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The purpose of this paper is to approximate the convective heat transfer using a few non-dimensional parameters in the design process of large synchronous machines. The computed convective wall heat transfer coefficient can be used in circuit models or can be defined in numerical heat conduction (HC) models to compute the thermal field in the solid domains without the time consuming computation of the fluid domain.

Computational fluid dynamics (CFD) has been used to include a wide range of different designs, operating conditions and cooling schemes to ensure accurate results for a wide range of possible machines. Neural networks are used to correlate the computed heat transfer coefficients to various design parameters. The data set needed to define the weights and bias layers in the network has been obtained by several CFD simulations. A comparison of the evaluated solid temperatures with those obtained using the conjugate heat transfer (CHT) method has been carried out. The results have also been validated with calorimetric measurements.

The validation of the HC model has shown that this model is capable of yielding accurate results in a few minutes, in contrast to the several hours needed by the CHT solution. The workflow to determine the convective heat transfer in a specific part of an electrical machine has been also been established. The approximation of the convective wall heat transfer coefficient is shown to be obtainable in sufficient detail by using a neural network.

The paper describes a method to approximate the convective heat transfer accurately in a few seconds, which is very useful in the design process. The heat convection can then be characterized in a HC model including the solid domains only. The losses can be defined as sources in the solid domains, e.g. copper and iron, obtained by electromagnetic calculations and the thermal field can hence be easily computed in these parts. This HC model has the main advantage that the time consuming computation of the fluid domain is avoided.

The novelty in this work is the approximation of the convective heat transfer by using a neural network with an accuracy of less than 5 percent as well as the development of a HC model to compute the temperature in the solid domains. The investigations presented pinpoint relevant issues influencing the thermal behavior of electrical machines.

The purpose of this work is to propose a numerical method based on computational fluid dynamics (CFD) for reconstructing the heat transfer inside electrical machines. The used conjugate heat transfer (CHT) method takes heat convection and heat conduction into account to determine the temperature rise and the thermal losses in stator duct models of large hydro generators. Three different test cases are studied with different slot section components. The numerical models are validated with measurement data for a range of different mass flow rates.

The work presented is based on the combination of two complementary approaches, namely numerical simulation and measurements. The measured data for the air mass flow and the heat losses are used as boundary conditions for the identification of the temperature distribution in the solid and fluid domains (using a commercial software for CFD). The CHT method is an additional application of CFD and is used to solve the energy equations in the solid domains. Therefore, it is possible to define a thermal source in the solid domains.

The data obtained by the numerical computation are compared with measurement data for different mass flow rates of the cooling fluid. The quality of the computed values depending on the different mass flow rates shows a good agreement with the measured data. The temperature distribution in the solid domains depending on different material properties is also pointed out in this investigation.

The topic describes a method for solving the heat transfer in the fluid as well as the solid domains. The losses can be defined as sources in the solid domains, e.g. copper and iron, obtained by electromagnetic calculations. This boundary condition defines the situation more accurately than, for example, a constant value of the heat flux or the temperature at the walls like in common used CFD simulations. Another advantage of CFD over other approaches is the consideration of the actual wall heat transfer coefficient.

The presented investigations show relevant issues influencing the thermal behaviour of electrical machines.

The purpose of this paper is to carry out an analytical approximation model (heat transfer model (HTM)) for the calculation of the heat transfer coefficient at the end winding bars of large hydro generators. These coefficients are needed for lumped parameter thermal models in the design process.

The computational fluid dynamics simulation in combination with conjugate heat transfer (CHT) validates the accuracy of the HTM. The theoretical approach describes the formulation of the heat transfer coefficient and the Gauss-Newton method has been applied to find the coefficients of the approximation model.

The paper describes the new analytical approximation model for the heat transfer coefficient at the end winding bars of hydro generators and shows also the validation to simulation results.

The analytical approximation model for the heat transfer coefficient at the end winding bars has been described and a comparison with CHT results has shown a good agreement.

The purpose of this paper is to present a new computational fluid dynamics model for large electrical machines to simulate the heat transfer at specific components to the appropriate ventilation method. The most damageable parts for overheating in generators are the end winding bars, pole windings and stator ducts.

The reduced model introduced is basically derived from the state-of-the-art pole section model (PSM) and enables faster computations for heat transfer and cooling simulations of electrical machines. The fundamentals of the two methods and the grid generation are described. Two PSMs and four different reduced models are presented and compared among each other to tune the reduced model.

As a topic of outstanding interest in large hydro generators, the heat transfer at the end winding bars is solved with the aid of the reduced model. This slot sector model (SSM) has been validated and the computation time has been reduced enormously in comparison to the state-of-the-art PSM.

The heat transfer has been carried out only for the end winding region of large hydro generators. The effect of the reduced model on the pole sections and stator ducts has not been investigated. Nevertheless, the reduced model is also valid for large motors.

This reduced model can finally be used for parametric studies with different cooling schemes and boundary conditions in the design process.

The comparison of various SSMs to PSMs shows an acceptable accuracy of the reduced model in combination with a rather low computation time. Due to modeling one slot only, the MFR-MP approach is an adequate and fast analyzing method for this kind of model structure.

Owing to the salient pole structure and stator slots of hydro-generator, the air gap magnetic field in the generator is unevenly distributed. High-frequency harmonic components contained in the inhomogeneous air gap magnetic field will have a negative impact on the generator performance. The purpose of this paper, therefore, is to improve the distribution of air gap magnetic field by using appropriate magnetic slot wedge, thereby improving the generator performance.

Taking a 24 MW, 10.5 kV bulb tubular turbine generator as an example, the 2 D electromagnetic field model of the generator is established by finite element method. The correctness of the model is verified by comparing the finite element calculation data with the experimental data. The influences of the permeability and thickness of the magnetic slot wedge on the generator performance are studied.

It is found that the intensity and harmonic content of the air gap magnetic field will change with the permeability of slot wedge and then the performance parameters of the generator will also change nonlinearly. The relationship between the eddy current loss, torque ripple, output voltage and other parameters of the generator and the permeability of slot wedge is confirmed. In addition, the variation of losses and torque with wedge thickness is also obtained.

The influence mechanism of magnetic slot wedge on the performance of hydro-generator is revealed. The presented results give guidelines to selecting suitable magnetic slot wedge to improve generator performance.

In this paper, we applied the finite element modeling to the stator temperature distribution of a hydroelectric generator. The electrical losses produce a temperature distribution in the stator of a synchronous generator. For the calculation and optimization of the temperature distribution, a full parameterized thermal model of the stator was created using the finite element method. Now it is possible to calculate the thermal effects of different parameter modifications and additionally we can optimize the heat transfer for the stator with variant calculations. The most important bar fitting systems and its thermal efforts are included in this thermal stator model. Our targets are to decrease the expensive and time‐consuming laboratory measurements in the future and improve the accuracy of the standard calculation software. To estimate the accuracy of the finite element model we build an additional laboratory model.

Aims to trace the legal bases for the protection of fundamental rights in the European Community and the European Union, but looks here at internal policy only. Though there was no basis in the Treaty of Rome (1957) for human rights, the European Court of Justice has declared that fundamental human rights are enshrined in the general principles of Community law and thereby protected by the Court. Investigates the Charter, in full, herein

This study aims to monitor seawater by determing two biological indicators, Escherichia coli and Enterococcus faecalis. The process of following standard procedures is mainly time-consuming. Thus, there is a demand for a biosensor, an appropriate device for rapid and accurate results that can give information about the microbiological quality of seawater in an effective and rapid way.

In the gold standard method for seawater monitoring, the filter method is applied as a condensation step. In this work, the authors evaluated six types of common syringe filters for bacteria concentration and then the best filter was used for seawater analysis for E. coli and Enterococci with loop-mediated isothermal amplification (LAMP) polymerase chain reaction (PCR).

Cellulose acetate filter had the highest efficiency (98%) for bacterial concentration. The limit of detection of the LAMP method was 104/1,000 mL for both E. coli and E. faecalis. The proposed method could be used for the development of seawater biosensors with advantages such as a simple heating element and the speed that the LAMP PCR presents.

The suggested protocol is proposed in an integrated in situ system, a biosensor, for seawater quality determination.