Effect of inclination on the convective boiling performance of a microchannel heat sink using HFE-7100

The effect of inclination on the convective boiling heat transfer characteristics of the dielectric fluid HFE-7100 within a multiport microchannel heat sink having a hydraulic diameter of 825 pm is studied. The inclinations spans from -90 degrees (vertical downward) to 90 degrees (vertical upward), and a flow visualization is also conducted in this study. It is found that the heat transfer coefficient for the vertical upward and horizontal is comparable, and the heat transfer coefficient for 45 degrees upward considerably exceeds other configurations. On the other hand, the enhancement of heat transfer coefficient under inclined arrangement is reduced with the rise of mass flux. The results also indicate that downward arrangements always impair the heat transfer performance, and more than 50% deterioration of heat transfer coefficient is encountered for G = 100 kg m(-2) s(-1) relative to that of 45 degrees arrangement. The flow visualization confirms that the heat transfer augmentation for upward inclination is due to the rise of slug velocity. (C) 2011 Elsevier Inc. All rights reserved.