Avaliação de um chiller de absorção numa unidade de cogeração e trigeração

Portugal é um país dependente da energia do exterior, devido à elevada percentagem de consumo de energia a partir de fontes primárias, como por exemplo o gasóleo. Para colmatar este cenário, têm vindo a criar-se incentivos para o uso de energias renováveis e para intensificação de medidas de eficiência energética, como os sistemas de cogeração, de forma a tornar os processos industriais nacionais mais autónomos e mais competitivos. O presente trabalho, centra-se na avaliação do chiller de absorção na central de trigeração da empresa Monteiro, Ribas-Indústria, SA, com a finalidade de identificar algum problema no funcionamento do chiller. Após efetuado o estudo do chiller, verificou-se que o coeficiente de performance do chiller apresenta valores que variam entre 0,75 e 0,81, que comparado com o valor especificado, não apresenta grande diferença. No que toca à potência do chiller, esta apresentou valores entre 948 e 1045 kW. Estes valores estavam bem abaixo da potência especificada pelos fornecedores. Assim, pretendeu-se propor medidas para melhor a potência obtida. Para o efeito foi sugerido o aquecimento da corrente que atua como fonte de calor para o chiller, a corrente de água quente. Embora a empresa apresente a solução para o problema, um permutador de vapor para o aquecimento da corrente de água quente, este não se encontra em funcionamento contínuo, levando a uma potência mais baixa.

Techno-economic analysis of three HVAC retrofitting options

Accounting for around 40% of the total final energy consumption, the building stock is an important area of focus on the way to reaching the energy goals set for the European Union. The relatively small share of new buildings makes renovation of existing buildings possibly the most feasible way of improving the overall energy performance of the building stock. This of course involves improvements on the climate shell, for example by additional insulation or change of window glazing, but also installation of new heating systems, to increase the energy efficiency and to fit the new heat load after renovation. In the choice of systems for heating, ventilation and air conditioning (HVAC), it is important to consider their performance for space heating as well as for domestic hot water (DHW), especially for a renovated house where the DHW share of the total heating consumption is larger. The present study treats the retrofitting of a generic single family house, which was defined as a reference building in a European energy renovation project. Three HVAC retrofitting options were compared from a techno-economic point of view: A) Air-to-water heat pump (AWHP) and mechanical ventilation with heat recovery (MVHR), B) Exhaust air heat pump (EAHP) with low-temperature ventilation radiators, and C) Gas boiler and ventilation with MVHR. The systems were simulated for houses with two levels of heating demand and four different locations: Stockholm, Gdansk, Stuttgart and London. They were then evaluated by means of life cycle cost (LCC) and primary energy consumption. Dynamic simulations were done in TRNSYS 17. In most cases, system C with gas boiler and MVHR was found to be the cheapest retrofitting option from a life cycle perspective. The advantage over the heat pump systems was particularly clear for a house in Germany, due to the large discrepancy between national prices of natural gas and electricity. In Sweden, where the price difference is much smaller, the heat pump systems had almost as low or even lower life cycle costs than the gas boiler system. Considering the limited availability of natural gas in Sweden, systems A and B would be the better options. From a primary energy point of view system A was the best option throughout, while system B often had the highest primary energy consumption. The limited capacity of the EAHP forced it to use more auxiliary heating than the other systems did, which lowered its COP. The AWHP managed the DHW load better due to a higher capacity, but had a lower COP than the EAHP in space heating mode. Systems A and C were notably favoured by the air heat recovery, which significantly reduced the heating demand. It was also seen that the DHW share of the total heating consumption was, as expected, larger for the house with the lower space heating demand. This confirms the supposition that it is important to include DHW in the study of HVAC systems for retrofitting.

Caracterização reológica das diferentes fases de extrato de inulina de raízes de chicória, obtidas por abaixamento de temperatura

Inulin is a functional food ingredient, generally employed as sugar or fat substitute in food systems. This ingredient can be found in several vegetal products, including chicory roots. As the solubility of inulin is susceptible to temperature changes, the product suffers a fractionalization resulting in two phases when cooled, originating a precipitated phase, more viscose, and a liquid phase, of lesser viscosity. The study of rheological properties of different phases of inulin extract is important for equipment designing, such as mixer and bombs. In this work, rheological behavior at three different temperatures (25; 40 and 50 ºC) was determined for liquid and precipitated phases of inulin liquid extract, extracted from chicory roots by hot water diffusion and cooled at two different temperatures (8 and -10 ºC), suffering phases separation. The precipitated phase was analyzed in two conditions: pure and with the addition of microencapsulating agents (maltodextrin and hydrolized starch). All of them presented a linear behavior, similar to that of the Plastics of Bingham. Some of them, however, were not an adequate fit to this model.

Durabilidade de compósito biomassa vegetal-cimento modificado por polímero

The durability of the cellulose-cement composites is a decisive factor to introduce such material in the market. Polymers have been used in concrete and mortar production to increase its durability. The goal of this work was the physical and mechanical characterization of cellulose-cement composites modified by a polymer and the subsequent durability evaluation. The work also evaluated the dispersion of acrylic polymer in composites made of Pinus caribaea residues. The physical properties observed were water absorption by immersion and bulk density. Rupture modulus and toughness were determined by flexural test. The specimens were obtained from pads, produced by pressing and wet curing. Samples were subjected to accelerated aging tests by repeated wetting and drying cycles and hot-water bath and natural aging. The scanning electron microscopy (SEM) allowed verifying the fiber and composite characteristics along the time. For the composite range analyzed, it was observed the polymer improved the mechanical properties of composites besides a significant decreasing in water absorption. The use of polymer improved the performance of vegetable fiber-cement composites when compared to the conventional mortar, due to water absorption decreasing.

Composite materials obtained from textile fiber residue

This article presents the use of fibers residue from textile industry to minimize environmental problems associated with material accumulation. Composite materials utilizing textile fiber residues and high density polyethylene were prepared. Effect of treatment with hot water on fibers to prepare composites was studied to provide an improvement in mechanical properties of these materials. This treatment on fibers was evaluated by X-ray diffraction and scanning electron microscopy techniques. Experimental results of mechanical properties indicated higher mechanical strength for treated fiber composites compared to the untreated fiber composites.

Storage as a tool to improve wood fuel quality

This work analysed the influence of storage in the quality of forest biomass for energy generation in the region of Lages, Brazil. Logs of Pinus taeda L. and Eucalyptus dunnii Maiden were harvested and piled during the four different seasons: spring, summer, fall and winter. The analyses were performed immediately after harvesting (without being stored), after two, four and six months of storage. The evaluated properties were: moisture content, gross and net calorific value, ash content and solubility in cold water, hot water and sodium hydroxide. The species composition, storage span, harvesting season and storage season influenced the forest biomass characteristics. In general, eucalyptus presented better results than pine, losing moisture faster, having less alteration in the chemical composition and producing greater energetic gain over storage time. For both species, the ideal storage time was four months. Furthermore, spring and summer were the best harvesting seasons. Thus, if the forest biomass is harvested at the end of winter or beginning of spring with subsequent storage during the summer, this biomass will have the best performance for energy production. (C) 2011 Elsevier Ltd. All rights reserved.

Sulfated galactans from Australian specimens of the red alga Phacelocarpus peperocarpos (Gigartinales, Rhodophyta)

Polysaccharides from the red alga Phacelocarpos peperocarpos were extracted with hot water, clarified, and precipitated with 2-propanol. The native preparation was highly sulfated (36.2% w/w). Alkali modification decreased the sulfate content by 2.0% w/w. The alkali-modified polysaccharide is composed mostly of galactose (Gal, 51 mol%) and 3,6-anhydrogalactose (AnGal, 41 mol%), with minor amounts of a mono-O-methylgalactose (MeGal, 1 mol%), xylose (Xyl, 6 mol%), and glucose (Glc, 1 mol%). The FTIR spectrum of the alkali-modified polysaccharide resembled K-carrageenan with absorption at 930 cm(-1) (indicative of AnGal) and 850 cm(-1) (Gal ii-sulfate). However, an additional, major band of absorption occurred at 820 cm(-1) indicating the presence of equatorial sulfate ester substitution at O-6 of Gal residues, A combination of linkage and C-13 NMR spectroscopic analyses showed that the polysaccharide was composed predominantly of a novel repeating-unit, O-beta-D-galactopyranosyl 4,6-disulfate)-(1 --> 4)-3,6-anhydro-alpha-D-galactopyranose. Minor structural variations also occurred, including alternative patterns of sulfation and the presence of terminal Xylp, The location of the terminal Xylp residues was not certain but evidence supported their attachment at O-3 of some 4-linked Galp residues. The cell-wall galactans remain unchanged during the life cycle of the alga. (C) 1996 Elsevier Science Ltd.

Hematopoietic response of rats exposed to the impact of an acute psychophysiological stressor on responsiveness to an in vivo challenge with Listeria monocytogenes: Modulation by Chlorella vulgaris prophylactic treatment

In this study, we investigated the hematopoietic response of rats pretreated with CV and exposed to the impact of acute escapable, inescapable or psychogenical stress on responsiveness to an in vivo challenge with Listeria monocytogenes. No consistent changes were observed after exposure to escapable footshock. Conversely, the impact of uncontrollable stress (inescapable and psychogenical) was manifested by an early onset and increased severity and duration of myrelossuppression produced by the infection. Small size CFU-CM colonies and increased numbers of clusters were observed, concurrently to a greater expansion in the more mature population of bone marrow granulocytes. No differences were observed between the responses of both uncontrollable stress regimens. CV prevented the myelossuppression caused by stress/infection due to increased numbers of CFU-GM in the bone marrow. Colonies of cells tightly packed, with a very condensed nucleus; in association with a greater expansion in the more immature population of bone marrow granulocytes were observed. Investigation of the production of colony-stimulating factors revealed increased colony-stimulating activity (CSA) in the serum of normal and infected/stressed rats treated with the algae. CV treatment restored/enhanced the changes produced by stress/infection in total and differential bone marrow and peripheral cells counts. Further studies demonstrated that INF-gamma is significantly reduced, whereas IL-10 is significantly increased after exposure to Uncontrollable stress. Treatment with CV significantly increased INF-gamma levels and diminished the levels of IL-10. Uncontrollable stress reduced the protection afforded by CV to a lethal dose of L. monocytogenes, with survival rates being reduced from (50%) in infected rats to 20% in infected/stressed rats. All together, our results suggest Chlorella treatment as an effective tool for the prophylaxis of post-stress myelossupression, including the detrimental effect of stress on the course and outcome of infections. (C) 2008 Elsevier Inc. All rights reserved.

Effect of fruit maturity on the response of 'Kensington' mango fruit to heat treatment

The effects of conditioning and hot water treatments on immature and mature 'Kensington' mangoes were examined. A hot water treatment of 47 degreesC fruit core temperature held for 15 min increased weight loss (50%), fruit softness (15%), disrupted starch hydrolysis and interacted with maturity to reduce the skin yellowness (40-51%) of early harvested fruit. Immature fruit were more susceptible to hot water treatment-induced skin scalding, starch layer and starch spot injuries and disease. Conditioning fruit at 40 degreesC for up to 16 h before hot water treatment accelerated fruit ripening, as reflected in higher total soluble solids and lower titratable acidity levels. As fruit maturity increased, the tolerance to hot water treatment-induced skin scalding and the retention of starch layers and starch spots increased and susceptibility to lenticel spotting decreased. A conditioning treatment of either 22 degrees or 40 degreesC before hot water treatment could prevent the appearance of cavities at all maturity levels. The 40 degreesC conditioning temperature was found to be more effective in increasing fruit heat tolerance than the 22 degreesC treatment; the longer the time of conditioning at 40 degreesC, the more effective the treatment (16 v. 4 h). For maximum fruit quality, particularly for export markets, it is recommended that mature fruit are selected and conditioned before hot water treatment to reduce the risk of heat damage.

Identification of micronutrient deficiency of wheat in the Peshawar Valley, Pakistan

A field experiment was conducted to study the effect of micronutrients, zinc (Zn), copper (Cu), iron (Fe), manganese (Mn), boron (13) and a commercial fritted micronutrient product called Zarzameen, on the yield and the yield components of wheat (Triticum aestivum L.), in the Peshawar valley, Pakistan. Different combinations of Zn, Cu. Fe. Mn, B, and Zarzameen were applied at the rate of 4.0, 2.0, 5.0, 2.0, 1.0 kg ha(-1) and 1.0 kg ha(-1), respectively, along with a basal dose of 100 kg ha(-1) nitrogen(N), 75 kg ha(-1) phosphorus (P) and 50 kg ha(-1) potassium (K). The fertilizer treatments (macro- and micronutrients) increased wheat dry matter, grain yield, and straw yield significantly over an unfertilized control. Soil tests for B and Zn were increased both at boot and harvesting stage, and Fe at boot stage, with the addition of micronutrients. Plants without B had showed classical B deficiency symptoms at grain formation stage, but not at vegetative stage. Boron concentration in the dry matter of wheat plants increased with the addition of the B fertilizer in the soil. Boron deficiency was not observed in plants containing >4 mg B kg(-1) at the boot stage, or in soils containing > 1.4 mg kg(-1) hot water soluble B.

Starch degradation in 'Kensington' mango fruit following heat treatments

Changes in carbohydrate metabolism of 'Kensington' mango fruit from 2 major production regions in Queensland were measured after conditioning fruit with hot air at 40degreesC for 0, 2, 4, 8 and 16 h or at 22degreesC for 16 h (control) followed by hot-water treatment at either 45degreesC fruit-core temperature for 30 min or 47degreesC fruit-core temperature held for 15 min. Advancing physiological maturity of 'Kensington' mango fruit was correlated with increased starch concentration within the mesocarp. An alpha-amylase inhibitor was present in unripe 'Kensington' mesocarp. alpha-Amylase activity was promoted by conditioning fruit at 40degreesC for 8 h, and this enhanced enzyme activity persisted until the fruit were ripe. Consequently, starch degradation was accelerated and the concentration of total soluble solids was higher in fruit conditioned at 40degreesC for 8 h than in fruit left at the lower temperature of 22degreesC for 16 h or not conditioned. Immediately on removal of fruit from hot-water treatment, activities of alpha-amylase and phosphorylase were inhibited. This inhibition was correlated with higher starch concentration and starch layer and starch spot injuries in these fruit. A positive correlation was also found between increased sucrose concentration and greater starch loss in 40degreesC conditioned 'Kensington' fruit. It is proposed that increased sugar concentration in the mesocarp increased the level of fruit heat tolerance.

Influência dos estrativos na resistência ao apodrecimento de seis espécies de madeira

O presente trabalho teve como objetivo avaliar o efeito da extração da madeira de seis espécies, quatro nativas (candeia, cedro, cerejeira e jacarandá-caviúna) e duas exóticas (E. citriodora e E. gumifera), em diferentes solventes, na resistência ao apodrecimento causado pelo fungo da podridão-parda Gloeophyllum trabeum. O material foi ensaiado na forma de serragem, em face da maior facilidade para os procedimentos de extração. Dentre os resultados, pode-se destacar a baixa perda de massa ocorrida na madeira de cedro (Cedrela fissilis), evidenciando sua elevada resistência natural ao fungo testado e, ainda, à incapacidade dos solventes utilizados na retirada de compostos que conferem resistência ao apodrecimento. As madeiras de candeia (Vanillosmopsis erythropappa), cerejeira (Amburana cearensis), jacarandá-caviúna (Machaerium scleroxylon) e de eucaliptos (Corymbia citriodora e Eucalyptus gummifera) também apresentaram elevada resistência natural, em função da baixa perda de massa ocorrida, quando expostas ao fungo G. trabeum. Essas madeiras, quando totalmente extraídas, apresentaram elevados valores de perda de massa. No que diz respeito ao material extraído por diferentes solventes de forma isolada, observou-se, na candeia, que o solvente mais eficiente na retirada de substâncias que conferem resistência ao apodrecimento foi o diclorometano. Com relação ao cedro, o mais eficiente foi o metanol. Na cerejeira, por meio da mistura de etanol/tolueno retiraram-se mais substâncias, ao passo que no jacarandá-caviúna foi o metanol. Nas madeiras de eucaliptos, o metanol foi mais eficiente na retirada de componentes tóxicos ao fungo utilizado neste estudo, devendo destacar ainda, no E. gummifera, a eficiência da água quente na retirada de tais compostos. No C. citriodora, os valores de perda de massa, em razão das extrações em água fria, em água quente, em diclorometano e ao natural (não-extraída), foram muito baixos.

Potencialidades dos extrativos do cerne da madeira de teca como preservativo natural e sua influência na cor de madeiras claras

Este estudo teve como objetivo avaliar o potencial preservativo dos extrativos do cerne da madeira de teca (Tectona grandis) e a capacidade dos mesmos na mudança de coloração de madeiras claras. Para tanto, os resíduos gerados no processamento mecânico do cerne da madeira de teca com 20 anos de idade foram coletados e utilizados para realização de extrações. Para avaliar a influência dos extrativos de teca na cor e resistência natural da madeira foi utilizado o alburno da madeira de teca com 10 anos, além da madeira de Pinus sp., em função de ser uma madeira de coloração clara e baixa resistência natural. Foram realizadas extrações em água quente e etanol absoluto. Para determinação da concentração das soluções de tratamento foi realizado um ensaio de toxidez ao fungo Postia placenta. Após definida a concentração, as soluções extraídas foram preparadas para a impregnação. Além disto, foi utilizada uma terceira solução, composta pela combinação das soluções extraídas em água quente e etanol absoluto. Para cada solução testada foi realizado o tratamento pelo método de célula-cheia (Bethell). Para testar a eficiência das soluções preparadas com extrativos de teca, foram realizados leituras colorimétricas e ensaios biológicos com fungos e térmitas xilófagos. A combinação dos extrativos testados promoveu um escurecimento e reduziu a desuniformidade da cor, fazendo com que as madeiras tratadas se aproximassem mais da cor da madeira de cerne do que das amostras sem tratamento das respectivas espécies. A solução de extrativos obtida em etanol absoluto e a combinação dos extrativos obtidos em água quente e etanol absoluto promoveram os melhores resultados na resistência da madeira tratada contra fungos e térmitas xilófagos, alterando significativamente a classe de resistência das respectivas espécies tratadas.

Execução de um projecto solar térmico para uma instalação de A.Q.S. da Escola Básica Guilherme Stephens

O presente documento tem como principal objectivo efectuar o projecto de dimensionamento de um sistema de águas quentes sanitárias para uma escola. Numa primeira fase foi elaborado uma pesquisa sobre o contexto energético, a nível mundial, europeu e nacional, bem como o seu contexto jurídico a nível europeu e nacional, e uma explicação superficial sobre os fundamentos da energia solar, onde se foca a importância da radiação solar e os vários tipos de sistemas solares térmicos, bem como os seus constituintes. Segue-se a abordagem ao caso de estudo onde foram efectuados inicialmente inquéritos como forma de determinar os consumos de água quente utilizada nessa escola. Continuou-se o estudo efectuando-se a variação de duas características do sistema solar: o tamanho dos depósitos e o tipo de colectores solares a aplicar. Após as simulações efectuadas para a determinação das soluções a aplicar ao sistemasolar e apresentadas ao longo do presente documento, foram efectuadas análises económicas como forma de se verificar a viabilidade do sistema a aplicar. Por último foram elaboradas conclusões sobre o sistema a aplicar e apresentados alguns cenários financeiros do mesmo.

Avaliação da contaminação dos condensados de uma fábrica de pasta para papel

O objectivo do presente trabalho foi caracterizar os condensados produzidos numa fábrica de pasta para papel para identificar e localizar pontos da sua contaminação. Para o efeito, foram recolhidas amostras de condensado e caracterizados os parâmetros condutividade, pH, sódio e sílica. A amostragem decorreu no período entre 15 de Setembro a 6 de Novembro de 2008. Através da análise dos resultados obtidos para as concentrações de sílica e de sódio de cada uma das correntes, foram identificadas como contaminadas as correntes de condensado provenientes do condensador do Turbogerador 4, da área dos Digestores Descontínuos, da Evaporação e do Aquecedor de Água Quente para o Branqueamento. A realização de um balanço pontual à sílica no tanque de condensados da Central permitiu concluir que a maior contribuição advém do condensador do Turbogerador 4. Na Evaporação ocorre contaminação do condensado quando as secções do Concentrador 1 são colocadas em serviço após lavagem. Durante o acompanhamento do arranque da Evaporação, uma das secções (1/B) registou um valor máximo na concentração de sódio no condensado de 135 mg/L Na. Do estudo resulta, enquanto não for reparado e/ou substituído o equipamento responsável pelas contaminações, a necessidade de admitir requisitos para controlo da qualidade da água da caldeira menos restritivos, nomeadamente para a razão sódio/fosfato. É necessário, contudo, o rigoroso acompanhamento da qualidade da água da caldeira (pH, sobretudo) para prevenir afastamentos inesperados dos limites de controlo. Durante a realização deste trabalho foram identificadas algumas situações a melhorar, tais como a uniformização dos valores de desvio para esgoto dos condensados e das unidades utilizadas, a adequação das escalas dos aparelhos de medida para as gamas de leitura de interesse, a verificação e calibração periódica do equipamento instalado em linha, a adopção do parâmetro “Sódio” para controlo da qualidade dos condensados, a instalação de sistemas de amostragem com arrefecimento em todas as correntes de condensados e a reparação ou substituição de algum equipamento instalado em linha que se encontra em muito mau estado e ainda a manutenção do equipamento mantendo-o em boas condições de limpeza.