Answer to Question #328649 in Chemical Engineering for SAVARA RAVITEJA

Question

A packed counter-current water cooling tower is used to cool

1.356 kg/s.m2

of water from 43.3 °C to 26.7 ºC. The air enters from the bottom

of the tower at 23.9 ºC with a wet bulb temperature of 21.1 ºC. The whole of the

resistance to heat and mass transfer can be considered as being within the gas

phase and the product of the mass transfer coefficient and the transfer surface

per unit volume of column (KG.a) may be taken as 1.207×10-7

kmol/s.m3

.Pa.

The tower operates at atmospheric pressure. Calculate the minimum air flowrate

and the necessary height of the tower when 1.5 times of minimum is used as

actual air flowrate.

Data: Latent heat of water at 0 ºC = 2501 kJ/ kg

Heat capacity of dry air = 1.005 kJ/ kg. ºC

Heat capacity of water vapour = 1.88 kJ/ kg. ºC

Density of air = 1.198 kg/ m3

Enthalpy of saturated air-water vapour data are as follows:

Hyi, kJ/kg dry air 84 97.2 112.1 128.9 148.2 172.1 197.2

Temperature, ºC 26.7 29.4 32.2 35 37.8 40.6 43.3

Answer 1

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