Performance assessment of density and level-set topology optimisation methods for 3D heatsink design

In this paper, two most prevalent topological optimisation approaches namely Density and Level set method are applied to a three dimensional heatsink design problem. The relative performance of the two approaches are compared in terms of design quality, robustness and computational speed. The work is original as for the first time it demonstrates the relative advantages and disadvantages for each method when applied to a practical engineering problem. It is additionally novel in that it presents the design of a convectively cooled heatsink by solving full thermo-fluid equations for two different solid-fluid material sets. Further, results are validated using a separate CFD study with the optimised designs are compared against a standard pin-fin based heatsink design. The results show that the Density method demonstrates better performance in terms of robustness and computational speed, while Level-set method yields a better quality design

Heat transfer characteristics of plate fin heat sink with longitudinal vortex generators

Purpose This study aims to provide an insight into the relationship between design parameters and thermal performance of plate fin heat sinks (PFHSs) incorporating longitudinal vortex generators (VGs) inside a PFHS channel. Design/methodology/approach A computational fluid dynamics model of a delta winglet pair VG mounted inside a PFHS geometry is detailed, and the model is validated by comparison with experimental data. The validated model is used to perform a virtual design of experiments study of the heat sink with bottom plate and vertical plate mounted VGs. Data from this study is used to regress a response surface enabling the influence of each of the assessed design variables on thermal performance and flow resistance to be determined. Findings The results of this study show that the thermal hydraulic performances of a PFHS with bottom plate mounted VG and vertical plate fin mounted VG are, respectively, 1.12 and 1.17 times higher than the baseline PFHS. Further, the performance variation of the heat sink with VG, relative to delta winglet’s arrangement (common flow up and common flow down), trailing edge gap length and Reynolds number were also evaluated and reported. Originality/value For the first time, performance characteristics of delta winglet VGs mounted inside the PFHS are evaluated against different design variables and a polynomial regression model is developed. The developed regression model and computed results can be used to design high performance PFHSs mounted with delta winglet VGs

Analysis of sandstone pore space fluid saturation and mineralogy variation via application of monostatic K-band frequency modulated continuous wave radar

In this paper we present the preliminary findings from a world first investigation into monostatic frequency modulated continuous wave (FMCW) radar analysis of porous sandstones and their fluid content. FMCW results, within 24 to 25.5 GHz, provide insights into the rock/pore system as well as into mineral and liquid distributions, both crucial for quantitative representation of the fluid-rock system for subsequent assessment of the sandstones. Sandstone samples, here characterised using known techniques of energy dispersive x-ray analysis, gaseous secondary electron and backscattered electron imaging are: Darney, Lazonby Locharbriggs and Red St. Bees sandstones, with FMCW results indicating that, in the K-Band, calculated values for relative permittivity, utilising free-space radiation reflection data, give results that are consistent with the known rock elemental constituents, where each sandstone has different distributions of the dominant quartz and subsidiary other minerals and of grain size and shape distributions. The experimental results support the sensitivity of this sensing modality to variances in rock properties in typical sandstones with complex relative permittivity, ε_r^*, values for unsaturated sandstones ranging from 5.76 to 6.76 and from 12.96 to 48.3 for partially saturated sandstones, with the highest values indicating high permittivity mineral inclusion and/or grain angularity

Numerical analysis of microwave processing problems using a multidomain solver approach

This work outlines the process undertaken in the formulation and validation of a numerical model for analysis of practical microwave processing problems. The proposed model adopts a novel multi-domain Eulerian-Lagrangian approach to the problem, defining two discrete numerical domains coupled through a set of data transfer algorithms. One of the numerical domains is defined for analysis of electromagnetic field distribution while the other is used for analysis of the thermophysical aspects of the problem. The thermophysical domain is restricted to the load being processed and is discretised in an Eulerian manner using an unstructured mesh for solution using a finite volume approach. The electromagnetic domain is discretised using a tensor-product rectilinear structured mesh for solution of Maxwell’s equations using a Yee finite difference time domain approach. The thermophysical load is represented within the electromagnetic domain through a mapped Lagrangian complex permittivity distribution rather than being defined explicitly. The two domains are coupled through mapping routines capable of defining the complex permittivity distribution within the electromagnetic domain and transferring the calculated power density distribution into the thermophysical domain. This interdomain coupling allows the meshes in the two domains to be non coincident, enabling the discretisation of the two domains to be completely independent of each other. This approach to analysis of coupled microwave processing problems is novel and provides a number of significant benefits over conventional single-domain methods. The primary benefit of the approach is that the electromagnetic and thermophysical parts of the analysis can be handled by different solvers using differing meshes. This is a very significant advance as the optimal approach to solving one of the parts be be extremely inefficient or indeed unfeasible for the other. The approach allows electromagnetic fields irradiating complex geometries placed inside a rectilinear microwave ovens to be analyses using a tensor product solver. The solution of the electromagnetic field distribution is typically the most computationally expensive part of a coupled solution of microwave heating. The ability to use a Yee finite difference solver rather than a conformal FDTD or finite element approach provides a very significant reduction in computational expense, enabling more complex analyses to be performed. Solution of thermophysical aspects of the problem are most effectively tackled using an unstructured spatial discretisation in cases with complex geometries. The adoption of an unstructured finite volume approach for the thermophysical part of the analysis provides an analysis capability far beyond that of the finite difference approach typically used in analyses with a finite difference electromagnetic solver. Further benefits stem from the inherent capability to alter the discretisation of the electromagnetic domain independently of the thermophysical domain, enabling cases with advection and/or rotation of the load within the oven to be considered with relative ease. Analysis of this type of problem is highly complex when using a single domain approach as the mesh needs to be redefined at regular interval during the solution. The capability to refine the discretisation of the electromagnetic domain also improves efficiency in cases where dielectric properties vary significantly during the process as mesh resolution can be varied as the process progresses. The primary drawback with the adoption of the multidomain approach is that the load is represented in the electromagnetic domain as a mapped Langrian complex permittivity distribution rather than being explicitly defined as part of the domain discretisation. There are therefore issues relating to the smearing of material boundaries which may influence wave scattering across the boundary adversely affecting accuracy of the electric field solution. In order to study the efficiency and accuracy of the approach a series of tests were conducted to assess the performance of each individual component of the analysis framework to ensure that these had been implemented effectively and to determine the magnitude of any apparent errors. The model was subsequently applied to a simple test case to ensure that the components were coupled in an effective manner. This test and validation process showed that individual components to be accurate and fit for purpose with errors due to data transfer between the two computational domains shown to be small. The results obtained from the validation case agreed relatively closely with experimental data demonstrating the implementation and efficacy of the model. The model was subsequently validated against two practical microwave processing problems - thawing of food within a domestic microwave oven and polymer curing using a dual-section microwave system. In the food thawing study, the solution obtained by the numerical model was validated against data obtained during an experimental study. The study was intended to meet the requirements of an industrial partner in research work that eliminated a range of simplifications adopted in alternate studies. The analysis therefore focussed on thawing of a challenging ’real-world’ material, placed in a complex shaped container. The load was placed on the rotating turntable of a domestic microwave oven. Results obtained from the numerical simulations agree moderately well with experimentally derived data. Primary disparities between experimental data and numerical solutions would appear to stem from inaccuracies in modelling the solid-liquid phase change in a complex multi-component material coupled with the very significant variation in dielectric loss over the melting temperature range. The microelectronics study focussed on curing of polymer materials in a microelectronics package using a dual-section microwave oven system. The requirement for this study was to predict the optimal process parameters for operation of the system. Numerical assessment of the development of key variables such as temperatures, degree of cure and stresses during the process was critical to this problem. Experimental measurements of these parameters during microwave processing were not feasible. Numerical comparisons of the microwave system with a conventional convection oven process have additionally been carried out. Key results from the study include optimal temperature profiles, final degree of cure distribution and residual stress magnitudes. Numerical data from the analyses are being integrated into an experimental study as part of ongoing work. An overall assessment of the numerical approach would indicate that it is a viable method of efficiently obtaining solutions to practical microwave processing problems. Further research is required to assess the influence of the smeared dielectric boundary in the finite difference solver on reflection, refraction and focussing effects on the accuracy of the numerical solution

Heat transfer characteristics of plate fin heat sink with longitudinal vortex generators

Purpose: This article aims to provide an insight into the relationship between design parameters and thermal performance of plate-fin heat sinks incorporating longitudinal vortex generators inside a plate fin heat sink channel. Design/Methodology/Approach: A computational fluid dynamics model of a delta winglet pair vortex generator mounted inside a plate-fin heat sink geometry is detailed, and the model is validated by comparison with experimental data. The validated model is used to perform a virtual design of experiments study of the heatsink with bottom plate and vertical plate mounted vortex generators. Data from this study is used to regress a response surface enabling the influence of each of the assessed design variables on thermal performance and flow resistance to be determined. Findings: The results show that the thermal hydraulic performance of a plate fin heat sink with bottom plate mounted vortex generator and vertical plate fin mounted vortex generator are respectively 1.12 and 1.17 times higher than the baseline plate fin heat sink. Further the performance variation of the heat sink with vortex generator, relative to delta winglet’s arrangement (common flow up and common flow down), trailing edge gap length and Reynolds number were also evaluated and reported. Originality/Value: For the first time, performance characteristics of delta winglet vortex generators mounted inside the plate fin heat sink is evaluated against different design variables and a polynomial regression model is developed. The developed regression model and computed results can be used to design high performance plate fin heat sinks mounted with delta winglet vortex generators

Integrated reliability and prognostics prediction methodology for power electronic modules

The article consists of a PowerPoint presentation on integrated reliability and prognostics prediction methodology for power electronic modules. The areas discussed include: power electronics flagship; design for reliability; IGBT module; design for manufacture; power module components; reliability prediction techniques; failure based reliability; etc

Numerical analysis of the performance of highly oriented pyrolytic graphite heat spreader in thermal management of microelectronics assemblies

An inverse analysis approach combining numerical and experimental analyses has been utilised to determine the in-situ effective material properties of Highly Oriented Pyrolytic Graphite (HOPG) in a microelectronics test assembly. The approach adopted uses a Finite Element analysis package to determine temperature distribution over a thermal test assembly. A Virtual Design of Experiments approach is used to define a series of analyses with discrete thermal material properties which is used in conjunction with a particle swarm optimisation algorithm to form a response surface function relating temperature to material property values at a number of monitoring points. Experimental data is used to form an error metric which is subsequently minimised to determine effective material properties of the HOPG material. Subsequently a series of studies contrasting the performance of the HOPG material with common heat spreader materials were performed. Results show that the effective thermal property values of the HOPG material seem to be greater than suggested in existing literature and that the HOPG material reduces peak assembly temperatures by a significant amount

IGBT module DPT efficiency enhancement via multimodal fusion networks and graph convolution networks

The dynamic electrical characteristics of insulated-gate bipolar transistor (IGBT) are of great significance in practical high power electrical applications and are usually evaluated through double pulse test (DPT). However, DPTs of IGBTs under various working conditions is time-consuming and laborious. Traditional estimation methods are based on detailed physical parameters and complex formula calculations, making deployment process challenging. This paper proposes a novel DPT efficiency enhancement method based on graph convolution network (GCN) and feature fusion technology, which can estimate and supplement switching transient waveforms of all working conditions. Thereby, dynamic electrical characteristics of the IGBT are obtained by estimated waveforms of DPT. This method proposes a multimodal attention fusion network (MAFN) to capture and fuse the features of switching transient waveforms between different positions thereby improving the expressive power and performance of the model. Moreover, this method is novel in that it is the first to utilise GCN to embed DPT data under multiple working conditions into a graph structure, which can use the graph structure information to fuse the features of spatially correlated working conditions data to obtain reliable estimation results. The method has been verified to be effective and accurate on real dataset collected on two batches of IGBTs

Modelling technologies and applications

Numerical modelling technology and software is now being used to underwrite the design of many microelectronic and microsystems components. The demands for greater capability of these analysis tools are increasing dramatically, as the user community is faced with the challenge of producing reliable products in ever shorter lead times. This leads to the requirement for analysis tools to represent the interactions amongst the distinct phenomena and physics at multiple length and timescales. Multi-physics and Multi-scale technology is now becoming a reality with many code vendors. This chapter discusses the current status of modelling tools that assess the impact of nano-technology on the fabrication/packaging and testing of microsystems. The chapter is broken down into three sections: Modelling Technologies, Modelling Application to Fabrication, and Modelling Application to Assembly/Packing and Modelling Applied for Test and Metrology