Effects of convergence and superhydrophobicity on the hydrothermal features of the tapered double-layer microchannel

Abstract

The performance of the tapered double-layer microchannels with the hydrophobic surfaces is studied numerically. Hydrothermal performance is analyzed by different parameters, such as pressure drop, pumping power, thermal resistance, Nu number, etc. The governing equations are solved by the finite volume method (FVM). User-defined functions (UDFs) are used to model temperature-dependent properties of water and hydrophobic and superhydrophobic surfaces. The effects of different parameters, including slip length, Re number, and tapered factors are examined. The results showed that by using the superhydrophobic surfaces, the pumping power decreases due to fluid slips, and the thermal resistance increases due to the temperature jump on the surface. It is found also that at Re = 50, the convergent microchannel with the superhydrophobic wall has a higher Nu number as compared with the direct microchannel at all values of slip length. However, at higher Re numbers, the Nu number of the convergent microchannel with superhydrophobic surfaces is lower than that of the direct microchannel with conventional surfaces. In addition, at Re = 50, the use of superhydrophobic walls decreases the thermal resistance in comparison with the conventional walls. The superhydrophobic surfaces give higher hydrothermal performance factors (η) for Re≤ 150, while they give lower performance factors at Re > 250. For Re ≤ 100, increasing the convergence of superhydrophobic microchannels increases the hydrothermal performance factors.