Numerical Thermal Model Research Articles

Thermal-biomechanical manikin applied in turbulent airflow and vibration systems in transient conditions

This paper applied a thermal-biomechanical manikin in turbulent airflow and vibration systems in transient conditions. This numerical model evaluated the thermal and biomechanical components to which the human body is subjected. The first one considers the first-order equations systems based on the thermal numerical model, while the second one considers the second-order equations systems based on the vibration numerical model. This second-order equations system is converted into a first-order equation system. The resolution of the thermal and biomechanical numerical models is made through the Runge-Kutta-Fehlberg method with error control. The thermal numerical model is used in the study of the steady-state and transient conditions when the skin is subjected to mean and turbulent airflow. The biomechanical numerical model is used in the study of the human body vibrations applied to the feet, that a standing person is subjected, using periodical and random vibration signals of the floor. The thermal analysis shows that with an air fluctuation velocity, the skin temperature reduces slightly. The amplitude of the vibration in the lower body section is higher than in the upper body section. The introduction of the randomised vibration, in the periodical vibration, the human body vibration increases the fluctuation level.

Numerical investigation of surface and volume thermal imaging of nickel-graphene foam sheets by finite element method

The detailed theoretical analysis of heat equations is applied to Nickel foam specimens with various pore-size coated graphene thin film of 200 nm thickness under laser excitation. 2D and 3D thermal numerical models were proposed by applying the finite element method. To explain the proposed numerical model, the influence of discretization parameters and the heat diffusion length were studied. The proposed model accurately predicts the thermal spreading in the specimens. The numerical model showed the sensitivity of the model for the structure variation to achieve an accurate thermal imaging when the used laser is of radius value is within of specimen pore size and modulated at low frequency.

3D CFD modelling and experimental validation of conjugate heat transfer in wheel hub motors in micro-mobility vehicles

An experimental and 3D CFD (computational fluid dynamics) based numerical investigation of the in-wheel hub internal permanent magnet synchronous machine (IPMSM) has been carried out to understand the thermal dynamics associated with the power loss within the motor. This study can serve as a clear case baseline for the future development of thermal management systems in micro-powertrain systems. Experimental results show that the maximum winding temperature of 65.9 °C has been observed on the end-windings (EW) for an operating condition of 500 rpm (base speed), 4.5 Nm. Stretching beyond this operating point would increase the winding temperature beyond 65.9 °C, potentially damaging the winding insulation’s capabilities and magnetic properties of the permanent magnets (PMs) and adversely affecting the performance of the wheel motors. The hysteresis and eddy current loss coefficients for the stator core have been identified as 14.5×10-2 and 1.6×10-4 respectively. The experimentally identified losses have been distributed among the motor components for the development of the numerical thermal model in commercial CFD software Star-CCM+™. The CHT (conjugate heat transfer) thermal paths show that 68.4 % and 31.4 % of the total power loss from the stator components undergo convection and conduction, respectively. This indicates that convection heat transfer dominates on the in-wheel hub IPMSM motor topology. Almost 34.5 % of the heat loss is transferred radially through the air gap to the Permanent Magnets. When the air gap size decreased by 80 %, the amount of convection heat transfer through the air gap increased by a factor of 2 (69 %) and reduced the winding temperature by 13 % (57.3 °C).

Interfacial inhomogeneous plastic deformation during rotary friction welding of dissimilar AA2219-SS321 joint combination with AA6061 interlayer

This research investigates the inherent radial non-uniformity within the rotary friction welding process, particularly concerning microstructure attributes like grain size, grain boundaries, misorientation angles, and interlayer presence along the radial axis. SS321-AA2219 rotary friction welding was carried out with and without an AA6061 interlayer. The numerical thermal model suggests increase in temperatures from the center to the periphery, due to non-uniform heat generation. Also, dissimilar material across the interface resulted in an asymmetric temperature profile along axial direction. Plastic deformation on the Aluminum side suggests dynamic recrystallization and grain refinement, whereas pronounced low-angle grain boundary (LAGB) formation near the SS side interface validates dynamic recovery. A radial non-uniformity in microstructure is observed, with metrics such as average grain size, LAGB fraction, and misorientation showing an increase from the center towards the periphery. The insertion of an interlayer alters process dynamics, manifesting in reduced temperatures and heightened forces, resulting in a more consolidated joint by enhancing the strength by 31 %. Interdiffusion of elements across the interface formed Fe-Al intermetallic compounds (IMC) confirmed with X ray diffraction. Fractography analysis elucidates the presence of rubbing marks and facet surfaces in interlayer-less joints, while joints with interlayer display sticking and dimples.

An enhanced analytical and numerical thermal model of frictional clutch system using functionally graded materials

Abstract When a component was built from a functionally graded material (FGM), the temperature of contact was determined using an analytical model (FGM). The analytical solution is applied using the concept of equivalent properties. In order to fully examine the dynamic of the equivalent property principle, a numerical analysis was done. The FGM (silicon carbide and aluminum) friction liner was used. It focuses on a few characteristics that have an impact, such as load, velocity, friction material type, and slip time, which appear in dimensionless form. The results show that for loads and velocities, the ratio of the rate of dissipation to the rate of generation of heat transfer is one, whereas the behavior differs for friction material and slip time. Furthermore, this study’s chosen FGM exhibits superior thermal behavior compared to Al and Sic, bolstering its viability as a friction liner in the clutch system.

Quantifying Downward Radiative Fluxes From Nighttime Martian Water Ice Clouds: Applications to Thermal Modeling of Surface Temperatures

AbstractDuring the first part of the Martian year (Ls = 50°–160°) a phenomenon occurs on Mars in the tropical and equatorial regions (30°N–10°S) known as the Aphelion Cloud Belt (ACB). During this time, there is prominent formation and diurnal variability of water ice clouds. Limited empirical attempts have been made to characterize the magnitude of radiative flux contributions from clouds to nighttime surface temperatures. In this work, we estimated the infrared (IR) flux contribution at ground level from the clouds by comparing surface temperature data from the Thermal Emission Spectrometer (TES) onboard Mars Global Surveyor (MGS) to calculated temperatures using the KRC numerical thermal model. We then generated a database of IR fluxes at the ground contributed by clouds spanning the entirety of the tropical and equatorial regions as a function of Solar Longitude (Ls) on Mars in one degree bins. We compared results with work presented elsewhere in the literature and found good agreement. We also found that temporal trends followed the general established range for the ACB but our analysis demonstrated the peak ACB values occurred at later times (Ls = 100°–140°) than previously published data sets using water ice opacity retrievals (Ls = 90°–110°). This database may be used in comparison to calculated Global Climate Model fluxes as well as a lookup tool for more precise estimation of surface and subsurface thermal environments in these regions.

Reynolds number based optimization on liquid cooling system for permanent magnet synchronous motor of electric vehicle

The electric motor thermal management system (TMS) is a pivotal unit for electric vehicles (EVs). To study the factors affecting cooling performance and cooling efficiency of spiral housing water jacket (HWJ), simulations were carried out on a 150 kW jacked-cooled permanent magnet synchronous motor (PMSM) with ethylene glycol & water (EGW) as coolant. The coupling between channel numbers (N) and coolant flow rate (Q) on winding average temperature (T) and pressure drop (P) were investigated focusing on the Reynolds number (Re) via analytical and numerical thermal models. The results indicated that the cooling performance was nearly the same for coolant under fully turbulent. Both the cooling performance and cooling efficiency were not conducive when N > 8, and meanwhile, N < 6 also hindered the heat extraction. Resorting to the investigation, a Re-based multi-objective optimization algorithm was put forward. Compared the optimized jacket N6Q12 (denoting 6 channels with 12 L per minute flow rate) with the sub-optimized N12Q6 at the same Re, winding average temperature T was found 6.5 deg C lower, and pressure drop P was reduced by up to 71.6 %.

Experimental‐Assisted Approach to Develop a Numerical Model for Simulating the Reaction Propagation in Reactive Multilayers

One outstanding feature of self‐propagating reactions is their ability to release heat of reaction over both temporal and spatial scales, enabling the sustained progression of the reaction after a local ignition. They propagate in the form of a continuous reaction front through the mixture of the starting materials. Previous research on reactive materials has predominantly focused on unraveling the microstructure property relationships influencing released energy in reacting multilayers. This involved considering coupled differential equations, including the heat conduction equation and Fick's law. In this study, the introduction of a purely thermal numerical macroscale model is made, incorporating two states of material properties that differentiate between the thermal characteristics before and after phase formation. The homogenization of material properties before the phase formation is accomplished through the consideration of directional‐temperature‐dependent thermal conductivity and temperature‐dependent‐specific heat capacity. The energy‐release function is derived using experimental data for the reaction velocity depending on bilayer thickness. This model allows for the exploration of reaction motion and temperature profiles, achieving qualitative conformity with experimental measurements for freestanding foil, and necessitating reasonable computational effort.

Thermal reaction of firebrand accumulation in construction materials

This paper presents research concerning the thermal firebrand reaction due to its accumulation in specimens of current construction materials commonly applied to the exterior of dwellings in southern Europe. An extensive fire experimental campaign is undertaken, in which firebrands are deposited on the plane surfaces of the material specimens and the temperature is measured on the top and bottom construction specimen surfaces. The materials chosen for this work are currently applied to either the roof, exterior walls and windows, and were recommended as either fire resistance or good behaviour for high temperatures. It will be possible to verify their firebrand reaction, more precisely, the type of ignition, the smoke, droplet production, and even their insulation capabilities. It is also tested for the efficiency of a metal mesh to prevent the entrance of firebrands into the air vents of façades and chimneys in dwellings. A thermal numerical model is also used to study the efficiency of the insulation properties of some construction materials for firebrand deposition by measuring the level of heat flux circulation during the full time analysis.

Quasi-3D Numerical Thermal Modelling of Electronic Systems in Package

The technology of three-dimensional (3D) packaging currently provides an increase in the efficiency of various electronic systems, bringing the volume of the package and heat dissipation into proper correlation. For many types of modern 3D packages the electro-thermal properties were not yet investigated. So the thermal modelling of 3D system in package (SiP) constructions became obliged for package designers. The commercial universal fully-3D simulators are not effective for practical engineers because of the complexity in using. The problem-oriented method called “Quasi-3D”was proposed and software tool Quasi-3D-Overheatwas developed to save the pre- and post-processing labour and CPU time. Numerical thermal modelling for different types of modern SiP structures: bridge-chip; p2 Pack; chip stack with TSV; embedded silicon fan-out was carried out and compared with measured temperatures. Simulation error was not more than 10–15%.

Passive cooling of two phase change materials installed in series

Portable transport passive-type refrigeration systems keep products in specific temperature ranges for several days without electricity. Phase change material (PCM) is often combined with insulation panels to form an insulated box.This paper presents the effect of utilizing multiple PCMs with different melting temperatures and heat capacities on product storage and product temperature abuse. Two PCMs with different transition temperatures were thermally coupled, forming a cascade passive refrigeration system. The primary PCM (water) had the largest storage capacity. At the same time, the secondary PCM acted as a thermal buffer to prevent the temperature abuse, namely freezing, of the product carried inside the box.Modifications were made to an existing state-of-the-art refrigerated transport box to install PCM-based passive refrigeration systems that extended the refrigeration performance while maintaining the same envelope and interior volume. Experiments were conducted at ambient temperatures of 20 °C, 35 °C, and 42 °C while the temperature inside the container remained below 6 ℃ for several days. Effective thermal resistance values for the insulated refrigerated transport box and between the PCMs and the product inside the box were determined experimentally. A semiempirical numerical thermal model was developed to predict the duration, and the average error between the predicted duration and the data was 9.7 %. Correlations from the literature were also compared to estimate the transport box performance for various configurations, and the results indicated that such correlations estimated the storage duration satisfactorily only for simple configurations of the insulated box.

Uncertainty assessment method for thermal runaway propagation of lithium-ion battery pack

To some extent, the thermal runaway issue pertaining to lithium-ion battery still present challenging problems, to put the safety-related issue under control in high-power and high-energy applications. One of these challenging issues relates to the underpinning stochastic uncertainties associated with thermal runaway propagation. Therefore, this study proposes a methodology to evaluate the uncertainty of thermal runaway propagation in Li-ion battery modules. Firstly, a numerical thermal runaway propagation model is developed for phase change material-based thermal management system and verified by experiments. Subsequently, the Adaptive Kriging High-dimensional model representation method is employed to construct a surrogate model, followed by global sensitivity analysis to evaluate the impact of six different influencing factors on thermal runaway propagation. Finally, the random fluctuation of the critical factors affecting thermal runaway propagation is integrated to analyze and quantify the uncertainty. The results show that the state of charge, the thermal conductivity of phase change material, and inter-cell spacing are critical factors affecting thermal runaway propagation. With the system parameters proposed in this paper, the critical state of charge range that significantly impacts the uncertainty of thermal runaway propagation is approximately 40% to 55%. The analysis of the propagation results and the cell temperature indicates that the highest level of uncertainty occurs at around 45% state of charge. In this case, the thermal runaway propagation is significantly impacted by changes in key factors, and the battery temperature exhibits high fluctuation levels. Furthermore, although there is a 59% likelihood of no propagation, the potential damage to all batteries becomes exceedingly significant once thermal runaway propagation occurs. The method proposed in this study effectively evaluates the uncertainty of thermal runaway propagation in battery systems. It identifies the causes of the uncertainty, which can be used to implement effective suppression measures to enhance safety.

Constraining Changes in Surface Dust Thickness on Mars Using Diurnal Surface Temperature Observations From EMIRS

AbstractDiurnal surface temperature data collected from the Emirates Mars Infrared Spectrometer have been used to characterize dust redistribution on Mars following a regional dust storm in January 2022. A comparative temporal analysis is conducted pre‐ and post‐dust storm to estimate net changes in surface dust thickness at Syrtis Major, Isidis Planitia, Tyrrhena Terra, Hesperian Planum, and Elysium Planitia. By leveraging data from a numerical thermal model, we relate differences in observed surface temperature to changes in the thickness of the surface dust layer. We describe the methodology for estimating net changes in surface dust thickness, including a description of the thermophysical model employed, provide a sensitivity analysis with respect to local time and surface properties, and discuss the implications of our findings. Surface temperature differences suggest both dust deposition and removal, with some regions experiencing a net removal as high as 340 μm, while other regions experienced net deposition reaching up to 120 μm. Visible‐wavelength imagery from the Emirates Exploration Imager, which is more sensitive to changes in surface dust distribution, is incorporated in our analysis to provide additional context. When the area of each region of interest is accounted for, we find that the dust storm had the potential to remove and/or deposit more than 1.51 × 109 and 1.20 × 109 kg, respectively, suggesting that dust reservoirs are capable of transporting vast quantities of dust over short timescales.

A macroscale heat transfer analysis of the build chamber in a commercial electron beam powder bed fusion (EB-PBF) additive manufacturing system during component fabrication

In this research, a 3D numerical thermal cavity radiation model was developed to predict the evolution of the macroscale thermal field within the build chamber of a commercial EB-PBF system. The model was applied to predict the evolution of the thermal field in a component during fabrication. A combination of quantitative and qualitative data extracted from an ARCAM Q20Plus machine was used to validate the model. The results indicate that the portion of heat transferred to the inner Heat Shield via cavity radiation was a strong function of the Start Plate’s temperature, reaching 88% of the total heat input at a peak temperature of ∼725 °C. Once validated, the thermal model was used to analyse heat transport within the build chamber during the fabrication of a component. The outcomes revealed variability in temperature within the hexagonal base, up to 118 °C, and the powder bed below the platform of 107 °C. Moreover, substantial temperature variations exceeding 200 °C were identified within the component, specifically between the hexagonal base and the platform.

Is the most recently active volcano in the Carpathian-Pannonian Region capable of further eruptions?

Debate on the future eruptive capability of Ciomadul (Csomád) volcano in the East Carpathians, Romania, has recently gained a new impetus and prompted wide media attention. A tentative of numerical thermal modeling claimed that the amount of magma currently present beneath the volcano is of 20–58 km3 in volume. However, these results can be challenged because the model applied considers unrealistic initial conditions and input parameters related to crustal structure and radiogenic heat production in the local area. Instead, we propose a geologically more plausible alternative hypothesis invoking the presence of relatively small amounts of fluids percolating from the upper mantle towards the surface which may explain the conducting anomalies pointed out beneath the volcano.

Comparative response of tiled finishes and bonded fire resistive coatings for normal weight concrete tunnel liners under high-intensity one-sided heating

Experimental tests were performed to examine the relative fire resistance provided by several bonded coatings for normal weight concrete (NWC) panels that emulate a tunnel liner: ceramic tiling on mortar, spray-applied fire resistive material (SFRM), and intumescent paint (IP). Sixteen panel specimens (150-mm [6-in.] thick, 457-mm [18-in.] wide, and 610-mm [24-in.] tall) were subjected to one-sided heating using a gas-fired radiant panel, which can apply heat flux at intensities similar to hydrocarbon fuel fire. All specimens were cast from a single batch of NWC (approx. 40 MPa compressive strength) with a single curtain of steel reinforcing bars at 38-mm (1.5-in.) cover to the heated face. All specimens were vertically loaded to a service level of compressive uniaxial stress (approx. 14% of ambient specified compressive strength), which remained relatively constant during each test. Four bare concrete panel specimens were tested as a control group, and a ceramic tile finish was installed on six specimens in accordance with a current state department of transportation specification. The other six specimens were coated with fire resistive material (three each with SFRM and IP) at thicknesses corresponding to a 1-hr fire resistance rating per manufacturer specifications. Thermally-induced explosive concrete spalling was observed in 3 of 4 control specimens, 4 of 6 tiled specimens, and none of the 6 SFRM/IP coated specimens. The tiled finishes delaminated and eventually became fully detached from the concrete surface, thus providing negligible fire resistance compared to that provided by the SFRM or IP. Temperature time histories recorded within the outer 25-mm (1.0-in.) thickness of the heated concrete were used to evaluate the relative thermal resistance of each surface finish, as well as to validate a simplified thermal numerical model used for a brief parametric study. Post-fire removal of the surface finishes is also demonstrated.

Numerical investigation of using a field of shallow boreholes with latent heat storage and solar injection in cold climates

Modeling heat transfer within a field of boreholes (borefield) is essential to correctly assess the long-term performance of a solar-assisted ground source heat pump, which uses the ground to store the injected solar thermal heat. A novel model was developed that uses a hybrid approach, combining a numerical thermal resistance and capacitance model for the borehole with an analytical g-function for the ground. The developed model has the capability to simulate the long-term performance of a borefield with the phase change that is occurring in the water content of the grout. The model is used to assess the benefit of phase change within a saturated sand mixture, acting as filling material in the borehole and thermal energy storage for solar heat injected in the ground. The injected solar heat compensates the ground thermal load imbalance caused by substantially higher heating demand than cooling demand in cold climate regions. Through long-term hourly simulations, results show that water content in the borehole helps keep the temperature constant at the vicinity of the borehole, particularly during peak hours, and that solar injection permits the design of a more compact borefield by concentrating the stored heat in the vicinity of the boreholes.

Numerical simulation of inductive heating in thermoplastic unidirectional cross-ply laminates

Thermoplastic Composites can be re-melted allowing them to be joined via welding. This is an attractive alternative to conventional methods that are used to join thermoset composite parts such as mechanical fastening and adhesive bonding. In this work the inductive heating of uni-directional (UD) plies of thermoplastic carbon fiber reinforced polymer (CFRP) laminates is investigated. The focus is on developing a numerical electromagnetic and thermal simulation model that captures the main processes involved in eddy current generation and heat generation, in particular in the interface areas of the UD plies. A measurement technique has been developed to obtain the electric properties of the ply material. Furthermore, to support the modelling of both the induction heating equipment and work piece a field measurement of the magnetic field surrounding the coil and work piece has been developed. Inductive heating experiments were carried out on several thick composite laminate plates with different ply lay-ups to compare and validate the electro-magnetic-thermal simulation model. The measured surface temperatures were compared with the results from the simulation model. The results of this work can be used to support the design of UD-ply laminates to improve their ability to be welded via inductive heating. In addition, the results of this work can be used to assist in pre-determining induction welding equipment settings and heating times.

HERMES CubeSat Payload Thermal Balance Test and Comparison with Finite Volume Thermal Model

Scientific payloads onboard CubeSats usually have complex geometries and occasionally narrower allowed temperature ranges with respect to the rest of the spacecraft. In these cases, the capability to correctly predict the thermal behaviour of the payload once in orbit is mandatory. To achieve this ability, a thermal balance test is required to correctly identify the thermal model of the payload. The test consists in the application of different external thermal boundary conditions together with the addition of heat dissipation to simulate the thermal load produced by active electronics during operation. Those experimental data are fundamental to validate the numerical thermal model and make its predictions reliable. This paper presents the configuration and procedures of the thermal balance test performed on the Demonstration Model of the payload to be embarked on each satellite of the HERMES constellation. The test data is compared with the results of a finite volume thermal model of the payload, proving the application of this method to be reliable for space thermal analyses. The obtained test results show the temperature jumps caused by the heat dissipation applied to active components. A weak correlation between the payload interface and internal equipment has been observed, thus proving that the payload is almost decoupled from the Service Module temperature variations. Based on test outcomes, some modifications in the payload design have been implemented, with the aim to lower the operative temperature on critical, temperature-sensitive equipment.

Algorithm-driven optimization of lithium-ion battery thermal modeling

Detailed modeling of battery thermal behaviour has high computational demand due to the presence of multi-scale and multi-physics phenomena. For battery module/pack level simulation, a simple and accurate battery heat generation estimation is urgently required. This paper investigates the optimization of thermal numerical modeling for cylindrical 21,700 lithium-ion batteries with a nominal capacity of 5 Ah. A 3-dimensional battery model was built in the Multiphysics simulation software, COMSOL. The heat source of the model adopts a commonly used heat generation model incorporating irreversible and reversible heat. Correction factors, as a function of the state of charge, were introduced to the calculation of irreversible heat item. The Particle Swarm Optimization (PSO) algorithm, written in MATLAB, was coupled with the COMSOL numerical model to minimize the prediction error by varying correction factors. Battery surface temperature data under the continuous discharge tests (0.5C–3.5C) and dynamic loads were experimentally obtained and used to validate the model. The simulation results of the unoptimized model showed a discrepancy of up to 5 °C with the experimental data. After optimization, the prediction error was reduced to less than 0.5 °C on average. The optimized model was applied to predict the thermal behaviour of a battery module (16 aged cells) using oil-based immersion cooling. The pristine battery module with coolant flow velocities of 0.01 m/s was chosen as the baseline. The results indicate that the aged battery modules with internal resistance of 50 mΩ and 75 mΩ require coolant flow velocities of 0.05 m/s and 0.12 m/s, respectively, to achieve the baseline temperature. The study highlights a high-precision and low-computational cost approach for heat generation calculation of lithium-ion batteries is provided, which contributes to the development of battery thermal management systems.