Experimental study of heat transfer and flow of delta winglets inline arrays in a tube heat exchanger for enhanced heat transfer

This experiment was carried out using delta winglet arrays of vortex generators (VG) with inline arrangement in a tube heat exchanger to study enhanced heat transfer and flow behaviour. The experiment was conducted for the turbulent flow (Re = 6000 to 27000). In this experiment, different parameters, pitch ratios (PR = 1.6, 2.4, and 4.8), lengths (L = 10, 15, and 20 mm), and attack angles (B = 0°, 10°, 20°, 30°, and 45°) were studied and then their effect on thermal performance was observed. Results indicate that the PR affected f and Nu significantly. For PR = 1.6, VGs showed the highest f and Nu for all of the cases. Vortex generators with L10 B45 PR4.8 achieved the best TPE with 1.23 at Re = 6000. Attack angle B indicated a significant impact on thermal performance and 45 degree showed the TPE of 1.23 at lower Re. Oil film flow and smoke flow visualization were employed to identify the flow vortices and understand flow mechanism. The oil film flow and smoke flow visualization clearly traced longitudinal vortex, and induced vortex, which induced impingement flow and recirculation zone that lead to significant heat transfer enhancement.