Shell and tube heat exchanger, empirical modeling using system identification

Abstract

In many industrial process and operations, shell and tube heat exchangers are one of the most important thermal devices that sustained a wide range of operating temperature and pressure. However, the nonlinearity nature of the heat exchangers, and the exclusions of disturbances and uncertainties in linear models, makes the task of mathematical modeling of the system becomes challenging. Here, the solution followed for such problems is experimentally finding linear mathematical model that includes the effect of disturbances. To avoid problem of the system nonlinearities, the overall system is partitioned in to three operating ranges. Then, experimentally generated input-output data has been used in the MATLAB in order to identify the three partitioned system models. For each particular operating range, input-output data has been collected and analyzed using MATLAB environment. After iterative procedure, the plant models are obtained with satisfactory accuracy and residual analysis within range of limits. The results showed that the first test, the second test and the third test models have the best fit of 80.28%, 81.16% and 80.86% respectively. Finally, the overall model is approximated to single linear model that represent all operating ranges.