Humid heat

The humid heat denoted, c, is the specific heat capacity of moist air expressed in J.kg .K . Therefore, it is the weighted sum of the respective specific heat capacities of dry air and pure water vapor  

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Similarly, the vapor enthalpy can be expressed in terms of humid heat and latent heat in relation to a base condition ... 

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... 

Humid heat c, is the heat capacity of 1 lb of diy air and the moisture it contains. For most engineering calculations, c, = 0.24 + 0.45H, where 0.24 and 0.45 are the heat capacities of diy air and water vapor, respec tively, and both are assumed constant. 

Since the Schmidt number, Prandtl number, latent heat of vaporization, and humid heat are all essentially independent of pressure, the adiabatic-saturation-temperature and wet-bulb-temperature hues will be substantially equal at pressures different from atmospheric. 

There are no hnes for humid heats on Fig. 12-36. These maybe calculated by... 

The term humid heat (s) is the number of Btu necessary to raise the temperature of 1 lb of dry air plus such water vapor as it contains by 1 F. Humid heat obviously increases with increasing vapor content of the air, and is therefore a function of... 

In addition, the humid heat is plotted as the abscissa in Figure 13.4 with the humidity as the ordinate. 

Humid heat is the heat required to raise unit mass of dry air and associated vapour through 1 degree K at constant pressure or 1.00 + 1.88J kJ/kg K. 

From Figure 13.4 in Volume 1, the humid heat of the entering air is 1.03 kJ/kg K and making a heat balance ... 

Derive" the equations for saturated volume, humid heat and the adiabatic cooling lines for the psychrometric chart. 

We can rewrite Equation 5.23 in a more usable form by defining average values for the humid heat, Cs, and the latent heat, X, and by neglecting superheat. These are common assumptions applied to cooling towers ... 

J4 = absolute humidity 0 = latent heat of vaporization at T0 C = heat capacity Cs = humid heat... 

For the case in which the exiting gas-vapor mixture is saturated, we have the term T, Jfas, Has. The liquid enters at T and the gas is humidified by evaporation of liquid and cooled. By expansion of the humid heat terms in the equation derived for problem 3.9,... 

Polyphenyldiethylsiloxane varnishes are solutions of phenyldiethylsi-loxane polymer in petrol, toluene or a mixture of petrol and turpentine. They are liquids ranging in colour from yellow to brown. The varnishes are heat-resistant they are used to produce insulating materials for temperatures up to 180 °C and high humidity. Heat-resistant insulation of polyphenyldiethylsiloxane varnishes is widely used in electric engines, in rotors of turbogenerators, etc. 

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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