Capacity and efficiency. Figure 8.12a compares random to corrugated sheet structured packing in terms of specific surface areas and packing factors. For random packings, the lines shown were taken from
Fig. 8.7. Specific surface areas plotted for structured packings are from Table 8.2, and the packing factors are from the manufacturers' publications (22,30,31). For structured packings, the packing factors become a function of liquid load when liquid load exceeds about 20 gpm/ft2 (30,31). For this reason, one line (heavy) was drawn for liquid loads lower than 20 gpm/ft2. The points for structured packings at higher liquid loads were connected by dashed lines parallel to the heavy line. Due to these approximations, Fig. 8.12a is unsuitable for a comparative evaluation among different structured packings.
Figure 8.12a shows an advantage for structured packings over random packings at low (<20 gpm/ft2) liquid rates. At a given capacity (i.e., a constant packing factor), structured packings offer a far greater specific surface area (therefore, greater efficiency). Alternatively, for a given specific surface area, structured packings achieve a lower packing factor (therefore, greater capacity). As liquid rate increases beyond 20 gpm/ft2, the above advantages dwindle rapidly.
Packing efficiency is not a function of the specific surface area
Legend: < 20 gpnVft2 + Bon ill a et al. (22) A Norton (30) o McNulty & hsieh (31) 30, 50 gpm/tt2 A Norton (30) • McNulty & Hsieh (31)
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