Gases specific heat capacity

The major alternatives are then as follows (assuming gas specific heat capacity Cpc and latent heat of evaporation are fixed) ... 

If the relationship between the pressure P, the molar volume v, the absolute temperature T and, additionally, the ideal gas specific heat capacity Cp of a pure substance are known, all thermodynamic properties of this substance can be calculated. The typical PvT behavior is shown in Figure 2.1 in a three-dimensional diagram. All thermodynamically stable states are represented by the surface. Depending on the values of the state variables P, v, T the substance exists as a solid (S), liquid (L), or a vapor phase (V) or as a combination of two or three phases. They can be characterized as follows. 

The correlation for the gas specific heat capacity of each species can be expressed as... 

In addition to estimating individual properties, LOADER-2 checks whenever possible that the thermodynamic consistency between properties is maintained. For example, the liquid heat capacity will be compatible with the enthalpy of vaporization and liquid enthalpy. The ideal-gas thermal conductivity will be compatible with the ideal-gas specific heat capacity. By fitting well-behaved representative equations to each property, the program produces a self-contained set of thermophysical property data, which can be used with the main PPDS system. 

Solution The gas-specific heat capacity is determined by eq. (3.4.6). The heat capacity of a mixture of two gases can be found due to the additivity properties of specific heat capacity this means that the heat required to warm each gas separately is equal to the heat required to warm the mixture to the same temperature miCviAf+m2Cv2 At = Solving this equation relative to... 

By using the simple Reynolds Analogy, obtain the relation between the heat transfer coefficient and the mass transfer coefficient for the gas phase for the absorption of a soluble component from a mixture of gases. If the heat transfer coefficient is 100 W/m2 K, what will the mass transfer coefficient be for a gas of specific heat capacity Cp of 1.5 kJ/kg K and density 1.5 kg/m- The concentration of the gas is sufficiently low for hulk flow effects to be negligible. 

Here, Q is the heat energy input per area p and Cp are the density and specific heat capacity, respectively and indices g, d, and s refer to the gas, metal, and liquid sample layers, respectively. With Eq. (106), the thermal conductivity of the sample liquid is obtained from the measured temperature response of the metal without knowing the thermal conductivity of the metal disk and the thickness of the sample liquid. There is no constant characteristic of the apparatus used. Thus, absolute measurement of thermal conductivity is possible, and the thermal conductivities of molten sodium and potassium nitrates have been measured. ... 

The dependence of gas specific heats on temperature was discussed in Chapter 3, Section 3.5. For a gas in the ideal state the specific heat capacity at constant pressure is given by ... 

Assuming plug flow of the gas and complete mixing of the solids, calculate the coefficient for heat transfer between the particles and the gas. The specific heat capacity of air is 0.85 kJ/kg K. 

The other extreme case is the adiabatic change, which occurs with no heat transfer between the gas and the surroundings. For a reversible adiabatic change, k = y where y = Cp/Cv, the ratio of the specific heat capacities at constant pressure (Cp) and at constant volume (C ). For a reversible adiabatic change of an ideal gas, equation 6.27 becomes... 

Nitrogen contained in a large tank at a pressure P = 200000 Pa and a temperature of 300 K flows steadily under adiabatic conditions into a second tank through a converging nozzle with a throat diameter of 15 mm. The pressure in the second tank and at the throat of the nozzle is P, = 140000 Pa. Calculate the mass flow rate, M, of nitrogen assuming frictionless flow and ideal gas behaviour. Also calculate the gas speed at the nozzle and establish that the flow is subsonic. The relative molecular mass of nitrogen is 28.02 and the ratio of the specific heat capacities y is 1.39. 

CPg specific heat capacity of gas phase at constant pressure J/kg/K... 

An exothermal reaction is to be performed in a 2.5 m3 stirred tank reactor as an isothermal semi-batch process at 80 °C. The specific heat of the reaction is 180kjkg 1, the specific heat capacity of the reaction mass is 1.8 kj kg 1 K 1, and the accumulation is 30%. The reaction is to be at atmospheric pressure and boiling point is 101 °C (MTT). There is a secondary reaction (decomposition) that is uncritical below 105 °C, that is, Tm4 = 105 °C. The decomposition energy is 150kjkg 1 and this decomposition releases 5 liters of a toxic, but not flammable, gas per kg reaction mass, measured at 25 °C and atmospheric pressure. 

In a countercurrent packed column, n-butanol flows down at the rate of 0.25 kg/m2 s and is cooled from 330 to 295 K. Air at 290 K, initially free of n-butanol vapour, is passed up the column at the rate of 0.7 m3/m2 s. Calculate the required height of tower and the condition of the exit air. Data Mass transfer coefficient per unit volume, hDa = 0.1 s 1. Psychrometric ratio, (h/hDpAs) = 2.34. Heat transfer coefficients, hL = 3hG. Latent heat of vaporisation of n-butanol, A = 590 kJ/kg. Specific heat capacity of liquid n-butanol, Cl = 2.5 kJ/kg K. Humid heat of gas , s = 1.05 kJ/kg K. 

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