Thermal effectiveness analysis of heat exchange tube with staggered louver-punched V-baffles

An experiment has been conducted to ascertain the optimal approach for enhancing the convective transmission of heat in a heat exchanger tube by periodically positioning staggered louver-punched V-baffle (SLVB) vortex generators on a perforated tape. The louver-punched V-baffles were staggered and set up with two patterns: V-apex directing upstream (VU) and downstream (VD), and each featured a louver-punched aperture to minimize friction loss. The aim of this work was to rise the thermal effectiveness as well as the Nusselt number ratio (Nu_R) at optimal effectiveness in order to cut down on overall dimension of heat exchangers. Consequently, the research findings focused on behaviors of heat transmission and frictional loss, incorporating generated entropy, through a variety of Reynolds numbers (Re) spanning 29,270 to 4762. The SLVB elements were designed and placed in VU and VD forms using three relative pitches (P_R = 0.5, 1.0, and 1.5) as well as six louver-flapped angles (θ = 0°, 10°, 20°, 30°, 45°, and 90°), all at the same attack angle (α = 52°), a baffle height ratio (B_R = 0.3) and a louver size ratio (L_R = 0.73). As demonstrated by the experiment, the θ = 20° generated the best heat transfer of all P_R values, up to 6.55 times greater than the smooth tube, despite having a lower friction loss than the θ = 0° (solid baffle). At P_R = 0.5, θ = 20° and smaller Re, the optimum thermal effectiveness factor (TEF) and Nu_R values were, respectively, about 2.65 and 6.55 for the VU SLVB and 2.52 and 6.04 for the VD one. It implied that the TEF strategies can be utilized to anticipate the best effectiveness under identical scenarios. Also, correlations for the critical parameters, namely, Nu, f, and TEF, were estimated and documented.