Search results

The purpose of this paper is to study the effect of a computational grid in computational fluid dynamics‐based mathematical modeling, focusing on but not limiting the attention to industrial‐scale boilers.

A full boiler model is used to show the difficulties related to judging iteration and discretization errors in boiler modeling. Then, a single jet is studied in detail to determine the proper degree of local grid refinement required in the vicinity of jets in the full boiler model. Both a nonreactive axisymmetric jet exhausting into a quiescent atmosphere and a reactive jet exhausting into a crossfiow are studied.

Over two million computational cells are required for the grid‐independent solution for a single jet. Local grid refinement is shown to be a good option for improving the results consistently without an excessive increase in the number of computational cells. Using relatively coarse grids of tetrahedral cells with a finite‐volume‐based solver may cause serious errors in results, typically by overpredicting the jet spreading rate and underpredicting the mean axial centerline velocity. Relatively coarse grids of hexahedral cells are less prone to error in a case where a jet exhausts into a quiescent atmosphere. However, their performance deteriorates when a crossfiow is introduced. As assumed, the differences in the predicted reaction rate and species concentrations are significant in the reactive case. It is confirmed that the standard k‐ε model tends to overpredict the axisymmetric jet spreading rate. The estimated inlet turbulence intensity is not among the most critical factors in modeling. Estimations of the axisymmetric jet centerline velocity from the analytical correlation may not coincide with the modeling results.

The error caused by the computational grid may easily dominate the errors caused by simplifying models used in industrial‐scale boiler modeling (turbulence, combustion, radiative heat transfer, etc.).

The present study deals with grid independency issues in industrial‐scale boiler modeling in a systematic and profound manner.

In the recent years the interest toward the use of biomass as a fuel for energy conversion, along with the continuous tightening of regulations, has driven the improvement of accurate design techniques which are required to optimize the combustion process and simultaneously control pollutant emissions. In this paper the use of a 3D Computational Fluid Dynamics approach is analyzed to that aim by means of an application to an existing 50 MW biomass fixed-bed combustion furnace fueled by grape marc. The paper aims to discuss these issues.

The studied furnace is an interesting example of biomass utilization as it may integrate biomass with organic residual by an industrial process. The numerical model has been implemented into an OpenFOAM solver, with an Eulerian-Lagrangian approach. In particular, the fully 3D approach here presented, directly solves for the gas and solid evolution in both the combustion bed and the freeboard. Special care has also been devoted to the treatment of radiating fluxes, having a remarkable influence, again, on the bed evolution.

Results have been compared to experimental data in terms of temperature showing a good agreement. Further comparisons have been done with literature available data for a similar power size biomass furnace showing reasonable similarities.

Emission formation processes in a biomass furnace are dealt with in this paper. The innovation lies in the use of a fully 3D numerical approach, that is validated with regard to temperature measurements gathered in a multi-MW experimental furnace.

Thermochemical conversion processes are one of the possible solutions for the flexible production of electric and thermal power from biomass. The pyrolysis degradation process presents, among the others, the interesting features of biofuels and high energy density bio-oil production potential high conversion rate. In this paper, numerical results of a slow batch and continuous fast pyrolyzers, are presented, aiming at validating both a tridimensional computational fluid dynamics-discrete element method (CFD–DEM) and a monodimensional distributed activation energy model (DAEM) represents with data collected in dedicated experiments. The purpose of this paper is then to provide reliable models for industrial scale-up and direct design purposes.

The slow pyrolysis experimental system, a batch of small-scale constant-pressure bomb for allothermic conversion processes, is presented. A DEM numerical model has been implemented by means of a modified OpenFOAM solver. The fast pyrolysis experimental system and a lab scale screw reactor designed for biomass fast pyrolysis conversion are also presented along with a 1D numerical model to represent its operation. The model which is developed for continuous stationary feeding conditions and based on a four-parallel reaction chemical framework is presented in detail.

The slow pyrolysis numerical results are compared with experimental data in terms of both gaseous species production and reduction of the bed height showing good predictive capabilities. Fast pyrolysis numerical results have been compared to the experimental data obtained from the fast pyrolysis process of spruce wood pellet. The comparison shows that the chemical reaction modeling based on a Gaussian DAEM is capable of giving results in very good agreement with the bio-oil yield evaluated experimentally.

As general results of the proposed activities, a mixed experimental and numerical approach has demonstrated a very good potential in developing design tools for pyrolysis development.

This paper aims to investigate a company’s corporate social responsibility (CSR) communications in a business network with regard to the flow of critical events related to CSR.

The paper focuses on the drama that unfolded at a Nordic-based multinational corporation, Stora Enso, after a critical event related to CSR and the specific signs and codes applied by the company to justify its actions. To achieve the aims, the authors conducted a dramaturgical and semiotic analysis of the company’s corporate communications in connection with various actions prior to or following the major critical event.

The findings consist of a five-act drama that unfolded around certain CSR communication activities at the company. The authors followed the company’s shift in communication strategy as they were compelled to adopt a more responsive and involved approach. The results also show the roles of the various business network actors in shaping CSR communications.

This case has practical uses for providing the framework to create effective messages at different stages of the communication process related to a major CSR event.

The originality of the study lies in its application of a dramaturgical and semiotic approach to the analysis of CSR communication. It also contributes to the scarce literature on CSR communication within business networks.

In recent years, using aberration-corrected transmission electron microscopy, the authors have achieved precisely detecting the structural evolution of passive film as well as its interface zone at atomic scale. The purpose of this paper aims to make a brief review to show the authors’ new understanding and perspective on the issue of critical factors determining stability of passive film of Fe-Cr alloy.

The introduction of single crystal enabled the authors to obtain a distinct metal/passive film interface and better characterize the structure of the interface region. The authors use aberration-corrected TEM to conduct cross-sectional observation and directly capture the details across the entire film at a high spatial and energy resolution.

Apart from the passive film itself, the interface zone, including metal/film (Me/F) interface and the adjacent metal side, is also the site which is attacked. Accordingly, the nature of the interface zone, such as microstructure, composition and atomic configuration, is one of the critical factors determining the stability of passive film.

Deciphering the critical factors determining the stability of passive film is of great significance and has been a fundamental issue in corrosion science. Great attention has been paid to the nature of the passive film itself. In contrast, the possible role of the interface between the passive film and the metal is rarely taken into account. Based on the advanced analytical tool with high spatial resolution, the authors have specified the significant role of interface structures on the macro-scale stability of passive film.

This paper aims to understand the effect of water jet cavitation peening (WJP) on stress corrosion cracking (SCC) behavior of alloy 600 and alloy 182 in high temperature water.

Surface and cross-section morphology, grain boundary microstructure, residual stress and strain distribution, hardness and surface roughness in water jet cavitation peened alloy 600 and alloy 182 were characterized.

A superior stress corrosion cracking resistance was obtained in 600MA, which can be attributed to the formation of the ultrafine grain layer and the higher magnitude residual compressive stress.

Relationship between WJP-induced microstructure and stress state change and SCC susceptibility was conducted. It could provide a theoretical basis for developing application of WJP in nuclear power plants.

Establishing accurately the behaviour of metallic components in their service environment is an important need for much of manufacturing industry. In fields such as high‐temperature processing, nuclear and marine engineering it is crucial to long‐term safety and to plant economics. A Finnish research team has developed some novel means for determining the corrosion mechanisms, occurring in a wide variety of working environments, enabling patterns of behaviour to be identified and analysed.

An inquiry into the constitution of the experience of patienthood. It understands “becoming a patient” as a production of a subjectivity, in other words as a process of individuation and milieu that occurs through an ontology of production. This ontology of production can, of course, also be understood as a political ontology. Therefore, this is, first of all, an inquiry into a mode of production, and, secondly, an inquiry into its relation to the issue of social justice – because of effects of digital divisions. In these terms, it also reflects on how expert discourses, such as in medical sociology and science studies (STS), can (and do) articulate their problems.

An integrative mode of discourse analysis, strongly related to discursive institutionalism, called semantic agency theory: it considers those arrangements (institutions, informal organizations, networks, collectivities, etc.) and assemblages (intellectual equipment, vernacular epistemologies, etc.) that are constitutive of how the issue of “patient experience” can be articulated form its position within an ontology of production.

The aim not being the production of a finite result, what is needed is a shift in how “the construction of patient experience” is produced by expert discourses. While the inquiry is not primarily an empirical study and is also limited to “Western societies,” it emphasizes that there is a relation between political ontologies (including the issues of social justice) and the subjectivities that shape the experiences of people in contemporary health care systems, and, finally, that this relation is troubled by the effects of the digital divide(s).

A proposal “to interrogate and trouble” some innovative extensions and revisions – even though it will not be able to speculate about matters of degree – to contemporary theories of biomedicalization, patienthood, and managed care.

The purpose of this study is to use a steady-state model structure to investigate earnings management (EM) theoretically in the context of different expense theories. Empirically, the objective is to apply the theoretical model to investigate the implicit choice of expense theories for reporting expenses. The study aims to present a new approach to analyze EM.

The study makes use of ten-year time-series data originally from 1,015 Finnish public and private firms to estimate the parameters of the steady-state model, and to investigate which expense theories the firms implicitly follow in financial reporting. The parameters are estimated using the restricted least squares regression method. The final sample included data from 631 firms fulfilling restrictions for the consistency of estimates.

The paper provides empirical insights about expense theories that Finnish firms implicitly follow in financial reporting. Evidence shows that the reporting of expenses mainly follows the units-of-revenue and the rate-of-return theories. Only a small number of firms follow the interest expense theory.

The study is based on a steady-state approach, and therefore, the research results may lack generalizability as only 62% of the original sample firms obtained consistent estimates. Therefore, researchers are encouraged to use more general models for further theoretical and empirical work.

The paper includes implications for a new approach to EM. It also gives implications how to analyze different expense theories in the context of EM both theoretically and empirically.

This paper develops a new approach to investigate EM.