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Flow and Heat Transfer in the Tree-Like Branching Microchannel with/without Dimples
Linqi Shui1, Jianhui Sun1, Feng Gao1
1Key Laboratory of NC Machine Tools and Integrated Manufacturing Equipment of the Education Ministry & Key Laboratory of Manufacturing Equipment of Shaanxi Province, Xi'an University of Technology, Xi'an 710048, China.
Entropy (Basel, Switzerland)
|December 3, 2020
Summary
Dimples in branching microchannels enhance heat transfer, with performance increasing with branching level. Optimal dimple spacing (s/D=3) minimizes entropy generation and improves thermal performance, despite some flow dead zones.
Area of Science:
- Fluid Dynamics and Heat Transfer
- Microscale Engineering
Background:
- Tree-like branching microchannels are crucial in various thermal management systems.
- Enhancing heat transfer in these microchannels is essential for system efficiency.
- The impact of surface modifications like dimples on microchannel performance requires detailed investigation.
Purpose of the Study:
- To numerically and experimentally investigate flow and heat transfer in tree-like branching microchannels.
- To evaluate the effectiveness of dimples in enhancing heat transfer.
- To analyze the influence of dimple geometry and flow conditions on thermal-hydraulic performance and entropy generation.
Main Methods:
- Numerical simulations using the SSG turbulence model, validated against experimental data from smooth branching microchannels.
- Experimental investigation of flow and heat transfer in both smooth and dimpled branching microchannels.
- Parametric studies involving varying Reynolds (Re) numbers and streamwise spacing to diameter ratios (s/D).
Main Results:
- Dimples significantly enhance average heat transfer, with greater improvement at higher branching levels.
- Flow dead zones in dimples at bifurcations and bends can impede turbulent flow and heat transfer.
- The Nusselt number ratio (Nu_a/Nu_s) and thermal enhancement factor (η) decrease with increasing Re number, while the friction factor ratio (f_a/f_s) varies nonlinearly.
- The dimpled case with s/D = 3 exhibits the lowest augmentation entropy generation (N) under high Re conditions and shows the best overall thermal performance.
Conclusions:
- Dimples are effective in enhancing heat transfer in branching microchannels, but their placement and geometry are critical.
- The optimal streamwise spacing to diameter ratio (s/D = 3) balances heat transfer enhancement with minimal performance degradation.
- The study provides valuable insights for designing efficient microchannel heat sinks with dimple-based enhancements.
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