Compressed gas temperature

Terminology involves drier outlet dew point at the line pressure or the pneumatic circuit. This is the saturation temperature of the remaining moisture contained in the compressed air or gas. If the compressed gas temperature is never reduced below the outlet dew point beyond the drying equipment, there will be no further condensation. 

Ap/t = p = rate of change of pressure, (Ap)max = maximum pressure increase, p ax maximum rate of change of pressure, = Induction period = time delay from admission of reactants to attainment of Pmax, AT = Reactant temperature excess, T = wall temperature, T) = Compressed gas temperature, T, = ignition delay, / = light emission intensity, Iw-ai = period of maximum rate of reaction given that (I20-60) = kp", Q = heat release rate. 

Fig. 6,7. Pressure and light output records typical of those observed from the two-stage ignition of hydrocarbons. These results were obtained by the authors during the combustion of n-pentane in a rapid compression machine. The duration of the compression stroke was 22 ms, as shown in the lower pressure record. The first- and second-stage time intervals, measured from the end of compression, are marked as ti and T2 respectively. Compressed gas temperature derived from (6.16) was 740 K [49].

Fig. 6.8). The overall consequence is for the ignition delay tt(= ti + T2) to decrease at both low- and high-compressed gas temperatures, but to exhibit an intermediate temperature range within which t, increases (Fig. 6.8) [49-51],... 

The compressed gas temperature calculated by (6.16) does not represent an appropriate reference temperature when the fuel + air mixture is so reactive that exothermic oxidation begins during the compression stroke. The pressure reached at the end of compression does not then arise solely form p-V work, and application of a thermodynamic relationship (6.16) based on the measured pressure is not valid. The ideal gas equation may be applied to the system in these circumstances, the compressibility factor... 

Fig. 6. 21. Ignition delays as a function of compressed gas temperature for the normal alkanes, n-butane to n-heptane, i-octane (2,2,4-trimethylpentane) and toluene in stoichiometric proportions in air. The results were obtained in a rapid compression machine at a compressed gas density of 128 mol m (0.65-0.75 MPa). Ignition in the ntc and lower temperature range was not observed under these experimental conditions [50].

It is worth re-emphasizing that the end gas temperature and pressure in the octane number tests depend on the fuel. High octane fuels are necessarily tested with higher compression ratios, with correspondingly higher compressed gas temperatures and pressures, than low octane fuels. From... 

The conclusions are not sensitive to the gas temperature calculated or the constants used. The initial compressed gas temperature could be more than 1000°K higher than calculated and still be insufficient to result in any appreciable decomposition at the TNT surface. 

Fig. 11.29 Shock compressed gas temperature variation in time for different variants of outflow (a, b, c) versus initial pressure and nozzle diameter...

The experiment could be repeated at a number of different temperatures and initial pressures to determine the shape of the two-phase envelope defined by the bubble point line and the dew point line. These two lines meet at the critical point, where it is no longer possible to distinguish between a compressed gas and a liquid. 

Erequenfly, the term compressed fluid, a more general expression than supercritical fluid, is used. A compressed fluid can be either a supercritical fluid, a near-critical fluid, an expanded Hquid, or a highly compressed gas, depending on temperature, pressure, and composition. 

The second Hquefaction process is carried out at temperatures from 261 to 296 K, with Hquefaction pressures of about 1600—2400 kPa (16—24 atm). The compressed gas is precooled to 277 to 300 K, water and entrained oil are separated, and the gas is then dehydrated ia an activated alumina, bauxite, or siHca gel drier, and flows to a refrigerant-cooled condenser (see Drying agents). The Hquid is then distilled ia a stripper column to remove noncombustible impurities. Liquid carbon dioxide is stored and transported at ambient temperature ia cylinders containing up to 22.7 kg. Larger quantities are stored ia refrigerated iasulated tanks maintained at 255 K and 2070 kPa (20 atm), and transported ia iasulated tank tmcks and tank rail cars. 

Decomposition Flame Arresters Above certain minimum pipe diameters, temperatures, and pressures, some gases may propagate decomposition flames in the absence of oxidant. Special in-line arresters have been developed (Fig. 26-27). Both deflagration and detonation flames of acetylene have been arrested by hydrauhc valve arresters, packed beds (which can be additionally water-wetted), and arrays of parallel sintered metal elements. Information on hydraulic and packed-bed arresters can be found in the Compressed Gas Association Pamphlet G1.3, Acetylene Transmission for Chemical Synthesis. Special arresters have also been used for ethylene in 1000- to 1500-psi transmission lines and for ethylene oxide in process units. Since ethylene is not known to detonate in the absence of oxidant, these arresters were designed for in-line deflagration application. 

L = line length, miles T = gas temperature, °R Z = gas compressibility factor D = pipe inside diameter, in. 

Compression of CNG to 20 MPa requires four stage compression. Provision of such facilities is costly, and it is an energy consuming process. There is also a substantial heat of compression which results in a temperature rise of the compressed gas. This means that in practice less than 230 VfV are stored when a CNG vessel is filled to 20 MPa unless the filling process is carried out isothermally. 

Fire Hazards - Flash Point Not pertinent (flammable liquefied compressed gas) Flammable limits in Air (%) 3-11 Fire Extinguishing Agents Let fire bum shut off gas supply cool adjacent exposures Fire Extinguishmg Agents Not To Be Used Not pertinent Special Hazards of Combustion Products Not pertinent Behavior in Fire Containers may explode Ignition Temperature (deg. F) 850 Electrical Hazard Data not available Burning Rate No data. 

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