The aim of this study is to investigate and optimize heat transfer and boiling
behavior in rectangular channels. In this regard, Near-Wall Active Vortex
Generators (NWAVGs) were employed to enhance the heat transfer rate in channels
with both smooth and wavy walls. While maintaining a constant Reynolds number
at specified values, the effects of different motion patterns, the number of vortex
generators, and various design parameters on the Darcy friction factor, Nusselt
number, and overall hydrothermal performance were analyzed. For smooth-wall
channels, the results indicate that the use of NWAVGs can increase the Nusselt
number by up to 185% and improve hydrothermal performance up to a value of
1.26. In contrast, for wavy-wall channels, despite the increased flow complexity,
the vortex generators were able to enhance the Nusselt number by up to 190%;
however, the maximum hydrothermal performance in this case was limited to 0.95.
Overall, the proximity of vortex generators to the wall plays a key role in improving
heat transfer. In the second part of the study, the effects of different channel
geometries—including smooth and wavy walls, with or without cylindrical
obstacles—on boiling behavior were investigated. The results demonstrate that
channel geometry plays a crucial role in the onset, intensity, and stability of the
boiling process. While the presence of cylinders enhances the heat transfer rate, it
may also introduce thermal instability. On the other hand, wavy walls contribute to
more uniform temperature distribution and thermal stability. The combination of
these two features, namely a wavy channel with cylindrical obstacles, exhibited the
most optimal performance in terms of outlet temperature, wall temperature
distribution, and vapor generation rate. This configuration can be considered a
suitable option for applications requiring high heat transfer and stable boiling, such
as electronic cooling systems and compact-scale heat exchangers.