Enhancement of the Thermohydraulic Performance in a Double Passage Square Duct with the Use of Inclined Ribs of 45°: A Comparative Computational Study.

The modern gas turbines need to run at very high inlet temperature to promote their power output. Thus, improvements in cooling technologies play a significant role for enhancing the gas turbine blade life. In this paper, thermohydraulic performance (THP) of a two-pass square channel with inclined ribs at 45° was scrutinized employing the k – ε realizable model with enhanced wall treatment in ANSYS Fluent. The calculations were performed for the rib pitch to height ratio (p / e) of 5-10, rib height to hydraulic diameter ratio (e / D h ) of 0.1-0.2, and Reynolds number (Re) of 20,000-40,000. Detailed analysis of the flow structure in a double passage square duct was carried out to understand the interaction of the rib and bend-induced secondary flows and its contribution to heat transfer enhancement for the rib configurations with distinct p / e and e / D h , which was not available in any other existing numerical or experimental investigations. The results revealed that the ribs with higher e / D h generated the stronger stream-wise secondary flows which led to the augmentation of the cooling performance with the disadvantage of pressure loss increment. The maximum THP of 26.55% was achieved with the ribbed configuration having p / e = 5 and e / D h = 0.1 at Re = 20,000. The new correlations were developed from the computational data to predict the normalized Nusselt number and friction factor (Nu / N u 0 and f / f 0 , where 0 is the correlation), taking the e / D h and flow Re into consideration. [ABSTRACT FROM AUTHOR]