International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

The objective of this study is to numerically investigate the fluid flow and heat transfer performance of a finned-tube heat exchanger (FTHEX). The analysis focuses on the implementation of three vortex generator (VG) configurations: rectangular winglet (RW), delta-winglet upstream (DWU), and delta-winglet downstream (DWD) — mounted on the fin surface in a “common-flow-up” orientation. Attack angles of 15°, 30°, and 45° are considered for each VG type to evaluate their impact on the heat exchanger’s heat transfer potential and friction losses. The air-side Reynolds number, based on the outside tube diameter, was varied within the range 684 ≤ Re ≤ 1532. The results indicate that among the tested configurations, the RWP setup with an attack angle of 45° achieves the highest enhancement in the airside Nusselt number, with improvements ranging from 20% to 45% compared to the reference configuration, but at the expense of a higher pressure drop. For attack angles αvg = 15° and αvg = 30°, the highest overall performance (TPF factor) is achieved with the rectangular winglet configuration across the entire Reynolds number range. At an attack angle of αvg = 45°, the heat exchanger with downstream delta winglets shows higher TPF values compared to the other configurations, except at Re = 1278.

At the present days the great attention is given to a problem of research of hydrodynamics and heat exchange in the pulsating flows. Experimental studies for the flow in smooth channels show that the pulsation of fluids flow significantly affects to the heat transferring and can be accompanied by both reduction and increasing in the intensity of the heat exchanging. This problem has a big practical importance in the study of unstable processes in a various moving and power plants. The results showed that with unsteady fluid’s flow with a alternating pulsations relative to the average velocity in a discretely rough channel is furthering to the intensification of the heat transferring. It is shown that flow pulsations significantly affecting on the heat transferring coefficient, and its average values. This fact opens up the possibility of using such currents to increase the energy efficiency of various technical devices.

Basic methodology has been developed for a numerical modeling and heat exchange in a smooth channel and in a channel with a discrete roughness in the form of semispherical dimples. The methodology provides a possibility of computerized parametric calculations that adequately enough model the examined physical phenomena and allow to determine their characteristics being of practical interest. The efficiency of the examined discretely rough surface was estimated based on the coefficients of heat transfer and hydraulic resistance.