Investigating Thermally Developing Gas Slip Flow Inside a Micro-annulus Including Viscous Dissipation and Axial Conduction Effects Using the Lattice Boltzmann Method

• Published in: Iranian journal of science and technology. Transactions of mechanical engineering 2024-03, Vol.48 (1), p.49-64
• Main Authors: Hami, Masoud, Kalteh, Mohammad
• Format: Article
• Language: English
• Subjects: Engineering; Mechanical Engineering; Research Paper
• ISSN: 2228-6187; 2364-1835
• DOI: 10.1007/s40997-023-00643-z

In the present paper, forced convection of a laminar gas flow inside two concentric micro-cylinders with constant wall heat flux condition is numerically investigated. For this purpose, the energy equation is solved in the continuum and slip flow regimes for the thermally developing condition using the lattice Boltzmann method. To the authors’ best knowledge, the simultaneous effects of viscous dissipation, rarefaction, axial conduction, and radius ratio in the thermally developing region of a micro-annulus channel have not been considered in the literature. In the present work, the effects of the mentioned parameters on the heat transfer characteristics are studied in detail. Furthermore, the lattice Boltzmann method is developed to apply the viscous dissipation source term in axisymmetric slip flows under constant wall heat flux condition. The results show that in the absence of viscous dissipation, due to energy balance in the fluid, the bulk fluid temperature is independent of the Knudsen number, and its value increases linearly along the microchannel. However, the bulk fluid temperature changes with the Knudsen number by including the viscous dissipation. Also, increasing the rarefaction effect, reduces the impacts of Brinkman number and radius ratio on the local Nusselt number. Moreover, the influence of viscous dissipation is more significant at higher radius ratios.