The numerical analysis to assess the second-law features of a solar water heater equipped with a dual-twisted tape turbulator; Developing a predictive model for useful thermal exergy based on the nonlinear calibration using the Chaos Control Method (CCM)

The solar thermal collectors are widely used for several applications nowadays. The improvement of their thermal performance helps to mitigate the initial costs and sizes of these components. In addition, the robust prediction of the solar thermal collectors' performance is a promising technique to eliminate the future numerical simulations of these devices. To this end, the present numerical research is performed to investigate how placing two similar twisted tape turbulators side by side inside the absorber tube of a solar water heater affects the second-law aspects of the device. The pattern of changes in outlet water temperature, useful thermal exergy (Qu,ex), and rate of entropy production due to heat transfer (Sg,th) and fluid flow (Sg,fr) in different values of Reynolds number (Re) and twist pitch (H) were presented and analyzed. Validation of the numerical method was done with the experimental results available in the literature. The negative effect of boosting the Reynolds number and twist pitch on the entropy was reported. In addition, the downward (9.31-11.43 %) and upward (2.51-4.97 %) influence of Re and H on the Sg,th were reported. Moreover, it was found that the growth in Re and H is associated with the growth (654.97-661.27 %) and reduction (2.39-3.20 %) of Sg,fr. Finally, the nonlinear calibration using the Chaos Control Method (CCM) was employed to determine a predictive model for the Qu,ex in terms of Re and H. The results demonstrated that two predictive models can estimate Qu,ex with high degree of accuracy with the correlation coefficient of R2=0.999 and RMSE of 0.089.