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T y p i c a l P i t f a l l s a n d How t o Avo i d T h e m 287

number should be minimized for industrial problems involving
many streams.

12.1.4 What Rules and Guidelines Must Be
Followed to Extract Data Properly?
As mentioned in Section 12.1.1, data extraction rules were first
introduced by Linnhoff et al. (1982) and frequently used with some
modifications thereafter (Smith, 1995; CPI, 2004 and 2005; Smith,
2005; Kemp, 2007). Most of this work is related to Heat Integration,
but the principles apply as well to mass (water) integration. These
rules are reviewed briefly in this section.
When two or more streams of different temperatures are mixed,
this nonisothermal mixing constitutes a heat exchange with
degradation of the higher temperature. In some cases, such mixing
can also cause cross-Pinch transfer problems—as in Figure 12.3(a),

FIGURE 12.3 Nonisothermal (a) 160°
stream mixing extracted as
(a) three streams and (b) two
streams.
110°

70° 40° 75° 35°

110° 160°

40° 70°
35° 75°

(b) 160°

110°

70° 40° 75° 35°

35° 160°
35° 70°