“…The enhancement of heat transfer and fluid flow characteristics were investigated experimentally in 1969 [23]. VGs can take various forms such as protrusions, wings, inclined blocks, winglets, fins, and ribs [24,25], and have been used to enhance heat transfer in different geometries such as circular and non-circular ducts under turbulent flow [26][27][28][29]. They have also been used in laminar flow [24,[30][31][32][33] which is effective to enhance the heat transfer rate, with flat plate-fins in rectangular channels [34][35][36], tube heat exchangers [17,37], heat sinks [30,38] and rectangular narrow channels [32,39].…”