Browsing by Author "Pires, Luís Carlos Carvalho"
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- Análise das condições de conforto em ambientes refrigeradosPublication . Fernandes, Eduardo; Silva, Pedro Dinho da; Gaspar, Pedro Dinis; Pires, Luís Carlos Carvalho; Nunes, JoséO presente estudo avalia as condições de frio a que os trabalhadores estão sujeitos no sector agroindustrial avaliando dois casos, uma empresa de distribuição alimentar e uma empresa de lacticínios. De forma a avaliar as condições de conforto térmico dos trabalhadores foram seguidos os procedimentos indicados em normas internacionais. Foram realizados inquéritos e efectuadas medições experimentais de forma a caraterizar as zonas e as condições em que os trabalhadores operam, bem como para avaliar os níveis de atividade de cada trabalhador. O trabalho desenvolvido permitiu identificar o tipo de exposição a que cada trabalhador está sujeito assim como determinar os índices característicos de conforto térmico, nomeadamente o índice IREQ. Os resultados mostram que ocorrem situações em que os trabalhadores possuem isolamento térmico adequado às condições onde estão inseridos mas que ainda assim manifestam sensações relacionadas com o desconforto térmico. Por outro lado, verificou-se também que alguns dos trabalhadores que possuem níveis de isolamento térmico supostamente insuficientes manifestam sensações térmicas neutras. Conclui-se assim que os trabalhadores apresentam uma tendência para uma aclimatação efectiva a ambientes frios que não aparece referida nas normas correspondentes.
- Breast Skin Temperature Evaluation in Lactating and Non-lactating Women by Thermography: An Exploratory StudyPublication . Gouveia, Ana; Pires, Luís Carlos Carvalho; Garcia, Nuno; Barbosa, Ana; Jesus, Ana; Pombo, Nuno; Soares, Marta; Oliveira, J. Martinez deDuring pregnancy and lactation, woman breasts feel changes like blood flow increasement, associated with a higher breast temperature. We performed an exploratory study of the breast skin temperature of lactating and non-lactating women based on thermography, with a qualitative analysis of the temperature patterns and a quantitative evaluation of the differences. Frontal breast thermograms of four non-lactating young women and four women with well-established lactation were acquired and analyzed. Qualitative analysis of the images obtained show some evidence of the existence of a characteristic skin temperature pattern for lactating women. Quantitative differences between thermograms were also noticed, especially when considering dispersion metrics: lactating women present higher breast skin temperature gradients and amplitudes. Results obtained, especially based on central tendency metrics, should be interpreted with caution because some of the acquisition conditions for non-lactating women may lead to some bias on the results. Further investigation will be performed to quantify breast skin temperature gradient and be able to classify images based in the breast skin temperature pattern.
- Caracterização do comportamento térmico de um armário exterior de telecomunicações móveisPublication . Patrício, Carlos Miguel Rosado; Silva, Pedro Dinho da; Pires, Luís Carlos Carvalho; Gaspar, Pedro DinisThe growing use of telecommunication technologies by society has led the industry to develop infrastructure to support this growth. The telecommunications outdoor cabinets are an important element in the telecommunications network, allowing host and protect the equipment needed to run the network in adverse conditions. The enclosure must have a proper thermal performance to ensure a temperature below 55 ° C, limit for the operation of equipment, and avoid an excessive consumption of electricity. This study aims to characterize the thermal performance of the cabinet using numerical studies with DesignBuilder/EnergyPlus. The development of the numerical model is followed by experimental studies using a real cabinet in operation, to ensure that the model is valid and allows to obtain reliable results. Results allowed to elaborate, quantitatively, a thermal characterization of the cabinet and improve the utilization profile.
- Characterization of the thermal performance of outdoor telecommunication cabinetsPublication . Silva, Pedro Dinho da; Pires, Luís Carlos Carvalho; Patrício, Carlos Miguel Rosado; Gaspar, Pedro DinisThe growing use of telecommunication technologies has led the industry to develop infrastructure to support this progress. The outer telecommunications cabinets are part of the Base Transceiver Station allowing to accommodate and protect from outer adverse conditions a set of electronic equipment needed to operate the mobile communication network. This kind of cabinets should have a proper thermal performance to ensure indoor air temperature below 55°C to avoid exceeding the maximum operating temperature of the electronic equipment. This work describes the analysis of the thermal performance of an outdoor telecommunication cabinet using the computational tool DesignBuilder. The simulation results are compared to the experimental data collected in real cabinet under normal operating conditions. The simulation results show that the air temperature predicted by the model is closer to the temperature measured experimentally inside the cabinet particularly when the weather data files of the computational model have a similar behavior to the actual weather data. Numerical studies show that the use of mechanical ventilation is effective in the extraction of heat generated inside the cabinet. However, there is a limit beyond which increasing the air flow rate does not result in a significant decrease of the cabinet air temperature. The studies also show the importance of the radiant properties and the geographical location of the cabinet. High values of the outer surface cabinet emissivity impair the thermal performance of the cabinet during the day and for some locations, an operational mechanical ventilation system may not be enough to maintain the indoor air temperature below 55°C. Overall, the use of DesignBuilder proved to be very effective for characterizing the thermal performance of telecommunications outdoor cabinets.
- Computational Modeling of the Thermal Behavior of a GreenhousePublication . Lebre, Bruno Miguel Carapito; Silva, Pedro Dinho da; Pires, Luís Carlos Carvalho; Gaspar, Pedro DinisThe need for production of all kinds of crops in high quantities and over the entire year makes the agricultural sector one of the major energy consumers. The optimization of this consumption is essential to guarantee its sustainability. The implementation of greenhouses is a strategy that allows assurance of production needs and possesses large optimization potential for the process. This article studies different greenhouse structures by computational simulation using EnergyPlus and DesignBuilder. First, a comparison was performed between the computational results and the measured values from a greenhouse prototype at different operating conditions. Overall, the comparison shows that the computational tool can provide a reasonable prediction of the greenhouse thermal behavior, depending on the differences between the weather data modeled and observed. An outdoor air temperature difference of 16 ◦C can cause a difference of about 10 ◦C between the air temperature predicted and measured inside the greenhouse. Subsequently, a selected set of case studies was developed in order to quantify their influence on the thermal performance of the greenhouse, namely: the greenhouse configuration and orientation; the variation of indoor air renewal; changes to the characteristics of the roof; the effect of the thermal mass of the walls; and location of the greenhouse. The results show that a correct greenhouse orientation, together with a polyethylene double cover with a 13 mm air layer, a granite wall of 40 cm thickness on the north wall, and variable airflow rate, may lead to a reduction of the greenhouse energy consumption by 57%, if the greenhouse is located in Lisbon, or by 43%, if it is located in Ostersund, during the harshest months of the heating season.
- O conforto automóvel e as tecnologiasPublication . Santos, Paulo Sérgio; Gonçalves, Luís Carlos Carrilho; Gaspar, Pedro Dinis; Pires, Luís Carlos CarvalhoFaz-se uma revisão das tecnologias aplicadas ao aumento do conforto automóvel. A ergonomia interna do automóvel desempenha um papel preponderante no conforto do condutor e passageiros, no seu bem-estar, confiança e sensação de descontracção na condução. A aplicação das ferramentas de prototipagem digital e a utilização de modelos termodinâmicos de simulação dos ocupantes veio ajudar a perceber e melhorar o comportamento termodinâmico do habitáculo e sua ergonomia. Novas tecnologias vieram melhorar o conforto a bordo do automóvel e aumentar os parâmetros de segurança.
- Development of an experimental unit for studying the solar drying processPublication . Parente, Daniel; Pires, Luís Carlos Carvalho; Silva, Pedro Dinho da; Nunes, JoséThe removal of moisture by drying, prevents the growth and reproduction of these microorganisms, which cause rotting, and minimizes many of the reactions of deterioration from moisture, revealing itself a crucial preservation method. Portugal is a country with great potential for exploitation of solar energy, the implementation of a drying system based on this renewable source, facing devices with high energy consumption and hence more expensive, is attractive. With this, the present work emerges, in order to, by building a sustainable drying model, evaluate their performance, so that can be a good solution. First, were done characterization tests with the dryer unload, studying the temperatures and the relative humidity (RH) inside the drying chamber. The influence of various air gap heights and of operation modes, under natural and forced convection were studied. The developed unit was subsequently used in cherry drying. The first drying test, allowed dry 15 kg cherry in 124 hours. The second with 25 kg was carried out under adverse conditions, therefore presented an additional drying time of 25 hours from the first. The results of the studies realized indicate great potential of the drying mechanism proposed, capable of reaching temperatures of 55 °C inside the drying chamber, for an ambient temperature and humidity of 31,7 ºC and 28%, respectively, and an intensity of solar radiation of 918 W/m2.
- Energy Requirements and Photovoltaic Area for Atmospheric Water Generation in Different Locations: Lisbon, Pretoria, and RiyadhPublication . Correia, Vasco; Silva, Pedro D.; Pires, Luís Carlos CarvalhoAtmospheric water generation (AWG) is a technological innovation that facilitates the extraction of water from the atmosphere using various techniques. In response to mounting concerns regarding water scarcity in multiple regions globally, AWG has emerged as a promising solution for providing potable water in areas where conventional water sources are limited or contaminated. AWG systems can be implemented across diverse settings, ranging from individual households to large-scale industrial operations, and can be powered by renewable energy sources. Despite the inherent challenges associated with upscaling AWG technology to ensure its affordability and reliability, it possesses the potential to make a significant contribution towards meeting the water requirements of communities in both developed and developing nations. This study aimed to investigate the performance and limitations of a commercially available dehumidifier, namely, the Trotec TTK140S (Heinsberg, Germany), through experimental analysis. Additionally, the feasibility of integrating this dehumidifier with a photovoltaic energy source was explored. Initially, the dehumidifier’s water production and energy consumption were assessed under specific conditions. Subsequently, a comparison was conducted across three different locations (Lisbon, Pretoria, and Riyadh) to evaluate the dehumidifier’s operation and ascertain the photovoltaic module area necessary for it to function independently. This approach effectively addresses one of the main drawbacks of the technology, namely, its substantial energy consumption.
- Estudo comparativo de processos de secagem da cerejaPublication . Nunes, José; Silva, Pedro Dinho da; Andrade, Luís P.; Pires, Luís Carlos Carvalho; Tomé, Rute; Gaspar, Pedro DinisA cereja fresca é um produto muito apreciado pelos consumidores devido às suas ótimas características organoléticas e nutricionais. Este produto é muito perecível e tem um período produtivo sazonal muito curto. Alguma quantidade de fruta perde o seu valor comercial quando ultrapassa o seu estado de maturação. Uma forma de valorizar este produto e o rendimento dos produtores é realizar a sua desidratação para obtenção de passas de cereja, com vantagens de estabilidade, valor nutricional e de comercialização. De entre os vários métodos atualmente possíveis para a realização da secagem é desejável a utilização daqueles que obtenham ótimos produtos desidratados e com baixos custos de funcionamento, nomeadamente com a energia. No presente estudo efetuámos a avaliação comparativa dos processos de secagem de cereja da Beira Interior por intermédio dos métodos da liofilização, secagem por ar quente e secagem solar. Apesar de algumas limitações o secador solar apresentou um bom desempenho para obtenção de passas de cereja com ótimas características de aw, cor, sabor, aspeto visual, para a secagem de cerejas com pré-tratamentos e não envolve custos com a energia, podendo ser preferido em relação aos outros dois métodos. Os restantes processos apresentaram como grande desvantagem o elevado consumo de energia.
- Estudo numérico do desempenho térmico de um armário exterior para equipamentos de telecomunicações móveisPublication . Duarte, Miguel Vicente; Silva, Pedro Dinho da; Pires, Luís Carlos Carvalho; Gaspar, Pedro DinisOutdoor cabinets that house telecommunication equipment are used to protect electronic equipment from the harsh environmental conditions. The number of outdoor cabinets used has been growing in recent decades, boosted by the world expansion of mobile telecommunications networks. The disposition of telecommunications equipment inside a cabinet (i.e., the thermal design) became a critical factor due to the miniaturization of electronic components and the increase of packing density. To mitigate this problem, energy-intensive cooling techniques (e.g., air conditioning) began to be used. Studies shown that approximately 25% of the total energy consumed in an outdoor cabinet is used for cooling. It is intended with this work, the thermal study of an outdoor cabinet using a CFD software to characterize its thermal behaviour, according to the influence of the environment temperature, the air flow through the cabinet and the heat dissipated in its interior by the telecommunications equipment. According the results obtained in this study it can be concluded that even for the less favourable case (TA=20.1 °C; Qar=60 m3 h -1 e qdis=480 W), none of the telecommunications equipment inside the cabinet is under risk, since the Tmax,cabinet ≈ 4 0°C is lower than the Tmax,recommended ≈55°C.
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