The importance of control considerations for heat exchanger network synthesis: a case study

Abstract

Cost optimization in the synthesis decision tree often leads to a reduced degree of freedom which degrades the process’s ability to reject disturbances as a consequence of low controllability. In fact, Heat Exchanger Networks (HENs) obtained by traditional synthesis procedures that ignore controllability aspects must be evaluated in this context a posteriori. The aim of this work was to develop a procedure that includes RGA and SVD measures of controllability, which are solely based on steady state information, thereby freeing the synthesis procedure of the cumbersome dynamic analysis. When a structure is defined during a traditional HEN synthesis procedure, a degree of freedom analysis is approached as a simulation problem. Next, an optimization is performed, since new variables are usually added to increase the degree of freedom of the HEN in order to render it controllable. A key point in the proposed procedure is the inference of controllability based on the proposed controllability measures, which also provide a control scheme by pairing controlled and manipulated variables during the process design. A HEN reported in the literature is used to illustrate the proposed procedure. The steady state simulator Aspen Plus and the dynamic simulator Aspen Dynamics (Aspentech, Inc.) were employed

A novel split cycle internal combustion engine with integral waste heat recovery

“…The specifications of the recuperator can be seen in Table 3. A one-dimensional recuperation system model was developed via AMEsim, and validated by the recuperator data modelled by Oliverira [26].…”

A Controllability Index for Heat Exchanger Networks

“…Westphalen el al 16 proposed some heuristic rules for the selection of heat exchangers for process control. Methodologies 4,5,8,16 for the selection of the manipulated variables in an HEN are well-documented and are not discussed in this paper.…”

“…Oliveira et al 8 analyzed in detail the interactions between the process control and design of a particular HEN, using steady-state optimization and the calculation of the condition number for the selection of manipulated variables. No information on the dynamic behavior was used in their problem formulation, and as a result, the designed network had poor controllability.…”