Use of a differential evolution algorithm for the optimization of the heat radiation intensity

summary:This article focuses on the heat radiation intensity optimization on the surface of an aluminium shell mould. The outer mould surface is heated by infrared heaters located above the mould and the inner mould surface is sprinkled with a special PVC powder. This is an economic way of producing artificial leathers in the automotive industry (e.g. the artificial leather on car dashboards). The article includes a description of a mathematical model that allows us to calculate the heat radiation intensity across the outer mould surface for every fixed location of the heaters. We also use this mathematical model for optimizing the locations of the heaters to generate uniform heat radiation intensity on the whole outer mould surface during the heating of the mould. In this way we obtain an even colour shade and material structure of the artificial leather. The problem of optimization is more complicated. Using gradient methods is not suitable because the minimized deviation function contains many local minima. A differential evolution algorithm is used during the process of optimization. The calculations were performed by a Matlab code written by the authors. The article contains a practical example including graphical outputs

Numerical Modelling of Heat Phenomena Induced by Heat Radiation

Disertační práce se zabývá problematikou optimalizace ohřevu kovových skořepinových forem pomocí soustavy infrazářičů. Práce se soustředí na diferenciální evoluční algoritmy, které využívá pro tuto optimalizaci. Na konkrétním příkladu je ukázáno, že klasický diferenciální evoluční algoritmus obecně zaručuje jen konvergenci k lokálnímu minimu ohodnocující funkce. Proto byla navržena vhodná modifikace tohoto algoritmu. Pro modifikovaný algoritmus je dokázána asymptotická konvergence ke globálnímu minimu ohodnocující funkce dle pravděpodobnosti. Dále jsou odvozena tvrzení popisující využití náhodných jedinců v procesu konvergence v případě stagnace modifikovaného algoritmu. Výsledek numerické optimalizace umístění zářičů nad formou je následně použit pro modelování nestacionárního teplotního pole v tělese formy v průběhu jejího ohřevu.Z praktického hlediska disertační práce přináší teoreticky podloženou a kvantifikovatelnou metodu polohování infrazářičů nad kovovou skořepinovou formou. Spolu s modelováním teplotního pole přináší praktický a účinný příspěvek k technologii výroby plastové imitace kůže (Slush Moulding Technology). Naproti tomu modifikovaný diferenciální evoluční algoritmus je univerzální a účinná optimalizační technika, která může být testována a použita v celé řadě optimalizačních úloh. Předložená teoretická tvrzení a závěry týkající se modifikovaného diferenciálního evolučního algoritmu mají obecnou platnost a jsou použitelná v celé řadě oborů i mimo oblast modelování teplotních jevů.The doctoral thesis deals with an optimization technique that can be used to find optimized positioning of infrared heaters over a shell metal mould. The thesis is focused on differential evolution algorithms that are used for this optimization. It is shown by means of a specific example that the classic differential evolution algorithm in general guarantees only convergence to a local minimum of the cost function. Therefore, a modification of the classic differential evolution algorithm is designed. For the modified algorithm asymptotic convergence in probability to the global minimum of the cost function is proved. Several statement are presented describing utilization of random individuals in the convergence process when stagnation of the modified algorithm takes place. The result of the numerical optimization of the infrared heaters positioning over the mould is subsequently used for modelling of the non-stationary temperature field in the mould in the course of its heating.From the practical point of view, the presented thesis brings a theoretically based and quantifiable method for infrared heaters positioning over the shell metal mould. Together with the temperature field modelling it brings a feasible contribution to the Slush Moulding Technology. On the other hand, the modified differential evolution algorithm is a universal and efficient optimization tool. It can be tested and utilized in a wide range of optimization tasks with very good prospects. The presented theoretical statements and conclusions concerning the modified differential evolution algorithm have general validity and go far beyond the area of heat phenomena modelling

On the GPU computing of massive forming process simulations

This contribution presents a modelling tool for massive forming processes that is based on a particle method. The introduced model is able to represent the realistic behaviour of different types of forming processes. As these systems usually require large amounts of particles, the potential of GPU Computing with CUDA as a possibility for performance enhancement of particle simulations is analyzed as well

Optimization of historic buildings that house artefacts considering climate change

Historic buildings, and the artefacts that are usually kept within these buildings, are a living representation of the past and it is essential to ensure that future generations have access to this heritage. In order to accomplish this, it is necessary to determine the conditions that the buildings are in and, if needs be, to make the required changes in order to preserve our cultural heritage. In addition, the foreseen changes of the indoor climate caused by climate change can endanger the preservation of these artefacts, since they are prone to various types of decay depending on the existing indoor conditions. One way of counteracting these changes, is the application of passive retrofit measures. However, the guideline was that retrofit measures were hardly ever used in cultural heritage because they could cause the building to lose its authenticity. Nowadays, more and more cases of historic buildings are subject to this type of measures. Indeed, these measures can lead to positive outcomes, such as decreasing the energy consumption of the buildings or mitigating the effects of climate change, but the welfare of the cultural heritage must be ensured before these measured can be applied. Hence, the main aim of this thesis is to determine the potential of passive retrofit measures in mitigating the negative effects of climate change in the indoor climate of historic buildings, whilst accounting for the artefacts’ preservation requirements. For this reason, the indoor climate of a 13th century church in Lisbon was used to develop and validate a whole-building hygrothermal model. Then, the model was run using future weather files to determine the future indoor conditions, which were then assessed using a risk-based analysis and an adaptive thermal comfort model. Finally, the effects of the passive retrofit measures in the building’s energy consumption, the artefacts’ conservation metrics and the occupants’ thermal comfort were assessed. The future weather files were developed based on the methodology described in standard EN 15927-4 and in Skartveit and Olseth model, which divides the global radiation into its direct and diffuse components. In addition, a methodology that aims to make large-sized hygrothermal studies more time-efficient is also presented. This methodology was based in the studies developed in this thesis. It was shown that the conditions for the preservation of artefacts that are housed in historic buildings will worsen, especially in Mediterranean climates when compared to humid Continental and Oceanic climates. The tested retrofit measures can mitigate, up to a certain extent, the negative effects imposed by climate change in terms of artefacts’ conservation requirements. However, the Mediterranean climates do not have the same margin as the other tested climates. In addition, it was also shown that there is a positive outcome of implementing these measures in terms of energy saving potential. These savings will even be higher if these measures are combined with a more adequate relative humidity and temperature setpoint strategy.Os edifícios históricos, e os artefactos que geralmente são guardados no interior destes edifícios, são uma representação viva do passado e é fundamental garantir que as gerações futuras também têm acesso ao património cultural. Para isso, é necessário determinar as condições interiores destes edifícios e, se necessário, aplicar as alterações necessárias de forma a promover a preservação do património. Além disso, as mudanças expectáveis dos climas internos causadas pelas alterações climáticas podem pôr em risco a preservação destes artefactos, uma vez que estes são propensos a vários tipos de deterioração consoante as condições internas. Uma forma de combater as mudanças expectáveis do clima interior deste tipo de edifico é a aplicação de medidas de reabilitação passivas. No entanto, era prática comum a sua aplicação em edifícios históricos ser muito restrita, uma vez que podiam provocar a perda de autenticidade destes edifícios. Actualmente é cada vez mais usual a aplicação destas medidas, que podem ter resultados bastante positivos, como a diminuição do consumo de energia dos edifícios ou a mitigação dos efeitos das alterações climáticas. No entanto, é necessário garantir que o património não sofre danos com a sua aplicação. O principal objectivo desta tese é determinar o potencial de mitigação dos efeitos negativos impostos pelas alterações climáticas no clima interior de edifícios históricos através do recurso a medidas de reabilitação passivas, tendo em conta os requisitos de preservação dos artefactos. Por este motivo, o clima interno de uma igreja do século XIII em Lisboa foi utilizado para desenvolver e validar um modelo higrotérmico. Numa fase subsequente o modelo foi corrido para ficheiros climáticos futuros de forma a determinar as condições internas futuras, que foram avaliadas recorrendo a uma análise de risco e a um modelo de conforto térmico adaptável. Por fim, foi avaliado o efeito das medidas de reabilitação passivas no consumo de energia do edifício, nas métricas de conservação dos artefactos e no conforto térmico dos ocupantes do edifício. Os ficheiros climáticos futuros foram construídos com base na metodologia descrita na norma EN 15927-4 e no modelo Skartveit and Olseth, que permite subdividir a radiação global na componente directa e difusa. É também apresentada uma metodologia que visa tornar os estudos higrotérmicos com inúmeros casos mais eficiente em termos temporais. Esta metodologia baseou-se estudos desenvolvidos nesta tese de doutoramento. Ficou demonstrado que as condições de preservação de artefactos guardados no interior de edifícios históricos vão piorar, especialmente em climas mediterrâneos quando comparados com climas húmidos continentais e oceânicos. As medidas de reabilitação passivas testadas podem mitigar, até certo ponto, os efeitos negativos provocados pelas alterações climáticas em termos de conservação de artefactos. No entanto, os climas mediterrâneos não têm a mesma margem que os outros climas testados. Além disso, também foi demonstrado que a implementação destas medidas apresenta um resultado positivo em termos de poupança energética. No entanto, esta poupança será ainda maior se estas medidas forem combinadas com uma estratégia de controlo de temperatura e humidade relativa mais adequada