Thermal Ageing of Some Insulating Fluids in Contact with Insulation Paper and Copper

2018 ◽  
Vol 68 (12) ◽  
pp. 2881-2885
Author(s):  
Iosif Lingvay ◽  
Gabriela Oprina ◽  
Livia Carmen Ungureanu ◽  
Alexandra Pica ◽  
Valerica Stanoi
Keyword(s):  
Experimental Data ◽  
Dissolved Oxygen ◽  
Copper Foil ◽  
Atmospheric Oxygen ◽  
Thermal Ageing ◽  
Dissolved Oxygen Concentration ◽  
Mineral Oils ◽  
Synthetic Ester ◽  
Cu2o Film ◽  
Transformer Oils

The behaviour of copper and insulation paper in various electrical insulating fluids (transformer oils) exposed to thermal ageing at 110�30C for 1000 hours in closed vessels (without access to atmospheric oxygen) has been studied. The processing of the comparative experimental data revealed in all cases that the concentration of dissolved oxygen in the investigated oils decreases exponentially during the heat treatment. In the presence of the copper foil, the oxygen is almost depleted (the dissolved oxygen concentration is approaching zero), indicating a higher affinity of the copper to oxygen than the affinity to oxygen of the investigated oils. In the presence of the copper foil and / or of the insulation paper, the degradation processes of the mineral oils have a pronounced character, explained by the catalytic activity of the Cu2O film that has been formed and by the paper degradation, respectively. A high thermo-oxidative stability was noticed in the case of natural triglyceride oils, particularly for the synthetic ester-based oil.

Studies on the Influence of Copper and Insulation Paper on the Accelerated Thermal Ageing of Some Insulating Fluids

2017 ◽  
Vol 68 (11) ◽  
pp. 2551-2555
Author(s):  
Iosif Lingvay ◽  
Gabriela Oprina ◽  
Valerica Stanoi ◽  
Alexandra Pica ◽  
Livia Carmen Ungureanu ◽  
...  
Keyword(s):  
Experimental Data ◽  
Heat Treatment ◽  
Thermal Stability ◽  
Thermal Stress ◽  
Closed System ◽  
Copper Foil ◽  
Atmospheric Oxygen ◽  
Thermal Ageing ◽  
Gas Content ◽  
Mineral Oils

The behaviour of some insulating fluids in contact with copper foil and / or insulation paper under thermal stress (110�30C for 1000 hours), in a closed system (the access of atmospheric oxygen being limited), has been studied by determining the changes in viscosity and concentration of CO2 and CO. The experimental data revealed that, following the applied heat treatment, the change in viscosity of the esters-based insulating fluids (both synthetic and vegetable) is approximately 7 times lower than in the case of the investigated mineral oils. It has also been found that, following the thermal ageing, the gas content of the mineral oils is substantially higher than in the esters-based oils (8 times higher for CO2 and 4 times higher for CO, respectively). The experimental results indicate superior values for the thermal stability and compatibility with the insulation paper of ester-based insulating fluids.

The respiratory behaviour of an air-breathing catfish, Clarias macrocephalus (Clariidae)

1987 ◽  
Vol 65 (2) ◽  
pp. 348-353 ◽  
Author(s):  
David J. Bevan ◽  
Donald L. Kramer
Keyword(s):  
Dissolved Oxygen ◽  
Atmospheric Oxygen ◽  
Breathing Frequency ◽  
Dissolved Oxygen Concentration ◽  
Significant Cost ◽  
Air Breathing ◽  
Aerial Respiration ◽  
Travel Costs ◽  
Clarias Macrocephalus ◽  
Do So

Clarias macrocephalus are continuous, facultative air breathers. Individuals (7.6–20.9 g) survived more than 25 days in normoxic water without surface access. Buoyancy decreased and water-breathing frequency increased when surface access was denied, but growth rate and the frequency of air-breathing attempts did not change. We examined air-breathing and water-breathing frequency in shallow (60 cm) and deep (235 cm) water under normoxic (8.0 mg O2∙L−1) and hypoxic (0.3, 0.7, 1.2, and 2.0 mg O2∙L−1) conditions to examine how changes in the travel costs of breathing affected the use of each respiratory mode. Air-breathing and water-breathing frequency increased as dissolved oxygen decreased from 8.0 to 2.0 mg O2∙L−1. Below this level air breathing continued to increase, but water breathing dropped sharply. At higher levels of dissolved oxygen (8.0 and 2.0 mg O2∙L−1), fish in deep water had lower air-breathing and higher water-breathing frequencies than fish in shallow water. Vertical distance travelled and time spent in air breathing increased with increasing depth and with decreasing level of dissolved oxygen. These results support the hypotheses that travel is a significant cost of aerial respiration and that fish respond to increases in this cost by decreasing their use of atmospheric oxygen when dissolved oxygen concentration permits them to do so.

An experimental study on aerobic denitrification with polyvinyl alcohol as a carbon source in biofilms

1995 ◽  
Vol 32 (8) ◽  
pp. 235-242 ◽  
Author(s):  
D.-Y. Bang ◽  
Y. Watanabe ◽  
T. Noike
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Surface Layer ◽  
Carbon Source ◽  
Organic Carbon ◽  
Polyvinyl Alcohol ◽  
Dissolved Oxygen ◽  
Aerobic Denitrification ◽  
Dissolved Oxygen Concentration ◽  
Organic Carbon Source

Aerobic denitrification occuring in the biofilms attached to a partially submerged RBC, was investigated. Denitrification using polyvinyl alcohol (PVA) as a organic carbon source, was well proceeded by aerobic RBC systems at 25 °C. At an influent C/N ratio of around 1.2, the maximum net-denitrification efficiency was about 78% at a TOC loading of 2g/m2/d. In a chemostat experiment, aerobic denitrification was well proceeded under the dissolved oxygen concentration of 3 to 6 mg/L. The PVA-decomposing bacteria, nitrifiers, and denitrifiers co-existed in the biofilm, but the population of PVA-decomposing bacteria and denitrifiers in the surface layer was 1 to 2 orders of magnitude higher than those in the middle and bottom layers. It may indicate that the surface layer had a higher denitrifying activity. The nitrogen mass balance obtained using the experimental data clearly indicates a reasoning for aerobic denitrification.

Thermochemical Stability of Some Transformer Oils- Flammable Gas Formation Due to the Thermal Aging

2018 ◽  
Vol 69 (7) ◽  
pp. 1621-1627
Author(s):  
Iosif Lingvay ◽  
Valerica Stanoi ◽  
Livia Carmen Ungureanu ◽  
Ana Maria Luchian ◽  
Gabriela Oprina
Keyword(s):  
Thermal Aging ◽  
Atmospheric Oxygen ◽  
Maximum Effect ◽  
Mineral Oils ◽  
Insulating Paper ◽  
Long Term Storage ◽  
Gas Formation ◽  
Flammable Gas ◽  
Transformer Oils

The amounts of flammable gases formed in some transformer oils during the long-term storage (1000 hours) at 110 � 3�C in closed containers (limited access to atmospheric oxygen) were determined qualitatively and quantitatively by gas chromatography technique. The comparative experimental results showed that when two types of mineral oils, one synthetic oil and two types of vegetable oils are in simultaneously contact with copper and insulating paper, the total amount of flammable gases formed by thermal aging is about 40 times higher in the mineral oils than in the ester based oils. It has also been established that the electrical-use copper foil catalyses the formation processes of the flammable gases, the maximum effect being for the mineral oils (an increase of 8 times of ethane and 25 times for methane gases). It has further been observed that the contact with the insulating paper during the thermal treatment of the ester based oils does not influence the formation of flammable gases, compared with the mineral oils where the amount of the formed gases is doubled.

Mass Appearance of Cyanobacterium Planktothrix rubescens in Lake Piaseczno, Poland

2003 ◽  
Vol 38 (1) ◽  
pp. 141-152 ◽  
Author(s):  
Danuta Krupa ◽  
Krzysztof Czernaś
Keyword(s):  
Dissolved Oxygen ◽  
Primary Production ◽  
Catchment Area ◽  
High Water ◽  
Water Bloom ◽  
High Water Temperature ◽  
Dissolved Oxygen Concentration ◽  
Planktothrix Rubescens ◽  
Assimilation Number ◽  
Bottom Zone

Abstract In 1989, Lake Piaseczno, Poland, exhibited a mass appearance of Planktothrix rubescens. During this time the pelagic and littoral areas exhibited significant increases in areal primary production (400 and 41 mg C m-2 h-1, respectively), chlorophyll α (100 and 6.9 mg m-2, respectively) and assimilation number (4 and 5.9 mg C m-2 h-1/mg chlα m-2, respectively). After the water bloom subsided, a reduction of dissolved oxygen concentration (down to 1.5 mg L-1) and high water temperature (10.2°C) in the offshore bottom zone was observed. While from 1991 to 1996, the primary production, chlorophyll α concentration and assimilation number values were decreasing, they were significantly higher than the values reported in 1986, prior to the mass cyanobacteria appearance. An indirect correlation with ion levels indicated that the outbreak of the cyanobacteria was linked with inflow of nutrients from the catchment area. The dramatic changes in the range and variability of the phytoplankton density indicate that the recent eutrophication of the lake has had profound effects on the structure and productivity of the aquatic community.

Effect of Physicochemical Variables on Algal Autoflotation

1992 ◽  
Vol 26 (7-8) ◽  
pp. 1769-1778 ◽  
Author(s):  
S.-I. Lee ◽  
B. Koopman ◽  
E. P. Lincoln
Keyword(s):  
Dissolved Oxygen ◽  
Oxygen Concentration ◽  
Retention Time ◽  
Contact Time ◽  
Pilot Scale ◽  
Dissolved Oxygen Concentration ◽  
Physicochemical Variables ◽  
Rise Rate ◽  
Mixing Intensity ◽  
Maximum Rise

Combined chemical flocculation and autoflotation were examined using pilot scale process with chitosan and alum as flocculants. Positive correlation was observed between dissolved oxygen concentration and rise rate. Rise rate depended entirely on the autoflotation parameters: mixing intensity, retention time, and flocculant contact time. Also, rise rate was influenced by the type of flocculant used. The maximum rise rate with alum was observed to be 70 m/h, whereas that with chitosan was approximately 420 m/h. The efficiency of the flocculation-autoflotation process was superior to that of the flocculation-sedimentation process.

scholarly journals Gas–liquid mass transfer characteristics of aviation fuel scrubbing in an aircraft fuel tank

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Li Chaoyue ◽  
Feng Shiyu ◽  
Xu Lei ◽  
Peng Xiaotian ◽  
Yan Yan
Keyword(s):  
Mass Transfer ◽  
Dissolved Oxygen ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Oxygen Concentration ◽  
Gas Holdup ◽  
Aviation Fuel ◽  
Volumetric Mass Transfer Coefficient ◽  
Dissolved Oxygen Concentration ◽  
Liquid Mass Transfer

AbstractDissolved oxygen evolving from aviation fuel leads to an increase in the oxygen concentration in an inert aircraft fuel tank ullage that may increase the flammability of the tank. Aviation fuel scrubbing with nitrogen-enriched air (NEA) can largely reduce the amount of dissolved oxygen and counteract the adverse effect of oxygen evolution. The gas–liquid mass transfer characteristics of aviation fuel scrubbing are investigated using the computational fluid dynamics method, which is verified experimentally. The effects of the NEA bubble diameter, NEA superficial velocity and fuel load on oxygen transfer between NEA and aviation fuel are discussed. Findings from this work indicate that the descent rate of the average dissolved oxygen concentration, gas holdup distribution and volumetric mass transfer coefficient increase with increasing NEA superficial velocity but decrease with increasing bubble diameter and fuel load. When the bubble diameter varies from 1 to 4 mm, the maximum change of descent rate of dissolved oxygen concentration is 18.46%, the gas holdup is 8.73%, the oxygen volumetric mass transfer coefficient is 81.45%. When the NEA superficial velocities varies from 0.04 to 0.10 m/s, the maximum change of descent rate of dissolved oxygen concentration is 146.77%, the gas holdup is 77.14%, the oxygen volumetric mass transfer coefficient is 175.38%. When the fuel load varies from 35 to 80%, the maximum change of descent rate of dissolved oxygen concentration is 21.15%, the gas holdup is 49.54%, the oxygen volumetric mass transfer coefficient is 44.57%. These results provide a better understanding of the gas and liquid mass transfer characteristics of aviation fuel scrubbing in aircraft fuel tanks and can promote the optimal design of fuel scrubbing inerting systems.

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