This article presents the results of a numerical CFD study of heat exchanger channels with passive heat transfer enhancement methods. Two types of channel geometry were analyzed with different flow turbulization methods. In case I, internal micro-fins were applied to the tube wall, which disturbed the flow directly in the boundary layer; the investigated relative fin heights ranged from 0.01 h/D to 0.08 h/D, and the dimensionless longitudinal spacing varied from 0.92 L/D to 3.27 L/D. In case II, an insert with repeating drop-shaped elements was used, causing fluid turbulization in the tube core; the relative droplet diameter ranged from 0.38 d/D to 0.73 d/D, with the same longitudinal spacing as for the fins. The influence of the geometry and longitudinal spacing of the disturbance elements on the thermal–flow characteristics of such channels, namely, the friction factor, Nusselt number, and thermal efficiency evaluated using the PEC, was investigated over a Reynolds number range of 5000 to 400,000. The results show that the insert produces a larger increase in the Nusselt number, whereas the micro-finned tube generally achieves higher PEC values due to lower hydraulic losses. The results clearly indicate that, in most cases, the PEC is higher for the finned tube, particularly at low Reynolds numbers not exceeding 50,000. In turn, for the insert, the longitudinal distance between the elements, L, has a significant influence on the PEC; as L increases, the PEC also increase, reaching its maximum value for the largest L.
Jasiński et al. (Wed,) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: