Role of gradients and vortexes on suitable location of discrete heat sources on a sinusoidal-wall microchannel.

The idea of using the compact device with higher heat transfer potential has encouraged researchers to use microchannels. Creating sinusoidal walls is a technique leading to better effectiveness and smaller size. In this study, the effects of discrete heat sources location on heat transfer and pressure drop are investigated, using graphene nanoplatelets/water inside a sinusoidal microchannel. For this, discrete heat sources are installed in a smooth microchannel (layout A) and compared with two sinusoidal-wall microchannels. In layouts B and C, the heating sources are installed above the convergent/diverging sections, respectively. Since the velocity and temperature gradients are higher in the converging region, the heat exchange and pressure drop for layout B are greater than other ones. In other words, installing heating sources in these regions with high-temperature gradient has a more obvious positive efficacy on heat exchange. For the best layout (B), although the heat exchange compared to the base layout (A) is 37.5% higher, the pressure drop and entropy generation are higher by 79% and 35.2%, respectively. By introducing a new figure of merit (FOM), it is found that layout B is in the desirable zone. [ABSTRACT FROM AUTHOR]