Air Calculations

The following provides a calculation method for determining the amount of air needed for perfect combustion of one cubic foot of any gaseous fuel. The following expression provides an estimate of the ratio of the volume of air needed to the volume of fuel (i.e., the air to fuel ratio, 0)  

In this equation all percentages are on a volume basis. The term XSA refers to the excess air over the stoichiometric requirement. The volumes of the air and gas must be measured at the same temperature and pressure. For consistency, it is best to first convert to actual conditions (i.e., from actual cubic feet (ACF) to standard cubic feet (SCF). The following formula can be used for this conversion  

The ACF is the actual cubic feet of gas measured at t[ °F and P, psig. SCF represents standard conditions at 70 °F and 14.6 psia. The formulas provided require input information on the pressure and temperature of the fuel gas, the fuel gas analysis by volume (or mole percent if the pressures are sufficiently low), and the percent excess air. The calculation provides the air to fuel ratio required for complete combustion. 

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Tbe partial results are shown in Figure 2-6.2.1. Tbe ranges of ignitable concentrations are superimposed on a spark ignition energy curve for bexane in air calculated from data in [56]. Both data sets are assumed to be characteristic ofn-hexane, unbiased by the presence of methylcyclopentane or hexane isomers (dimethylbutanes and methylpentanes). 

The specific heat capacity of humid air calculated per kilogram of dry air is... 

A hot-air balloon will rise when the density of its air is 15% lower than that of the atmospheric air. Calculate the density of air at 295 K, 1.0 atm (assume that dry air is 78% N2 and 22% O2 ) and determine the minimum temperature of air that will cause a balloon to rise. 

The composition of a gas derived by the gasification of coal is, volume percentage carbon dioxide 4, carbon monoxide 16, hydrogen 50, methane 15, ethane 3, benzene 2, balance nitrogen. If the gas is burnt in a furnace with 20 per cent excess air, calculate ... 

Air calculated atmospheric lifetimes 32 h due to reaction with 03 in 24-h period, 2.9 h with OH radical during daytime, and 3.6 h for N03 radical during nighttime for clean atmosphere 10 h for reaction with 03 in 24-h period, 1.4 h with OH radical during daytime, and 22 min with N03 radical during nighttime in moderately polluted atmosphere (Atkinson et al,1984a, Winer et al. 1984) ... 

Air calculated lifetimes x = 4.6 h due to reaction with 03 in 24-h period, x = 4.6 h with OH radical during daytime, and x = 20 min for N03 radical during nighttime for clean atmosphere x = 1.4 h for reaction with 03 in 24-h period, x = 2.3 h with OH radical during daytime, and x = 2 min with N03 radical during nighttime in moderately polluted atmosphere (Atkinson et al.1984a, Winer et al. 1984) calculated atmospheric lifetimes of 5.6 h, 5.1 h and 11 min for reaction with 03, OH and N03 radicals respectively for clean tropospheric conditions at room temp. (Atkinson et al. 1986) calculated tropospheric lifetimes of 3.4 h, 4.6 h and 2.0 h due to reactions with OH radical, 03 and N03 radical respectively at room temp. (Corchnoy Atkinson 1990). 

Air calculated tropospheric lifetime ranging from 1.9 to 2.4 h for dimethylnaphthalenes using a global tropospheric 12-h daytime average OH radical concentration of 2.0 x 106 molecule cm-3 for the reaction with OH radical (Phousongphouang Arey 2002). 

Air calculated atmospheric lifetime of 4 h due to reaction with OH radical (Atkinson Aschmann 1986) the atmospheric lifetimes of naphthalene and alkyl-substituted naphthalenes due to reaction with OH radicals and with N205 can be calculated to range from 4 to 13 h and 20-80 d, respectively (Atkinson Aschmann... 

Air calculated lifetime of 3 d due to reaction with OH radical, assuming an average daytime atmospheric OH radical concn of 1 x 106 molecule/cm3 (Atkinson et al. 1984) ... 

Both parts (a) and (b) of Example 6-1 illustrate that rates of molecular collisions are extremely large. If collision were the only factor involved in chemical reaction, the rates of all reactions would be virtually instantaneous (the rate of N2-02 collisions in air calculated in Example 6-l(a) corresponds to 4.5 X107 mol L-1 s-1 ). Evidently, the energy and orientation factors indicated in equation 6.4-2 are important, and we now turn attention to them. 

The table shows the values u0 for various percentage compositions of mixtures of CO with air, calculated according to the formula of the theory of flame propagation [5]... 

PROBLEM 14.1 Hydrogen is used to inflate weather balloons because it is much less dense than air. Calculate the density of gaseous H2 at 25°C and 1 atm pressure. Compare your result with the density of dry air under the same conditions (1.185 X 10-3 g / cm3). 

In a basal metabolism measurement timed at exactly 6 minutes, a patient exhaled 52.5 L of air, measured over water at 20°C. The vapor pressure of water at 20°C is 17.5 torn The barometric pressure was 750 torn The exhaled air analyzed at 16.75 volume % oxygen, and the inhaled air at 20.32 volume % oxygen (both on a dry basis). Neglecting any solubility of the gases in water and any difference in total volumes of inhaled and exhaled air, calculate the rate of oxygen consumption by the patient in cm3 (S.T.P.) per minute. 

Air calculated tropospheric lifetime of 8-17 d due to calculated rate constant of gas-phase reaction with OH radical for dichlorobiphenyls (Atkinson 1987) ... 

Air calculated tropospheric lifetime of 8-17 d due to calculated rate constant of gas-phase reaction with OH radicals for dichlorobiphenyls (Atkinson 1987) the tropospheric lifetime of 3.4-7.2 d based on the experimentally determined rate constant for gas-phase reaction with OH radicals for dichlorobiphenyls (Kwok et al. 1995)... 

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