CAPITAL-COST TARGETS FOR HEAT-EXCHANGER NETWORKS COMPRISING MIXED MATERIALS OF CONSTRUCTION, PRESSURE RATINGS AND EXCHANGER TYPES

Recent developments in pinch technology allow the capital/energy tradeoff in heat exchanger networks to be set prior to design. Targets for both energy and capital costs are required. The published work on capital cost targets assumes all network exchangers obey a single cost law. This means in practice that their materials of construction, pressure rating and design type must be assumed uniform. This paper develops a method which allows capital cost targets to take account of differences in exchanger specification. The enhancement applies cost factors to each stream, determined by the exchanger design it requires. A case study demonstrates that variations in exchanger specification can considerably alter the capital/energy tradeoff. As a result, the structure of the global cost-optimum network can change. These structural changes for cost optimality are thus caused by differences in exchanger specification. In many cases, without correct initialization of the design to allow for these differences, the global optimum-cost network cannot be found. © 1990.