A. Introduction

So far only problems with on Pinch and two utilities (one hot, one cold) have been considered. We shall now look at problems with no Pinches or several Pinches, and with more than two utilities.

B. Problems without a Pinch

Consider the Composite Curves in Figure 1a. They are set for ΔT_min = 20 K. As ΔT_min is reduced, utilities decrease as expected. However, when ΔT_min = 14 K is reached, the curves line up at the hot end and the process no longer needs utility, Figure 1b.

In Figure 1c ΔT_min below 14 K no longer saves utilities. Instead, cold utility is simply switched from one end of the problem to the other.