Thermohydraulic characteristics and entropy generation in a heat exchanger tube with teardrop-shaped dimples: A CFD approach

• + Proposes a new tube configuration with teardrop-shaped dimples for flat tubes. • + Analysis of thermohydraulic characteristics and entropy generation in new tube configurations. • + Propose an optimal configuration that maximizes thermohydraulic performance. This paper proposes a new tube configuration with teardrop-shaped dimples for flat tubes. It aims to provide a thermohydraulically advantageous tube configuration that can be applied in practical heat exchanger tubes. The influence of the Reynolds number (Re = 10,000−20,000), relative dimple pitch (P s = 2−4), relative minor axis length of dimple (d s = 0.4−0.6), and relative dimple depth (h s = 0.1−0.2) on the thermohydraulic characteristics and entropy generation was investigated under a constant temperature boundary condition. Furthermore, an optimization analysis of the maximum thermohydraulic performance (THP) was conducted using the response surface methodology (RSM). The results indicate that the Nusselt number and entropy generation increased with increasing Re, increasing d s , increasing h s , or decreasing P s . The friction factor increases when Re decreases, d s increases, h s increases, or P s decreases. The dimpled tubes improve the heat transfer rate by up to 54.7 %, but the friction factor increases by up to 278.1 % compared to in smooth tubes. The dimples have the smallest d s and h s , which helps reduce entropy generation. According to the maximum THP target, the optimal parameter was Re = 10,000, P s = 2, d s = 0.6, and h s = 0.1987, which yields a THP of 1.0345 (confirmed by numerical result); the HTR and S gen increased by 47.5 % and 24.9 %, respectively, compared to with the smooth tube.