Akademik Veri Yönetim Sistemi
Journal of the Brazilian Society of Mechanical Sciences and Engineering, cilt.45, sa.10, 2023 (SCI-Expanded)
Flow boiling in micro-pin fin structured heat sinks is an up-to-date thermal management technique. However, due to micro-sized flow passages, bubble blockage is a problem for this type of heat sinks, too. In addition, mixing and bubble breakup are important phenomena for enhancement of heat transfer. Taking more advantages of potential of this unique technique depends on removing of relevant shortcomings and supporting influential mechanisms; therefore, new geometries being designed based on bubble-dynamic characteristics should be developed, and relevant thermo-hydrodynamic characteristics should be analyzed. Therefore, the present paper experimentally analyzes boiling performance of water flow in a micro-pin fin heat sink having a new type of geometry. The heat sink has four sections, and in each section, the micro-fins are positioned in staggered form according to previous sections, also the number of fins in each section is fewer than the one of the former sections. In this paper, for the first time in the literature, combined influence of regional staggered pin fin arrangement and regional cross-sectional enlargement on thermo-hydrodynamic characteristics of flow boiling in micro-pin fin heat sinks is investigated. The new type of heat sink (NT) is compared with conventional type (CT) in which the micro-pin fins are uniformly located throughout the heat sink. Saturated flow boiling experiments are conducted at a heat flux range of 132–272 kW m−2 (90 W to 180 W with 10 W increments), and at a constant mass velocity of 174 kg m−2 s−1 for constant inlet temperature of 75 °C. It is concluded that staggered pin fins with decreasing number significantly boost thermal and flow characteristics. Compared to the conventional type, two-phase heat transfer coefficient increases up to 94.5%, and pressure drop decreases up to 18.3% via NT. The wall superheat for NT is lower than those obtained for CT for the whole database, which physically means that NT keeps the heating surface at lower temperature for the same heat load. Prevention of bubble blockage problem, suppression of flow reversal, enhancement of bubble disjunction, decrease of vapor-waiting time on heat transfer surface, and more effective convective boiling characteristics are the main underlying reasons of performance enhancement.