Membrane and Desalination Technologies - TCE Moodle Website

422 K.C. Ng et al.
SDWP [kg of water/kg-silica gel]
9.0
8.5
8.0
7.5
7.0
6.5
6.0
5.5
SDWP
PR
5.0
100 200 300 400 500 600 700 800
0.30
900
Adsorption/Desorption Cycle Time [s]
Fig. 9.19. Performance of the four-bed adsorption desalination system (44).
Table 9.8
Rated conditions (44)
Hot water inlet (desorber) Cooling water inlet (adsorber) Cooling water inlet (condenser)
Temperature Flow rate Temperature Flow rate Temperature Flow rate
( C)
(LPM) ( C)
(LPM) ( C)
(LPM)
85 48 29.5 48 30 120
Mass of silica gel (kg) 36
Switching time (s) 40
shows the improvements in SDWP and PR with the rage of operation time at the rated
operation condition shown in Table 9.8. The chilled water inlet temperature to the evaporator
is kept constant at 30 C. Experimental data show that the SDWP of the plant is increased by
twofold, to about 8.2 kg of water/kg of adsorbent per day.
Figure 9.20 shows the effect of the hot water inlet temperature on the cycle SDWP and PR
using a half-cycle time of 360 s. It is noted that the SDWP increases linearly with increasing
hot water inlet temperatures. The improvement is attributed to the increased in vapor flow
within the AD cycle at higher driving source temperatures. However, the increase in PR is
only marginal. The increase in SDWP occurs due to the larger temperature difference
between heat source and heat sink. Figure 9.21 shows the effects of chilled water inlet
temperatures on the cycle performance, with and without heat exchange between the chilled
water coming out from the evaporator and the cooling water supplied to the adsorber.
Experimental results show that the SDWP increases linearly with the increase in chilled
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
Performance Ratio [–]