Тепловая модель силового сухого трансформатора

Рассмотрена модель силового сухого трансформатора, содержащая в отличие от существующих моделей, несколько однородных тел: магнитопровод, обмотка, изоляция, внутренняя охлаждающая среда и внешняя охлаждающая среда. Кроме того, модель описывает тепловые процессы в незащищенном силовом сухом трансформаторе и силовом сухом трансформаторе, помещенном в защитный кожух. Проведенные экспериментальные исследования подтверждают адекватность предложенной тепловой модели.The model of the power dry-type transformer is considered in the paper including in contrast to existing models a number of homogeneous bodies: magnetic core, winding, insulation, internal cooling agent and external cooling agent. In addition to this the model describes thermal processes in an unprotected power dry-type transformer and power dry-type transformer placed in the protective housing. Experimental studies confirm the adequacy of the thermal model proposed

A novel approach to reduce the computation time for CFD : hybrid LES-RANS modelling on parallel computers

Large Eddy Simulation is a method of obtaining high accuracy computational results for modelling fluid flow. Unfortunately it is computationally expensive limiting it to users of large parallel machines. However, it may be that the use of LES leads to an over-resolution of the problem because the bulk of the computational domain could be adequately modelled using the Reynolds averaged approach. A study has been undertaken to assess the feasibility, both in accuracy and computational efficiency of using a parallel computer to solve both LES and RANS type turbulence models on the same domain for the problem flow over a circular cylinder at Reynolds number 3 900 To do this the domain has been created and then divided into two sub-domains, one for the LES model and one for the kappa-epsilon turbulence model. The hybrid model has been developed specifically for a parallel computing environment and the user is able to allocate modelling techniques to processors in a way which enables expansion of the model to any number of processors. Computational experimentation has shown that the combination of the Smagorinsky model can be used to capture the vortex shedding from the cylinder and the information successfully passed to the kappa - epsilon model for the dissipation of the vortices further downstream. The results have been compared to high accuracy LES results and with both kappa - epsilon and Smagorinsky LES computations on the same domain. The hybrid models developed compare well with the Smagorinsky model capturing the vortex shedding with the correct periodicity. Suggestions for future work have been made to develop this idea further, and to investigate the possibility of using the technology for the modelling of mixing and fast chemical reactions based on the more accurate prediction of the turbulence levels in the LES sub-domain.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Managing Stakeholders or the Environment? The Challenge of Relating Indicators in Practice

Many organizations present their environmental work in the form of annual reports and use the indicators in them for follow-up. However, internal communication and management is needed for environmental improvements. The indicators found in reports may be suitable for external communication, but are they also suitable internally and operationally? This article reviews the existing literature on environmental indicators. With the help of an operational approach, from organisation theory, and a life-cycle approach, indicators are analysed. The analysis shows that formulating indicators for internal management is not an easy task; available guidelines are of little help. It is concluded that the environment can be managed internally by relating indicators. Therefore, an additional set of indicators for internal management and a wider responsibility for the life cycle are recommended. The analysis and recommendations are illustrated with examples drawn from the field of property management

Supply chain sustainability performance measurement of small and medium sized enterprises using structural equation modeling

Sustainability of small and medium sized enterprises (SMEs) is significant as SMEs contribute to GDP substantially in every economy. This research develops an innovative sustainable supply chain performance measurement model for SMEs. Prior researches predominantly use balanced score card (BSC) approach that presume causal relationship of criteria and Data Envelopment Analysis (DEA), which derive efficiency of units from a few input and output criteria. While DEA is effective for policymakers, BSC is more suitable for individual SME. The proposed method that uses structural equation modeling (SEM) approach to derive the relationship of criteria and criteria weights formulates regression-type models for a specific region as well as for specific SME. The SEM-based supply chain sustainability performance measurement model is beneficial to policymakers as they can determine means for improvement at a regional level. The proposed method could also facilitate managers/owners of individual SMEs with measures for improving their supply chain sustainability performance. The method has been applied to three varied geographical locations in the UK, France and India in order to demonstrate its effectiveness

Environmental management systems, practices and outcomes: Differences in resource allocation between small and large firms

This paper argues both small and large firms use different resource allocation patterns to benefit from implementing environmental management practices (EMPs) and environmental management systems (EMS). Results from the multi-group structural equation analyses of a survey of manufacturing firms in two countries support the resource allocation arguments - large firms use resource-demanding EMPs such as green product design and green production to improve outcomes in environmental, cost-reduction and business performance, while small firms choose resource-light EMPs such as green logistics and green packaging to gain only environmental and cost-reduction benefits. The paper advances the existing resource-advantage view by revealing different resource allocation patterns and provides meaningful recommendations through which policy makers can address various resource allocation constraints among small and large enterprises

Products in environmental management systems : drivers, barriers and experiences

Do standardised environmental management systems (EMS) lead to improved environmental performance? This depends on to what extent these systems lead to changes in important flows of material and energy, which for manufacturing companies, in turn, mean that the product development process is important. Consequently, it appears vital to investigate the connection between EMS and ‘Design for the Environment’ (DFE), i.e. the connection between these management systems and concepts that deal with environmental issues in product development. This paper presents product-oriented environmental management systems (POEMS), including characteristics of existing models, experiences from projects where these models have been tested and experiences concerning the product connection in ‘normal’ EMS. It includes a discussion of important factors influencing to what extent DFE activities are integrated into EMS and/or the outcome of such integration. There are many motives for integrating the two concepts. Firstly, DFE thinking might enrich EMS by contributing with a life-cycle perspective. If EMS encompassed products' life cycles to a greater extent, they would be a better complement to the often facility-oriented legal requirements and authority control. Secondly, EMS might remove the pilot project character of DFE activities and lead to continuous improvement. Thirdly, integration could lead to successful co-operation, both internally and externally. However, existing studies show that there is a mixed picture concerning the extent ‘normal’ EMS currently encompass products