Local analysis of an increasing pin-fin density device under experimental flow boiling conditions

Pin-finned surfaces have emerged as a promising solution for flow boiling technology, with population density identified as an interesting design parameter for enhancing heat transfer and suppressing flow instabilities. This work presents an experimental study of an increasing variable density pin-finned surface combined with jet-impingement technology under flow boiling conditions. At a constant inlet temperature of 75 °C, flow rates of 100 and 200 ml/min of deionized water were conducted under heat fluxes of almost 60 W/cm2. The major innovation of this work relies on the extensive local study of bubble dynamics, flow patterns, heat transfer and boiling curves. A total of 7 thermocouples were distributed in 5 different regions to obtain a thermal characterization of the heatsink behalf along the flow path. Results show that, for a given thermal load, the cooling device can operate in multiple flow regimes within different regions, each influencing both global and local heat transfer accordingly. A heat transfer enhancement of over 30 % and 10 % across the heatsink was achieved for the 100 ml/min and 200 ml/min flow rate tests, respectively. Quantitatively, the maximum local heat transfer coefficient (hth,i) was 7320 and 10890 W/°C·m2. For the onset of nucleate boiling (ONB), which occurred at 12.93 W/cm2 and 22.81 W/cm2 respectively, the wall superheat ranged from 0.54 °C to 2.69 °C and from 0.91 °C to 4.27 °C. The critical heat flux (CHF) was reached at 32.34 W/cm2 and 58.11 W/cm2. Authors stated that a local flow boiling analysis provides a comprehensive heatsink cooling performance that would allow a better heatsink design optimization.

This work is part of R + D + I Project PID2021-123634OB-I00, funded by MCIN/AEI/10.13039/501100011033. Jaume Camarasa would like to thank Universitat de Lleida for supporting his research by “Ajut UdL per a la contractacio ´ de personal predoctoral en formacio ´ (2023–2026)”. David Beberide would like to acknowledge the financial support of the grant “Doctorados Industriales convocatoria 2022” (DIN2022- 012868) funded by MCIU/AEI/10.13039/501100011033. The authors would like to thank Generalitat de Catalunya for the project awarded to their research group Sustainability in Energy, Machinery and Buildings (2021 SGR 01370).