Modelling of the Corynebacterium glutamicum biosynthesis under aerobic fermentation conditions

This work concerns the modelling of the Corynebacterium glutamicum biosynthesis. At the beginning, the impulsive growth model of C. glutamicum under glutamate inhibition is established. According to this model, the analysis of the bioprocess stability is presented. Then, new objective functions are proposed and optimisation of C. glutamicum growth is presented. The results of the optimisation indicate that, although the growth of C. glutamicum is an aerobic process, the maximum of biomass productivity occurs under controlled penetration into the area of aerobic fermentation. Analytical results presented in this work are validated by numerical simulations.     

Analytical analysis and optimisation of the Rayleigh step slider bearing

In tribology, the Rayleigh step is known as a bearing with the highest load capacity amongst all other possible bearing geometries. In classical resources on tribology, it is also shown that there is an optimum geometry for the Rayleigh step providing the highest load capacity. However, the analyses are confined to a special case where the effect of hydrostatic pressure is neglected. Furthermore, the possible optimum parameters in terms of the friction force and/or friction coefficient as well as the lubricant flow rate have not been discussed. In this study, the Rayleigh step is comprehensively analysed including the effect of variations of pressure at the boundaries on the optimum parameters. In addition, the bearing is also optimised considering lubricant flow rate, friction force and friction coefficient. It is shown that the optimum bearing parameters are strictly dependent on the variations of the pressure at the boundaries. It is also verified that the optimum point(s) in terms of load capacity are not necessarily equal to the optimum point(s) considering friction coefficient and/or lubricant flow rate even though if there is no pressure difference between bearing endings.     

Genetic Optimisation of Gears

This paper examines the possibility of using a stochastic optimisation method (genetic algorithm) and penalty selection methods for computer-aided design of gears. The examples show that using genetic algorithms in order to optimise gears is a very efficient method.     

A systematic methodology for optimising the energy performance of buildings in Bahrain

Today, a great deal of effort is ongoing all over the world to find methods for optimising the energy performance of buildings. Such efforts can be seen in the European Energy Performance of Building Directive (EPBD). This directive aims to ensure energy saving and CO₂ emission reduction without compromising the local conditions and people's comfort. In the Gulf States, however, there is a need for such methods due to their economic and environmental benefits. This study introduces a simple but reliable methodology for optimising building energy performance in Bahrain. The methodology is based on building management systems (monitoring, analysing and targeting future performance), simulation tools and other technologies. This methodology was implemented using Visual DOE and was directly related to collectively gathered data gained form experimental works and practical applications. By means of the introduced methodology, energy consumption was obtained together with energy cost and CO₂ emissions. The applicability of this methodology was demonstrated through optimising a case office building in Bahrain.     

Drying air-induced disturbances in multi-layer coating systems

A range of new experimental techniques is developed to quantify drying-air induced disturbances on low viscosity single and multi-layer coating systems. Experiments on prototype slide-bead coating systems show that the surface disturbances take the form of a wavelike pattern and quantify precisely how its amplitude increases rapidly with wet thickness and decreases with viscosity. Heat transfer measurements show that the redistribution of water to form an additional lower viscosity carrier layer while increasing the solids concentration of the upper layer or layers enables the maximum drying rate, for which drying-air induced surface disturbances are acceptably small, to be increased with significant commercial benefits.     

A generalized analysis for cascading single fluid vapor compression refrigeration cycles using an entropy generation minimization method

This paper focuses on cascading an ideal vapor compression cycle and determining the optimal intermediate temperatures based on the entropy generation minimization method. Only superheating and throttle losses of the cycle are considered since they are inherent to the ideal vapor compression refrigeration cycle. The second law equations have been developed in terms of specific heats and temperature ratios with the intent of reducing involved property modeling. Also the entropy generation was expressed in terms of a single independent variable and minimized to develop an advanced rule for selecting optimum intermediate temperatures. Results for a cascade system operating between reduced temperatures of 0.684 and 0.981 with R-134a as the working fluid are presented. The approximate method presented here predicted the optimum intermediate reduced temperature for a two-stage system to be 0.88, a difference of 2% from the optimum. The method presented was a much better predictor of the optimum temperature than the geometric mean method which was 0.82, a difference of 5% from the optimum. The entropy generation distribution of the optimum solution was investigated. For a two-stage system, the lower stage and higher stage entropy generation was 44% and 56%, respectively. In comparison to the single stage, the two-stage reduced losses by 78%.     

The Development and Application of a Novel Optimisation Strategy for Solid Oxide Fuel Cell‐Gas Turbine Hybrid Cycles

A combined power system with solid oxide fuel cell (SOFC) and gas turbine (GT) is modelled and analysed thermodynamically in this paper. A novel optimisation strategy including the design of optimal parameters is proposed and applied to the hybrid system. Different sources of irreversible losses are specified, and entropy analyses are used to indicate the multi‐irreversibilities existing, and to assess the work potentials of the system. Expressions of the power output and efficiency for both the subsystems and the SOFC‐GT hybrid system are derived. The optimal performance characteristics are presented and discussed in detail through a parametric analysis. The developed model is expected to provide not only a convenient tool to determine the optimal system performance and component irreversibility, but also an appropriate basis to design similar complex hybrid power plants. This new approach can be further extended to other energy conversion settings and electrochemical systems. Decision makers should therefore find the methodology contained in this paper useful in the comparison and selection of advanced heat recovery systems.     

Optimisation of monolithic lining concepts of channel induction furnace

Abstract

For the possible energy savings and extension of the volume capacity, the monolithic lining of a channel induction furnace was optimised in the following manner. Orthogonal array method is utilised to systematically design the lining concepts, and the finite element simulations including the temperature dependent properties of monoliths are carried out to determine the temperatures and stresses during the preheating and holding. In terms of the main effect analysis materials for the monolithic lining are recommended. Moreover, a thickness–thickness–temperature isothermal map is provided to show the acceptable thickness range of working and insulating linings. Nevertheless, for the final decision the deliberate consideration for the cost effectiveness of a certain lining concept is also necessary.     

The influence of the legal and economical environment and the profile of activities on the optimal design features of a natural-gas-fired combined heat and power plant

The paper deals with the effect of some selected quantities occurring in the legal and economical environment on the optimal values of some selected design quantities of a natural-gas-fired CHP plant. This trend of investigations results from the newly observed legal changes in the legislation concerning new forms of mechanisms supporting the combined production of electricity and heat. Special stress was exerted on changes resulting from the formulation of two directives, viz. 2003/7/EC and 2004/8/EC.For the purpose of realising this task, a reference structure of a CHP plant was selected. For the steam-water part of the plant thirteen quantities were selected, determining the design features of the most essential components of this part of the system. These quantities served as decision variables in processes of optimisation. As the objective function the break-even price of electricity was assumed.The second part of the paper presents the results of sensitivity analyses of the fundamental indices of the energy and economical effectiveness to failures in the adherence of the optimal values of the respective design quantities, as well as the results of investigations on the effect of the operation time of the plant in the course of one year.     

MODELISATION D'UN SECHOIR SOLAIRE A POISSONS FONCTIONNANT EN CONVECTION NATURELLE

A mathematical model of the behaviour of a fish solar dryer has been described. This model has allowed an optimization of the design of this dryer (solar-chimney area and height, insolator area, etc...). The natural convection had to pulse drying air inside apparatus, whose capacity should be 30 kg of fresh fish.

Then the dryer has been built in National Fishing School of Anjouan (Comores Island). The first results mean a good fit between theoretical and experimental results.

The air-insolator, used for air heating, is a porous type, made with blacked coco fibers, crossed by the drying air. This local material is confirmed as a good thermic interface.

The most sensitive parameter, on the drying time, is the thickness of the fish slices. The choice of the fish quality is also very important: each different fish is characterized by one or several specific value of the water diffusivity constant, D_m. The model uses experimental values for the calculation.

Then the Fick's diffusion equation may be solved by decomposition of the moisture content inside fish slice (Fourier analysis).

Un modeéle matheématique du comportement d'un seéchoir solaire, destineé aà seécher du poisson, a eété eécrit. II a permis d'optimiser au mieux la geéomeétric de ce seéchoir qui a pu eêtre construit sur le site de I'eécole Nationale de peêche d'Anjouan aux Comores. II s'agit d'un seéchoir fonctionnant grace aà la convection naturelle, et dont la capacite est d'environ 30 kg.

L'air de seéchage est chauffeé par un capteur solaire de type absorbeur poreux, reéaliseé en bourre de noix de coco noircie. Le choix de ce mateériau local est bien suÛr volontaire; il s'est par ailleurs aveéreé comme un excellent milieu d'eéchange thermique.

Le parameètre le plus sensible sur la dureée de sechage est l'eépaisseur des filets de poisson. La qualiteé du poisson est aussi un choix important, chacun posseédant une constante de diffusiviteé de l'eau, D_m, bien speécifique. Le modeèle utilise les valeurs expeérimentales de cette constante. L'eéquation de Fick, qui reégit la migration de l'eau dans un mateériau poreux, peut alors eâtre reésolue en utiiisant une deécomposition en seérie de Fourier, de la reépartition de l'eau dans les tranches de poisson.