Yes / The application of vacuum venting for the removal of air from mould cavity has been introduced in injection moulding with the intent to enhance micro/nano features replication and definition. The technique is adopted to remove air pockets trapped in the micro-features, which are out of reach for conventional venting technologies and can create considerable resistance to the melt filling flow. Nonetheless, several studies have revealed a negative effect on replication that could possibly arise from the application of vacuum venting. Although the incomplete filling of micro-scale features has often been attributed to poor venting, the limited research examining the application of vacuum venting has produced mixed results. In this work, the effect of air evacuation was experimentally investigated, monitoring mould and polymer temperature evolution during the micro injection moulding process by means of a high speed infrared camera and a sapphire window, which forms part of the mould wall. The results show that air evacuation removes a mould surface heating effect caused by rapid compression of the air ahead of the flow front and subsequent conduction of that heat into the mould surface. Hence, with the increase of the surface-to-volume ratio in micro-cavities, air evacuation has a detrimental effect on the cavity filling with polymers that are sensitive to changes of the mould temperature.

No description available.

No description available.

The project elaborated design of optimization venting of molds exhibiting bubbles or low quality weld lines. Based on a literature study of the injection mold venting, the use of vacuum venting, namely the VACUUMJET system of the Spanish CUMSA manufacturer, has been proposed. The experiments proved the elimination of bubbles in the part and the marked improvement of visual quality of the weld lines. The effect on the closing force was not confirmed. The use of the system is more economical for larger batches production, or when high quality parts are required that allow price increasing.

Over the past years, catastrophic dust explosion incidents have caused numerous injuries, fatalities and economical losses. Dust explosions are rapid exothermic reactions that take place when a combustible dust is mixed with air in the presence of an ignition source within a confined space. A variety of strategies are currently available to prevent dust explosion accidents. However, the recurrence of these tragic events confirms flaws in process safety for dust handling industries. This dissertation reports advances in different approaches that can be followed to prevent and mitigate dust explosions. For this research, a 36 L dust explosion vessel was designed, assembled and automated to perform controlled dust explosion experiments. First, we explored the effect of size polydispersity on the evolution of aluminum dust explosions. By modifying systematically the span of the particle size distribution we demonstrated the dramatic effect of polydispersity on the initiation and propagation of aluminum dust explosions. A semi-empirical combustion model was used to quantify the laminar burning velocity at varying particle size. Moreover, correlations between ignition sensitivity and rate of pressure rise with polydispersity were developed. Second, we analyzed the effect of particle size and crystalline levels in the decomposition reactions of explosion inhibitor agents (i.e., phosphates). We fractionated ammonium phosphate- monobasic (NH_4H_2PO_4) and dibasic ((NH_4)_2HPO_4) at different size ranges, and synthesized zirconium phosphate (Zr(HPO_4)_2·H_2O) at varying size and crystalline levels. Particle size was found to be crucial to improve the rate of heat absorption of each inhibitor. A simplified model was developed to identify factors dominating the efficiency of dust explosion inhibitors. Finally, we conducted computational fluid dynamic (CFD) simulations to predict overpressures in dust explosions vented through ducts in large scale scenarios. We particularly focused on the adverse effects caused by flow restrictions in vent ducts. Critical parameters, including ignition position, geometric configuration of the vent duct, and obstructions of outflow such as bends and panels were investigated. Comparison between simulation and experimental results elucidated potential improvements in available guidelines. The theoretical analyses complemented the experimental work to provide a better understanding of the effects of particle size on the evolution of dust explosions. Furthermore, the validation of advanced simulation tools is considered crucial to overcome current limitations in predicting dust explosions in large scale scenarios.

Orientador: Flavio Luis Schmdit / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-26T04:59:10Z (GMT). No. of bitstreams: 1 Scucuglia_Marcio_M.pdf: 2766345 bytes, checksum: df718c4c465f3ea8e35d990cbd5ffbc6 (MD5) Previous issue date: 2014 / Resumo: Tanques assépticos são equipamentos aplicados em linhas de processamento de produtos longa-vida, com o objetivo de estocar o produto previamente esterilizado até o envase asséptico, mantendo a condição de esterilidade comercial obtida nas etapas anteriores. Para evitar a recontaminação do produto, o equipamento deve ser levado a condição de esterilidade, sendo aplicado um procedimento de aquecimento, desaeração e esterilização. Por ser uma etapa crítica, o ciclo de esterilização é validado por protocolos específicos que visam garantir a integridade da operação. A demanda de equipamentos com capacidades cada vez maiores e as implicações desse aumento na eficiência da esterilização tornaram importante uma análise mais detalhada dos resultados obtidos nos protocolos atuais. Este trabalho teve por objetivo avaliar os ciclos de esterilização de um tanque asséptico, baseado na distribuição de temperatura e pressão em seu interior, e a partir dos resultados, aumentar a compreensão dos fenômenos envolvidos na esterilização e quantificar sua eficiência. A análise das variáveis revelou que o ciclo de desaeração do tanque asséptico não foi completa, com retenção de ar representando de 13 a 23% do volume total do equipamento. Como consequência o processo de esterilização ocorreu em condição de não saturação de vapor. Esta situação altera o mecanismo de destruição térmica de microrganismos da condição úmida para não-úmida, na qual a resistência térmica dos esporos é mais elevada, levantando a questão da real eficiência dos processos e protocolos de esterilização atuais. .A aparente garantia da esterilidade comercial dos processos atuais pode ser explicada pelo uso de temperaturas e tempos excessivos. A revisão de procedimentos, protocolos e critérios de sucesso dos projetos existentes pode resultar em maior segurança quanto à eficiência de esterilização e redução de custos. Um novo protocolo de validação é proposto em refletindo os novos critérios de sucesso estabelecidos neste trabalho / Abstract: Aseptic tank systems are applied to production lines for shelf-stable, long-life products in order to store sterile product until aseptic filling, maintaining the commercial sterility condition achieved from previous production steps. To avoid microbial recontamination of the product, a sterility condition must be achieved in the aseptic tank system through the application of a heating, venting, and sterilization cycle. This cycle must be submitted to specific validation protocols to ensure operational integrity. The demand for larger capacity systems and the implication of this volume increase on sterilization efficiency require a more detailed review of the results obtained from current validation protocols. The purpose of this work was to evaluate an aseptic tank¿s sterilization cycles, through study of temperature distribution and internal pressure, in order to better understand key phenomena in aseptic tank sterilization and to quantify its efficiency. The analysis showed that the venting cycle was insufficient, with remaining air on the order of 13%-23% of the total tank volume. Consequently, the subsequent sterilization process was not conducted at the saturation point for steam. This different condition changes the kinetics for thermal destruction of microorganisms from a wet state to a dry state in which thermal resistance of spores is higher. This finding raises a question regarding the true efficacy of the sterilization process and validation protocols currently applied. The apparent success of current sterilization processes could be explained by the usage of excessive temperature and time. The review of procedures, protocols, and success criteria of current projects could result in greater assurance of sterilization efficacy and in cost reduction. A new validation protocol is proposed to reflect the new success criteria developed in this work / Mestrado / Tecnologia de Alimentos / Mestre em Tecnologia de Alimentos

Understanding the controls on the distribution and type of hydrothermal venting in modern oceanic spreading environments is key to developing tools for exploration and understanding the metallogeny of ancient massive sulfide deposits. Compared to mid-ocean ridges, subduction zones are characterized by additional tectonic complexities, including arc-ridge collisions, arc rotations, pre-existing structures, and variable distances to the arc. This thesis addresses the question, “How do tectonic complexities associated with subduction influence the structure and volcanic evolution of a back-arc basin, and how do they affect the distribution and type of hydrothermal venting?” A multi-scaled approach was used to address this question in the nascent back-arc region of the New Hebrides and in the more advanced stages of opening of the Mariana back-arc basin. In the New Hebrides, an arc-ridge collision segmented the volcanic front and affected the southern and northern back-arc regions in different ways. In the southern Coriolis Troughs (CT), voluminous eruptions are closely linked to the ridge collision, forming a large shield volcano in the near-arc region (Nifonea Volcano). The caldera-hosted eruptions produced high-temperature but short-lived magmatic-hydrothermal activity restricted to the shield volcano. In the northern Jean Charcot Troughs (JCT), ridge collision caused a reversal in the rotation of the arc, reducing extension in the south and increasing extension in the north. Unlike the CT, extension in the JCT is strongly affected by pre-existing structures, which form irregular widely-spaced grabens and volcanic ridges and magmatism in the central part of the back-arc. Here, hydrothermal venting is focused along deeply penetrating faults, associated with widespread tectonic extension. Detailed studies of the mineralogy and geochemistry of the ore and alteration at the Tinakula deposit reveal that massive sulfide accumulation in the region dominated by tectonic extension is characterized by longer-lived, lower-temperature venting than at Nifonea. Hydrothermal activity in the JCT at Tinakula is dominated by (1) long-lived heat from an underlying magma source; (2) fluid circulation along a fissure with long-lived or reactivated permeability; (3) enrichment in fluid-mobile elements such as Ba that are transported at low temperature; (4) mixing of cold seawater with hydrothermal fluids within the permeable volcaniclastic substrate and at the seafloor; (5) water depth controls on maximum hydrothermal vent temperatures; and (6) reduced permeability of the host volcaniclastic succession at the site of mineralization caused by precipitation of alteration minerals and sulfates, focusing fluid flow. The different styles of volcanic and hydrothermal activity closely resemble those of mid-ocean ridge environments in areas that are dominated by tectonic rather than magmatic extension. A comparison with the more advanced stages of rifting and segmentation of the Mariana back-arc demonstrates that Mid-Ocean Ridge (MOR)-type structural and magmatic controls on hydrothermal activity are important during all stages of back-arc basin evolution. This work highlights the diversity of volcanic eruption styles and hydrothermal venting from the earliest stages of back-arc rifting to the advanced stages of basin opening and shows that processes normally associated with MOR-type spreading are directly analogous to back-arc basin systems. However, additional tectonic complexities (e.g., ridge-arc collisions) have a major impact on the location and type of magmatic and hydrothermal activity at back-arc spreading centers, with important implications for understanding ancient volcanic-hosted massive sulfide deposits that mainly formed in back-arc basins.

In a nuclear power plant, the last barrier under normal and accident operations is the containment building. This is normally constructed from concrete reinforced with steel bars, which are prestressed to enhance the overall capability to withstand thermodynamic stresses like over-pressurisation and high temperatures. The failure of this final barrier will lead to the release of radioactivity to the surrounding environment. To examine the effects of thermo-hydraulic stresses on PWR containment following a LOCA, a model is proposed with simulated scenarios performed at the Koeberg Nuclear Power Station as a case study. The accidents were simulated using the Koeberg engineering simulator to obtain the output data. The scenario for the proposed model correlates the critical mass flow from a double-ended guillotine break to the containment pressure and temperature increase. Different containment filtered venting systems (CFVS) are also investigated in this study as severe accident management systems. CFVS have historically been included in boiling water reactor (BWR) designs, but following the Fukushima Daiichi nuclear accident, they are being introduced as severe accident management systems to manage the threat of containment over-pressurisation in pressurised water reactors (PWR). Finally, the rate of change in containment pressure and temperature is analysed and compared to literature, with the incorporation of a simulated filtered venting system to the PWR containment building.

Roof venting is often utilised in large warehouses to remove smoke in order to reduce damage to a building and its contents, and to maintain access for fire-fighters. In New Zealand, the Compliance Document for the New Zealand Building Code C clauses recommends 15 % opening area for unsprinklered single floor buildings. This opening area is required to be designed for effective fire venting. There is no justification for why 15 % is required, and no definition of how fire venting qualifies as being effective. Fire Dynamics Simulator (FDS) was used to simulate the performance of various roof venting strategies in two different-sized industrial warehouses (both larger than 1,500 m²) with a 50 MW fire with both a rapid and an extreme t³ growth rate. In particular, roof venting areas of 15 %, 10 %, and 5 % of the floor area were tested with each of the following inlet areas for make-up air: 100 %, 50 %, and 0 % of roof venting area. In each of these cases, the vents were treated as permanently-open holes in the roof. It was shown that roof venting with 15 % geometric area is ample to provide and maintain tenability for fire-fighters. With sufficient inlet area for make-up air, smaller venting areas could also be employed. Further simulations were run to test the effect of square-shaped vents that opened simultaneously at 100°C compared with square-shaped vents that opened sequentially at 100°C, 200°C, and 300°C, and strip-shaped vents that opened progressively as each portion of a vent reached activation temperatures of 200°C and 300°C. Vents that opened at 100°C were intended to represent mechanical vents, while vents opening at higher temperatures were intended to represent plastic sky-light or drop-out type vents. The activation temperature proved to be more influential than the opening sequence or shape: there was a significant advantage to be gained by having vents that activated at 100°C as opposed to 200°C or 300°C. The role of downstands in aiding the effectiveness of roof venting was also investigated, with downstand depths of 10 %, 20 %, and 30 % of the ceiling height being simulated. Downstands were shown to be incredibly useful for exhausting smoke and hot gases, provided their installation was appropriately coordinated with placement of roof venting. It is concluded that a clear definition of effective fire venting must not only include the area of roof venting, but equally important is the definition of required inlet area for make-up air, as it plays a crucial role in the effectiveness of the specified roof venting area. In addition, the clear aerodynamic area should be specified. This could be achieved by use of a discharge coefficient that describes the proportion of the roof venting area that is clear aerodynamic area for a particular material, vent, and geometric area. Development of a clear definition of effective fire venting will help to determine how an economic fire protection system can be continued to be used, while going a long way to ensuring predictable and tenable conditions for fire-fighters in New Zealand.

Ce travail est consacré à l’étude des interactions entre dispositifs de désenfumage naturel et systèmes d’extinction (sprinkleur). Deux campagnes expérimentales à grande échelle utilisant conjointement sprinkleur et désenfumage naturel ont été menées dans des halls d’essais du CNPP. Au total, 98 essais instrumentés ont été réalisés en faisant varier le type et la position du foyer et les temps d’activation respectifs des deux dispositifs de sécurité. Les données recueillies incluent principalement des hauteurs libres de fumées, des champs de température et des temps de déclenchement automatique des sprinkleurs. L’ensemble de ces résultats permet la constitution d’une base de données pour la création de cas de validation en utilisant le logiciel FDS (Fire Dynamics Simulator). Des simulations utilisant les données d’entrée relatives aux différents essais sont réalisées et les résultats numériques sont confrontés aux mesures. Le bon accord entre ces résultats permet d’utiliser FDS pour effectuer des bilans de masse et d’énergie pour les différents scénarios étudiés. En utilisant les connaissances accumulées au cours de ces campagnes, des simulations de scénarios incendie dans deux bâtiments existants ont été réalisées. Pour chaque géométrie, différents temps de déclenchement du désenfumage sont testés et les résultats (niveaux de température, temps et nombre de déclenchements de sprinkleurs, transfert de chaleur et de masse) sont comparés / This work is devoted to the study of interactions between smoke and heat exhaust ventilation systems (SHEAVS) and automatic fire sprinklers. Two real scales experimentation campaigns involving sprinklers and SHEAVS have been carried out in fire test facilities at CNPP (France). A total of 98 instrumented tests have been conducted with various fuel type, experimental configuration and activation time of both systems. Collected datas include smoke free layer height, temperature field and automatic sprinkler activation time. These results are used to build a database in order to create a validation case for the software Fire Dynamics Simulator (FDS). Numerical simulations of several tests are conducted using experimental data as input parameters. Results are then confronted to measurements. A good agreement between these results allows us to use FDS in order to realize mass and energy balances for various scenarios. Using knowledge acquired during both campaigns, numerical simulations of fire scenarios in two actual facilities have been conducted. For both configuration, various SHEAVS activation time have been tested and results (temperature levels, time and number of activated sprinklers, heat and mass transfer) have been confronted