Development of a Numerical Model for a Compact Intensified Heat-Exchanger/Reactor

Abstract

A heat-exchanger/reactor (HEX reactor) is a kind of plug-flow chemical reactor which combines high heat transfer ability and chemical performance. It is a compact reactor designed under the popular trend of process intensification in chemical engineering. Previous studies have investigated its characteristics experimentally. This paper aimed to develop a general numerical model of the HEX reactor for further control and diagnostic use. To achieve this, physical structure and hydrodynamic and thermal performance were studied. A typical exothermic reaction, which was used in experiments, is modeled in detail. Some of the experimental data without reaction were used for estimating the heat transfer coefficient by genetic algorithm. Finally, a non-linear numerical model of 255 calculating modules was developed on the Matlab/Simulink platform. Simulations of this model were done under conditions with and without chemical reactions. Results were compared with reserved experimental data to show its validity and accuracy. Thus, further research such as fault diagnosis and fault-tolerant control of this HEX reactor could be carried out based on this model. The modeling methodology specified in this paper is not restricted, and could also be used for other reactions and other sizes of HEX reactors.Processes 2019, 7, 454 2 of 20 essential to completely understand the dynamic characteristics of a new piece of equipment in terms of process safety [8,22] and further control. Like most cases, a cell-based model was used in this paper, i.e., each cell is modeled by means of energy and mass balances [23][24][25][26][27]. The aim of this paper was to implement the concept of general modeling and validate it on a particular intensified HEX reactor which has already been studied at LGC (Laboratoire de Génie Chimique) [9]. During modeling, the thermal and hydrodynamic performances of the pilot under the condition of a chemical reaction which brings highly non-linear features were investigated. Once the detailed model is set up and validated, further research, for example on optimal control, adaptive control, fault diagnosis, and fault tolerant control could be carried out on it.The first part of this paper gives a brief description of the specific intensified HEX reactor. After that, mathematical equations, as well as model structure, are presented according to different parts of the pilot. In addition, parameters which were used to identify the heat transfer coefficient are identified using a genetic algorithm with some of the experimental data. Simulations were carried out in order to investigate the performance of the model. Considering the different aspects involved in the model (hydrodynamic, heat transfer, and reaction), the validation study was conducted in two parts: experiments with water and experiments with the highly exothermic reaction of sodium thiosulfate oxidation. Finally, the results of simulations and real experiments are compared in order to demonstrate the relevance and precision of the developed model.

The Fault Tolerant Control Design of an Intensified Heat-Exchanger/Reactor Using a Two-Layer, Multiple-Model Structure

“…Thus, dynamics of the HEX reactor with the reaction can be given [ 20 ]: where , , , , are temperature of the process channel, temperature of the utility channel, temperature of the plate-wall, concentration of , and concentration of respectively. , and are the input flow rate of process and utility channels.…”

“… is a pre-exponential factor of the reaction; is the activation energy; R is the perfect gas constant and is the unit heat generated by the reaction. Detailed values of these parameters can be found in [ 20 ].…”

Observer-Based Fault Tolerant Control for an Intensified Heat Exchanger/Reactor

“…In these methods, the notion of residual signals, which is the difference between the process measurements and their redundancies, is introduced to detect and isolate the fault. For the HEX reactor system presented in Figure 1, model-based methods have priority since the mathematical model has already been investigated in [14]. This model takes into account both heat transfer and the chemical reaction.…”

Experimental Study on Forced Convection Heat Transfer from Plate-Fin Heat Sinks with Partial Heating

“…Therefore, efficient cooling of these devices is essential and various cooling methods have been developed. In addition, the efficient cooling is also essential for various thermal systems such as transcritical CO 2 refrigeration systems [3], ice storage tanks [4], wind tunnels [5], and heat exchanger/reactors [6]. The most common cooling method is the use of plate-fin heat sinks under forced convection.…”