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- 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.
- 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.
- Thermal performance, usage behavior and food waste of domestic refrigerators in a university student community: findings towards cities sustainabilityPublication . Galvão, Diogo Alexandre Sobreiro; Gaspar, Pedro Dinis; Silva, Pedro Dinho da; Pires, Luís Carlos CarvalhoFood safety and quality as well as storage conditions leading to food waste are related to the reduced thermal performance of domestic refrigerators, the mismanagement of food stored in it or the misuse of the equipment. This paper analyses the operative conditions of refrigerators in the student community of the University of Beira Interior (Covilhã, Portugal). A test sample of 51 appliances in the student households was instrumented with temperature dataloggers. Simultaneously, surveys on the use of refrigerator and food waste were applied to the students, ultimate users of the appliances. The students, with an average of 23 years old, mostly female (65.9%), live alone (6%), with their parents (24%), or with other students (71%). The test sample of appliances had, on average, a nominal electrical power of 126 W and an inner volume of 205 liters. It was found that the average storage temperature was 5.5ºC. The storage temperature in the appliances increased with the number of people who used it. This figure was largely due to improper use behaviour, in particular the number of times that the refrigerator door was open unnecessarily. The joint analysis of these data allows relating the use behaviour of with food waste. The comparison with similar studies conducted in the past shows that the average storage temperature in the current study is lower, mainly due to the technological evolution of appliances as well as the global awareness concerning food safety and food waste. The results of this work, apart from offering results about the performance of the operative conditions of refrigerators in a community not studied so far, highlights the need for further awareness of good practices to reduce food waste and simultaneously ensure food safety of the perishable food products stored in domestic refrigerators. These results could be extrapolated to the remaining people in order to develop strategies to improve cities sustainability.
- Experimental comparison between R409A and R437A performance in a heat pump unitPublication . Duarte, Miguel Vicente; Pires, Luís Carlos Carvalho; Silva, Pedro Dinho da; Gaspar, Pedro DinisThis paper reports an experimental comparison between the use of the refrigerants R409A and R437A in a heat pump unit designed and developed to work with R12. Although the use of both refrigerants in new equipments were abolished in EU and US according the new F-Gas Regulation of EU and SNAP, they still being used as options for R12 in old equipments, especially in developing countries. Both refrigerants were studied for the same test conditions, according to two groups of tests: group A (variation of the heat source temperature) and group B (variation of refrigerant flow rate). The results obtained showed that the R437A presents a higher discharge pressure and a lower discharge temperature. The heating and cooling capacities of both refrigerants were similar, as well as the exergetic efficiency. For the group A of tests the COP of both refrigerants was similar and for the group B of tests the R409A presented an average COP 15% higher. According to the results obtained it is recommended the use of R409A in old equipments (as transition refrigerant) until the acquisition of equipments operating with refrigerants with low-GWP becomes technically and economic feasible.
- 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.
- Experimental study of a hybrid solar photovoltaic, thermoelectric and thermal modulePublication . Matias, Flávio; Pires, Luís Carlos Carvalho; Gaspar, Pedro Dinis; Silva, Pedro D.Nowadays, solar energy, which can be photovoltaic and thermal, is a clean and reliable source of energy for the production of electric and thermal power. However, new ways for improving photovoltaic efficiency are fundamental for an extensive application of this technology. Most of the energy absorbed by the PV panel converts itself into heat, which usually is lost and does not have any energetic value. The performance of a combined photovoltaic (PV), thermoelectric generator (TEG) and water heating panel is tested in practice. The thermoelectric set is applied on the back of the PV panel so that the two devices have approximately the same temperature. On the other face of the thermoelectric set, there is the water heating panel, which consists of an aluminium heat exchanger specially designed for this hybrid module. The exposed surface of the hybrid panel has an area of about 2.72 dm2. Experimental tests were conducted in direct solar exposure during July. The experimental results indicate that the maximum global module efficiency was 91.3% for an irradiance of 1089 W/m2. The power peak production was 29.7 W, at 2 p.m., with an irradiance value of 1230 W/m2.
- Evaluating the thermal performance and environmental impact of agricultural greenhouses using earth-to-air heat exchanger: An experimental studyPublication . Hamdane, Samia; Pires, Luís Carlos Carvalho; Silva, Pedro Dinho da; Gaspar, Pedro DinisThe thermal performance and environmental impact of agricultural greenhouses (GH) connected to earth-to-air heat exchanger (EAHE) systems depend on the ambient temperature, soil temperature, EAHE system, and greenhouse specifications. The impact of an EAHE system on the temperature and humidity of a GH microclimate, as well as its effects on CO2 emissions and heating energy consumption, are determined experimentally. Two scaled-down models of agricultural GHs (2 × 1.4 × 1.4 m3) were developed. Each GH was equipped with a heater. A spiral EAHE system was integrated into only one of the GHs. The temperature differences in the microclimate range from 3.5 °C to 7.5 °C, with the microclimates of GH + EAHE and GH being quite similar. In summary, the EAHE system helped to reduce the hourly energy consumption of the heating system by more than 40%. It also reduced emissions to the environment by more than 100 g (CO2)/hour. The EAHE coefficient of performance (COP) for the cooling mode has a higher average value than that for the heating mode. The closed-loop performed better in cooling mode, while the open-loop performed better in heating mode. When the difference between the set temperature in the heater and the air outlet temperature of the EAHE system is smaller, the heater performs better in reducing energy consumption and CO2 emissions of the heater. The COPheating range is between 0 and 3.4 and the COPcooling range is between 0.5 and 7.3. The energy consumption ranges between 0 and 1.41 kWh and the CO2 emissions are between 0 and 359.55 g. Thus, using EAHE in agricultural greenhouses improves thermal performance and reduces environmental impact, providing an overall benefit in terms of energy consumption and environmental sustainability.
- Experimental study and numerical simulation of the interior flow in a telecommunications cabinetPublication . Delgado, Christopher B.; Silva, Pedro Dinho da; Pires, Luís Carlos Carvalho; Gaspar, Pedro DinisThe sector of information and communication technologies, especially telecommunications, has grown in a relentless way, leading to an increase in the number of necessary infrastructure to ensure the geographical coverage of the service, having the outdoor telecommunications cabinets (OTC) been an increasingly preferred choice of this type of infrastructure. These cabinets need cooling systems to maintain interior temperatures between desired values, but an effective cooling depends directly on the air flow inside. This paper includes the experimental results of the internal flow and heat transfer in a model a of real OTC, in order to characterize its thermal behavior. The internal air flow is visualized through experimental methods and compared with numerical predictions. The flow occurs mainly in turbulent regime, possessing greater magnitude on the back area of the OTC, where also exist some recirculation zones that can difficult an effective cooling. The results allow to conclude that forced ventilation is an effective method of OTC cooling, combined with low energy consumption.
- Experimental evaluation of water production from atmospheric air by vapour compression refrigerationPublication . Miranda, Rui; Pires, Luís Carlos Carvalho; Silva, Pedro Dinho daThe problem of water scarcity is nowadays one of the themes under discussion around the world. Currently arise increasingly prevention measures, as well as have been developed and improved systems of production, treatment and storage of water. Based on this serious problem lived by a considerable part of the world's population, the present work proposes the use of a simple dehumidification system to obtain water from a renewable source of water, the Earth's atmosphere. Results will be presented concerning the capacity and costs of this type of equipment to produce water. Although the extracted water, from the atmospheric air by condensation of water vapour, in vapour compression refrigeration systems, require treatment and to be mineralized, this equipment can be used in any house as a source of drinking water. The work includes conducting experimental studies, in a climatic test chamber, using a commercial equipment with a dehumidifying capacity of 20 l/day, for values of 30 ºC and 80% of relative humidity and temperature, respectively. This equipment has an operating range of 5-32 ºC for the temperature and 30-90% for the relative humidity. The tests were realized with The largest production of water occurred for ambient conditions, inside the climate chamber of 43 ºC and 43%, temperature and relative humidity, respectively, being obtained 0,3 l/h.
- 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.
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