Effect of louver-perforated V-type baffles on thermal effectiveness and entropy in round tube

An experimental investigation was conducted to assess the influence of insertion of a louver-perforated V-type baffle (LVB) vortex generator into a consistent heat-fluxed tube on thermal performance. This study aimed to optimize thermal effectiveness to boost energy savings and reduce the heat exchanger size. The experiments focused on investigating the thermal features, as well as estimating the entropy of turbulent flow at Reynolds numbers (Re) varying between 4750 and 29,290. The LVBs were positioned in two different arrays on a supporting tape during the present experiment: "V-down" and "V-up," with the V-apex oriented upstream and downstream, respectively, at a fixed attack angle ($\alpha$ = 52°). At one relative baffle height (B_R = 0.3) and pitch (P_R = 1.0), the LVBs dealt with six louver flapped angles ($\theta$ = 0°, 10°, 20°, 30°, 45°, and 90°) in addition to three louver-hole sizes and locations (θ₁, θ₂ and θ₁₂). Comparative analysis was also conducted on data obtained from the current smooth tube. According to the findings, the louver angle ${\theta }_1$ = 20°, located on the baffle's trailing end, had the greatest relative Nusselt number (Nu_R), which was 5.9 times for V-down and 6.38 times for V-up. Furthermore, compared to the V-down and V-up solid baffles ($\theta$ = 0°), their friction losses were lessened. The V-up LVB reached its minimum value at ${\theta }_1$ = 20°, corresponding to the lowest Re. At ${\theta }_1$ = 20°, the V-up LVB attained its minimum entropy generation (${\dot{S}}_{gen}^{\prime }$) and maximum reduced entropy factor (S_R) around 20.3. At a comparable ${\theta }_1$ = 20°, the maximal thermal effectiveness factor (TEF) of V-down and V-up were approximately 2.39 and 2.59, respectively. The estimation and documentation of correlations were also performed for the parameters under consideration, namely Nu, f, and TEF.