CFD Modeling of Complex Chemical Processes: Multiscale and Multiphysics Challenges

Computational fluid dynamics (CFD), which uses numerical analysis to predict and model complex flow behaviors and transport processes, has become a mainstream tool in engineering process research and development. Complex chemical processes often involve coupling between dynamics at vastly different length and time scales, as well as coupling of different physical models. The multiscale and multiphysics nature of those problems calls for delicate modeling approaches. This book showcases recent contributions in this field, from the development of modeling methodology to its application in supporting the design, development, and optimization of engineering processes

A Problem of Particulate Contamination in an Automated Assembly Machine Successfully Solved by CFD and Simple Experiments

Assembly of hard disk drives (HDDs) needs to be done in an automated assembly machine (AAM) virtually free of particulate contamination that can cause them to malfunction. Fan filter units (FFUs) are installed above the AAM to reduce the number of suspended particles in the recirculating air flowing over and around them. At one time, several HDDs were found to be defective. To find out the root cause of this problem, computational fluid dynamics (CFD) was used to investigate the airflow over and around the AAM. It was found that the cause of the high particle counts was improper air speed from the FFUs. The optimal FFUs air speed needed to be in the range of 0.35–0.65 m/s in which the airflow would block out nearby airborne particles and purge away particles generated by the AAM effectively which would, in effect, reduce the particle counts down below the threshold level of class 100 clean room. A few available measurement tools at the factory were then used to perform validating measurements against the simulation results, and the validation was positive. This optimal speed range was implemented at the factory after which the level of contamination was reduced to an acceptable level

Applications of Advanced Computational Modelling for Principal Underground Mining Hazards Management and Control

Underground coal mining is facing increased threats from the hazards of spontaneous combustion and heating of coal, abnormal mine gas emissions, and harmful dust concentrations in underground workings, due to increased production outputs and extraction depth of cover. To control and mitigate these engineering problems, there is a need to gain critical knowledge of spontaneous heating in the longwall (LW) goaf, gas migration patterns onto the LW face, and ventilation dynamics and dust dispersion in complex underground environments. Advanced Computational Fluid Dynamics (CFD) modelling can be used to simulate various scenarios portraying these hazards that may occur in underground LWs and provide much-needed knowledge and fundamental science that can be used to develop robust and effective control and mitigation strategies against these hazards. A comprehensive literature review has been conducted to understand these principal mining hazards (PMH), with a particular emphasis on the applications of CFD modelling in the prevention management and control of those PMH arising during coal extraction process. The insufficiencies and gaps in research on spontaneous combustion in active LW goaf, gas migration onto the LW face, and dust dispersion and transport in the development heading were identified. In addition, several field studies were carried out in underground coal mines in Australia to gain a better understanding of these mining issues and collate essential data for the CFD modelling studies. In recent years, goaf heating and spontaneous combustion incidents have been reported in several Australian underground coal mines during normal production cycles. The onset of these heating incidents was dictated by many operational and environmental parameters. Based on the site-specific conditions of an underground coal mine, where the coal seam gas is of approximately 80% carbon dioxide (CO2) and 20% methane (CH4) with a gas emission rate of 2000 l/s, CFD models were developed and validated with field gas monitoring data collected from the Tube Bundle System. The CFD models incorporated a user defined function (UDF) of gas emission and permeability variations in a three-dimensional (3D) space of computational domain representing the LW panels and goaf areas. Simulation results indicated that better goaf inertisation could be achieved when nitrogen (N2) was injected via cut-throughs (C/T) at about 250 m behind the LW face on the maingate (MG) side and surface boreholes at 100 m and 700 m on the tailgate (TG) side, with a total injection rate greater than 1750 l/s. The oxygen concentration on the MG and TG side dropped below 5% at distances of 120 m and 75 m behind the LW face, with a confined oxidation zone area of 35375 m2, which was approximately one-third of the oxidation zone area without inert gas injection. The impact of geological variations (i.e., coal seam orientations and goaf gas composition) on spontaneous combustion prevention and management was further studied using CFD models. The influence of ventilation design and operational parameters (e.g., tightness of the goaf seals) on spontaneous combustion control was also investigated by additional CFD models based on field data. During LW sealing-off, the ventilation flow dynamics change within the goaf, which considerably increases the risk of spontaneous combustion and gas explosion. To prevent these hazards, CFD models were developed and calibrated with field gas monitoring data to simulate a range of operational scenarios of different ventilation arrangements. The modelling studies indicated that at least six gas sensors should be employed and positioned appropriately to ensure effective goaf atmosphere monitoring for risk management during the LW sealing-off process. Extensive CFD-DPM (Discrete phase model) coupling modelling studies were conducted to investigate dust-related issues in LW gateroad development panels. Based on site-specific conditions, a CFD model incorporating a Continuous Miner (CM), Shuttle Car (SC) and exhausting ventilation tube was established and validated with onsite dust monitoring data. Three scenarios of CM cutting at the middle, floor and roof positions were considered and simulated. In all cases, the simulation results indicated that high levels of dust exposure would occur to left-hand-side (LHS) operators and consequently they should be equipped with high-quality personal protective equipment and stay behind the ventilation duct inlet during coal cutting process, while miners standing at the right-hands-side (RHS) of the CM for roof and/or rib bolting and machine operation should stay immediately behind the bolting rig where dust concentration was relatively low. The studies conducted in this thesis provided new insights into the current goaf inertisation practices to effectively manage and control spontaneous heating in LW goaf by considering geological variations and mining design. Furthermore, the CFD modelling study of gas flow dynamics during the panel sealing-off process provides new knowledge of ventilation and goaf gas dynamics, which is critical to the positioning of gas monitoring sensors to reliably measure goaf atmosphere changes, thus minimizing spontaneous heating and gas explosion risks with much-improved mine safety. The research work also shed light on the dust and ventilation behaviour in gateroad development panels, and provided several recommendations for operators’ locations and dust mitigation strategies to improve the health and safety of miners. The research outcomes from this study contribute to the improvement of current practices and guidance for PMH management and control in underground mines and tunnelling projects

Numerical study on scaling effects and decoupled network-based simulation of gaseous explosion

This research seeks to improve the prediction efficiency of gaseous explosions realized by numerical simulations in a full-scale underground network using a decoupled method. To provide quick predictions of overpressure distribution of methane explosions in underground airway networks, a two-section theory is employed. The explosion space is divided into a driver section and a blast-wave section. Governing equations including conservation of mass, momentum, and energy, together with chemical reaction and turbulence models are solved for the driver and the blast-wave sections using computational fluid dynamics (CFD) solver ANSYS Fluent (3D-based) and Flowmaster (1D-based) respectively. The three dimensional (3D) and one dimensional (1D) numerical analyses are preceded separately (decoupled). In the driver section, the numerical calculation results with three variables (FLSF, HDSF, and concentration) considering the size of explosion space and methane concentration level for the driver section are stored in a database tool Microsoft SQL Server Express aims to generate a methane explosion source database. To validate the selected combustion and turbulent models, a series of lab-scale methane explosion experiments were conducted. In the blast-wave section, the influences of geometric changes are quantified by using 2D Euler equations, whereas the simulation results are used to adjust the 1D network-based modeling. The decoupled method is applied in two case studies and proved capable to predict the pressure distribution of methane explosions that occurs in a complex airway network. --Abstract, page iii

Atas das 8as Jornadas de Segurança aos Incêndios Urbanos e as 3as Jornadas de Proteção Civil (8JORNINC-3JORPROCIV)

Este livro de ATAS contém os artigos apresentados às 8as Jornadas de Segurança aos Incêndios Urbanos e às 3as Jornadas de Proteção Civil (8JORNINC-3JORPROCIV), que decorreram no Porto, Portugal. Na presente edição das 8JORNINC-3JORPROCIV foram submetidos 50 trabalhos, tendo sido aceites 42. Os trabalhos foram distribuídos em 8 sessões paralelas temáticas, em adição a 2 sessões plenárias, apresentados no dia 2 de junho de 2023. O evento foi iniciado e promovido em Portugal, sob a organização do professor Doutor João Paulo Rodrigues, com as 1as Jornadas de Segurança aos Incêndios Urbanos, em 2005, na Universidade de Coimbra, bem como nos anos seguintes, as 2as Jornadas de Segurança aos Incêndios Urbanos em 2011 e as 3as Jornadas de Segurança aos Incêndios Urbanos em 2013, também na Universidade de Coimbra. As edições seguintes aconteceram em diferentes locais: as 4as Jornadas de Segurança aos Incêndios Urbanos em 2014, no Instituto Politécnico de Bragança; as 5as Jornadas de Segurança aos Incêndios Urbanos em 2016, no Laboratório Nacional de Engenharia Civil em Lisboa; as 6as Jornadas de Segurança aos Incêndios Urbanos e 1as Jornadas de Proteção Civil em 2018, na Universidade de Coimbra; e as 7as Jornadas de Segurança aos Incêndios Urbanos e 2as Jornadas de Proteção Civil, em 2021, no Instituto Politécnico de Castelo Branco. As 8JORNINC apresentam grande importância num contexto atual de vários e graves incêndios urbanos, florestais e de interface em Portugal. A pertinência do tema da segurança na prevenção e no combate a incêndios, quer pelas consequências emergentes deste tipo de acidentes, quer pela necessidade de redução das ocorrências, do número de vítimas mortais, feridos, prejuízos materiais, patrimoniais, ambientais e sociais, leva a que as Jornadas se destinem a um leque alargado de profissionais e público em geral. As 3JORPROCIV têm como objetivo promover conhecimentos nas áreas da prevenção civil, de riscos e planos de emergência. Pretendem assim, contribuir para a atualização dos conhecimentos técnicos e científicos da segurança e proteção civil, no âmbito do planeamento e prevenção perante cenários de crise e emergência. As Jornadas de Proteção Civil permitem partilhar um leque de conhecimentos multidisciplinares suscetíveis de impulsionar uma intervenção por parte de técnicos, especialistas e dos agentes da proteção civil. A visão interdisciplinar e integradora dos problemas e desafios que a proteção civil apresenta será refletida na prevenção e mitigação dos riscos inerentes a uma situação de acidente. Os trabalhos apresentados nesta edição, permitirão o avanço das 8JORNINC-3JORPROCIV, através da divulgação dos recentes desenvolvimentos e do conhecimento nos domínios da segurança ao incêndio e proteção civil. Por fim, a comissão organizadora das 8JORNINC-3JORPROCIV gostaria de agradecer: - o apoio dos patrocinadores e das instituições do Sistema Científico e Tecnológico; - a todos os autores que partilharam os seus excelentes trabalhos; - e aos elementos da Comissão Científica que auxiliaram no processo de revisão. Todos em conjunto, tornaram possível a realização destas Jornadas.info:eu-repo/semantics/publishedVersio

Análise do risco de incêndio edifício: remodelado em Castelo Branco

As notícias dão-nos com frequência informação de incêndios urbanos, por vezes em prédios antigos, alguns devolutos e que se alastram aos prédios contíguos, levando a grandes prejuízos, quer materiais, quer em perdas de vidas humanas, ou mesmo danos em património cultural. É, por isso, essencial identificar os riscos de incêndio nos edifícios. Assim, existem metodologias próprias que nos permitem conhecer e controlar os problemas detetados, de modo a conseguir assegurar uma segurança contra incêndio em edifícios, o mais eficaz possível. Nesse sentido, o presente trabalho pretende avaliar a segurança de um edifício, segundo métodos de análise de risco como o método ARICA, o método de Gretener e o método de FRAME e também segundo o Regime Jurídico de Segurança Contra Incêndio em Edifícios.info:eu-repo/semantics/publishedVersio

Evacuação de Edifícios – Caso de estudo de um edifício escolar

O objetivo deste trabalho é o levantamento dos aspetos que influenciam o tempo de evacuação num edifício escolar, desde o comportamento humano às caraterísticas físicas do edifício e às metodologias possíveis de adotar para a gestão da emergência, com vista a calcular o tempo necessário e disponível para a evacuação do referido edifício. A evacuação de edifícios em situação de incêndio tem como propósito a proteção da vida humana que é inseparável das condições de emergência as quais são afetadas por fatores de difícil determinação e que necessitam de ser definidos para estimar o tempo e as condições de evacuação.info:eu-repo/semantics/publishedVersio

Library buildings around the world

"Library Buildings around the World" is a survey based on researches of several years. The objective was to gather library buildings on an international level starting with 1990