Theoretical Entropy Generation Analysis for Forced Convection Flow Around a Horizontal Cylinder

Using an entropy generation analysis, heat exchangers can be designed with optimal efficiency. This study delves into the irreversibility of forced convection heat transfer and friction flow around a horizontal cylinder, revealing that pressure drops induce entropy generation that varies in accordance with Reynolds numbers. The investigation encompasses four groups of Re_D, covering ranges of 0.4_D<4, 4_D<40, 40_D<4000, and 4000_D<40000. The study aims to elucidate the relationship between the entropy generation number (Ns), Re_D, the irreversibility distribution ratio (∅), the optimal Reynolds number (Re_D,opt), and the Bejan number (Be), particularly where entropy generation has a minimal effect. Additionally, it seeks to determine the relationship between the duty parameter and Re_D,opt across all Re_D ranges. The findings highlight the optimum design point for forced convection around a horizontal cylinder. At this point, the entropy generation number reaches its minimum value when Ns=1 and the ratio Re_D/Re_D,opt=1, marking the optimal point for irreversibility or entropy generation. At this juncture, the irreversibility distribution ratio ∅ equals 0.5, and the optimal Bejan number stands at 0.667.