Numerical investigation on heat transfer augmentation in a triangular solar air heater tube fitted with angular-cut varied-length twisted tape

Abstract

Heat transfer augmentation is an important method being employed to manage the challenges of high energy density devices to improve efficiency and prevent total damage. This method is also important to save on energy cost and reduce the overall bulkiness of heat transfer (HT) equipment. Present numerical investigation reports thermohydraulic characteristics for flow through a triangular solar air heater tube fitted with angular cut and varied length twisted tape inserts. Influence of different length twisted tape, angular cut angle (θ), and twist ratio (Y) on thermohydraulic characteristics has been investigated for Reynolds number (Re) ranging from 10,000 to 50,000. Air (Prandtl number = 0.707) is used as the working fluid. The shear stress transport model is used as the turbulence model. Thermal energy transport coefficient is more in full-length twisted tape compared to short-length entry twisted tape and short-length middle twisted tape. Similarly, twist ratio (Y) has more influence on Nusselt number compared to the angular cut angle (θ). Friction factor decreases with increase in twist ratio. For all the tested cases, the thermohydraulic performance (η) are greater than unity. Exergy analysis is done and presented. The current study also reported statistical analysis of the heat and fluid flow by using an ANN approach. The machine learning model is assessed and found accuracy of 98.5% on unidentified data. Substantial data for HT and thermal performance are generated, which is very much advantageous for the designing a solar air heaters.