The numerical investigation of a solar thermal collector with double-twisted tape insert absorber tube; the prediction of outlet temperature through a machine learning model

Solar thermal collectors are devices that can be mounted on rooftops of buildings for domestic hot water or space heating applications. The higher the thermal performance of this instrument the lower the cost and size of that. Here, the three-dimensional numerical analysis of water flow inside the absorber of a solar thermal collector with a dual-twisted tape turbulator is investigated. The influences of Re number and twisted pitch distance (4; 100 mm, 150 mm, and 200 mm) on the water outlet temperature (Tout), useful heat (Qu), and pressure drop (AP) are scrutinized. The results disclosed that the highest Tout and tube wall temperature (Twall) are obtained at Re=800, which are respectively 2.97 % and 1.6 % higher than those at Re=2000. On the other hand, an insignificant influence for the escalation of 4 from 100 mm to 200 mm on Tout was observed (e.g. 0.0395-0.001 % reduce). Meanwhile, the Re intensification from 800 to 2000 exhibited a AP of 68 % at different 4s, while the escalation in 4 at different Re numbers led to diminishing AP by almost 7.70 %. Besides, the lowest and highest Qu values at 4s of 100 mm, 150 mm, and 200 mm are respectively, associated with Re numbers of 1600 and 800, 1600 and 800, and 1200 and 800. Furthermore, a second-order polynomial with six coefficients was presented using the artificial neural network and group model for data handling model with a high coefficient of correlation (R2=0.99824) and low root mean square error (RMSE=0.05109), which is capable of estimation Tout using two input parameters of 4 and Re.