Thermal Investigation of GaAs Microwave Power Transistors

2004 ◽  
Vol 1 (1) ◽  
pp. 1-8 ◽  
Author(s):  
G. Hanreich ◽  
M. Mayer ◽  
M. Mündlein ◽  
J. Nicolics
Keyword(s):  
Thermal Behavior ◽  
Chip Thickness ◽  
Thermal Response ◽  
Electrical Circuit ◽  
Thermal Design ◽  
Simulation Tool ◽  
Temperature Dependent ◽  
Thermomechanical Stress ◽  
Die Bonding ◽  
Numerical Solver

The lower thermal conductivity of gallium arsenide (GaAs) compared to silicon (Si) requires a careful thermal design for optimizing device performance and reliability. In this paper a recently developed thermal simulation tool (TRESCOM II) is applied for investigating the thermal behavior of a heterojunction GaAs power field effect transistor (FET). Main features of the simulation tool are an easy model creation procedure and an efficient numerical solver. Moreover, the tool allows to consider temperature dependent material properties and temperature dependent boundary conditions. The investigation of the thermal behavior of the power transistor has two goals. First goal is to establish the temperature distribution within the active layer of the FET to allow predictions of thermal-electrical interactions. A deeper insight into thermal-electrical interaction will lead to better equivalent circuit models used in electrical circuit design. Due to the fact that reliability of the component is mainly determined by thermal load and induced thermomechanical stress, second goal of this work is to investigate the influence of chip thickness and die bonding variations on the thermal behavior. Thermal response on different power levels is investigated and the influence of chip thickness tolerances and die bonding on the thermal performance of the device is discussed.

A Methodological Approach for Supporting the Thermal Design of Li-Ion Battery for Customized Electric Vehicles

2014 ◽  
Author(s):  
Daniele Landi ◽  
Paolo Cicconi ◽  
Michele Germani
Keyword(s):  
Thermal Behavior ◽  
Electric Vehicle ◽  
Electric Vehicles ◽  
Combustion Engine ◽  
Thermal Design ◽  
Battery Pack ◽  
Scale Production ◽  
Li Ion Battery ◽  
Suitable Alternative ◽  
Li Ion

An important issue in the mechanical industry is the reduction of the time to market, in order to meet quickly the customer needs. This goal is very important for SMEs that produce small lots of customized products. In the context of greenhouse gas emissions reduction, vehicles powered by electric motors seem to be the most suitable alternative to the traditional internal combustion engine vehicles. The market of customized electric vehicles is a niche market suitable for SMEs. Nowadays, the energy storage system of an electric vehicle powertrain consists of several Li-ion cells arranged in a container called battery pack. Particularly, the battery unit is considered as the most critical component in electric vehicle, because it impacts on performance and life cycle cost. Currently, the design of a battery pack mostly depends on the related market size. A longer design time is expected in the case of a large scale production. While a small customized production requires more agility and velocity in the design process. The proposed research focuses on a design methodology to support the designer in the evaluation of the battery thermal behavior. This work has been applied in the context of a customized small production. As test case, an urban electric light commercial vehicle has been analyzed. The designed battery layout has been evaluated and simulated using virtual prototyping tools. A cooling configuration has been analyzed and then prototyped in a physical vehicle. The virtual thermal behavior of a Li-ion battery has been validated at the test bench. The real operational conditions have been analyzed reproducing several ECE-15 driving cycles and many acceleration runs at different load values. Thermocouples have measured the temperature values during the physical experiments, in order to validate the analytical thermal profile evaluated with the proposed design approach.

Sensitivity Analysis for Nonlinear Heat Conduction

2000 ◽  
Vol 123 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Kevin J. Dowding ◽  
Bennie F. Blackwell
Keyword(s):  
Heat Conduction ◽  
General Procedure ◽  
Model Parameters ◽  
Nonlinear Heat Conduction ◽  
Temperature Dependent ◽  
Sensitivity Equations ◽  
Verification Problem ◽  
Temperature Variable ◽  
Numerical Solver ◽  
Temperature Dependent Properties

Parameters in the heat conduction equation are frequently modeled as temperature dependent. Thermal conductivity, volumetric heat capacity, convection coefficients, emissivity, and volumetric source terms are parameters that may depend on temperature. Many applications, such as parameter estimation, optimal experimental design, optimization, and uncertainty analysis, require sensitivity to the parameters describing temperature-dependent properties. A general procedure to compute the sensitivity of the temperature field to model parameters for nonlinear heat conduction is studied. Parameters are modeled as arbitrary functions of temperature. Sensitivity equations are implemented in an unstructured grid, element-based numerical solver. The objectives of this study are to describe the methodology to derive sensitivity equations for the temperature-dependent parameters and present demonstration calculations. In addition to a verification problem, the design of an experiment to estimate temperature variable thermal properties is discussed.

scholarly journals High-Fidelity Calculation of Effective Thermal Response of Composite Media With Heat Generation Source

2020 ◽  
Author(s):  
Kevin Irick ◽  
Nima Fathi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Nuclear Fuel ◽  
Heat Generation ◽  
Thermal Response ◽  
Thermal Conditions ◽  
Unit Cell ◽  
High Fidelity ◽  
Conductive Heat

Abstract The complexity of conductive heat transfer in a structure increases with heterogeneity (e.g., multi-component solid-phase systems with a source of internal thermal heat generation). Any discontinuity of material property — especially thermal conductivity — would warrant a thorough analysis to evaluate the thermal behavior of the system of interest. Heterogeneous thermal conditions are crucial to heat transfer in nuclear fuel assemblies, because the thermal behavior within the assemblies is governed significantly by the heterogeneous thermal conditions at both the system and component levels. A variety of materials have been used as nuclear fuels, the most conventional of which is uranium dioxide, UO2. UO2 has satisfactory chemical and irradiation tolerances in thermal reactors, whereas the low thermal conductivity of porous UO2 can prove challenging. Therefore, the feasibility of enhancing the thermal conductivity of oxide fuels by adding a high-conductivity secondary solid component is still an important ongoing topic of investigation. Undoubtedly, long-term, stable development of clean nuclear energy would depend on research and development of innovative reactor designs and fuel systems. Having a better understanding of the thermal response of the unit cell of a composite that represents a fuel matrix cell would help to develop the next generation of nuclear fuel and understand potential performance enhancements. The aim of this article is to provide an assessment of a high-fidelity computational model response of heterogeneous materials with heat generation in circular fillers. Two-dimensional, steady-state systems were defined with a circular, heat-generating filler centered in a unit-cell domain. A Fortran-based finite element method (FEM) code was used to solve the heat equation on an unstructured triangular mesh of the systems. This paper presents a study on the effects of a heat-generating filler material’s relative size and thermal conductivity on effective thermal conductance, Geff, within a heterogenous material. Code verification using the method of manufactured solution (MMS) was employed, showing a second-order accurate numerical implementation. Solution verification was performed using a global deviation grid convergence index (GCI) method to assess solution convergence and estimate solution numerical uncertainty, Unum. Trend results are presented, showing variable response in Geff to filler size and thermal conductivity.

Dynamic thermal response of aluminum films induced by femtosecond-pulsed lasers with temperature dependent optical properties

Optik ◽  
2017 ◽  
Vol 142 ◽  
pp. 218-225 ◽  
Author(s):  
Qing Lin ◽  
Naifei Ren ◽  
Yunpeng Ren ◽  
Qiqi Wang ◽  
Ning Xue ◽  
...  
Keyword(s):  
Optical Properties ◽  
Thermal Response ◽  
Pulsed Lasers ◽  
Temperature Dependent ◽  
Aluminum Films

Transient thermal behavior of radial fins of rectangular, triangular and hyperbolic profiles with temperature-dependent properties using DTM-FDM

2017 ◽  
Vol 24 (3) ◽  
pp. 675-682 ◽  
Author(s):  
Sobhan Mosayebidorcheh ◽  
Mohammad Rahimi-Gorji ◽  
D. D. Ganji ◽  
Taha Moayebidorcheh ◽  
O. Pourmehran ◽  
...  
Keyword(s):  
Thermal Behavior ◽  
Temperature Dependent ◽  
Temperature Dependent Properties ◽  
Transient Thermal

Geometrical nonlinear thermal response of sandwich panels with temperature dependent mechanical properties—Extended high-order approach

2019 ◽  
Vol 21 (5) ◽  
pp. 1700-1725 ◽  
Author(s):  
Yeoshua Frostig ◽  
George Kardomateas
Keyword(s):  
Mechanical Properties ◽  
Sandwich Panel ◽  
Mechanical Response ◽  
Numerical Study ◽  
Thermal Response ◽  
High Order ◽  
Theory Approach ◽  
Temperature Dependent ◽  
The Core ◽  
Compressive Loads

The thermal and the thermo-mechanical responses of a sandwich panel with a compliant core are investigated within the framework of the extended high-order approach where the core properties are temperature dependent or independent. Loads schemes include thermal field within temperature working range simultaneous with in-plane compressive loads applied to the core only and to the face sheets and core in the form of the uniform end—shortening of edge of panel. The mathematical formulations use the extended high-order sandwich panel theory approach that takes into account the in-plane rigidity of the core and uses the deformation patterns of the high-order sandwich panel theory. The linear and nonlinear field equations along with the appropriate boundary conditions are presented. A numerical study is conducted, and it investigates the thermal response with temperature independent and temperature dependent mechanical properties of the core as well as the thermo-mechanical response due to in-plane compressive loads. The results include displacements, stress resultants, and stress at critical locations along the panel as well as equilibria curves. They reveal that, in general, the panel with temperature independent properties response remains almost linear while with temperature dependent ones it takes a general nonlinear response. The addition of an external mechanical load changes the response from a linear/nonlinear one that may be allowable stress controlled to a case where loss of stability occurs.

scholarly journals Breadth of the thermal response captures individual and geographic variation in temperature‐dependent sex determination

2019 ◽  
Vol 33 (10) ◽  
pp. 1928-1939 ◽  
Author(s):  
Anna L. Carter ◽  
Brooke L. Bodensteiner ◽  
John B. Iverson ◽  
Carrie L. Milne‐Zelman ◽  
Timothy S. Mitchell ◽  
...  
Keyword(s):  
Sex Determination ◽  
Geographic Variation ◽  
Thermal Response ◽  
Temperature Dependent

scholarly journals Experimental and Numerical Study on the Characteristics of the Thermal Design of a Large-Area Hot Plate for Nanoimprint Equipment

2019 ◽  
Vol 11 (17) ◽  
pp. 4795 ◽  
Author(s):  
Gyujin Park ◽  
Changhee Lee
Keyword(s):  
Stainless Steel ◽  
Thermal Behavior ◽  
Thermal Performance ◽  
Numerical Study ◽  
Heat Pipes ◽  
Thermal Design ◽  
Maximum Temperature ◽  
Large Area ◽  
Hot Plate ◽  
Heating And Cooling

A numerical study was conducted on the thermal performance of a large-area hot plate specifically designed as a heating and cooling tool for thermal nanoimprint lithography processes. The hot plate had the dimensions 240 mm × 240 mm × 20 mm, in which a series of cartridge heaters and cooling holes were installed. Stainless steel was selected to endure the high molding pressures. To examine the hot plate’s abnormal thermal behavior, ANSYS Fluent V15.0, which is commercial CFD code, was used to perform computational analysis. A numerical model was employed to predict the thermal behavior of the hot plate in both the heating and cooling phases. To conduct the thermal design of a large-area hot plate for nanoimprint equipment, we selected the model to be studied and proposed a cooling model using both direct and indirect cooling methods with and without heat pipes. In addition, we created a small hot plate and performed experimental and computational analyses to confirm the validity of the proposed model. This study also analyzed problems that may occur in the stage prior to the large-area expansion of the hot plate. In the case of a stainless steel (STS304) hot plate for large-area hot plate expansion, the heat pipes were inserted in the direction of the cartridge heaters to address the problems that may occur when expanding the hot plate into a large area. As a result, the heating rate was 40 °C/min and the temperature uniformity was less than 1% of the maximum working temperature of 200 °C. For cooling, when considering pressure and using air as the coolant for the ends, a cooling rate of 20 °C/min and thermal performance of less than 13.2 °C (less than 7%) based on the maximum temperature were obtained. These results were similar to the experimental results.

scholarly journals Transient Simulation for the Thermal Design Optimization of Pulse Operated AlGaN/GaN HEMTs

Micromachines ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 76
Author(s):  
Huaixin Guo ◽  
Tangsheng Chen ◽  
Shang Shi
Keyword(s):  
Power Density ◽  
Power Amplifiers ◽  
Pulse Width ◽  
Thermal Response ◽  
Thermal Design ◽  
Transient Simulation ◽  
Gate Width ◽  
Channel Temperature ◽  
Gan Hemts ◽  
Transient Thermal

The thermal management and channel temperature evaluation of GaN power amplifiers are indispensable issues in engineering field. The transient thermal characteristics of pulse operated AlGaN/GaN high electron mobility transistors (HEMT) used in high power amplifiers are systematically investigated by using three-dimensional simulation with the finite element method. To improve the calculation accuracy, the nonlinear thermal conductivities and near-junction region of GaN chip are considered and treated appropriately in our numerical analysis. The periodic transient pulses temperature and temperature distribution are analyzed to estimate thermal response when GaN amplifiers are operating in pulsed mode with kilowatt-level power, and the relationships between channel temperatures and pulse width, gate structures, and power density of GaN device are analyzed. Results indicate that the maximal channel temperature and thermal impedance of device are considerably influenced by pulse width and power density effects, but the changes of gate fingers and gate width have no effect on channel temperature when the total gate width and active area are kept constant. Finally, the transient thermal response of GaN amplifier is measured using IR thermal photogrammetry, and the correctness and validation of the simulation model is verified. The study of transient simulation is demonstrated necessary for optimal designs of pulse-operated AlGaN/GaN HEMTs.

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