Many applications require smaller, faster, and more powerful electronic devices, leading to excess heat that needs to be removed from the system. Micro-finned tubes are a preferred method to increase the heat-transfer performance of cooling systems. There are a limited number
of studies on the fin geometry of micro-finned tubes with respect to thermohydraulic performance and entropy-generation analysis, especially for diameters under 10 mm. To address this literature gap, this study numerically investigates the entropy generation rates and thermohydraulic
performance of 8-mm-diameter horizontal tubes with square, circular, and triangular fins compared with those of a smooth tube. In this regard, numerical studies were conducted at constant heat flux with Reynolds numbers ranging from 400 to 2000 in the laminar regime and from 5000
to 9000 in the turbulent regime, using computational fluid dynamics. The Nusselt number increased by 140%, 218%, and 180% for the square, circular, and triangular finned tubes, respectively, compared with the smooth tube in the laminar flow regime. In the turbulent region, the Nusselt number increased by 3.4%, 29%, and 7.5% for the square, circular, and triangular finned tubes, respectively. Since the tube with circular-fin geometry demonstrated the greatest heat-transfer capability in both laminar and turbulent regimes, numerical analyses were conducted on circular-fin tube models with pitch lengths of 3-6 mm to enhance heat-transfer performance. The device with a 3-mm pitch length demonstrated greater thermohydraulic performance despite having slightly higher entropy generation rate and friction factor than the other versions. The
findings of this study offer valuable insights to inform the design of more efficient thermal systems.