An approach to the problem of synthesising single-stage heat exchange systems taking into account the uncertainty of the initial information

Abstract

To solve the problems of synthesising complex technological systems it is necessary to solve discrete-continuous problems of nonlinear programming. To ensure the functioning of a synthesized system, it is necessary to take into account changes in the operating conditions. This in turn involves considering hard or soft constraints and the integral form of the objective function in the optimization problem. The paper suggests an approach to the problem of synthesising optimal single-stage heat exchange systems taking into account changing operating conditions. The approach is based on partitioning the region that characterises the change in the operating conditions of the synthesized system into subregions of lower dimension and size. The problem of synthesising one-stage heat exchange systems is solved by decomposing the initial superstructure, which includes all possible structures of single-stage heat exchange systems for a given set of hot and cold streams. The decomposition is carried out at the level of an individual heat exchanger and the associated uncertainty subregion. This allows us to decompose the original problem into subproblems for designing optimal efficient heat exchange subsystems for two streams. Solving these problems we can obtain efficiency estimates for the heat exchange subsystems that do not depend on changes in the undefined parameters. The efficiency estimation is calculated by solving the subsystem design problem with regard to the corresponding uncertainty subregion. The solution is based on a single-stage optimisation problem with soft constraints. The optimal structure for the system is determined by solving the assignment problem based on the obtained estimates. We can thus construct a flexible, optimal single-stage heat exchange system by selecting and combining subsystems with the best efficiency characteristics.