In addition, a conventional 3-D conjugate heat transfer simulation of the vane was executed for contrast. Results show that this method shortens the time of the heat transfer analysis process significantly and ensures accuracy. It proves that the data-driven method is effective for the evaluation of a modern gas turbine cooling design and is an improvement compared to the traditional three-dimensional heat transfer analysis method.

Transient three-dimensional radiative heat transfer analysis of a turbulent diffusion flame-with a focus on the effect of angular discretization scheme

Radiation modeling is a challenging and computational expensive task for turbulent combustion modeling of various fuels. Radiative intensity varies greatly in the angular direction due to turbulent fluctuations of temperature and species fields. A large number of rays are needed in the discrete ordinates method (DOM) or the finite volume method (FVM) to describe the angular variations. Determining the adequate number of rays is essential for the efficient modeling of radiation heat transfer. For this purpose, the effect of angular scheme on predicting the transient three-dimensional radiation heat transfer of a turbulent diffusion flame is investigated. Results show that a smaller number of rays produce strong ray effects and may generate significant errors for radiative heat flux prediction on surrounding walls, while the angular scheme has negligible influence on the radiative heat source. Transient radiative heat fluxes on different walls are also analyzed in detail, and they show completely different contours with unimodal frequency behavior. Recommendation for radiation modeling strategies is proposed for turbulent combustion modeling.

Direct numerical simulation of natural convection between an enclosure and multiple circular cylinders: An influence of horizontal arrangement of cylinders

The work involves a three-dimensional numerical analysis of the buoyancy-driven heat transfer in an enclosure having four heated cylinders for Rayleigh number, Ra = 10 4 -10 6 , and Prandtl number, Pr = 0.7. An in-house direct numerical simulation code, finite volume-based immersed boundary method incorporates the inner cylinder's virtual wall boundary and computes the governing transport equations. Heat and flow characteristics at different Ra and spacing between cylinders are discussed by using three-dimensional vortices and isotherms. The effect of heat and flow on three-dimensionality and heat transfer features are captured and reported. Limitations of two-dimensional simulation for capturing the physics of the problem and the importance of the three-dimensional analysis for the present study are highlighted.

Three-dimensional analysis of heat transfer and entropy production of jet impingement hybrid nanofluid cooling a porous media-filled heat sink

ABSTRACT In this study, a numerical assessment was carried out on heat transfer and entropy production of a three-dimensional heat sink exposed to an impinging jet, where the area between the heat sink fins is filled with aluminum foam saturated with A L 2 O 3 − C u / w a t e r hybrid nanofluid. Darcy-Brinkman-Forchheimer’s model with the local thermal equilibrium was considered. The effects of various important parameters such as Reynolds number 400 ≤ R e ≤ 1600 , volumetric concentrations 1 % ≤ φ h n f ≤ 5 % , Darcy number 10 − 5 ≤ D a ≤ 10 − 1 , porosity 0.1 ≤ ε ≤ 0.6 , and the diameter of nanoparticles 20 n m ≤ d n ≤ 60 n m on fluid flow, heat transfer, drop pressure, and entropy generation were investigated. A finite-volume approach with SIMPLE algorithm was employed to solve continuity, momentum, energy, and entropy equations with the help of the Ansys-Fluent 14.5 program. Regarding the validation of the computational approach used in this paper, a strong consensus has been reached with other findings available in the literature. Outcomes indicated that boosting Darcy number D a and porosity ε of the used porous material helps increase the heat exchange rate by up to 72 % and 40 % , respectively. On the other hand, we obtained a 7 % enhancement in the heat transmission rate when using nanoparticles with a diameter d n of 20 n m instead of nanoparticles with a diameter of 60 nm. Furthermore, it has been demonstrated that boosting D a , ε and d n minimize drop pressure by various proportions. Based on the entropy production analysis, it is possible to infer that entropy due to heat transfer is more dominant than other types of entropy with all parameters analyzed. Also, it can be deducted that as the values of ε and D a grow and the values of d n decline, the total entropy production ( S p , t ) rises up to 55 % , 75 % and 3 % , respectively. The same findings were reached with the Bejan number B e , but different percentages. Finally, three correlations of Nusselt number with several variables with an error not exceeding 15 % have been suggested. The proposed study’s findings may be utilized to define appropriate process factors for improved thermodynamic efficiency of heat sinks using hybrid nanofluids and porous media.

Three-dimensional numerical analysis of flow and heat transfer of bi-directional stretched nanofluid film exposed to an exponential heat generation using modified Buongiorno model

The heat transfer characteristics of copper/water nanofluid flow over a bi-directional stretched film are theoretically studied. The used mathematical model accounts for nanofluid effective dynamic viscosity and thermal conductivity. The model of the current study utilizes the modified Buongiorno model to scrutinize the effect of haphazard motion, nanoparticles' thermo-migration, and effective nanofluid properties. 3D flow is driven by having the nanofluid film elongation in two directions. The thermal analysis of the problem considers the nonlinear internal heat source and Newton heating conditions. In modeling the problem, the Prandtl boundary layer approximations are employed. Moreover, the nonlinear problem set of governing equations for investigating the transport of water conveying copper nanoparticles was non-dimensionalized before being treated numerically. The current parametric study investigates the impact of governing parameters on nanoparticles velocities, temperature, and concentration distributions. The presence of copper nanoparticles leads to a higher nanofluid temperature upon heating. The temperature enhances with the nanoparticles Brownian movement and thermo-migration aspects. Furthermore, involving a heat source phenomenon augments the magnitude of the heat transfer rate. Moreover, the velocity ratio factor exhibits decreasing behavior for x-component velocity and increasing behavior for y-component velocity. In conclusion, the study results proved that for larger values of Nb and Nt the temperature is higher. In addition, it is clear from the investigations that the Lewis number and Brownian motion factor decline the nanoparticle concentration field.

Numerical Simulations of a Postulated Methanol Pool Fire Scenario in a Ventilated Enclosure Using a Coupled FVM-FEM Approach

Numerical investigations have been carried out for a postulated enclosure fire scenario instigated due to methanol pool ignition in a chemical cleaning facility. The pool fire under consideration is radiation-dominated and poses a risk to the nearby objects if appropriate safety requirements are not met. The objective of the current study was to numerically evaluate the postulated fire scenario and provide safety recommendations to prevent/minimize the hazard. To do this, the fire scenario was first modeled using the finite volume method (FVM) based solver to predict the fire characteristics and the resulting changes inside the enclosure. The FDS predicted temperatures were then used as input boundary conditions to conduct a three-dimensional heat transfer analysis using the finite element method (FEM). The coupled FVM–FEM simulation approach enabled detailed three-dimensional conjugate heat transfer analysis. The proposed FVM–FEM coupled approach to analyze the fire dynamics and heat transfer will be helpful to safety engineers in carrying out a more robust and reliable fire risk assessment.

A three-dimensional analysis of heat transfer based on mesoscopic method in nanoscale Si-MOSFET and Gr-FET

Thermal diffusion in the metal oxide semiconductor field effect transistor has received increased attention across a number of disciplines in recent years. This paper studies a three-dimensional (3D) heat conduction process in a MOSFET device based on Silicon (Si) and Graphene (Gr) materials. In order to perform analyses, a mesoscopic method was applied, based on lattice Boltzmann method (LBM) with D3Q15 model accounting the specularity parameter effects. The present study found that the maximal temperature is spotted at the interface whose value is 308.7 ​K and 324.5 ​K for the Gr-FET and Si-MOSFET, respectively, at t ​= ​30 ps and p ​= ​0.5. Also, the obtained results indicate that the specularity parameter has an important role in the phonon heat transport and thus in reducing the temperature in the nanotransistors. The preference of graphene device and the unique properties of graphene material make this material a good candidate for future nanoelectronics systems generation.

Effects of Thin Film Heat Spreader on Hot Spots Mitigation in Heat Sinks

Abstract The effects of graphene platelets and diamond-based thin film heat spreaders on maximum temperature of integrated electronic circuits were investigated. A fully three-dimensional conjugate heat transfer analysis was performed to investigate the effects of thin film material and thickness on the temperature of a hot spot and temperature uniformity on the heated surface of the integrated circuit when subjected to forced convective cooling. Two different materials, diamond and graphene, were simulated as materials for thin films. The thin film heat spreaders were applied to the top wall of an array of micro pin fins having circular cross sections. The integrated circuit with a 4 × 3 mm footprint featured a 0.5 × 0.5 mm hot spot located on the top wall, which was also exposed to a uniform background heat flux of 500 W cm−2. A hot spot uniform heat flux of magnitude 2000 W cm−2 was centrally situated on the top surface over a small area of 0.5 × 0.5 mm. Both isotropic and anisotropic properties of the thin film heat spreaders made of graphene platelets and diamond were computationally analyzed. The conjugate heat transfer analysis also incorporated thermal contact resistance between the thin film and the silicon substrate. It was found that isotropic thin film heat spreaders significantly reduce the hot spot temperature and increase temperature uniformity, allowing for increased thermal loads. Furthermore, it was found that thickness of the thin film heat spreader does not have to be greater than a few tens of microns.

Multi-objective optimization of multi-stage heat sink of electric aircraft using three-dimensional thermal network analysis

The efficiency, reliability, and safety of aircraft have been improved by substituting hydraulic and mechanical systems with electric systems. Furthermore, in future electric aircraft, where fan-driving engines are partially replaced by electric motors, solving the thermal management of heat generation from the motor-controlling power-devices will become a crucial problem. In this study, three-dimensional steady thermal network analysis (TNA) was carried out to analyze the temperature field in a heat sink, for motor-controller air cooling, which is expected to be used for the future electric aircraft. The numerical procedure used was verified by comparing the results of TNA with those of three-dimensional fluid-solid conjugate heat transfer analysis using finite volume method. After the verification, TNA was carried out for an aircraft flight scenario, where the optimum geometry of the heat sink was investigated, minimizing the following three objective functions: the pressure loss of air flow through the heat sink, the maximum local wall temperature of the heat sink at the surface of motor controller, and the weight of the heat sink. In this multi-objective optimization, the design of experiments technique was used to decide the space-filling points for the six design parameters. The three objective functions at each sampling point were calculated using TNA. A response surface was created for each objective function. A multi-objective optimization on the response surfaces, using a genetic algorithm, was iteratively carried out to find the Pareto optimal solutions for the air-cooled multi-stage heat sink. From the results of the Pareto optimal solutions, the effects of the design parameters on the objective functions were discussed. In addition, multiple regression analysis was performed for quantitative evaluation of the results of the Pareto optimal solutions, and the dominant design parameters for each objective function were identified.

Model order reduction of three-dimensional transient heat transfer analysis to one-dimensional by using Krylov-subspace concerning cooling effect of air

In semiconductors packages, heat generation density is increasing due to miniaturization. Since heat generation is caused by voltage input at the packages, electronic components are usually cooled by air. In recent years, electrification is widely spread among many engineering products like motor vehicles, and the amount of semiconductors packages installed in those products as well. To make the electronic components more densely installed, co-simulation of heat transfer analysis and electrical circuits is needed at designing products. In this paper, by using the Krylov-subspace model order reduction method, the accuracy of one-dimensional heat transfer analysis model concerning cooling effect of air is evaluated. By using the method, co-simulated with electrical circuits is possible.

Three-dimensional thermal analysis of multidirectional (perfect/porous) functionally graded plate under in-plane heat flux

The present work is based on transient three-dimensional heat transfer analysis of multidirectional functionally graded material (FGM). Here, three dimensional (3D) FGM structure graded in multiple directions is considered. The extended Voigt’s micromechanical scheme along with multivariable power law is used to evaluate effective thermal properties. The imperfection within the material is incorporated by considering symmetric even porosity. Here, in-plane heat flux is applied at the top and right edges of the plate. The transient heat transfer response of a multidirectional functionally graded plate is computed using commercially available ANSYS APDL software. The elemental space is discretised by coupled field hexahedral element SOLID 226. The mesh refinement and verification tests are conducted to demonstrate the accuracy and robustness of the model. Finally, an inclusive report is presented to exemplify the effect of heterogeneity and imperfection of multidirectional functionally graded (metal/ceramic) panels through numerous numerical illustrations.

Prediction of residual stresses in high-strength S690 cold-formed square hollow sections using integrated numerical simulations

In general, residual stresses are induced in structural members during various fabrication processes, such as welding, bending, press-braking, folding, flame cutting and punching. The presence of those residual stresses in cold-formed square hollow sections (CFSHS) primarily caused by i) transverse bending (or cold-forming), and ii) longitudinal welding, is widely considered to have modified both initial stress and strain conditions of these steel members significantly. Hence, these residual stresses are widely considered to have significant adverse effects onto the structural performance of these CFSHS under various actions.In order to examine and quantify both magnitudes and distributions of these residual stresses in S690 CFSHS, an investigation is undertaken to measure residual stresses due to transverse bending and longitudinal welding. Moreover, an approach of integrated numerical simulations is adopted in which a total of three co-ordinated finite element models are established together with various element types and block data transfers to generate compatible meshes for the following three analyses: i) two-dimensional plane-strain bending analyses with large plastic deformations and springback, ii) three-dimensional heat transfer analyses for transient temperature distributions under a heat source, and iii) three-dimensional thermomechanical analyses for welding-induced residual stresses.The predicted results of these three analyses have been carefully calibrated against various experimental data, such as surface temperatures during welding, and residual stresses and strains after welding. Good comparisons between the measured and the predicted data of these S690 CFSHS are demonstrated. The complete residual stress distributions within typical S690 CFSHS due to transverse bending and longitudinal welding are illustrated in three-dimensional plots while simplified residual stress patterns of these sections with specific values and parameters are also provided for subsequent advanced structural analyses and design.The proposed modelling technique for transverse bending and longitudinal welding with compatible meshes of two-dimensional and three-dimensional models with various element types and block data transfers is demonstrated to be highly effective. The technique is readily applicable to simulate residual stresses of all fabricated sections manufactured with transverse bending and longitudinal welding, and, thus, the simulated residual stresses can be employed in subsequent structural analyses of all fabricated members.