Environmental Engineering Reference
In-Depth Information
Table 6 shows the atmospheric transmittance and the figures in this table were
determined by calculations from the total solar radiation values on a tilted surface using the
Bouger's and Berlage's formulae[5]. Generally, there is a tendency on any given clear day for
the atmospheric transmittance at dawn and dusk when the solar altitude is low to work out on
the high side and for it to be on the low side around midday when the solar altitude is high.
Table 6 gives the values for the atmospheric transmittance at noon everyday and consequently
the air mass (air mass= sin(h) where h is the solar altitude) is ranging from 1.0 to 1.5. Since
values yielded for cloudy days are assumed to be meaningless, the same table gives the mean
atmospheric transmittance values for the above five days in each month as the monthly
averages. This indicates that the closer the atmospheric transmittance is to 1.0, the purer is the
air, and seasonal changes are apparent in that it is high during winter and low during summer.
The monthly average daily mean, maximum and minimum ambient temperatures are
shown in table 7. Table 8 shows the monthly average daily maximum relative humidity in
Abu Dhabi and table 9 shows the seawater salinity. The results of the TDS analysis of
seawater are indicated in table 9. Variations are visible in the measured values with the
salinity being slightly higher in summer months compared to winter months.
Table 7. Monthly average daily mean, max. and min. ambient temperatures (1985)
Month
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
Mean
20.2
19.4
22.8
26.1
30.5
32.1
34.0
35.2
32.3
29.4
25.5
21.0
24.8
23.9
28.2
31.8
36.3
37.8
39.9
42.6
39.0
34.5
29.9
25.6
Maximum
Minimum
16.7
15.7
18.7
21.3
25.9
27.2
30.0
30.7
27.3
24.8
21.5
17.1
Table 8. Monthly average daily maximum relative humidity in Abu Dhabi (1985)
Month
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
Humidity
90.9
82.6
82.0
81.5
77.6
80.4
78.0
77.6
87.8
85.2
87.3
83.6
Table 9. Seawater salinity
Sampling date
25 Sep. 84
2 Jan. 85
2 Mar. 85
17 Jul. 85
22 Oct. 85
TDS (ppm)
52,100
51,200
51,900
53,500
53,000
7. Operating Characteristics
In this section the results of plant characteristics during the first year of operation is
presented. Typical measured performance for each of the main plant subsystems, e.g. heat
collecting subsystem, heat accumulator subsystem and evaporator subsystem, are presented.
The major performance parameters for the whole plant are also shown.
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