2022/03/17 by F. Municchi, I. El Mellas, Municchi, F. +6
Energy · Engineering · Physics and Astronomy · #FOS: Physical sciences #Fluid Dynamics (physics.flu-dyn) #Heat Transfer and Boiling Studies #Heat Transfer and Optimization #Solar Thermal and Photovoltaic Systems #physics.flu-dyn
paper · pdf · doi:10.48550/arxiv.2203.09305
29 pages, 16 figures
arxiv created 2022/03/17 · openalex publication_date 2022/03/17 · arxiv updated 2022/03/18 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
This article presents a computational study of saturated flow boiling in non-circular microchannels. The unit channel of a multi-microchannel evaporator, consisting of the fluidic channel and surrounding evaporator walls, is emulated and the conjugate heat transfer problem is solved. Simulations are performed using OpenFOAM v2106 and the built-in geometric Volume Of Fluid method, augmented with self-developed libraries to include liquid-vapour phase-change and improve the surface tension force calculation. A systematic study is conducted by employing water at atmospheric pressure, a channel hydraulic diameter of Dh = 229 um, a uniform base heat flux of qb = 100kW/m2, and by varying the channel width-to-height aspect-ratio and channel fin thickness in the range AR = 0.25-4 and Wf = Dh/8-Dh, respectively. The effects of conjugate heat transfer and channel aspect-ratio on the bubble and evaporative film dynamics, heat transfer, and evaporator temperature are investigated in detail. This study reveals that, when the flow is single-phase, higher Nusselt numbers and lower evaporator temperatures are achieved for AR < 1. In the two-phase flow regime, the trends of the Nusselt number versus the aspect-ratio are mixed, although for smaller channel fins an ascending trend of Nu for increasing aspect-ratios is apparent. Nonetheless, due to conjugate heat transfer, Nusselt numbers and evaporator base temperatures follow different trends when varying the aspect-ratio, and channels with AR < 1 seem to promote lower evaporator temperatures than higher aspect-ratio conduits, despite exhibiting slightly worse two-phase convective heat transfer performances.