Assessment of first law performance characteristics and Chilton-Colburn analogy in diamond and hourglass microchannels

• Published in: Applied thermal engineering 2023-03, Vol.223, p.120017, Article 120017
• Main Authors: Goli, Sandeep, Saha, Sandip K., Agrawal, Amit
• Format: Article
• Language: English
• Subjects: Chilton-Colburn analogy; Diamond microchannel; Hourglass microchannel; Performance evaluation index; Pressure penalty factor; Thermal enhancement factor
• ISSN: 1359-4311
• DOI: 10.1016/j.applthermaleng.2023.120017

•The entire design parameter space, specifying all significant physical traits, is analyzed.•The simulations results are validated with in-house experiments.•Diamond/hourglass microchannels perform better than uniform microchannels for most design variables.•Diamond shape shows better performance than hourglass shape for most parameters.•The Chilton-Colburn analogy is extended to non-uniform geometries.•Useful correlations for fluid flow and heat transfer characteristics are proposed for both geometries. The first law analysis is deployed to delineate the potential of diamond (diverging-converging) and hourglass (converging–diverging) microchannels to enhance the performance of microscale thermal devices for various engineering needs. The selection of the design variables ensures that they account for salient physical aspects, such as the divergence-convergence effect (divergence-convergence angle, width ratio), geometrical and flow considerations (depth, length, Reynolds number), and conjugate effect (substrate material and thickness). The study demonstrates that diamond/hourglass microchannels perform better than uniform microchannels, with some exceptions, such as a higher aspect ratio (higher depth) and a shorter length. The proposed geometries also underperform at a low divergence-convergence angle and higher width ratio for a few Reynolds numbers. The results also reveal that diamond microchannels perform better than hourglass, except for shorter lengths and higher depths. Interestingly, proposed geometries with shorter lengths or higher depths exhibit flow recirculation zones at smaller divergence-convergence parameters than the critical limitations outlined in the literature. The Chilton-Colburn analogy is applied to develop a quantitative relationship between fluid flow and heat transfer characteristics. The heat transfer coefficients are determined within ±18 % based on the proposed correlation, thus helpful for initial design approximations of proposed topologies. Lastly, the current research also provides insight into design combinations that maximize the capabilities of recommended geometries through sensible manipulation of the physical traits. The findings of this work thus contribute to the design and development of microscale devices with proposed flow layouts for diverse thermal applications.