Latent heat vaporisation

Equilibrium constant for an ideal mixture Thermal conductivity Thermal conductivity of a mixture Latent heat of vaporisation Latent heat at normal boiling point Molecular mass (weight)... 

Where 8 is the solubility parameter A the energy of vaporisation V the molar volume A// the latent heat of vaporisation R the gas constant T the temperature M the moleeular weight D the density. 

If H is the enthalpy of the humid gas per unit mass of dry gas, Ha the enthalpy of the dry gas per unit mass, Hw the enthalpy of the vapour per unit mass, Ca the specific heat of the gas at constant pressure, Cw the specific heat of the vapour at constant pressure. 0 the temperature of the humid gas, 0a the reference temperature, X the latent heat of vaporisation of ihe liquid at 6 0 and the humidity of the gas. 

It can be seen from Figure 13.5 that for the air-water system a straight line, of slope equal to the enthalpy of dry saturated steam (2675 kJ/kg), is almost parallel to the isothermals. so that the addition of live steam has only a small effect on the temperature of the gas. The addition of water spray, even if the water is considerably above the temperature of the gas, results in a lowering of the temperature after the water has evaporated. This arises because the. latent heat of vaporisation of the liquid constitutes the major part of the enthalpy of the vapour. Thus, when steam is added, it gives up a small amount of sensible heat to the gas, whereas when hot liquid is added a small amount of sensible heat is given up and a very much larger amount of latent heat is absorbed from the gas. 

Water may be sprayed into the gas at such a rate that, on complete vaporisation, it gives the required humidity. In this case, the temperature of the gas will fall as the latent heat of vaporisation must be supplied from the sensible heat of the gas and liquid. 

X Latent heat of vaporisation per unit mass, at datum temperature J/kg i. r- ... 

X Modified latent heat of vaporisation per unit mass defined by (13.68) J/kg 1 T 2... 

The vapour enthalpies are calculated from the molar heat capacity functions for the vapour components and the latent heats of vaporisation at standard temperature. The vapour overflow, V, is then obtained from the energy balance as... 

Latent heat of vaporisation at the base temperature + sensible heat to heat the vapour to the boiling point. 

Boiling point of ethyl alcohol at 1 bar = 78.4°C. Latent heat of vaporisation = 9.22 kcal/mol. 

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