Heat Transfer Augmentation in Thermally Enhanced Square Duct with Different Working Fluids.

The improvement in the efficiency of the thermal system can be achieved by disrupting the laminar flow of fluid and boundary layer separators. Passive techniques are already incorporated by industries because it increases heat transfer rate up to many folds. The numerical investigation purpose is to find techniques for heat transfer augmentation in the square duct in the laminar flow regime. The thermo-hydraulic characteristics of ribs and helical screw tape (HST) insert fitted in the square ducts have been presented. The effect of rib orientations on the Nusselt number has been analyzed by the Finite volume-based commercial software ANSYS "Fluent". A SIMPLE algorithm has been used. The fluids having different Prandtl numbers are investigated under an imposed uniform wall heat flux boundary condition. The combination performance is better than the bare and ribbed square ducts. The 45° angled ribs with HST performance is better than the combination of transverse ribs with HST. At Reynolds number 200, the Nusselt number achieved by 45° angled ribs with HST is 4.3% higher than the 30° angled ribs with HST, 22.26% higher than the 60° angled ribs, and 35.82% higher than the transverse ribs with HST. Among the three working fluids, the Nusselt number for Servo-therm oil is the highest because Servo-therm oil minimizes entropy generation. Also, the thermal enhancement factor is greater than one for all considered cases and it is the highest for Servo-therm oil is the highest. [ABSTRACT FROM AUTHOR]