Density combustible gases

Explosives and propellants are mixtures of fuel and oxidizer. The intensity of combustion is determined by the heat of combustion per pound of material, the material s density, the gas volume generated per volume of material, and the rate of deflagration or detonation. The latter, the most important variable, is determined by the speed at which fuel and oxidizer molecules combine. 

Methane leaks from a tank in a 50 m3 sealed room. Its concentration is found to be 30 % by volume, as recorded by a combustible gas detector. The watchman runs to open the door of the room. The lighter mixture of the room gases flows out to the door at a steady rate of 50 g/s. The flammable limits are 5 and 15 % by volume for the methane in air. Assume a constant temperature at 25 °C and well-mixed conditions in the room. The mixture of the room gases can be approximated at a constant molecular weight and density of 25 g/mol and 1.05 kg/m3 respectively. After the door is opened, when will the mixture in the room become flammable ... 

The flow of combustion products behind the flame front has a non-zero vorticity. When the gas crosses the flame front, which represents the gas-dynamic discontinuity surface where the velocity, pressure, density and gas temperature are step-like changing, the vorticity of combustion products is generated (Zeldovich, 1944, 1966, 1979, 1980 Borisov, 1978 Zeldovich et al. 1979 Tsien, 1951 and Chernyi, 1954). 

Gedanken Flame Experiment. In order to illustrate how the problems caused by the requirements of temporal and spatial resolution and geometric and physical complexity are translated into computational cost, we have chosen to analyze a gedanken flame experiment. Consider a closed tube one meter long which contains a combustible gas mixture. We wish to calculate how the physical properties such as temperature, species densities, and position of the flame front change after the mixture is ignited at one end. The burning gas can be described, we assume, by a chemical kinetics reaction rate scheme which involves some tens of species and hundreds of chemical reactions, some of which are "stiff."... 

The burning velocity Vq can be related to this wave thickness as follows. The mass of combustible material per unit area per second flowing into the wave is PqVq, where po is the density of the initial combustible gas mixture. The deflagration wave consumes these reactants at a rate wd (mass per unit area per second). Hence mass conservation implies that PqVq = wd, which, in conjunction with equation (1), yields... 

Observable Characteristics - Physical State (as normally shipped) Liquid Color. Clear Odor. None. Physical and Chemical Properties - Physical State at 15 V and 1 atm. Liquid Molecular Weight 71 (solute only) Boiling Point at 1 atm. Data not available (Vapor Pressure 0.033 atm at 125 °C Freezing Point 183, 84, 357 Critical Temperature Not pertinent Critical Pressure Not pertinent Specific Gravity 1.05 at 25 °C Vapor (Gas) Density NoipetivaEsAxRatioqfSpecificHeatsofVapor (Gas) Not pcttin ta.-. Latent Heat of Vaporization NotpottmanX-, Heat of Combustion Not pertinent Heat of Decomposition Not pertinent. 

The distribution of thickness of density of the adherent layer around the tube perimeter is not uniform. On the rear surfaces of the tubes, as a result of eddies in the combustion gas flow, the deposit thickness is the greatest and the density is the lowest (170-250 kg/m ). On the side surfaces, the density of the deposits is greater, up to 400 kg/m this is the point of maximum density and minimum thickness of the deposit. 

There is no specific detailed guidance available in the industry or from regulatory bodies on the siting of combustible gas detectors. Due to the wide variety of material that needs to be detected, variances in ambient environmental conditions, variations in process composition, temperatures and pressures, the ability to predict the manner in which gas releases can be detected by placement to detectors is not available as of yet. Most detectors are suggested to be placed near sources of potential leakages. For example, per NFPA 15, gas detectors are to be located with consideration for the density and temperature of the potential flammable gas release and its proximity to the equipment where leakage could occur. In API 14C (for oflshore structures) gas detection is to be provided in enclosed classified areas, in all enclosed areas that there is natural gas fired prime movers, and in buildings where personnel sleep and there is a flammable gas source. 

Equation 14.14, the critieal mass flux is a function not only of the critical heat flux at the siuface, but also of the convective heat transfer coefficient at the surface, the density and specific heat capacity of the combusting gas, the enthalpy of combustion of this gas and the ignition, flame and ambient temperatures which persist. Stoliarov and Lyon, [58-59] reported good predictivity of their model with respect to cone calorimetric mass and heat flux data... 

The information about the chemical composition can be used to calculate physical properties of the gas, such as heating (calorific) value and relative density. Combustion characteristics, products of combustion, toxicity, and interchangeability with other fuel gases may also be inferred from the chemical composition. 

Landfill gas is usually slightly lighter than air which promotes its release into the atmosphere. Density of LFG lowers with the increase of CH concentration, which is colourless and combustible gas that burns with blue flame (Itodo et al. 2007). Due to the presence of harmful substances, flammability and odour character, the aim is to reduce LFG emissions to the environment, subjecting it to utilization. The choice of the method of landfill gas utilization is influenced by its quality and quantity (Figure 2.1). When the concentration of CH in LFG is in the range of 35 0% and the output exceeds 30 m h, it is technically... 

Gas-phase reactions play a fundamental role in nature, for example atmospheric chemistry [1, 2, 3, 4 and 5] and interstellar chemistry [6], as well as in many teclmical processes, for example combustion and exliaust fiime cleansing [7, 8 and 9], Apart from such practical aspects the study of gas-phase reactions has provided the basis for our understanding of chemical reaction mechanisms on a microscopic level. The typically small particle densities in the gas phase mean that reactions occur in well defined elementary steps, usually not involving more than three particles. 

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