Session: 12-06-01: Boiling Heat Transfer and Flow Instabilities

Paper Number: 163766

Augmentation of Pool Boiling Heat Transfer at Saturation and Subcooled Temperatures With Open Microchannel Surfaces 

Effective thermal management is becoming increasingly critical in high-power-density applications such as data centers, nuclear power modules, and aerospace electronics, where reliability and compact design must coincide with elevated heat dissipation demands. Pool boiling, particularly under subcooled conditions, is a promising technique to enhance heat transfer due to its high efficiency in latent heat removal. However, the performance of boiling systems is highly sensitive to surface structure and fluid thermodynamic state. While numerous studies have examined boiling on micro- and nano-structured surfaces using dielectric fluids, limited work has systematically evaluated the combined influence of microchannel geometry and subcooling using deionized (DI) water on copper substrates under controlled laboratory conditions.

This study aims to fill this gap by experimentally investigating the pool boiling behavior of DI water on plain and open microchannel copper surfaces. Specifically, three surface configurations were tested: a smooth polished surface, and two microchannel-enhanced surfaces with groove depths of 0.5 mm (MC-05) and 1.0 mm (MC-10). All surfaces were tested under three bulk subcooling conditions: 0 K (saturation), 5 K, and 10 K, at atmospheric pressure. The primary objectives were to quantify how subcooling level and microchannel depth affect the heat transfer coefficient (HTC) and critical heat flux (CHF), and to evaluate how well classical correlations (Rohsenow, Zuber, Kutateladze) predict heat transfer on bare copper surfaces.

The experimental setup included a custom-built pool boiling chamber, in-situ calibrated T-type thermocouples embedded within a copper heater block, and a data acquisition system synchronized with a high-speed camera for bubble dynamics visualization. Heat flux was incrementally increased in controlled steps until the boiling crisis was reached, and the onset of CHF was detected via thermal overshoot criteria. Data reduction procedures applied Fourier’s law with second-order finite differencing to determine surface heat flux and superheat.

Experimental results demonstrate that subcooling increases CHF for all surface types due to improved rewetting and vapor condensation, which suppresses vapor blanket formation. However, subcooling simultaneously leads to a decrease in HTC, especially at low superheat, as additional thermal energy is required to initiate nucleation. Among the tested surfaces, MC-10 achieved the highest CHF across all subcooling levels, indicating that deeper microchannels facilitate better vapor removal and liquid replenishment. Interestingly, the plain surface showed a more linear HTC trend and smaller HTC degradation with subcooling, while MC-05 exhibited moderate enhancement but limited performance under low superheat conditions. High-speed visualization confirmed that MC-10 supports more frequent bubble departures and reduced coalescence at elevated subcooling, in contrast to the chaotic behavior observed on plain surfaces.

These findings underscore the importance of jointly optimizing subcooling level and surface geometry to achieve high thermal efficiency and stability. The results offer valuable design guidance for passive boiling-based cooling systems, particularly in modular nuclear reactors and compact electronic platforms. By demonstrating the trade-off between HTC and CHF in varying subcooling and geometric configurations, this study advances the understanding of subcooled pool boiling and supports the development of next-generation two-phase thermal management technologies.

 

Presenting Author: Mehmet Arik Auburn University

Presenting Author Biography: Dr. Arik obtained his BSc degree in mechanical engineering from İstanbul Technical University, İstanbul, Turkey. He completed MSc degree at the University of Miami, USA. His PhD degree was awarded at the University of Minnesota (USA), focusing on the thermal management of advanced electronic components and Microelectromechanical systems (MEMS), in 2001. He has worked at the General Electric Global Research Center in Niskayuna, NY, on the thermal management of electronics as a senior research scientist and project leader. He has performed research in air-cooled and liquid cooled power electronics, photonics packages, microfluidic systems, defense systems, energy technologies and medical systems.

Dr. Arik has joined department of mechanical engineering at Ozyegin University as a full time faculty member in 2011. He established a group of researchers (ARTgroup) over 16 people consisting of graduate students, research engineers, and support staff since 2012 focusing on energy, medical, electronics, defense and solid state lighting technologies. He established EVATEG center (Energy Efficient Lighting Technologies Research, Development, Education and Demonstration Center). This center has been established in collaboration with more than 10 global universities and research institutions and over 15 global companies.

Dr. Arik's current research interests include solid-state lighting, electronics cooling, microfluidics devices, energy, medical, defense systems, and Six Sigma. He is a member of ASME and IEEE. He is an ASME fellow. He holds over 100 US/EU/Asia and world patents, and more than 20 applications are pending. He published over 125 papers in international journals and conferences, 4 books and book chapters in the fields of electronics cooling, energy systems, and MEMS.

Authors:

Efe Tevfik Ozyegin University
Mete Budakli Istanbul Technical University
Kourosh Naji Ozyegin University
Mehmet Arik Auburn University