APPLICATION OF THE SIMULTANEOUS MATCH NETWORK OPTIMIZATION APPROACH TO THE PSEUDO-PINCH PROBLEM

A main assumption of many heat exchanger network design techniques has been to require no heat flow across the pinch point. This assumption decomposes the original network synthesis problem into two subnetwork problems that can be solved independently. A disadvantage of this type of approach is that the resulting networks may contain more than the minimum number of units, which may increase the investment cost. The pseudo-pinch problem in heat exchanger network design relaxes the assumption of no heat flow across the pinch point. This short note proposes using three temperature approaches to formulate this problem. The HRAT, or heat recovery approach temperature, is used to calculate the utility levels. The TIAT, or temperature interval approach temperature, is used in partitioning the temperature range, and the minimum temperature approach ΔTmin, provides a lower bound on temperature differences in heat exchangers. This short note illustrates how the TIAT controls the amount of cross pinch heat flow, and demonstrates how the pseudo-pinch problem can be solved with the simultaneous match network optimization model of Floudas and Ciric (Computers chem. Engng 13, 1133-1152, 1989). The technique is illustrated with three examples. © 1990.