Thermal performance prediction of a solar air heater with a C-shape finned absorber plate using RF, LR and KNN models of Machine learning

•To forecast the thermal performance of solar air heaters with a C-shaped finned absorber, RF, LR, and KNN models have been utilised.•For this study, correlations for Nu, f, and η are suggested.•The best model for estimating the thermal performance of solar air heaters was found to be the RF model.