Implementation of Adaptive Observer and Mathematical Model Validation of the Evaporator of an Absorption Heat Transformer

This article presents the implementation of an adaptive observer to validate a falling film evaporator mathematical model. The evaporator consists of four coils, and each coil has four tubes. The heating flow in the first and third coils flows from bottom to top. Meanwhile, the heating flow in the second and fourth coils flows from top to bottom. The mathematical model of the evaporator is parameterized with the geometry data of the experimental device. Since the mathematical model depends on the film breakdown onset Reynolds number (ReOnset) to estimate the evaporator temperatures, an adaptive observer is applied to estimate this unknown parameter (ReOnset). The observer design is developed through the evaporator mathematical model. The research aims to estimate the ReOnset at different operating conditions to accurately estimate the evaporator temperatures since there is no general correlation for estimating it or a sensor to measure this parameter. Once the ReOnset is estimated at different operating conditions, the ReOnset results are injected into the model for validation. The results of implementing the observer showed that the temperature estimation errors are between 0.00003% and 0.02815%. Moreover, the temperatures simulated with the model using the ReOnset estimated with the observers had errors between 0.04012% and 0.14160%.