Transient Thermal Simulation Research Articles

Research on Thermal Simulation Improving the Components’ Soldering Quality in Electronic Module

This paper describes a method that could exactly optimize and improve the soldering quality of the electronic module. Firstly, a sample of temperature measurement was proposed. Through the temperature rising, heat preservation, temperature rising, soldering and cooling, the sensors could able to accurately and sensibly record and present each temperature data which set on the sample. At the same time the soldering cure was also measured. Secondly, through the analysis and research of vapor-phase soldering technology based on condensation theory, referring to the relevant modeling and simulation analysis methods, a thermal simulation model was established (size: 13.7mm × 45mm × 16.5mm). The ANSYS was used in this thermal simulation and the measured temperature curve, material parameters and other boundary conditions were loaded. The transient thermal simulation method was adopted and the temperature variation on sample during vapor-phase soldering was simulated. A maximum error of 2.67°C between simulation and measurement results, error rate is only 1.2%. Therefore, this simulation method can effectively perform the change of temperature with time in the real vapor-phase soldering process. After that, the optimized vapor-phase soldering temperature curve and soldering process parameters were used to carry out the vacuum vapor-phase soldering test in the assembly. The dimensions, materials and other parameters of the components used in the test were completely consistent with the simulation model. Two Sn63Pb37 solder rings were used in the test and the vacuum was also carried out. Through the X-ray inspection results, the optimized vapor phase soldering temperature curve has no soldering voids and well soldering consistency, which meets the requirements of high-quality soldering and improves the assembly quality of electronic products.

Efficient transient thermal simulation with Laguerre-based finite-element method and domain decomposition

In this article, a Laguerre-based finite-element method (LBFEM) combined with domain decomposition is proposed for large-scale transient thermal simulation. The unconditionally stable marching-on-in-order scheme is obtained using the weighted Laguerre polynomials and Galerkin testing procedure to eliminate the time variable of the temperature field. An effective data filtering method is utilized to reduce the number of basis functions and improve the efficiency of simulation. To handle the large-scale problems, a domain decomposition scheme named finite element tearing and interconnecting (FETI) is applied. The entire computational domain can be divided into a series of small-scale subdomains to reduce the computational resources. Numerical results are presented to demonstrate the accuracy and efficiency of the proposed method.

The effects of incident solar radiation on the collector efficiency using coolant hybrid nanofluid via simulation of solar tower system with the parallel heat exchangers

BackgroundGreen energy market will contribute to three fifth of the world's electric power generation and two fifths of the fuel market by the mid of the present century. The annual transient thermal performance simulation of a solar tower power plant with parallel heat exchanger is performed. MethodThe heat transfer process for the two tanks is performed in which a heat loss from the tanks is considered. Two-phase heat transfer analysis at the heat exchanger is studied. The hourly reflected radiation is determined from DNI data. Nanofluid coolants are used for the flat-plate solar collector. FindingsIt is found that the temperature profile of the melted salt at the exit of the receiver fluctuates with higher frequency. The appropriate performance of the solar collector using SiO2 dispersed nanoparticles in water, is also provided. GO-DW mono nanofluid shows a better performance; however, GO/SiO2-DW hybrid nanofluid has more cost-efficiency.

PACT: An Extensible Parallel Thermal Simulator for Emerging Integration and Cooling Technologies

Thermal analysis is an essential step that enables co-design of the computing system (i.e., integrated circuits and computer architectures) with the cooling system (e.g., heat sink). Existing thermal simulation tools are limited by several major challenges that prevent them from providing fast solutions to large problem sizes that are necessary to conduct standard-cell level thermal analysis or to evaluate new technologies or large chips. To overcome these challenges, we introduce a SPICE-based parallel compact thermal simulator (PACT) that achieves fast and accurate, standard cell to architecture-level, steady-state, and transient parallel thermal simulations. PACT utilizes the advantages of multicore processing (OpenMPI) and includes several solvers to speed up both steady-state and transient simulations. PACT can be easily extended to model a variety of emerging integration and cooling technologies by simply modifying the thermal netlist. In addition, PACT can also be used with popular architecture-level performance and power simulators. In comparison to a state-of-the-art finite-element method (FEM)-based simulator (COMSOL), PACT has a maximum error of 2.77% and 3.28% for steady-state and transient thermal simulations, respectively. Compared to a popular compact thermal simulator, HotSpot, PACT demonstrates a speedup of up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.83\times $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$186\times $ </tex-math></inline-formula> for steady-state and transient simulations, respectively. We also show the applicability and extensibility of PACT through modeling emerging integration and cooling technologies, such as monolithic 3-D integrated circuits and liquid cooling via microchannels, and full-system simulation integration on a 2.5-D system with silicon-photonic network-on-chips (PNoCs).

Investigations of heat source models in transient thermal simulation of pulsed MIG welding of AA6061-T6 thin sheet

The automobile and aviation industries are exhaustively working on weight reduction by replacing steel with aluminium alloy. However, joining the aluminium alloy body panel is remain a big challenge because of the inherent properties of aluminium. The dynamic behaviour of arc plasma in the pulsed MIG welding process is a multifaceted heat mass transfer phenomenon involving chemical, electro-magnetic, and fluid dynamics. Numerical simulation using FEA techniques are greatly helpful in understanding responses of weld bead and material behaviour. Simultaneously it reduces time and cost consuming experimental trial and error approach. The approximation of the welding arc heat source is paramount for precise prediction in the welding process simulation model. The article focuses on the comparison, suitability and effects of various moving heat source models by developing the transient thermal simulation of pulsed MIG welding of 1mm thick AA6061-T6 sheet in ANSYS workbench. Moving heat source models were developed as ANSYS APDL command subroutine. It is observed that for 1mm thin sheets Gaussian surface heat source model is also valid. The difference in temperature field is not prominent in comparison with Goldak’s double ellipsoidal heat source model.

Computational Investigation of Heat Transfer and Mass Flow in GTA Welding of AA6061 Plates

Computational approach or numerical simulation is a trend in recent manufacturing technology, in the present study a computational approach is made for a pulse type GTAW to analyze the heat transfer and mass flow behavior using FEA software ANSYS 19.0. Transient thermal simulations are carried at three different heat inputs in the form of voltage and currents with the welding speed of 70mm/min. The heat source profiles are obtained with the different heat inputs from experimental investigations. The same heat source profiles are modeled using the Solid EDGE software and called in the ICEM CFD to generate grids with unstructured tetrahedral mesh and grids are also made for the workpiece by modelling for a dimension of 150mm × 100mm having 6mm thickness same as the experimental workpiece. The generated Finite element model is called in ANSYS Workbench for transient thermal simulations to obtain the temperature distributions and the heat source models are also called in ANSYS Fluent for velocity field. The heat source models selected and the temperature field obtained from the computational numerical simulations are in good agreement with the experimental results indicating validation of the simulation process made.

Simulation of a CubeSat with internal heat transfer using Finite Volume Method

Estimating temperature is essential both to design reliable CubeSats and to keep it under maximum operating efficiency. This paper presents the transient thermal simulation of a CubeSat 1U, where the heat transfer by conduction and radiation (external and internal) are solved considering a typical CubeSat mission launched from the International Space Station. The objective is to obtain the temperature field based on the Finite Volume Method (FVM), with inner heat transfer by radiation. The Gebhart method computes the internal heat exchange through successive reflections, and an obstruction model supports the calculation of view factors. Three boundary conditions for the inner side of the CubeSat are tested: without internal heat transfer by radiation, or zero emissivity (ϵ=0.0), with intermediate internal heat transfer by radiation (ϵ=0.5), and maximum internal heat transfer by radiation (ϵ=1.0). The results show a significant impact of the internal heat transfer by radiation in the temperature field of both inner and outer parts of the satellite, and therefore it should not be ignored. Good agreement of transient temperature is found between the FVM and another more straightforward formulation based on the Lumped Method, although the three-dimensional effects are significant and cannot be obtained with such a simplified model.

Transient Thermal Analysis of the Circuit Breaker Current Path with the Use of FEA Simulation

The finite element analysis (FEA) is an essential and powerful numerical method that can explicitly optimize the design process of electrical devices. In this paper, the employment of the finite element method (FEM) as ANSYS is proposed in order to aid electrical apparatus engineering and modeling of low voltage modular circuit breakers. The procured detailed model of a miniature circuit breaker (MCB) was undergoing transient thermal simulations of the current path. Acquired data were juxtapositioned with experimental data procured in the laboratory. The reflection of the simulation approach was clearly noted in the experimental results. Mutual areas of the modeled element expressed similar physical properties and robustness errors while tested in the specific conditions—faithfully reflecting those that were experimented with. Moreover, the physical phenomena essential for electrical engineering could be determined on the model stage. These types of 3D models can be used to analyze the thermal behavior of the current path during the current flowing condition.

Temperature-Dependent Viscosity Model for Silicone Oil and Its Application in Viscous Dampers

Silicone fluids belong to the group of pseudoplastic non-Newtonian fluids with complex rheological characteristics. They are considered in basic and applied researches and in a wide range of industrial applications due to their favorable physical and thermal properties. One of their specific field of applications in the automotive industry is the working fluid of viscous torsional vibration dampers. For numerical studies in the design and development phase of this damping product, it is essential to have thorough rheological knowledge and mathematical description about the silicone oil viscosity. In the present work, adopted rheological measurement results conducted on polydimethylsiloxane manufactured by Wacker Chemie with initial viscosity of 1000 Pas (AK 1 000 000 STAB silicone oil) are processed. As a result of the parameter identification by nonlinear regression, the temperature-dependent parameter curves of the Carreau–Yasuda non-Newtonian viscosity model are generated. By implementing these parameter sets into a Computational Fluid Dynamics (CFD) software, a temperature- and shear-rate-dependent viscosity model of silicone fluid was tested, using transient flow and thermal simulations on elementary tube geometries in the size range of a real viscous torsional vibration damper’s flow channels and filling chambers. The numerical results of the finite volume method provide information about the developed flow processes, with especial care for the resulted flow pattern, shear rate, viscosity and timing.

Thermal characterization of GaN lateral power HEMTs on Si, SOI, and poly-AlN substrates

In this work, the thermal behavior of GaN HEMTs is studied with a three-fold contribution: (i) test structures for resistive thermometry are introduced and manufactured; (ii) subsequently, those are used to perform the on-wafer thermal characterization of small and power HEMTs on SOI, and poly-AlN (QST®) with the aim of comparing the thermal resistance with respect to the reference Si counterpart; (iii) finally, 3D thermal FEM models validated with the experimental results obtained in the previous step are used to perform transient thermal simulations to analyze the effects of substrate thinning, thereby providing as output the thermal impedance (also as equivalent network) and the Safe Operating Area.

Unravelling the lithospheric-scale thermal field of the North Patagonian Massif plateau (Argentina) and its relations to the topographic evolution of the area

The North Patagonian Massif (NPM) area in Argentina includes a plateau of 1200 m a.s.l. (meters above sea level) average height, which is 500–700 m higher than its surrounding areas. The plateau shows no evidence of internal deformation, while the surrounding basins have been deformed during Cenozoic orogenic events. Previous works suggested that the plateau formation was caused by a lithospheric uplift event during the Paleogene. However, the causative processes responsible for the plateau origin and its current state remain speculative. To address some of these questions, we carried out 3D lithospheric-scale steady-state and transient thermal simulations of the NPM and its surroundings, as based on an existing 3D geological model of the area. Our results are indicative of a thicker and warmer lithosphere below the NPM plateau compared with its surroundings, suggesting that the plateau is still isostatically buoyant and thus explaining its present-day elevation. The transient thermal simulations agree with a heating event in the mantle during the Paleogene as the causative process leading to lithospheric uplift in the region and indicate that the thermo-mechanical effects of such an event would still be influencing the plateau evolution today. Although the elevation related to the heating would not be enough to reach the present plateau topography, we discuss other mechanisms, also connected with the mantle heating, that may have caused the observed relief. Lithosphere cooling in the plateau is ongoing, being delayed by the presence of a thick crust enriched in radiogenic minerals as compared to its sides, resulting in a thermal configuration that has yet to reach thermodynamic equilibrium.

Energy efficiency, thermal resilience, and health during extreme heat events in low-income housing in Argentina

Extreme heat events result in higher indoor temperatures in buildings, increased energy consumption, and more frequent health problems, mainly between the children, the elderly over 65, and vulnerable low-income people. The indoor environment plays a key role in reducing the effects of extreme heat events. While the benefits of passive cooling measures on thermal and environmental aspects are well known, their effects on resilience are less well explored. This paper aims at studying the indoor environment in low-income housing from the energy and heat resilience points of view, during extreme hot periods, together with possible passive cooling measures to be applied in the houses in order to improve both, heat resilience and energy efficiency. A low-income neighbourhood in La Pampa, central Argentina, was selected as a case study. Transient thermal simulation, electricity consumption bills obtained from the Energy Company, and health statistics from the data-base of the nearby hospital were used. We conclude that the houses are not capable to manage hot/heat wave periods in a resilient way because of their energy inefficient design. Moreover, the cooling equipment is sub-used due to economic reasons. Indoor temperatures exceeded 33 °C and Heat Index reached “Extreme caution” health risk level. Sudden changes in the meteorological conditions seems to increase the number of consultations of health disorders previous or after the hot periods. The best set of passive strategies is to favour night ventilation together with shading of the envelope (i.e., by trees, climbing plants, green walls, or by installing ventilated opaque façades) and an improved roof (light colour coating and addition of thermal insulation). These strategies could both, improve the heat resilience and the thermal behavior of the indoor environment while reducing the electricity consumption in the hottest months of summer.

Efficient transient thermal analysis based on spectral element time domain method with curvilinear hexahedrons

AbstractIn this paper, a three‐dimensional transient thermal simulation algorithm based on spectral element method is proposed. This algorithm uses distorted hexahedron for mesh generation, which not only keeps the high efficiency of hexahedron element calculation, but also improves the flexibility of mesh generation. It supports efficient forward difference and unconditionally stable backward difference in time step. Through practical examples and comparison with commercial software, the reliability and stability of the algorithm are verified, and it has obvious advantages in memory consumption and computing efficiency.

Research on the simulation technology of the combined effects of transient thermal shock and a triaxial 6-DOF

During the reentry of a spacecraft, it will encounter extreme environment of transient thermal shock and a triaxial 6-DOF. Currently, there is a lack of experimental verification means. Taking a second power supply as an example, the finite element simulation model is established, and the model is verified by the heat balance test and random vibration modal test. The thermal response distribution of rapid temperature change, low-temperature holding and high-temperature holding phrases is obtained through the transient thermal shock simulation; Based on the multi-stress simulation of the workbench, the stress-strain response distribution under the triaxial 6-DOF random vibration is obtained. According to the principle of stress coupling, the thermal response distribution matrix and stress-strain response distribution matrix are applied to the finite element model of electronic products at the same time, and then the transient thermal shock and the triaxial 6-DOF coupling simulation is realized, which provides a theoretical guidance for test verification of the extreme environment during the reentry of a spacecraft.

Use of a numerical weather prediction model as a meteorological source for the estimation of heating demand in building thermal simulations

Thermal simulations are a commonly used tool for energy efficiency analysis of buildings. Regional meteorological station networks are a prime source of weather data inputs, required for building thermal simulations. However, local measurements from weather stations are not always available, and when they are, accessing these data can be expensive. This paper analyses a novel use of a numerical weather prediction mesoscale model, the Global Forecast System (GFS) sflux model, as a source of input data for transient thermal simulations. Two interpolation techniques (nearest neighbour and universal kriging) were used to generate local weather datasets from GFS outputs at 27 locations spread over an area of 29,574 km2 in Galicia (northwest Spain). The performance of the GFS estimations was tested against weather measurements obtained from a governmental weather agency. A reference building with the most common features was selected for running thermal simulations in the TRNSYS environment, focusing on heating demand, with estimated weather data as input. The results highlight that GFS-interpolated datasets consistently performs better than using measured data from the nearest weather station. This clearly supports the use of GFS as an appropriate weather source for building simulations, providing good-quality, free and global-scale local weather inputs.

Graphite-Embedded High-Performance Insulated Metal Substrate for Wide-Bandgap Power Modules

Emerging wide-bandgap (WBG) semiconductor devices such as silicon carbide (SiC) metal-oxide semiconductor field-effect transistors (MOSFETs) and gallium nitride high-electron-mobility transistors can handle high power in reduced semiconductor areas better than conventional Si-based devices owing to superior material properties. With increased power loss density in a WBG-based converter and reduced die size in power modules, thermal management of power devices must be optimized for high performance. This article presents a graphite-embedded insulated metal substrate (thermally-annealed-pyrolytic-graphite-embedded insulated metal substrate-IMSwTPG) designed for WBG power modules. Theoretical thermal performance analysis of graphite-embedded metal cores is presented, with design details for IMSwTPG with embedded graphite to replace a direct-bonded copper (DBC) substrate. The proposed IMSwTPG is compared with an aluminum nitride-based DBC substrate using finite-element thermal analysis for steady-state and transient thermal performance. The solutions' thermal performances are compared under different coolant temperature and thermal loading conditions, and the proposed substrate's electrical performance is validated with static and dynamic characterization. Using graphite-embedded substrates, junction-to-case thermal resistance of SiC MOSFETs can be reduced up to 17%, and device current density can be increased by 10%, regardless of the thermal management strategy used to cool the substrate. Reduced transient thermal impedance of up to 40% of dies owing to increased heat capacity is validated in transient thermal simulations and experiments. The half-bridge power module's electrical performance is evaluated for on-state resistance, switching performance, and switching loss at three junction temperature conditions. The proposed substrate solution has minimal impact on conduction and switching performance of SiC MOSFETs.

Short-term supply reliability assessment of a gas pipeline system under demand variations

It is the basic responsibility for pipeline companies to satisfy the gas demand of customers. A methodology is proposed to assess the short-term supply reliability of a gas pipeline system under demand variations in this paper. Based on the failure rate and repair rate of the pipe segments and compressor units obtained through historical operational data, the probability under different structural failure scenarios of a gas pipeline system is computed through the stochastic process and probability theory. Indices from aspects of adequacy, availability, and shortage rate are developed to reflect the supply reliability. To reflect the assessment results intuitively, the cumulative probability function is adopted to reflect the supply adequacy and availability, and the probability distribution is adopted to reflect the supply shortage rate during the assessment period. For all scenarios, supply reliability is calculated through batch transient hydraulic and thermal simulations of a gas pipeline system by Stoner Pipeline Simulator considering practical operational processes and legal constraints. The proposed methodology is performed based on the Trans-Asian gas pipeline A-B system, and the functions of cross-over valves on supply reliability of the Trans-Asian gas pipeline A-B system is studied.

Electrical–Thermal Cosimulation of Coaxial TSVs With Temperature-Dependent MOS Effect Using Equivalent Circuit Models

A coupled electrical–thermal cosimulation with consideration of the temperature dependence of the metal-oxide-semiconductor (MOS) effect is performed for coaxial through silicon vias (C-TSVs) by using equivalent electrical and thermal circuit models. In the equivalent electrical circuit (EEC) model, the dependence of the MOS capacitance on bias voltage, operation frequency, oxide charge density, and temperature is studied, and further verified by measurement results from a previous publication. A 3-D equivalent thermal circuit (ETC) model with lump components, including thermal resistance and thermal capacitance analytically calculated from the geometry and material parameters of C-TSVs, is proposed for transient thermal simulation. The accuracy of the EEC and ETC models is verified by comparisons with full-wave simulations. Transient electrical–thermal co-simulation is performed for the C-TSVs with the EEC and ETC models. Results reveal that the temperature dependence of depletion width and corresponding MOS capacitance leads to considerable variations in the S-parameters of C-TSVs.

Thermal Transient and Thermal Stress on Radiated Heat Float Glass

To conduct an experiment of thermal radiation. The researchers conducted a simulation to study the behavior of the damage float glass using Mecway 10 FEA software. The ambient time and temperature on the first float glass sheet sustaining thermal transient and thermal stress are the most important parameters to find out the part of float glass. Analyzing the results of all simulations of radiant heat and convection in transient thermal simulations on the surface of float glass to be crack and knowing the estimated time until cracked float glass with thermal stress analysis. Giving heat radiation to the exposed glass surface, to be assumed by heat exposure from 0 to 20 minutes which is 32º to 600ºC with 19 mm glass thickness using Mecway 10 FEA software. Then did a comparison of the radiation heat value convection flow rate and so that the glass experiences a thermal crack. In this process, the results of the comparison will also be reviewed and discussed at the limit of the amount of heat radiation so that the cracked glass or thermal crack. The difference in temperature and stress will increase with adding radiation heat on the glass. Critical time and temperature differences are given as reference values ​​to predict Thermal stress in computerized applications.

Efficient Transient Thermal Simulation of ICs and Packages With Laguerre-Based Finite-Element Method

In this article, an efficient approach based on Laguerre-based finite-element method (LBFEM) is proposed for transient thermal simulation of integrated circuits (ICs) and packages. The unconditionally stable marching-on-in-order scheme is developed by the weighted Laguerre polynomials and Galerkin testing procedure. In order to handle complicated ICs and packages, the finite-element method (FEM) is employed for spatial discretization and to obtain the Laguerre coefficients. The treatment of different kinds of boundary conditions is also discussed in detail. The accuracy and efficiency of the proposed method are demonstrated by numerical examples.