Search results

The purpose of this paper is to analyse the thermal environment of two engineering testing centres cooled via different means using computational fluid dynamics (CFD), focussing on the indoor temperature and air movement. This computational technique has been used in the analysis of thermal environment in buildings where the profiles of thermal comfort parameters, such as air temperature and velocity, are studied.

A pilot survey was conducted at two engineering testing centres – a passively cooled workshop and an air-conditioned laboratory. Electronic sensors were used in addition to building design documentation to collect the required information for the CFD model–based prediction of air temperature and velocity distribution patterns for the laboratory and workshop. In the models, both laboratory and workshop were presumed to be fully occupied. The predictions were then compared to empirical data that were obtained from field measurements. Operative temperature and predicted mean vote (PMV)–predicted percentage dissatisfied (PPD) indices were calculated in each case in order to predict thermal comfort levels.

The simulated results indicated that the mean air temperatures of 21.5°C and 32.4°C in the laboratory and workshop, respectively, were in excess of the recommended thermal comfort ranges specified in MS1525, a local energy efficiency guideline for non-residential buildings. However, air velocities above 0.3 m/s were predicted in the two testing facilities, which would be acceptable to most occupants. Based on the calculated PMV derived from the CFD predictions, the thermal sensation of users of the air-conditioned laboratory was predicted as −1.7 where a “slightly cool” thermal experience would prevail, but machinery operators in the workshop would find their thermal environment too warm with an overall sensation score of 2.4. A comparison of the simulated and empirical results showed that the air temperatures were in good agreement with a percentage of difference below 2%. However, the level of correlation was not replicated for the air velocity results, owing to uncertainties in the selected boundary conditions, which was due to limitations in the measuring instrumentation used.

Due to the varying designs, the simulated results of this study are only applicable to laboratory and workshop facilities located in the tropics.

The results of this study will enable building services and air-conditioning engineers, especially those who are in charge of the air-conditioning and mechanical ventilation (ACMV) system design and maintenance to have a better understanding of the thermal environment and comfort conditions in the testing facilities, leading to a more effective technical and managerial planning for an optimised thermal comfort management. The method of this work can be extended to the development of CFD models for other testing facilities in educational institutions.

The findings of this work are particularly useful for both industry and academia as the indoor environment of real engineering testing facilities were simulated and analysed. Students and staff in the higher educational institutions would benefit from the improved thermal comfort conditions in these facilities.

For the time being, CFD studies have been carried out to evaluate thermal comfort conditions in various building spaces. However, the information of thermal comfort in the engineering testing centres, of particular those in the hot–humid region are scantily available. The outcomes of this simulation work showed the usefulness of CFD in assisting the management of such facilities not only in the design of efficient ACMV systems but also in enhancing indoor thermal comfort.

This paper aims to improve the finite element modelling of transformers subjected to DC excitation, by including core joint details.

Geomagnetically induced currents (GICs) or leakage DC can cause part-cycle, half wave saturation of a power transformer’s core. Practical measurements and finite element matrix (FEM) simulation were carried out using three laboratory-scale, untanked single-phase four limb transformers resembling real power transformers in terms of the core steel and parallel winding assemblies. “Equivalent air gaps” at the joints, based on AC measurements, were applied to the FEM models for simultaneous AC and DC excitation.

Measurements confirm that introducing equivalent air gaps at the joints improves the FEM simulation of transformers carrying DC.

The FEM simulations based on the laboratory transformers are exemplary, showing the difference between modelling core joints as solid or including equivalent air gaps. They show that, for more representative results, laboratory transformers used for research should have mitred core joints (like power transformers).

This research shows why joint details are important in FEM models for analysing transformer core saturation in the presence of DC/GICs. Extending this, other core structures of power transformers with mitred joints should improve the understanding of the leakage flux during half-wave saturation.

To describe a new approach to the performance evaluation and benchmarking of analytical laboratory services and their associated supply chains.

Life cycle and industrial process approaches are adapted for consideration of the environmental performance of multidisciplinary laboratories as found in large multifunctional facilities. Models are developed to facilitate performance evaluation.

The laboratory product model (LPM) considers laboratory service delivery from a whole‐of‐life perspective. It defines an information product as a standard unit of production that facilitates performance evaluation of laboratories using both normalised and absolute values. Performance evaluation boundaries are extended beyond the internal laboratory processes to incorporate the supply chain, i.e. from sample collection to the end use of the information product.

Application of the research is limited by the availability of relevant corporate data. Future work could address routine collection of data appropriate to environmental performance evaluation so as to reduce the need for extensive life cycle inventories.

Focus is on a practical approach to improving the environmental performance of laboratory services through objective evaluation of laboratory and facility performance. The research provides a means of comparing laboratories founded in different disciplines, e.g. chemistry and microbiology.

Addresses laboratory supply chain issues by providing new tools for performance evaluation and benchmarking of laboratories. It uses new approaches to laboratory performance evaluation that help achieve sustainability.

Examines the tenth published year of the ITCRR. Runs the whole gamut of textile innovation, research and testing, some of which investigates hitherto untouched aspects. Subjects discussed include cotton fabric processing, asbestos substitutes, textile adjuncts to cardiovascular surgery, wet textile processes, hand evaluation, nanotechnology, thermoplastic composites, robotic ironing, protective clothing (agricultural and industrial), ecological aspects of fibre properties – to name but a few! There would appear to be no limit to the future potential for textile applications.

The purpose of this paper is to explore the potential of lesson study for the development of a science of teaching cast in the form of John Dewey's “laboratory model” of learning to teach.

The early sections compare the “laboratory” with the “apprenticeship” and “rationalist” models of learning to teach, which emphasise the primacy of practice and theory respectively. The unity of theory and practice embodied in the “laboratory model” is outlined, linking the development of teachers’ theoretical understanding with the development of their practice. A distinction between pedagogy and teaching is drawn. The later sections examine the potential of lesson study to develop as a teachers’ based pedagogical science, particularly when informed by variation theory. The paper concludes by suggesting ways in which different theories of learning can be integrated into learning study, and points to ways in which particular studies can contribute to the systematic construction of pedagogical knowledge.

There can be no pedagogy without casting teaching as an experimental science, in which pedagogical theories are appropriated, tested and further developed as a source of pedagogical principles. Pedagogy therefore consists of a science of teaching in which teachers actively participate in knowledge construction. Lesson study when informed by an explicit learning theory, such as variation theory, provides a strong basis for the development of a practitioner‐based science of teaching.

The paper creates original links across disparate work in the field of teaching and learning.

Doubly fed induction generator DFIG applied in over 50 percent of modern variable speed wind power systems and interesting also for adjustable speed diesel generation sets or multi‐megawatt water turbines is troublesome in the mean of maintenance of slip‐rings and brushes. Especially, it concerns isolated power systems and offshore wind turbines. Application of brushless DFIG in such cases eliminates the mentioned problem. Constructions of the machine and consequently the model and mathematical description is more complicated than classical slip‐ring DFIG, therefore it is still developed in several scientific institutions to obtain adequate performance. The following work is dedicated to mathematical description, modelling and implementation of the control method for autonomous operation in the laboratory model of brushless DFIG.

Analysis and simulation of the machine model and laboratory tests on a small scale prototype of brushless DFIG.

It has been proven that sensorless direct voltage control of DFIG can be applied for both slip‐ring and brushless machines, as it does not require machine parameters.

Brushless DFIG development is far from the performance needed by industrial implementation. Lower efficiency and higher reactive power needed by the machine, in comparison to classical DFIG of the same power range, result from double air gap seen by magnetic flux. However, the constructions of prototype machines are better and better, and their capabilities become closer to DFIG.

Variable and adjustable speed generation systems such as wind turbines, diesel generation sets, water turbines.

Standalone power systems with DFIG described in several papers require quite complicated control methods based on the mathematical equations of the machine model. Thus, these methods have to be significantly modified for the brushless version of this machine type, due to the fact of a much more complicated model. The proposed sensorless method of the output voltage control requires only redesign (tuning) of the PI controllers responsible for control of the rotor current, stator voltage amplitude and frequency.

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.

This paper presents a maturity model for digital transformation effectiveness in laboratories (labs) with education and research purposes.

The model was developed using design science research methodology, expert interviews and case studies.

The model fulfills three practical goals: (1) to establish comparability of the effectiveness of the digital transformation of labs, (2) to provide lab operators from academia and industry with a guide for (further) transformation and (3) to build initial trust among lab users. In addition, the maturity model contributes to the literature on digital lab transformation by capturing, describing, structuring and evaluating relevant dimensions, items and levels. Model strengths and weaknesses, areas for improvement, international applicability and practical and reusable recommendations are presented as well as the added value in assessing lab functionalities and lab sustainability.

Although originally developed as a maturity model driven by lab education, the model is also suitable for the transformation of research labs in manufacturing technology management. Digital labs can efficiently support industry training and research and development activities as well as simulate the development of new processes prior to their implementation.

Especially for these use cases, the authors see application potentials for the use of online labs from an organizational perspective and from the perspective of stakeholders such as industry users and operators with a manufacturing background, who use and develop transformed labs for teaching and research.

The purpose of this paper is to elaborate a method of computer analysis of high‐speed motor with specific parameters and verifying the obtained results, i.e. computer models by experimental (laboratory) tests.

In order to determine motor properties from the viewpoint of energy conversion, a model using FEM was worked out with the help of Maxwell software. To determine static and dynamic properties of both motor and drive, Matlab/Simulink models were used; one of these models was a built‐in (library) model, the other one was proposed by the authors.

The new analysis method and model of high‐speed motor have been carried out.

The permanent magnet brushless direct current high‐speed motor was the subject of the research. In the first part of the research, the properties of the motor were determined by using finite element method.

The laboratory prototype can be a starting point in establishing the production of the high‐speed motors with rotational speed in the range of 50,000‐100,000 rpm.

At this moment, there are several possible application of the high‐speed motor and it should be expected that other new applications can appear in near future after the start of the production.

The paper shows that the computer‐based analysis method determines the motor properties accurately. It is also pointed out that a motor with half‐open slots has advantageous properties. The new simulation model of high‐speed motor has been carried out. This model allows taking into account some imperfections caused by slots and rectangular cross‐section magnets.

This contribution aims to introduce an effective low cost polymer-nanocomposite for possible application to achieve a super protection for highly damaged ancient Egyptian wall paintings.

SiO2 and Al2O3 nanoparticles were synthesized by the sol-gel method. Then, the polymer-nanocomposite was prepared by simple mixing and dispersing the nanoparticles into the tetraethoxysilane polymer solution, with the aid of an ultrasonic dismembrator. The application of the polymer-nanocomposite and other polymeric nanodispersions, on laboratory models, was performed by the brushing technique. Next, the materials stability was evaluated by means of digital optical microscope, colorimetry, FE-scanning electron microscope, measuring the static contact angle and water absorption rates.

The results were promising in creating a superhydrophobicity and the static contact angle (?S) measured for the polymer-nanocomposite reached 135o. An average of three measurements of the water absorption rate after polymer-nanocomposite treatment was 0.66 g/m2 s, compared to 2.60 g/m2 s for the control model (untreated). Further, an average of color difference (?E*) for the treated surface was 2.78, and after the accelerated thermal aging was 3.6. Observing the surface morphology, the polymer-nanocomposite enhanced the roughness of the treated surface and showed a high resistance to laboratory salt weathering.

Preparation of a polymer-nanocomposite by adding SiO2 and Al2O3 NPs to tetraethoxysilane polymer has been proposed. As a promising conservation material, the produced polymer-nanocomposite helped to form an efficient protective film.

This paper attains to develop an economic polymer-nanocomposite to maintain a high protection to damaged ancient Egyptian wall paintings and similar objects.