Flammability Measurements of Difluoromethane

1999 ◽  
Vol 122 (1) ◽  
pp. 92-98 ◽  
Author(s):  
W. L. Grosshandler ◽  
M. K. Donnelly ◽  
C. Womeldorf
Keyword(s):  
Room Temperature ◽  
Flammability Limit ◽  
Dry Air ◽  
Counterflow Flame ◽  
Alternative Approach ◽  
Stretch Condition ◽  
Lean Limit ◽  
The Rich ◽  
Flame Method ◽  
Refrigeration Machine

Difluoromethane (CH2F2, or R-32) is a candidate to replace ozone-depleting chlorofluorocarbon refrigerants. Because CH2F2 is flammable, it is necessary to assess the hazard posed by a leak in a refrigeration machine. The currently accepted method for determining flammability, ASTM E 681 has difficulty discerning the flammability boundary for weak fuels such as CH2F2. This article describes an alternative approach to identify the limits of flammability, using a twin, premixed counterflow flame. By using the extinction of an already established flame, the point dividing flammable from nonflammable becomes unambiguous. The limiting extinction mixture changes with stretch rate, so it is convenient to report the flammability limit as the value extrapolated to a zero stretch condition. In the burner, contoured nozzles with outlet diameters of 12 mm are aligned counter to each other and spaced 12 mm apart. The lean flammability limit of CH2F2 in dry air at room temperature was previously reported by the authors to be a mole fraction of 0.14, using the twin counterflow flame method. In the current study, relative humidity was not found to affect the lean limit. Increasing the temperature of the premixed fuel and air to 100°C is shown to extend the flammability limit in the lean direction to 0.13. The rich limit of CH2F2 found using the counterflow method is around 0.27. The uncertainties of the measurements are presented and the results compared to data in the literature. [S0022-1481(00)02501-9]

Carbon Dioxide Effects on the Flammability Characteristics of Biogas

2014 ◽  
Vol 493 ◽  
pp. 129-133
Author(s):  
Nurkholis Hamidi
Keyword(s):  
Carbon Dioxide ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Flame Speed ◽  
Flammability Limit ◽  
Flammability Limits ◽  
Rich Mixture ◽  
Flammability Characteristics ◽  
The Rich ◽  
Observation Results

Flammability limits and flame speed of methane-carbon dioxide-air mixtures have been studied to understand the effect of carbondioxide on the flammability characteristic of biogas. The fuel of biogas discussed in this study was made by mixing gases of methane and carbon dioxide. The carbon dioxide was varied from 0% (by volume) untill reach the flammability limit of the stoikhiometri biogas-air mixtures. The observation was done using a cubic combustion bomb with the dimension of 500 mm x 200 mm x 10 mm with the initial condition being at room temperature and atmospheric pressure. The ignitor was set at the top of combustion bomb, so the flame propagated downward. Base on the observation results, the presence of carbon dioxide in the fuel ofbiogas caused the flammability limits of biogasair mixture narrower. The biogas-air mixture was still flammable with the highest content of carbon dioxide of 62.5 %vol when the mixture was sthoichiometri. Compared to methane-air mixture, the presence of carbon dioxide in biogas caused a reduction in the flame speed. The stoichiometri mixture has the highest flame speed when the carbon dioxide was not present in the fuel. However, when the carbon dioxide was added in the fuel, the rich mixture has the highest flame speed. This is a consequence of the rich biogas-air mixture having a higher fraction of the carbon dioxide components from the fuel compared to the stoichiometri and lean biogas-air mixture. The result also indicated that at the upper limit the flame still propagated downward to closed to the endwall. However, at the lower limit (lean mixtures), the flame did not intend to propagate downward, it was just at the top and propagate sideward.

Spectroscopic Evidence for Atmospheric Stabilization of Aluminum Borohydride in Polydimethylsiloxane Grease

2012 ◽  
Vol 66 (5) ◽  
pp. 591-594 ◽  
Author(s):  
Premkumar Sivasubramanian ◽  
Rana Mohtadi ◽  
Ragaiy Zidan ◽  
Kutty Pariyadath ◽  
Chad L. Leverette ◽  
...  
Keyword(s):  
Vibrational Spectroscopy ◽  
Room Temperature ◽  
Spectroscopic Evidence ◽  
Dry Air

Raman and infrared vibrational spectroscopy were used to confirm the presence of aluminum borohydride dissolved in a commercial polydimethylsiloxane vacuum grease at room temperature. Spectroscopic evidence for an adduct between the aluminum borohydride and polydimethylsiloxane is also presented. Once dissolved in the polydimethylsiloxane grease, the aluminum borohydride was stabilized with respect to its usual pyrophoric reactivity in wet or dry air.

Effect of Cold Working and Annealing on Oxidation Rates of Copper in Dry Air at Room Temperature

CORROSION ◽  
1968 ◽  
Vol 24 (12) ◽  
pp. 407-410 ◽  
Author(s):  
P. K. KRISHNAMOORTHY ◽  
S. C SIRCAR
Keyword(s):  
Room Temperature ◽  
Lattice Distortion ◽  
Cold Working ◽  
Oxide Films ◽  
Dry Air ◽  
Oxidation Rates ◽  
Substrate Metal ◽  
Thin Oxide Films ◽  
Thin Oxide ◽  
Kinetics Of

Abstract The effect of plastic deformation and further annealing on the kinetics of growth of thin oxide films on copper at 30 C (86 F) has been investigated. Oxidation rate was found to decrease markedly with increasing deformation. Further annealing showed an increase in the rate, the most pronounced changes occurring during the recrystallization stage. Results are interpreted in the light of Cabrera-Mott theory of growth of very thin oxide films on metals. The change in rate has been related to the concentration of cation vacancies in the Cu2O semi-conductor, which is dependent on the lattice distortion and defect concentration of the substrate metal.

scholarly journals The tribological properties of Al-brasses in various environments

2017 ◽  
Vol 61 (3) ◽  
pp. 91-94
Author(s):  
M. Lovíšek ◽  
T. Liptáková ◽  
J. Bronček ◽  
S. Dundeková
Keyword(s):  
Tribological Properties ◽  
Room Temperature ◽  
Tribological Behavior ◽  
Cold Drawing ◽  
Operating Conditions ◽  
Air Cooling ◽  
Normal Loading ◽  
Dry Air ◽  
Similar Chemical ◽  
Made In

Abstract Tribological properties of Al-brass pipes of various producers were studied in different environments. The tested brasses have very similar chemical composition, but they differ in microstructure due to mainly by heat treatment after cold drawing. Microstructure as well as roughness of surface influence chemical and mechanical properties which are important in operating conditions. The experiments of tribological behavior were made in various environments, dry air, cooling treated water and 3.5 % solution of NaCl at room temperature 21 ± 2°C. The tribological tests were carried out on the Linear Tribometer at normal loading 5 N by the method ball on plate for the duration of 5500 s. The measured friction coefficients were evaluated by the program DIAdem and the diagrams were created from signal generated by software NSignal Express

Do the rich pollute more? Mexican household consumption by income level and CO2 emissions

2019 ◽  
Vol 13 (3) ◽  
pp. 694-712 ◽  
Author(s):  
Mónica Santillán Vera ◽  
Angel de la Vega Navarro
Keyword(s):  
Climate Change ◽  
Household Consumption ◽  
Mitigation Strategies ◽  
Consumption Patterns ◽  
Content Type ◽  
Income Levels ◽  
Alternative Approach ◽  
Per Capita ◽  
The Rich ◽  
Using Data

Purpose The purpose of this paper is to quantitatively examine if varying household consumption activities at different income levels drove CO2 emissions to different degrees in Mexico from 1990 to 2014. Design/methodology/approach The paper applied a simple expenditure-CO2 emissions elasticity model – a top-down approach – using data from consumption-based CO2 emission inventories and the “Household Income and Expenditure Survey” and assuming a range of 0.7-1.0 elasticity values. Findings The paper results show a large carbon inequality among income groups in Mexico throughout the period. The household consumption patterns at the highest income levels are related to significantly more total CO2 emissions (direct + indirect) than the household consumption patterns at the lowest income levels, in absolute terms, per household and per capita. In 2014, for example, the poorest household decile emitted 1.6 tCO2 per capita on average, while the wealthiest decile reached 8.6 tCO2 per capita. Practical/implications The results suggest that it is necessary to rethink the effect of consumption patterns on climate change and the allocation of mitigation responsibilities, thus opening up complementary options for designing mitigation strategies and policies. Originality/value The paper represents an alternative approach for studying CO2 emissions responsibility in Mexico from the demand side, which has been practically absent in previous studies. The paper thereby opens a way for studying and discussing climate change in terms of consumption and equity in the country.

scholarly journals Tuning ferromagnetism at room temperature by visible light

2020 ◽  
Vol 117 (12) ◽  
pp. 6417-6423 ◽  
Author(s):  
Bálint Náfrádi ◽  
Péter Szirmai ◽  
Massimo Spina ◽  
Andrea Pisoni ◽  
Xavier Mettan ◽  
...  
Keyword(s):  
Room Temperature ◽  
Magnetic Moments ◽  
Ferromagnetic State ◽  
Perovskite Oxide ◽  
External Control ◽  
Digital Information ◽  
Alternative Approach ◽  
Ferromagnetic Domains ◽  
Radical Method ◽  
Oxide Perovskite

Most digital information today is encoded in the magnetization of ferromagnetic domains. The demand for ever-increasing storage space fuels continuous research for energy-efficient manipulation of magnetism at smaller and smaller length scales. Writing a bit is usually achieved by rotating the magnetization of domains of the magnetic medium, which relies on effective magnetic fields. An alternative approach is to change the magnetic state directly by acting on the interaction between magnetic moments. Correlated oxides are ideal materials for this because the effects of a small external control parameter are amplified by the electronic correlations. Here, we present a radical method for reversible, light-induced tuning of ferromagnetism at room temperature using a halide perovskite/oxide perovskite heterostructure. We demonstrate that photoinduced charge carriers from theCH3NH3PbI3photovoltaic perovskite efficiently dope the thinLa0.7Sr0.3MnO3film and decrease the magnetization of the ferromagnetic state, allowing rapid rewriting of the magnetic bit. This manipulation could be accomplished at room temperature; hence this opens avenues for magnetooptical memory devices.

scholarly journals Microstructure and Properties of Bulk Ultrafine-Grained Cu1.5Cr0.1Si Alloy through ECAP by Route C and Aging Treatment

Crystals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 207 ◽  
Author(s):  
Tingbiao Guo ◽  
Xiaoyang Tai ◽  
Shiru Wei ◽  
Junjie Wang ◽  
Zhi Jia ◽  
...  
Keyword(s):  
Aging Process ◽  
Room Temperature ◽  
Aging Treatment ◽  
Material Strength ◽  
X Ray Diffraction ◽  
Channel Angle ◽  
X Ray ◽  
Ultrafine Grained ◽  
The Rich ◽  
Electron Back Scattered Diffraction

The evolutions of the microstructure and its effect on the mechanical and electrical conductivity properties of Cu1.5Cr0.1Si alloy after equal channel angle pressing (ECAP)-C path deformation and aging treatment have been investigated using scanning electron microscopy (SEM), x-ray diffraction (XRD), and electron back-scattered diffraction (EBSD). It was found that after the ECAP-C deformation at room temperature, with an extension of aging time, the strong (111) macro orientation formed in the Cu1.5Cr0.1Si alloy. The ultrafine crystals formed by ECAP and the rich chromium phase precipitated along grain boundaries during the aging process greatly improved the material strength. After aging at 350 °C for 4 h, the tensile strength, elongation, and conductivity reached 528 MPa, 15.27%, and 78.9% IACS, respectively. The fracture mode of the alloy was ductile fracture. The steady-oriented {111} <110> texture was beneficial to improving the conductivity of the material.

scholarly journals P.1.30 Assessment of sick building syndrome among employees in the commercial centers in Niš, serbia

2019 ◽  
Vol 76 (Suppl 1) ◽  
pp. A85.2-A85
Author(s):  
Bojana Miladinovic ◽  
Maja Nikolic ◽  
Aleksandra Stankovic ◽  
Sci Visa Tasic
Keyword(s):  
Logistic Regression ◽  
Room Temperature ◽  
Ventilation System ◽  
Sick Building Syndrome ◽  
Binary Logistic Regression ◽  
Static Electricity ◽  
Cross Sectional ◽  
Quality Of Working Life ◽  
Dry Air ◽  
Sick Building

Sick Building Syndrome (SBS) is a diseases associated with indoor air quality accompanied with various nonspecific symptoms that occur in the occupants of a building. This syndrome has been the subject of serious scientific investigation in the past years, but there are not enough studies in transition countries.The aim of this study was to investigate the symptoms of the syndrome among employees in the commercial centers in Niš, Serbia.MethodsThe cross-sectional study was conducted amongst employees of two commercial centers in the city of Niš, Serbia. In this study the MM-040EA questionnaire was used with two additional questions and 1152 employed were interviewed during the period of three years. Data extracted from the questionnaires were analyzed using the chi-square test and binary logistic regression.ResultsThe prevalence of SBS was high. The most common symptoms reported by employees included high room temperature (74.9%), stuffy air (73.5%), and dry air (75.7%), while rare complaints were towards static electricity (47.3%) and low room temperature (45.2%). Binary logistic regression showed that too low room temperature (p=0.002), dry air (p=0.015), static electricity (p=0.007) and noise (p=0. 024) were the most important factors for the high symptoms score. A relatively small number of sick absence (13.4%) was found among subjects working in the investigated commercial centers.ConclusionThe high prevalence of SBS symptoms in the environment of commercial centers was almost associated with factors of unpleasant microclimate. So improvement of environmental conditions such as increasing the efficiency of the ventilation system, increasing fresh air flow in the sector and noise prevention , as well as enhancing the quality of working life will motivate the employees and increase productivity in the workplace. The occupational health care workers play an important role in educating of workers and their employers.

Laboratory Studies on the Behaviour of the Douglas-fir Beetle, Dendroctonus pseudotsugae Hopkins

1966 ◽  
Vol 98 (9) ◽  
pp. 953-991 ◽  
Author(s):  
M. D. Atkins
Keyword(s):  
Room Temperature ◽  
Douglas Fir ◽  
Single Source ◽  
Laboratory Studies ◽  
Population Changes ◽  
Dendroctonus Pseudotsugae ◽  
Dry Air ◽  
Light Gradient ◽  
Preferred Temperatures ◽  
Behavioural Types

AbstractThe behaviour of Dendroctonus pseudotsugae Hopk. in different physiological states was studied in relation to temperature, light, and host.Newly emerged beetles preferred temperatures near the threshold for flight. When conditioned in dry air at room temperature for 16 hours they preferred cooler temperatures.At room temperature, most newly emerged beetles settled in the brightest zone of a light gradient (55 foot-candles), although some settled in dimmer zones. If the beetles' emergence was delayed or if they were stored after emergence, more remained in the zone between 0.5 and 10 foot-candles.In light-dark tests at room temperature most newly emerged beetles were photopositive, but some were indifferent and a few were photonegative. Increasing the temperature and humidity increased the proportion of photonegative individuals. Newly emerged females oriented more directly to a single source of light than males, bur after conditioning or aging both reacted similarly.Females were separated into three behavioural types based on their reactions. Photopositive individuals flew more readily than indifferent or photonegative beetles; some photonegative females showed no inclination to fly.Photopositive females were usually host negative but photonegative females were host positive. The proportion of these behavioural types within different samples varied. A group that emerged early contained a higher incidence of photopositive host-negative individuals than a group that emerged late, or was stored for 10 days after emergence. But host-negative beetles would attack logs after starvation, flight exercise, or exposure to more attractive hosts.Host-positive females contained less fat than host-negative siblings. The decline in lipids during aging, starvation or flight thus may induce behavioural changes.There is a co-ordination of successive activities in the Douglas-fir beetle similar to that reported for aphids. The initial urge to disperse outweighs responses to host stimuli, but this balance changes as the beetles fly or as host stimuli increase. The balance between thresholds for dispersal and attack also varies in relation to the conditions under which the emerging beetles developed. Consequently, each individual behaves differently when it emerges. The behaviour of a population changes as the season progresses and from year to year owing to changes in the state of individuals and in the attractiveness of hosts.

scholarly journals Enhancement of SnO2 for gas sensing applications

2021 ◽  
Vol 32 (3) ◽  
pp. 63
Author(s):  
O. S. Mahdi ◽  
Nadheer Jassim Mohammed
Keyword(s):  
Thin Films ◽  
Room Temperature ◽  
Gas Sensing ◽  
Rf Magnetron Sputtering ◽  
Ethanol Vapor ◽  
Gas Sensitivity ◽  
Sensing Applications ◽  
Sno2 Thin Films ◽  
The Rich ◽  
Reactive Rf Magnetron Sputtering

Thin films of SnO2 were deposited by reactive RF magnetron sputtering. It was shown that the films possess gas sensitivity to ethanol vapor at room temperature. XRD, SEM, and EDX measurements of thin films were investigated. Annealing of SnO2 thin films at 800 °С is polycrystalline and grain size of SnO2 in the range about 12 nm. The growth of SnO2 with annealing to 800 °C leads to the percolation nanorods structure. EDX clearly explains the rich of Sn reached 70% annealing. The conductivity of SnO2 nanorods has been increasing at room temperature for ethanol vapors. 

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