Thermal performance and exergy evaluation in a tube with perforated delta-baffle vortex generators

The article conducts an experimental study into heat transfer and exergy characteristics of a tube-type heat exchanger contained with delta-baffle vortex generators to enhance convection heat transmission. There are two phases to the investigation: solid delta baffles (DB) and perforated delta baffles (PDB). In the first DB phase, the specific DB parameters of four relative pitches (P R = 0.75–1.5) and three blockage ratios (B R = 0.4–0.6) are explored for a broad variety of Reynolds numbers (Re) from 4760 to 29,260. The studies are performed at a consistent attack angle (α) of 45° utilizing a forward-inclined DB configuration (F-DB), which exhibits superior thermal performance relative to the backward-inclined DB configuration (B-DB). The F-DB markedly improves thermal performance in contrast to a plain tube, achieving peak friction factor ( f ) and Nusselt number (Nu) values up to 27.51 and 5.9 times above those of the plain tube, respectively. The optimal thermal enhancement factor (TEF) and exergy efficiency for the F-DB are 2.57 and 0.9933, respectively, attained at B R = 0.5 and P R = 0.75. In the second phase, forward perforated delta baffles (F-PDB) with an adjustable louver-flap angle (θ = 20°, 30°, 45°, and 60°) are generated by employing a novel perforation technique on the optimal F-DB cases. The F-PDB reaches a peak TEF of 2.68 at θ = 45°, outperforming values recorded in prior studies. Lastly, the experimental correlations for f and Nu have been formulated for both F-DB and F-PDB designs.