For turbulent flow, it is well known that the heat transfer modes
outside laminar sublayer include conduction and convection,
whereas the heat transfer mode inside viscous sublayer is usually
dominated by conduction. As a result, the thermal resistance is
mainly occupied in viscous sublayer. The longitudinal vortex generators (LVGs) can be mounted on channel wall to continuously
disturb the viscous sublayer along the main flow direction and to
produce longitudinal vortices (LVs) inducing strong swirling
motion, therefore, it may greatly enhance heat transfer [1].