An Extended Approach for the Integration of Heat Pumps into HENS Multi-Period MILP Superstructure Formulation for Industrial Applications

Abstract

This paper deals with the extension of the linearized superstructure formulation for heat exchange network synthesis (HENS) proposed by Beck and Hofmann (2018a). The energy consumption of heat pumps as a function of the temperature lift and the thermal energy flow is approximated by a convex linearization. This allows for a linear extension of the cost function that takes the size and the energy consumption of heat pumps into account. As given problem an existing process and a predetermined heat pump characteristic is assumed. A test case consisting of two hot and two cold process streams has been constructed to investigate the proposed optimization method. The test case has been optimized with and without the extended approach for comparable results. The HEN resulting from the newly developed approach has 16.1 % lower total annual costs (TAC) and a 48.1 % lower external energy demand than the network resulting from the HENS without storages or heat pumps. This improvements come with the drawback of a more complex HEN with 15 installations compared to the simple HEN with 7 installations.