scholarly journals Critical Conditions for the Ignition of a Gel Fuel under Different Heating Schemes

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7083
Author(s):  
Olga Gaidukova ◽  
Pavel Strizhak
Keyword(s):  
Storage Conditions ◽  
Heat Emission ◽  
Heat Fluxes ◽  
Critical Conditions ◽  
Fuel Vapor ◽  
Reaction Conditions ◽  
Exponential Factor ◽  
Data Dependencies ◽  
Heating Scheme ◽  
Necessary And Sufficient

A model was developed to research the critical conditions and time characteristics of the ignition of gel fuels in the course of conductive, convective, radiant and mixed heat transfer. MATLAB was used for numerical modeling. Original MATLAB code was established pursuant to the developed mathematical model. For gel fuel ignition at initial temperatures corresponding to cryogenic storage conditions with different heating schemes, a numerical analysis of interconnected processes of heat and mass transfer in the chemical reaction conditions and exothermic and endothermic phase transitions was conducted. The model was tested by comparing the theoretical results with the experimental data. Dependencies were established between the key process characteristic (i.e., the ignition delay time) and the ambient temperature when the following parameters were varied: emissivity, heat emission coefficient, activation energy and pre-exponential factor of the fuel vapor oxidation reaction. The critical values of the main parameters of the energy source were determined. For these values, gel fuel ignition conditions were consistently realized for each heating scheme. The critical heat fluxes necessary and sufficient for the ignition of typical gel fuels were determined.

Influence of Temperature and Oxygen Concentration on the Radiation Induced Oxidation of Phenylalanine

1995 ◽  
Vol 50 (9) ◽  
pp. 864-870 ◽  
Author(s):  
P. Krajnik ◽  
R. M. Quint ◽  
S. Solar ◽  
N. Getoff ◽  
G. Sontag
Keyword(s):  
Oxygen Concentration ◽  
Room Temperature ◽  
Degradation Process ◽  
Storage Conditions ◽  
Food Storage ◽  
Reaction Conditions ◽  
Influence Of Temperature ◽  
Influence Of Temperature On ◽  
Radiation Induced ◽  
Induced Changes

AbstractThe formation of tyrosine isomers by γ-radiolysis of neutral aqueous phenylalanine solutions was found to be strongly dependent on oxygen concentration and temperature. Changing the dose rate did not influence the degradation process. In the presence of 0.25 x 10-3 mol dm-3 oxygen at room temperature the yields of o-tyrosine as well as of m- and p-tyrosine drop from G(o-Tyr) = 0.5 and G(m-Tyr) = G(p-Tyr) = 0.4 at a dose of 0.3 kGy to 0.18 and 0.16 at 2.5 kGy, respectively. In solutions containing 1.25 x 10-3 mol dm-3 oxygen the initial yields remain unchanged but decrease at 2.5 kGy only to G(o-Tyr) = 0.3 and G(m-Tyr) = G(p-Tyr) = 0.20. Under the latter reaction conditions also 3,4-dihydroxyphenylalanine was found.Samples irradiated in frozen state did not show remarkable radiolysis of phenylalanine and tyrosine formation. In the range between 5 and 20°C no essential influence of temperature on the phenylalanine radiolysis and tyrosine yields was observable. The obtained results are important for methods using the tyrosine yields as markers for the detection of irradiated food. Storage conditions and irradiation temperature play an essential role on radiation induced changes of food.

scholarly journals Revising the definition of anthropogenic heat flux from buildings: role of human activities and building storage heat flux

2021 ◽  
Author(s):  
Yiqing Liu ◽  
Zhiwen Luo ◽  
Sue Grimmond
Keyword(s):  
Heat Flux ◽  
Energy Consumption ◽  
Energy Balance ◽  
Human Activities ◽  
Building Energy ◽  
Heat Emission ◽  
Heat Fluxes ◽  
Anthropogenic Heat ◽  
Anthropogenic Heat Flux ◽  
The Difference

Abstract. Buildings are a major source of anthropogenic heat emissions, impacting energy use and human health in cities. The difference between building energy consumption and building anthropogenic heat emission magnitudes and time lag and are poorly quantified. Energy consumption (QEC) is a widely used proxy for the anthropogenic heat flux from buildings (QF,B). Here we revisit the latter’s definition. If QF,B is the heat emission to the outdoor environment from human activities within buildings, we can derive it from the changes in energy balance fluxes between occupied and unoccupied buildings. Our derivation shows the difference between QEC and QF,B is attributable to a change in the storage heat flux induced by human activities (∆So-uo) (i.e., QF,B = QEC − ∆So-uo). Using building energy simulations (EnergyPlus) we calculate the energy balance fluxes for a simplified isolated building (obtaining QF,B, QEC, ∆So-uo) with different occupancy states. The non-negligible differences in diurnal patterns between QF,B and QEC caused by thermal storage (e.g. hourly QF,B to QEC ratios vary between −2.72 and 5.13 within a year in Beijing, China). Negative QF,B can occur as human activities can reduce heat emission from building but are associated with a large storage heat flux. Building operations (e.g., open windows, use of HVAC system) modify the QF,B by affecting not only QEC but also the ∆So-uo diurnal profile. Air temperature and solar radiation are critical meteorological factors explaining day-to-day variability of QF,B. Our new approach could be used to provide data for future parameterisations of both anthropogenic heat flux and storage heat fluxes from buildings. It is evident that storage heat fluxes in cities may also be impacted by occupant behaviour.

scholarly journals Analysis of Fire Characteristics based on the Thickness and Incident Heat Flux of Wood

2020 ◽  
Vol 34 (4) ◽  
pp. 13-21
Author(s):  
Sun-Woo Hwang ◽  
Won-Hee Park ◽  
Chang-Yong Kim
Keyword(s):  
Heat Flux ◽  
Average Rate ◽  
Medium Density Fiberboard ◽  
Heat Emission ◽  
Heat Fluxes ◽  
Particle Board ◽  
Combustion Heat ◽  
Incident Heat Flux ◽  
Piloted Ignition ◽  
Fire Characteristics

This study tested the wood used in building interiors; each type had various incident heat fluxes based on their thickness. The combustion characteristics measured were effective heat of combustion, heat release rate peak and arrival time, maximum average rate of heat emission, and piloted ignition temperature. The wood specimens used in the experiment were 4.8 to 18 mm thick. 25, 35, 50, and 60 kW/m<sup>2</sup> were applied to the incident heat flux that the wood specimens were exposed to. The wood specimens tested were two types of medium-density fiberboard (each with a different density), treated red pine, particle board, and plywood. A comprehensive comparison of different fire characteristics was conducted to analyze the fire patterns corresponding to each type of wood in this way, the risk of fire was studied. The risk of fire was particularly high for particle board. The results of quantifying the fire characteristics of the types of wood studied could function as important input data with which to calculate the fire load of composite combustibles.

A New Catalyst on Di(1-Naphthyl)methane Hydrocracking and Kinetics Analysis

2011 ◽  
Vol 236-238 ◽  
pp. 771-774
Author(s):  
Xiao Ming Yue ◽  
Zhi Min Zong ◽  
Bing Sun ◽  
Ying Hua Wang ◽  
Yu Qing ◽  
...  
Keyword(s):  
Activation Energy ◽  
Reaction Times ◽  
Order Reaction ◽  
Model Reaction ◽  
Coal Liquefaction ◽  
Kinetics Analysis ◽  
Reaction Conditions ◽  
Exponential Factor ◽  
Active Constituents ◽  
First Order

A new catalyst with two active constituents interacting with activated carbon was prepared. As a model reaction for coal liquefaction, the hydrocracking of di(1-naphthyl)methane (DNM) was investigated under different reaction conditions over the catalyst. The results show that the catalyst converts DNM hydrocraking into 1-methylnaphthalene and naphthalene with high selectively, without any hydrogenation product. Kinetic analysis indicates that DNM hydrocracking in the temperature range of 170-300 °C could be considered as a first order reaction. The activation energy E and pre-exponential factor A for DNM hydrocracking for different reaction times were calculated.

scholarly journals KINETIC STUDY ON HYDROTHERMAL COMPOSITION OF GLUCOSE IN NAOH SOLUTION WITH ZNO AS CATALYST

2021 ◽  
Vol 5 (1) ◽  
pp. 7
Author(s):  
Bregas Siswahjono Tatag Sembodo ◽  
Addiva Febrioka ◽  
Adistya Hilga Pratiwi Aprilia
Keyword(s):  
Liquid Phase ◽  
Heating Temperature ◽  
Biomass Conversion ◽  
Critical Conditions ◽  
Solid Residue ◽  
Exponential Factor ◽  
Ms Analysis ◽  
Processed Material ◽  
Residual Glucose ◽  
Naoh Solution

<p>Hydrothermal liquifaction is a biomass conversion process, where the structure of the biomass is convert into liquid components under super critical conditions with a high temperature. In this study, glucose is used as biomass. The purpose of this study was to study the reaction kinetics and determine the hydrothermal decomposition of glucose in NaOH solution. This experiment used 10 grams of glucose and dissolve it in 80 mL of NaOH solution then put it in an autoclave. Experiments were carried out by varying the heating temperature carried out in an autoclave with a magnetic stirrer. After heating at various temperatures, the autoclave is immediately cooled down. The processed material is filtered to separate insoluble solids from the liquid phase. The solid residue that has been separated from the liquid phase is then dried in an oven at 105°C for 24 hours. The composition of the filtrate was analyzed using the GC-MS method and the glucose concentration was analyzed using the Lane Eynon method. Prior to GC-MS analysis, the filtrate was distilled at atmospheric pressure until a solid residue remained. The sample analyzed is the result of distillation with a temperature above 100°C to ensure that there is no water and residual glucose in the sample. The results of GC-MS analysis of product samples from the hydrothermal decomposition process had 3 peaks. The first peak shows the compound 1,3 Dipalmitin which has an area of 14.74%, the second peak shows the Olealdehyde compound which has an area of 32.35%, and the third peak shows the 1,2-Epoxyhexadecane compound which has an area of 52.91%. The kinetics results in hydrothermal decomposition of glucose in this experiment obtained a reaction order of 2 with an activation energy (Ea) of 15.91 KJ / mol and a pre-exponential factor of 66.12.</p>

scholarly journals Critical Ignition Conditions of Wood by Cylindrical Firebrands

2021 ◽  
Vol 7 ◽  
Author(s):  
Hamed Salehizadeh ◽  
Raquel S. P. Hakes ◽  
Michael J. Gollner
Keyword(s):  
Heat Flux ◽  
Oriented Strand Board ◽  
Thermal Conditions ◽  
Heat Fluxes ◽  
Critical Conditions ◽  
Small Scale ◽  
Test Surface ◽  
Transient Heating ◽  
Wind Speeds ◽  
Critical Ignition

This study investigated the thermal conditions preceding ignition of three dense woody fuels often found on structures by firebrands, a major cause of home ignition during wildland-urban interface (WUI) fires. Piles of smoldering cylindrical firebrands, fabricated from wooden dowels, were deposited either on a flat inert surface instrumented with temperature and heat flux sensors or on a target fuel (marine-grade plywood, oriented-strand board, or cedar shingles) to investigate critical conditions at ignition. The former provided thermal data to characterize the time before and at ignition, while the latter provided smoldering and flaming ignition times. Tests were conducted in a small-scale wind tunnel. Larger firebrand piles produced higher temperatures at the center of the pile, thought to be due to re-radiation within the pile. Ignition was found to be dependent on target fuel density; flaming ignition was additionally found to be dependent on wind speed. Higher wind speeds increased the rate of oxidation and led to higher temperatures and heat fluxes measured on the test surface. The heat flux at ignition was determined by combining results of inert and ignition tests, showing that ignition occurred while transient heating from the firebrand pile was increasing. Ultimately, critical ignition conditions from firebrand pile exposure are needed to design appropriate fire safety standards and WUI fire modeling.

scholarly journals Modeling Near Critical and Supercritical Fuel Injection and Mixing in Gas Turbine Applications

2018 ◽  
Author(s):  
C. Lettieri ◽  
G. Subashki ◽  
Z. Spakovszky
Keyword(s):  
Fuel Injection ◽  
Droplet Evaporation ◽  
Combustion Stability ◽  
Critical Conditions ◽  
Fuel Vapor ◽  
Scaling Analysis ◽  
Supercritical Regime ◽  
Supercritical Conditions ◽  
Evaporation Models ◽  
The Impact

This paper presents a numerical framework for characterizing fuel injection in modern combustors. The approach utilizes scaling analysis to describe the droplet evaporation in non-dimensional and fluid-independent terms. The results of the model are validated against published experimental data of isolated droplets evaporating at subcritical and near-critical conditions. The model is incorporated in a spray calculation framework and extended to the supercritical regime to assess the impact of different fluid-properties and evaporation models on temperature and fuel vapor distributions. The results suggest that in a non-convective environment the transient and quasi-steady evaporation rates vary exponentially with Lewis number. Furthermore, the results show fluid-independent behavior of the droplet evaporation, indicating that a single-component fluid can potentially be used as a modeling surrogate for jet fuel. The first-principles analysis demonstrates that classical evaporation models overestimate transient evaporation and underestimate quasi-steady evaporation, with discrepancies up to 70% at supercritical conditions. This is due to limitations in fuel-property description and the lack of non-isothermal droplet characterization at near-critical conditions. The temperature profiles are typically under-predicted and fuel vapor concentrations are over-predicted in standard spray calculations with subcritical evaporation models. As such the proposed framework breaks new ground in modeling of supercritical fuel injection. The improved quality in the predicted fuel concentration and temperature distribution can enable more accurate assessment of flame position, improving the estimation of combustion stability margins and NOx emissions. The model can be incorporated in commercial codes to guide the design of combustors operating at supercritical conditions.

The Rivalta’s test as a diagnostic variable in feline effusions – evaluation of optimum reaction and storage conditions

2013 ◽  
Vol 41 (05) ◽  
pp. 297-303 ◽  
Author(s):  
Y. Fischer ◽  
K. Weber ◽  
C. Sauter-Louis ◽  
K. Hartmann
Keyword(s):  
Room Temperature ◽  
Storage Conditions ◽  
Observer Variation ◽  
Major Influence ◽  
Test Results ◽  
Reaction Conditions ◽  
Robust Test ◽  
Optimum Reaction ◽  
Diagnostic Sensitivity And Specificity ◽  
And Storage

Summary Objective: The Rivalta’s test is used to diagnose feline infectious peritonitis (FIP) in cats with effusion. Only little information on the influence of sample storage and reaction conditions on test results is available, and diagnostic sensitivity and specificity to diagnose FIP vary considerably between few available studies. This study determined the influence of storage of effusion, modifications on reaction conditions, and inter-observer variation. Material and methods: The Rivalta’s test was repeated up to 21 days after storage at room temperature, in the refrigerator, or freezer. The test was performed by two independent, blinded investigators. It was also performed using different volumes of acetic acid, different acids, and different kinds of water. Results: Even after storage for 21 days, test results were comparable. While inter-observer variation revealed substantial disagreement, different modifications in performance showed no major influence on test outcome. Conclusion: The Rivalta’s test seems to be a very robust test concerning storage conditions. Modifications in reaction condition also do not substantially influence outcome. However, the test is subjective and depends on the evaluating person.

Effect of organic additives on storage stability of camel liver catalase against environmental conditions

2021 ◽  
pp. 1-7
Author(s):  
Mustafa Zeyadi
Keyword(s):  
Hydrogen Peroxide ◽  
Polyethylene Glycol ◽  
Bovine Serum Albumin ◽  
Bovine Serum ◽  
Storage Stability ◽  
Storage Conditions ◽  
Native Enzyme ◽  
Organic Additives ◽  
Reaction Conditions ◽  
Thermal Stable

The storage stability of catalase is very low under practical reaction conditions. Therefore, this study is aimed to evaluate the storage stability of catalase from camel liver by treated it with polyethylene glycol (PEG), glycerol, bovine serum albumin (BSA) and glucose against different storage conditions. The effect of some additives as stabilizers on the storage stability of camel liver catalase at 4°C and 30°C after 30 and 90 days was studied. The enzyme with additives at 5%concentration was more stable at 4 and 30°C for 90 days of incubation than native enzyme. The activity of catalase was more thermal stable in presence of 5%additive. The activity of enzyme with 5%BSA and glucose was retained 60%of its activity at 60°C. At pH 11 the catalase with glucose retained 30%of its activity. The native enzyme lost 80%of its activity in presence of 5 mM β-mercaptoethanol, where the enzyme with additive retained 30–46%of its activity. At 8 M urea, the native enzyme and enzyme with 5%of all additives retained 28%and 61–77%of its activity, respectively. The catalase with additives retained 50–90%of its activity in presence of different dyes. The results appeared that the catalase with additives may be used for elimination of excess of hydrogen peroxide after bleaching of textile.

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