The purpose of this study is the development of an automated two-dimensional airfoil shape optimization procedure for small horizontal axis wind turbines (HAWT), with an emphasis on high thrust and aerodynamically stable performance. The procedure combines the Computational Fluid Dynamics (CFD) analysis with the Response Surface Methodology (RSM), the Biobjective Mesh Adaptive Direct Search (BiMADS) optimization algorithm and an automatic geometry and mesh generation tool. In CFD analysis, a Reynolds Averaged Numerical Simulation (RANS) is applied in combination with a two-equation turbulence model. For describing the system behaviour under alternating wind conditions, a number of CFD 2D-RANS-Simulations with varying Reynolds numbers and wind angles are performed. The number of cases is reduced by the use of RSM. In the analysis, an emphasis is placed upon the role of the blade-to-blade interaction. The average and the standard deviation of the thrust are optimized by a derivative-free optimization algorithm to define a Pareto optimal set, using the BiMADS algorithm. The results show that improvements in the performance can be achieved by modifications of the blade shape and the present procedure can be used as an effective tool for blade shape optimization.

Thermoelectric generators (TEGs) have the ability to convert waste heat into electrical energy under unfavorable conditions and are becoming increasingly popular in academia, but have not yet achieved a broad commercial success, due to the still comparably low efficiency. To increase the efficiency and economic viability of TEGs, research is performed on the materials on one hand and on the system connection on the other. In the latter case, the net output power of the cooling system plays a key role. At first glance, passive cooling seems preferable to active cooling because it does not affect the net electrical output power. However, as shown in the present review, the active cooling is to be preferred for net output power. The situation is similar in air and water-cooling. Even though air-cooling is easier to set up, the water-cooling should be preferred to achieve higher net output power. It is shown that microchannel cooling has similar hydraulic performance to conventional cooling and inserts increase the net output power of TEG. As the review reveals that active water-cooling should be the method of choice to achieve high net output power, it also shows that a careful optimization is necessary to exploit the potential.

The electric power produced by a thermoelectric generator (TEG) is strongly influenced by the applied heat sink. While a TEG is aimed at harvesting waste heat, the optimization of the efficiency of the heat sink is a key task for the design of waste heat recovery systems implementing TEG. A TEG model is proposed and implemented in an open source toolbox for field operation and manipulation (OpenFOAM) for the purpose of performing optimizations of the heat sink, using a commercially available TEG as basis. This model includes the multi-physics thermoelectric coupled effects. Conservation principles of energy and current are considered simultaneously. This includes the thermal and electric conduction, Seebeck effect, Peltier effect, Thomson effect, and Joule heating. Particular attention is given to a proper modeling of the boundary conditions. The thermoelectric model is implemented in such a way that it can readily be combined with other physical models in OpenFOAM. The model is validated by comparing the predictions to analytical results, measurements as well as the simulation data of other authors.

Within the framework of a Reynolds averaged numerical simulation (RANS) methodology for modeling turbulence, a comparative numerical study of turbulent lifted H₂/N₂ flames is presented. Three different turbulent combustion models, namely, the eddy dissipation model (EDM), the eddy dissipation concept (EDC), and the composition probability density function (PDF) transport model, are considered in the analysis. A wide range of global and detailed combustion reaction mechanisms are investigated. As turbulence model, the Standard k-ε model is used, which delivered a comparatively good accuracy within an initial validation study, performed for a non-reacting H₂/N₂ jet. The predictions for the lifted H₂/N₂ flame are compared with the published measurements of other authors, and the relative performance of the turbulent combustion models and combustion reaction mechanisms are assessed. The flame lift-off height is taken as the measure of prediction quality. The results show that the latter depends remarkably on the reaction mechanism and the turbulent combustion model applied. It is observed that a substantially better prediction quality for the whole range of experimentally observed lift-off heights is provided by the PDF model, when applied in combination with a detailed reaction mechanism dedicated for hydrogen combustion.

Designs of heat exchangers are quite often disconnected to the performance of thermoelectric generators (TEG). In this work, the TEG and the heat exchanger are numerical modelled simultaneously in a computational fluid dynamics (CFD) environment (OpenFOAM) to maximize the output power of the system while minimize the hydraulic power required. A preliminary work was done where the modelling of the heat exchanger, a single laminar slot jet, and the modelling of a 16 element TEG are validated. The considered heat exchanger is a laminar slot jet consists of a linear array of discrete heat sources which accord with the geometry of a thermoelectric generator. The considered 16 element TEG is modelled using the temperature dependent material properties which require a solution of a system of nonlinear differential equations, namely the conservation of energy and the conservation of electric current. The conjugate heat transfer OpenFOAM solver chtMultiRegionFoam is extended by an additional differential equation for the solid region to model the conservation of current. The conservation of energy is expanded by additional source terms based on Peltier/Thomson effect and Joule heat. To simplify the calculation, interface and 1D resistor load boundary conditions are developed and implemented. The heat exchanger and the TEG model, both, are validated by comparisons with measurements, where a good agreement is observed.

Designs of heat exchangers are quite often disconnected from the performance of thermoelectric generators (TEG). In the present work, the TEG and the heat exchanger are modeled in a coupled manner in a computational fluid dynamics environment (OpenFOAM). To this purpose, the previously developed OpenFOAM solver, tegFOAM, is extended by incorporating temperature dependent material properties in TEG, and conjugate heat transfer. In the TEG domain, the heat conduction and electric fields are solved in a coupled manner, whereas the convective heat transfer on the cooling side is coupled with the heat conduction in TEG. The implementation with respect to the temperature dependent material properties of TEG is validated by comparisons with experimental and computational results of other authors. For validating the applied prediction procedure for the convective cooling, a configuration out of the literature is investigated, which resembles a typical TEG cooling arrangement quite closely, where a single laminar slot jet is impinging onto a linear array of discrete heat sources. Subsequently, the complete, coupled model is applied to predict the performance of a TEG consisting of 16 elements.