Optimization of the operating time of a heat exchanger: thermo-economic criterion

Fouling of heat exchangers is one of the most common problems in the industry. This phenomenon considerably reduces the heat exchange coefficients over time and therefore decreases the performance of the exchanger, hence the need for periodic cleaning. In this study, we propose an optimization of the operating time of a heat exchanger subjected to fouling before stopping the installation for cleaning. The model we develop for a concentric two-pipe heat exchanger with a laminar flow regime is based on a thermo-economic criterion. This criterion takes into account, on the one hand, the thermal aspect of the transfer and, on the other hand, the costs generated by the shutdown of the installation, those related to the cleaning of the exchanger, as well as those related to energy losses caused by the malfunction of the exchanger due to its fouling. Various dimensionless parameters were introduced into the model in order to evaluate the parametric sensitivity of the operating time t1. The results show a strong influence of the parameters on the operating time.