This work compares the temperature distribution and hot-spot temperatures obtained in a disc-type winding of a power transformer when using as dielectric liquid a mineral oil or natural esters. The comparison is made with a reference case for mass flow rate and temperature in the inlet and uniform losses for the discs. A further comparison is performed by increasing the mass flow rate at the inlet form 0.78 kg/s to 0.9 and 1.0 kg/s, thus nine case studies are considered in this work. These cases have been analyzed via CFD techniques using the software COMSOL Multiphysics® with a 2D-axysymmetrical model using the Conjugate Heat Transfer module. For the analysis, the hotspot factor H is considered as an indicator of the cooling circuit efficiency since the losses are uniform. Results shows that for the base case, the hot-spot temperature obtained for the mineral oil is 9-11°C higher than the obtained with esters whereas for the increased mass flow rate, hot-spot temperature of mineral oil is equal or even lower than the obtained for natural esters. The analysis of the hot-spot factor shows the dependence of the cooling circuit efficiency on the kind of oil and inlet conditions. ; The research leading to these results has received funding from multiple sources over years, but we would specifically like to acknowledge the support received in the later stages from the Spanish Plan Estatal de I+D under the grant agreement DPI2015-71219-C2-1-R. Also A.Santisteban would like to thank the University of Cantabria and the Government of Cantabria for the supporting of his Ph.D. scholarship.
In the last years the use of biodegradable fluids as liquid insulation for distribution and power transformers is becoming more common. The main biodegradable fluids are the natural and synthetic esters, although biodegradable hydrocarbons have been recently proposed as well. Biodegradable fluids have a much lower environmental impact than mineral oil, limiting the risk of soil contamination in case of leaks what makes them a suitable solution for some applications, as off-shore transformers or railway transformers. Additionally, these fluids have higher flash point than conventional mineral oils what reduces dramatically the risk of fire and collateral damage derived from explosion and fire. Despite of these advantageous factors, there are still some aspects that hinders the spread of their use, such as the difference on thermal properties, the lack of accepted maintenance procedures and the price. This paper presents the current situation of biodegradable insulating fluids, analyzing some of their properties and discussing the aspects that are still to be investigated to make them a real alternative to petroleum-based fluids ; This work was supported in part by the European Union's Horizon 2020 Research and Innovation Programme through the Marie Sklodowska-Curie under Grant 823969, in part by the Ministry of Universities and Innovation Economy through Grants DPI2015-71219-C2 and PID2019-107126RB-C21.
In recent years, the use of biodegradable fluids as liquid insulation for distribution and power transformers is spreading. The main biodegradable fluids used are natural and synthetic esters, although biodegradable hydrocarbons have been recently proposed. Biodegradable fluids have a much lower environmental impact than mineral oil, limiting the risk of soil contamination in leaks, which makes them a suitable solution for applications such as offshore transformers or railway transformers. Additionally, these fluids have a higher flash point than conventional mineral oils, which dramatically reduces the risk of fire and collateral damage derived from explosion and fire. Despite these advantageous factors, there are still some aspects that hinder the broadening of their use, such as the difference in thermal properties or the lack of accepted maintenance procedures for transformers that use them as liquid insulation. This paper presents the current status of biodegrad able insulating fluids, analyzing some of their properties and discussing the aspects that are still to be investigated in order to make them a real alternative to petroleum-based fluids. ; Part of the work was performed during secondments and short visits between University of Valle, University Carlos III of Madrid and University of Cantabria executed in the framework of the BIOTRAFO project "Raising knowledge and developing technology for the design and deployment of high-performance power transformers immersed in biodegradable fluids", H2020-MSCA-RISE-2018- 823969, 2019-21. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 823969. Also, we acknowledge the support of the Spanish Ministry of Science and Innovation by means of the National Research Project Asset management of biodegradable-fluid-based transformers (PID2019-107126RB C21/AEI/10.13039/501100011033 and PID2019-107126RB-C22/AEI/ 10.13039/501100011033).
Petrol bazlı yağlayıcıların çevresel etkileri ve fosil yakıt rezervlerinin kısıtlı olması doğaya uygun yağlayıcı alternatiflerinin aranmasına sebep olm gelişimi mineral esaslı bazyağlarına dayanmaktadır. Bazyağlarının iyi teknik özellikleri ve düşük fiyatı mineral esaslı bazyağı teknolojisini desteklemiştir. Neyazıkki bazyağı sonlu bir kaynaktır. Mineral yağ sebebiyle oluşan kirlilikler üretimi kadar kolay doğaya karışamamaktadır. Bununla birlikte, mineral esaslı bazyağlarının sebebi genellikle politik nedenlere bağlıdır. Varolan stokları da her zaman aynı fiyatla fiyatla temin etmek mümkün olmamaktadır. Bir diğer olumsuz yanı ise mineral yağların doğaya karışma süresinin oldukça uzun sürmesidir. Zincir yağları, trafik ve inşaat sektörlerinde kullanılan yağlar açık yağlama sistemlerine ait olduğu için genellikle doğaya bırakılır. Ayrıca genel kapalı yağlama sistemlerinde de yanlışlıkla doğaya deşarj etme gibi riskli durumlarla karşılaşılmaktadır. Bu sebeple yağlayıcılar mümkün olan her alanda biyoparçalanabilir olmalıdır. Batı Avrupa Bioyağlayıcılar Market araştırmasına göre (2004): toplam 4.750.000 ton/yıl'lık yağlayıcılar pazarında, bioyağlayıcıların yeri 172.000 ton/yıl'dır (Whitby, 2004). Aynı araştırmaya göre kompresör ve zincir yağlayıcılarıının önemli bir kısmı bioparçalanabilir olarak üretilmektedir. Marketteki bioyağlayıcı ihtiyacı, motor yağı ve hidrolik yağlar olarak gözükmektedir. Günümüzde, otomativ üreticileri, kullanılan yağlayıcıların çevresel performansları ile ilgili bir talepte bulunmamaktadırlar, çünkü bu yağlayıcılar yüksek katkı maddesi içerdiklerinden çok karmaşık ürünlerdir. Bu sebeple, çevre dostu motor yağları formulasyon çalışması daha da zorlaşmaktadır. Hidrolik yağlar, Türkiye ve Batı Avrupa marketinde, çevre dostu yağlayıcı formulasyonları için üzerinde çalışılabilecek en uygun adaydır. Yağ asidi esterleri, yağlayıcılarda ihtiyaç duyulan, yüksek viskozite indeksleri, yüksek parlama noktaları ve düşük uçuculukları ile etkin sınır yağlayıcılığı sağlarlar. Buna karşılık, bioparçalanabilir yağlayıcılar, mineral yağlayıcılar ile karşılaştırıldığında, oksidasyon stabilitesi ve düşük sıcaklık karakteristikleri göz önüne bulundurulduğunda daha düşük performans sergilemektedir. Bu çalışmada, farklı yağ asidi esterlerinin oksidasyon ve aşınma önleme üzerine etkileri ile hidrolik yağların fiziksel ve kimyasal özellikleri araştırılacaktır. Çalışmanın ilk basamağında, beş farklı yağ asidi esteri, termal oksidasyon stabilitesi ve akış özellikleri bakımından incelenecektir. Yağ asidi esterleri, Türkiye'deki yaygınlıkları, fiyatları ve viskozite sınıflarına göre seçilmiştir. Çalışmanın ikinci basamağında, en iyi sonucu veren; kanolo yağı ve trimetiloleat (TMP TO) hidrolik yağ formulasyonu karışımı çalışmasında kullanılmıştır. Hidrolik yağlarda, ISO VG 46 sınıfında DIN 51524 normlarına göre en iyi yağlayıcılık performansını elde edebilmek için farklı yağ karışımları hazırlanmıştır. Sonuçlar ortaya çıkarmıştır ki: hidrolik yağ formulasyonlarında esterler kullanıldığında, yağlayıcının yapısındaki polar grupların varlığından dolayı, formule edilen yağlayıcı, yüksek sıcaklık değişimlerine ve parçalanmadan kaynaklanan bozulmalara dayanmakta ve mükemmel yağ filmi oluşturmaktadır. Çalışmanın sonunda, oksidasyon performansı incelenen esterlerin ana bileşen, katkı maddesi ve kalınlaştırıcı olarak hidrolik yağ formülündeki kullanım yerine karar verilmiştir. Yüksek sıcaklık ve ağır hidrolik uygulamalarında; sıcaklığın 150 C dereceden daha yüksek olduğu, TMP TO hidrolik yağ formülasyonunda yalnızca katkı maddesi olarak kullanılabileceği ortaya çıkmıştır. Orta zorluktaki uygulamalarda, özellikle orman ve inşaat alanında TMP TO hidrolik yağ formülünde baz yağı olarak kullanılabilinir.
In the last years the use of biodegradable fluids as liquid insulation for distribution and power transformers is becoming more common. The main biodegradable fluids are the natural and synthetic esters, although biodegradable hydrocarbons have been recently proposed as well. Biodegradable fluids have a much lower environmental impact than mineral oil, limiting the risk of soil contamination in case of leaks what makes them a suitable solution for some applications, as off-shore transformers or railway transformers. Additionally, these fluids have higher flash point than conventional mineral oils what reduces dramatically the risk of fire and collateral damage derived from explosion and fire. Despite of these advantageous factors, there are still some aspects that hinders the spread of their use, such as the difference on thermal properties, the lack of accepted maintenance procedures and the price. This paper presents the current situation of biodegradable insulating fluids, analyzing some of their properties and discussing the aspects that are still to be investigated to make them a real alternative to petroleum-based fluids. ; This work was supported in part by the European Union's Horizon 2020 Research and Innovation Programme through the Marie Sklodowska-Curie under Grant 823969, in part by the Ministry of Universities and Innovation Economy through Grants DPI2015-71219-C2 and PID2019-107126RB-C21.
In recent years, the use of biodegradable fluids as liquid insulation for distribution and power transformers is spreading. The main biodegradable fluids used are natural and synthetic esters, although biodegradable hydrocarbons have been recently proposed. Biodegradable fluids have a much lower environmental impact than mineral oil, limiting the risk of soil contamination in leaks, which makes them a suitable solution for applications such as offshore transformers or railway transformers. Additionally, these fluids have a higher flash point than conventional mineral oils, which dramatically reduces the risk of fire and collateral damage derived from explosion and fire. Despite these advantageous factors, there are still some aspects that hinder the broadening of their use, such as the difference in thermal properties or the lack of accepted maintenance procedures for transformers that use them as liquid insulation. This paper presents the current status of biodegradable insulating fluids, analyzing some of their properties and discussing the aspects that are still to be investigated in order to make them a real alternative to petroleum-based fluids. ; Part of the work was performed during secondments and short visits between University of Valle, University Carlos III of Madrid and University of Cantabria executed in the framework of the BIOTRAFO project "Raising knowledge and developing technology for the design and deployment of high-performance power transformers immersed in biodegradable fluids", H2020-MSCA-RISE-2018- 823969, 2019-21. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 823969. Also, we acknowledge the support of the Spanish Ministry of Science and Innovation by means of the National Research Project Asset management of biodegradable-fluid-based transformers (PID2019-107126RB-C21/AEI/10.13039/501100011033 and PID2019-107126RB-C22/AEI/ 10.13039/501100011033).
Phthalic acid esters are used as plastic softeners and also can be found in food packaging materials. European legislation defines specific migration limits of plastic additives for plastic materials that come into contact with food. This study monitors the phthalic acid ester concentrations in yogurts after manufacturing and then after a 3-week storage. The studied yoghurts were natural yogurt with 1 % of chia flour, natural yogurt with 5 % of chia flour, natural yogurt with 1 % of bamboo fibre, natural yogurt with 5 % of bamboo fibre and natural yogurt. The analysed phthalic acid esters were dibutyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP). The average phthalate concentrations in plastic cups were detected for DBP of 59.5 µg/g and for DEHP of 9.0 µg/g of the plastic material. Higher DBP concentrations than DEHP concentrations were also found in all studied yogurts. The average DBP concentrations in yogurts were detected from 1.8 µg/g up to 5.0 µg/g of the original matter and the average DEHP concentrations were determined from 0.5 µg/g up to 1.0 µg/g of the original matter. No statistically significant difference was found when comparing phthalic acid ester concentrations in yogurts immediately after production and after three weeks of storage. However, in our study in all cases of yogurts, the DBP concentrations were higher than the specific migration limit set by the legislation (0.3 mg/kg) and the DEHP concentrations were in all cases of yogurts lower than the specific migration limit set by the legislation (1.5 mg/kg). ; OA
16 Páginas; 2 Figuras; 1 Tabla ; Bioaccessibility is a key factor in the successful development of functional foods, particularly when the food matrix is quite different from that of the natural source(s) of the target bioactive ingredient. Although staple foods contain xanthophylls, the amounts are relatively low to achieve the desired beneficial effect in health, and during baking degradative reactions may contribute to reduce such amounts. The addition of water-soluble formulation of lutein as an ingredient in the cupcake recipe to fortified the amounts of this xanthophyll in the final product, showed satisfactory stability degree and resistance to the baking process. Indeed, the in vitro bioaccessibility reached adequate efficiency levels, ranging 30-80% of the initial lutein content. Activity of pancreatic lipase over lutein esters was low, but the hydrolysed lutein was completely incorporated into micelles. Indeed, the main micellar lutein content remained in its esterified form what could facilitate subsequent hydrolysis by other mucosal hydrolytic enzymes. These results point to fortified staple foods as functional foods that may help to diminish the risk of degenerative processes related with deficient lutein intake/incorporation in humans. ; This work was supported by the Ministry of Economy and Competitiveness (grant number AGL2013-42757R). Dr. Xavier is a fellow of the Brazilian Government (CAPES, 238163/2012-1). ; Peer reviewed
AbstractAlthough China has been the main manufacturer and consumer of phthalate esters (PAEs), human health ambient water quality criteria (AWQCs) have not been proposed for these chemicals. In this study, the distribution and bioaccumulation of six PAEs (dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), butyl benzyl phthalate (BBP), bis (2-ethylhexyl) phthalate (DEHP), and di-n-octyl phthalate (DnOP)) were investigated in 11 edible fish species collected from Poyang Lake, China. The results showed that the total concentrations of the six PAEs in the fish ranged between 118.63 and 819.84 μg/kg wet weight (mean of 327.50 ± 190.44 μg/kg). DMP, DEP, DBP, and DEHP were detected in all samples, of which DEHP and DBP were two of the most predominant phthalates, accounting for more than 90% of the total PAEs. The DEHP concentrations in fish with different habitat preferences were different, demersal species were significantly higher than pelagic species (p < 0.05). The mean natural logarithmic bioaccumulation factors (log BAFs) of PAEs increased with increasing lipophilicity of the substances, which yielded the following regression equation: log BAF (L/kg) = 0.103 log Kow + 2.158 (r2 = 0.940, p < 0.05, n = 4). Using this quantitative structure–activity relationship to calculate BAFs for the remaining undetected substances (BBP and DnOP) to derive AWQCs. According to the natural parameters, the human health AWQCs relating to PAE concentrations for water and fish consumption were derived as 9.4 × 103 (DMP), 5.0 × 102 (DEP), 4.2 × 101 (DBP), 1.1 (BBP), 8.6 × 10− 2 (DEHP), and 2.0 (DnOP) μg/L. Human health risk assessment indicated that the dietary intake of DEHP may exert a carcinogenic effect on residents of the Poyang Lake region. The results provide important input to assess the health risk posed by PAEs contaminated surface water.
Over the last few decades the insulating performance of transformer oils has been broadly studied under the point of view of nanotechnology, which tries to improve the insulating and heat dissipation performance of transformer oils by suspending nanoparticles. Many authors have analyzed the thermal and dielectric behavior of vegetable oil based-nanofluids, however, very few works have studied the evolution of these liquids during thermal aging and their stability. In this paper has been evaluated the performance of aged vegetable oil based-nanofluids, which have been subjected to accelerated thermal aging at 150 °C. Nanoparticles of TiO2 and ZnO have been dispersed in a commercial natural ester. Breakdown voltage, resistivity, dissipation factor and acidity of nanofluid samples have been measured according to standard methods, as well as stability. Moreover, it has been analyzed the degradation of Kraft paper through the degree of polymerization (DP). The results have showed that although nanoparticles improve breakdown voltage, they increase the ageing of insulation liquids and dielectric paper. ; This project has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 823969.The authors of this research wish to thank the Ministry of Economy for its financial support for the National Research Project: Improvement of Insulation Systems of Transformers through Dielectric Nanofluids (DPI2015-71219-C2 1-R).
Oil-immersed transformers, whose lifespan is defined by cellulose insulation's lifetime, utilize frequently mineral oil. However, this insulating fluid is being replaced by alternative liquids such as natural and synthetic esters. This replacement requires to guarantee a similar behavior of solid insulating materials immersed in them. Although there are different authors who have concluded that Kraft paper reduces its deterioration rate when it is immersed in biodegradable fluids, there are few works that have analyzed the effect of insulation liquids on the mechanical properties of other cellulosic materials such as diamond dotted paper (DDP) during laboratory tests. This paper shows a comparative analysis of four paper/oil specimens (a standard Kraft paper and a diamond dotted paper aged in both mineral oil and natural ester) under controlled laboratory accelerated thermal ageing. This work focuses on changes in mechanical properties such as the energy consumed per unit volume of the failure zone (E R ), rupture strength (σ R ) and strain under ultimate strength (ε cm ). ; This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 823969-BIOTRAFO
Free-standing polyesters films from mono and polyhydroxylated fatty acids (C16 and C18) have been obtained by non-catalyzed melt-condensation polymerization in air at 150°C. Chemical characterization by Fourier transform infrared spectroscopy and 13C Magic Angle Spinning Nuclear Magnetic Resonance (13C MAS–NMR) has confirmed the formation of the corresponding esters and the occurrence of hydroxyl partial oxidation, which extent depends on the type of hydroxylation of the monomer (primary or secondary). Generally, polyester films obtained are hydrophobic, insoluble in common solvents, amorphous and infusible as revealed by X-ray diffraction and differential scanning calorimetry. In ω-polyhydroxy acids, esterification reaction with primary hydroxyls is preferential and, therefore, the structure can be defined as linear with variable branching depending on the amount of esterified secondary hydroxyls. The occurrence side oxidative reactions like the diol cleavage are responsible for chain cross-linking. Films are thermally stable up to 200–250°C though this limit can be extended up to 300°C in the absence of ester bonds involving secondary hydroxyls. By analogy with natural occurring fatty polyesters (i.e., cutin in higher plants), these polymers are proposed as biodegradable and non-toxic barrier films or coatings to be used, for instance, in food packing. ; Funding is provided by the Spanish Ministerio de Economía y Competitividad under project CTQ2011-24299 and by the Consejería de Economía, Innovación, Ciencia y Empleo of the Andalussian Government (Junta de Andalucía-FEDER) grant TEP-7418. JH-G acknowledges the support of the Marie Curie Intra-European Fellowship (BIOPROTO project). ; Peer reviewed ; Peer Reviewed
