Heat exchanger networks with different shell and tube configurations

Abstract

In a growing energy consumption world, energy efficiency has become mandatory. In this context, the design of heat exchanger networks (HEN) is of crucial importance, but most of the approaches to HEN design consider only shell and tube (S&T) heat exchangers with a perfect counter current heat transfer. However, the 1-2 heat exchanger, (one shell pass, and two tubes pass), is likely the most common in the chemical industry. In this work, we present a two steps sequential algorithm that allows the design of HEN to capture the main details of the heat exchangers (number of tubes pass, number of shells, logarithmic mean correction factors) that influence the cost estimation. The first stage is based on an extended transportation model. It uses the concept of temperature intervals and considers the possibility of heat transfer between the hot and cold streams inside those intervals. Then, it is possible the a priori calculation of the logarithmic mean temperature difference between matches, the efficiency factor, and the number of shells in series, maintaining the area linear in the model. The second step uses a superstructure with all the possible alternatives in which the heat exchangers predicted by the first stage model can exchange heat to design the final heat exchanger network.