Detailed evaluation of a heat exchanger in terms of effectiveness and second law

Abstract

In this study, experiments were conducted to investigate the effects of semicircular strip turbulators placed in the inner tube of a concentric heat exchanger on its exergy loss rate (E*) and effectiveness (e). The Reynolds number (Re), pitch (p), diameter (d), thickness (t) and arrangement style (a) were the design parameters for the study. The changes in these parameters had significant effects on exergy loss rate and effectiveness compared to the results found with the smooth empty tube. The results of the study are given graphically as the change in the exergy loss rate and the change in effectiveness with the number of transfer units (NTU). The largest exergy loss rate and effectiveness values were found to be 0.263 and 0.556, respectively. It was concluded that the effectiveness of the heat exchanger increased with increasing NTU, while the exergy loss rate is decreased. Since the increase in effectiveness will mean an increase in heat transfer, it can also cause an increase in irreversibility. For this reason, multi-performance characteristics have been determined since evaluating the effectiveness together with the exergy loss rate caused by irreversibility will provide more realistic results. Thus, the optimum parameter combination was found, where the maximum effectiveness and the smallest exergy loss rate values were obtained. Finally, the artificial neural network (ANN) model of the study was created and the hyperparameters of the model were determined by the Bayesian optimisation method. In the created ANN model, MSE and R values of effectiveness and exergy loss rate were found as 5.3238e-04, 2.18177e-06 and 0.963, 0.998, respectively. According to these results, it has been confirmed that the proposed ANN model can be used successfully in the modelling of the heat exchanger.