Carbon dioxide heat capacity ratio

When actual data are not available, a useful approximate rule for ordinary temperatures and pressures, is to take y as 1.67 for monatomic gases, 1.40 for diatomic gases, 1.30 for simple polyatomic gases, such as water, carbon dioxide, ammonia and methane. It may be noted that the heat capacity ratio for hydrogen gas increases at low temperatures toward the vfdue for a monatomic gas. This matter will be explained in Chapter VI. 

Heat capacity ratio, k = Cp/c, = 1.04 for gases with molar mass > 100. The value of k increases to 1.67 as the molar mass decreases. For air =1.4 and for such gases as ethylene, carbon dioxide, steam, sulfur dioxide, methane, ammonia = 1.2-1.3. Temperature rise between feed 1 and exit 2 ... 

The addition of carbon dioxide (up to 15% volume content) or water steam (up to 30% volume content) has little effect on the H2 + air mixture detonation velocity. The heat capacity ratio remains in the range of y = 1.36-1.4 and the sound speed -in the range of c = 320-350 m/s. 

Noncombustible diluents reduce the laminar flame velocity due to a decrease in the flame temperature. Figure 2.21 illustrates the flame temperature T/, decrease and the decrease of the expansion ratio a in two lean H2 + air mixtures (

water steam or carbon dioxide is added. As a diluent, CO2 has a stronger effect because of its high heat capacity. If the water is added in the form of small drops, the picture is different, but here we are considering a gaseous diluent effect. 

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