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

Paper Number: 167053

Experimental Investigation of Flow Boiling Heat Transfer, Pressure Drop, and Flow Instability in a Mini-Channel With a High Length-to-Diameter Ratio for Hydraulic Diameters of 3.0 and 4.8 Mm 

As electronic components continue to advance, increased heat generation amplifies the need for effective thermal management. While single-phase cooling is widely used, it lacks sufficient heat transfer performance. In contrast, two-phase cooling, which utilizes both latent and sensible heat, offers superior cooling performance and helps maintain uniform surface temperatures. Among phase-change technologies, mini/micro-channel heat sinks are particularly advantageous due to their high heat transfer coefficients, compact designs, low coolant requirements, and ease of fabrication.

The development of large heat sinks is becoming increasingly important for future electronic thermal management systems. As power densities rise, managing high thermal loads with small heat sinks becomes more challenging, particularly in applications such as defense electronics and aerospace, where large surface areas are essential for effective heat dissipation. Despite this growing demand, research on large mini/micro-channel heat sinks remains limited, and most existing correlations have been developed for small-sized heat sinks.

This study investigates heat transfer coefficient, pressure drop, flow instability, and flow characteristics in heat sinks with mini-channels featuring a large length-to-diameter ratio. The aluminum heat sink used in this study has a base area of 843 mm in length and 24 mm in width, with channels of two different hydraulic diameters: three channels measuring 2 mm in width and 6 mm in height, and two channels measuring 4 mm in width and 6 mm in height. Five flow patterns were identified: bubbly, slug, transition, wavy-annular, and smooth-annular flow. A comparison of the observed flow patterns with previous flow regime maps revealed that maps incorporating non-dimensional parameters and extensive databases provided accurate predictions, effectively accounting for the thermophysical properties of different fluids and a broad range of flow conditions. This study also examined the effects of hydraulic diameter, heat flux, and mass flux on flow instability. The results indicate that flow instability decreases with increasing mass flux, decreasing heat flux, and larger hydraulic diameter, while stable flow characteristics were observed near the inlet. Additionally, this study compares the heat transfer coefficient, pressure drop, dryout incipience, and critical heat flux data with previous correlations. Dryout incipience was identified as the point where the local heat transfer coefficient sharply decreased, while critical heat flux was determined as the heat flux at which the temperature failed to converge and increased abruptly. The comparison with previous correlations was conducted using various error metrics, including mean absolute error, the percentage of data points within 30% and 50% absolute error, and mean relative error.

Presenting Author: Jae-Yoon Park Sungkyunkwan University

Presenting Author Biography: Jae_Yoon is a M.S./Ph.D. Combined Course in the Department of Mechanical Engineering at Sungkyunkwan University, South Korea. His research focuses on flow boiling heat transfer, pressure drop characteristics, and mini-channel cooling systems.

Authors:

Jae-Yoon Park Sungkyunkwan University
jinyoung Kim Sungkyunkwan University
Seong-Jin Oh Sungkyunkwan University
Myung-Bae Cha Sungkyunkwan University
Sung-Min Kim Sungkyunkwan University