HUMIDIFICATION AND WATER COOLING 327
350
300
250
200
150
100
50
280 290 300
Temperature (qK)
0 310 320 330
(qL 2 'HG 2 )
(qL 1 'HG 1 )
Enthalpy (
H
G
kJ /kg)
Figure 13b.
bulb temperature. From Fig. 13.4, at 295 K and 60% humidity, the wet-bulb temperature
of the inlet air is 290 K and at the best water might be cooled to 291 K. In the present
case, therefore, 291 K will be chosen as the water outlet temperature.
Thus an operating line of slope:LCL/GD 1 .66 and bottom coordinates:L 1 D291 K
andHG 1 D 47 .5 kJ/kg is drawn as shown in Fig. 13c. At the top of the operating line:
L 2 D330 K andHG 2 D 112 .5kJ/kg
As an alternative to the method used in Problem 13.8, the approximate method of Carey
and Williamson (equation 13.54) is adopted.
At the bottom of the column:
HG 1 D 47 .5kJ/kg,Hf 1 D 52 .0kJ/kg ∴H 1 D 4 .5kJ/kg
At the top of the column:
HG 2 D 112 .5kJ/kg,Hf 2 D382 kJ/kg ∴H 2 D 269 .5kJ/kg
At the mean water temperature of 0. 5 330 C 291 D 310 .5K:
HGmD 82 .0kJ/kg,HfmD 152 .5kJ/kg ∴HmD 70 .5kJ/kg
∴ Hm/H 1 D 15 .70 andHm/H 2 D 0. 262
and from Fig. 13.17:fD 0 .35 (extending the scales)