Specific heats of mixtures

Po = density of combustion products at initial temperature Tq Cp = average specific heat of mixture considered to be constant from Tq to maximum fireball temperature... 

Figure 21 is a diagram by McKinley and Brown [6] showing the relative enthalpies of nitric and sulphuric acids and their mixlures. Another diagram (Fig. 22) shows the relationship between the specific heat of mixtures of acids and their composition. 

The specific heats of mixtures of fused metals have been determined, and the partial molar heat capacities ( 63.11) calculated.i... 

The specific heat of mixtures of liquids can rarely be calculated additively from the specific heats of the components. There is generally a considerable deviation from the law of mixtures, and the calculated value is always larger than one would expect. Mixtures of hquids which are closely related chemically, such as ethyl and methyl alcohol, chloroform and carbon disulphide, behave normally mixtures of water with alcohol, or of alcohol with other organic hquids, show large deviations. It is noteworthy that heat is evolved on mixing these hquids, an indication that chemical combination also is taking place. This is probably the reason for the alteration in the heat capacity, since the specific heat of liquid chemical compounds cannot be calculated additively from the specific heats of the components. The regularities shown by sohd bodies do not hold even approximately for hquids. 

Specific heat of mixture [J/kg]. Also, molar heat capacity of mixture [J/mol] Capillary number (Section 12.3) [ —]... 

The specific heat of gases at constant pressure is calculated using the principle of corresponding states. The for a mixture in the gaseous state is equal to the sum of the C g of the ideal gas and a pressure correction term ... 

Cg = humid heat for humidity H in units of kj / (kg-K) and = latent heat of vaporization at / in kj /kg. The slope of the constant-enthalpy adiabatic cooling line is —C j which is the relationship between temperature and humidity of gas passing through a totally adiabatic direct-heat dryer. The humid heat of a gas—vapor mixture per unit weight of dry gas includes the specific heat of the vapor... 

Physical and Chemical Properties - Physical State at 15 X and I atm. Liquid Molecular Weight Mixture Boiling Point at I atm. 310 - 395, 154 - 202, 427 - 475 Freezing Point Not pertinent Critical Temperature Not pertinent Critical Pressure Not pertinent Specific Gravity 0.93 1.05 at 25°C (liquid) Vapor (Gas) Density Not pertinent Ratio of Specific Heats of Vapor (Gas) Not pertinent Latent Heat of Vaporization Not pertinent Heat cf Combustion (est.) -17,600, -9,800, -410 Heat of Decomposition Not pertinent. 

A useful rule of thumb is that the turbine work in a STIC plant is increased by a factor of about (1 + 25), since the specific heat of the steam is about double that of the specific heat of the dry gas. This is in agreement with the example given above and with the earlier detailed calculations by Fraize and Kinney [3]. (Their work was based on the assumption that the mixture of air and steam in the turbine behaved as a semi-perfect gas, with specific heats being determined simply by mass averaging of the values for the two components.)... 

Assuming a constant specific heat of the vapor, the temperature of the mixture is given hy... 

Equal masses of liquid A, initially at 100°C, and liquid B, initially at 50°C, are combined in an insulated container. The final temperature of the mixture is 80°C. All the heat flow occurs between the two liquids. The two liquids do not react with each other. Is the specific heat of liquid A larger than, equal to, or smaller than the specific heat of liquid B ... 

Specific Heats of Solid Mixtures.—The specific heat of a homogeneous solid mixture of solid components is not usually additively composed of the specific heats of the latter. W. Spring (1886) found that the total heat capacity of alloys of lead and tin was always greater than the sum of those of the components, but above the melting-point the two were equal. A. Bogojawlensky and N. Winogradoff (1908) find, however, that the heat capacities of the isomorphous mixtures ... 

Specific Heat of Nitric Acid, Sulfuric Acid, and Water Mixtures.. . Nitration of Hexamine at 20°C and —35.5°C. 

Fig 20 Specific heat of nitric acid, sulfuric acid, and water mixtures McKinley and Brown (Ref 28a)... 

Specific heat of each species is assumed to be the function of temperature by using JANAF [7]. Transport coefficients for the mixture gas such as viscosity, thermal conductivity, and diffusion coefficient are calculated by using the approximation formula based on the kinetic theory of gas [8]. As for the initial condition, a mixture is quiescent and its temperature and pressure are 300 K and 0.1 MPa, respectively. 

We can now estimate the order of magnitude of the acoustic growth rate expected for this mechanism. Consider a lean hydrocarbon-air flame. Si 0.3 m/s. The ratio of the specific heats of the mixture is C /C = 1.4. 

The desired product is P, while S is an unwanted by-product. The reaction is carried out in a solution for which the physical properties are independent of temperature and composition. Both reactions are of first-order kinetics with the parameters given in Table 5.3-2 the specific heat of the reaction mixture, c, is 4 kJ kg K , and the density, p, is 1000 kg m . The initial concentration of /I is cao = 1 mol litre and the initial temperature is To = 295 K. The coolant temperature is 345 K for the first period of 1 h, and then it is decreased to 295 K for the subsequent period of 0.5 h. Figs. 5.3-13 and 5.3-14 show temperature and conversion curves for the 63 and 6,300 litres batch reactors, which are typical sizes of pilot and full-scale plants. The overall heat-transfer coefficient was assumed to be 500 W m K. The two reactors behaved very different. The yield of P in a large-scale reactor is significantly lower than that in a pilot scale 1.2 mol % and 38.5 mol %, respectively. Because conversions were commensurate in both reactors, the selectivity of the process in the large reactor was also much lower. 

The specific heats of liquid mixtures can be estimated, with sufficient accuracy for most technical calculations, by taking heat capacities of the components as additive. 

Dimplon, W. Estimating Specific Heat of Liquid Mixtures, Chemical Engineering, Oct. 2, 1972, p. 64. 

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