Carbon 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. 

The increase in the temperature ratio comes about because nitrogen and carbon monoxide are only slightly dissociated, even at the 5515°K. temperature, while the water molecule would be more than 19% dissociated at 3120°K., and the hydrogen molecules would also be more than 20% dissociated. The ideal chemical reaction for generation of high temperature, then, is between unstable species to form very stable products (i.e., undissociated) that have a small heat capacity. 

The heat capacity of a sample of thorinm dicarbide was measnred by adiabatic calorimetry from 5 to 350 K and was found to be of normal sigmoid shape without transitions or thermal anomalies. The sample was a composite of seven different samples, prepared from the elements and annealed at 5 h at 2273 K, crashed and reheated to above 2273 K for a further 5 h to obtain a sample of uniform composition. The C/Th ratio was analysed to be (1.98 + 0.03), the major impurity being 0.79 wt% carbon, for which the heat capacities were corrected. There is no mention of oxygen contamination or analysis. At 298.15 K, the values of C for ThQ 9s and (5 ° (298.15 K) - (0 K))... 

The feed stream to the reactor is based on a 2 1 molar flow rate ratio of hydrogen to carbon monoxide. This corresponds to an inlet CO mass fraction of a, inlet = 0.875. The heat capacity of the mixture for this specific problem reduces to... 

Determine the equilibrium composition that is achieved at 300 bar and 700 K when the initial mole ratio of hydrogen to carbon monoxide is 2. You may use standard enthalpy and Gibbs free energy of formation data. For purposes of this problem you should not neglect the variation of the standard heat of reaction with temperature. You may assume ideal solution behavior but not ideal gas behavior. You may also use a generalized fugacity coefficient chart based on the principle of corresponding states as well as the heat capacity data listed below. 

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. 

Fig. 32. Reversible capacity of microporous carbon prepared from phenolic resins heated between 940 to 1 I00°C plotted as a function of the X-ray ratio R. R is a parameter which is empirically correlated to the fraction of single-layer graphene sheets in the samples.

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