Session: 13-02 Heat Transfer Testing & Instrumentation

Submission Number: 177117

Influence of Entrance Effects and Relative Roughness on Cooling Performance in Additively Manufactured Channels 

Expanding the design space, additive manufacturing (AM) has potential to increase heat exchanger efficiencies, which is essential for technologies limited by high temperatures like electronics. In thermal management systems, small volume constraints can lead to low length-to-diameter (L/D) ratios and considerable entrance effects. Entrance regions are especially important if low pressure drops are required resulting in slow flow rates with longer entrance lengths. For AM channels, flow behavior in the entrance region becomes more complex because of high surface roughness and geometric inaccuracies inherent to the AM process. This study aims to understand how cooling performance is impacted by flow development in AM channels with low L/D ratios. Using direct metal laser sintering (DMLS), test coupons were manufactured with various lengths and hydraulic diameters. Two AM enabled turbulator designs were investigated: diamond pyramid arrays and broken wavy ribs. Computed tomography (CT) and optical profilometry were used to evaluate geometric deviations and surface roughness. Test coupons were experimentally tested to quantify heat transfer and pressure loss. Findings show that additive roughness contributes to earlier transition and deviation from laminar theory trends. For channels with the same cross section, shorter channels with L/D=20 increase pressure loss and heat transfer up to 26% and 30%, respectively, compared to longer channels with L/D=70.  In turbulator channels, the highest heat transfer augmentations were observed for transitional Reynolds numbers (2000-4000). However, the turbulator geometries studied were not as effective when integrated into channels with smaller hydraulic diameters due to resolution limitations. 

Presenting Author: Abbigail Altland Pennsylvania State University

Presenting Author Biography: Abbigail Altland is a Ph.D. student at the Pennsylvania State University where she conducts research at the Experimental and Computational Convection Laboratory (ExCCL). She also received her bachelor’s degree at the Pennsylvania State University during which she worked as a member of the Zhu Group studying day-time radiative cooling. In her current research, she investigates how different types of rough surfaces impact heat transfer with applications in gas turbine engines and heat exchangers.

Authors:

Abbigail Altland Pennsylvania State University
Stephen Lynch Pennsylvania State University
Karen Thole Pennsylvania State University
Robert Pearson Lockheed Martin
Kevin Birchenough Lockheed Martin