Cooling tower transfer units, calculation

Equation 3 Is quite accurate for calculating the number of transfer units for the example cooling tower... 

Calculate N,og and Table 1, from Predict the number of Transfer Units for Cooling Towers, by Kamal Adham Khodaparast, Chemical Engineering Progress, Vol. 88, No. 4, pp. 67-68 (1992). Reproduced by permission of the American Institute of Chemical Engineers. 1992 AlChE. ... 

An analysis of multi-unit cocurrent crossflow cooling towers is made. Towers were placed in series and the results obtained were compared with that of multi-unit countercurrent crossflow cooling towers. The experimental data on the multi-unit cocurrent crossflow cooling tower were, analyzed in terms of enthalpy efficiency of single-unit, heat capacity ratio and number of transfer units. An outline of design calculations of multi-unit cocurrent crossflow cooling towers is presented. 4 refs, cited. 

Water is to be cooled in a small packed column from 330 to 285 K by means of air flowing countercurrently. The rate of flow of liquid is 1400 cm3/m2 s and the flow rate of the air, which enters at a temperature of 295 K and a humidity of 60%, is 3.0 m3/m2 s. Calculate the required height of tower if the whole of the resistance to heat and mass transfer may be considered as being in the gas phase and the product of the mass transfer coefficient and the transfer surface per unit volume of column is 2 s-1. 

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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