Flow and heat transfer optimization in ultra- compact heat exchangers enabled by additive manufacturing

Thesis

This thesis investigates the optimization of flow and heat transfer in ultra-compact heat exchangers through the use of additive manufacturing (AM) techniques. The study begins with an analysis of Internal Longitudinal Fins Channels (ILFC) and Central Inclined Finned Channels (CIFC). While ILFC improves heat transfer, it increases pressure drop, thereby compromising performance. A parametric study on CIFC demonstrates a 115% performance improvement due to the introduction of swirl flow, optimizing thermal-hydraulic efficiency. Further exploration of swirl devices reveals substantial gains, with optimal configurations achieving a 166% improvement over smooth channels. The use of materials with higher thermal conductivity also provides a 9% performance boost. These findings were validated through numerical simulations and experimental setups developed at the Oxford Thermofluids Institute (OTI), which featured modular designs for testing various cooling techniques. Additionally, the thesis includes the design and testing of a heat exchanger comprising nine cells, using constant inlet fluid temperatures for more realistic temperature profiling across the cells. This approach contrasts with previous models assuming constant wall temperatures. A novel manifold design was developed and tested, ensuring superior flow uniformity across heat exchanger cells, confirming its effectiveness compared to conventional manifold designs.

Authors: Almaghrabi, M

• DOI: 10.5287/ora-kzj7bk1xv
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English