Numerical Study of Microconvective Water-Flow Characteristics with Variations in Properties

Abstract

A numerical program is developed to solve two-dimensional continnum-based governing differential equations for liquid flow in axisymmetric circular microchannel geometry. The effects of variable thermal properties in single-phase laminar forced convection with constant wall heat flux boundary conditions are studied. The numerical analysis of fully developed flow behavior investigates the effect of ρ(T), μ(T), and k(T) on convection and friction characteristics in isolation and in combination. For the case of heated water, μ(T) variation and k(T) variation increases the Nusselt number due to the following effects: (1) nonnegligible radial convection causes flattening of the axial velocity profile, (2) reduction in wall temperature and axial bulk mean fluid temperature causes significant axial conduction along the flow. The effect of ρ(T) and μ(T) variation on friction is indirect as follows: the viscosity gradient and shear stress at the wall reduce along the flow; therefore, the Poiseuille number deviates from constant properties solution (Po = 64). The investigations also showed that pressure drop significantly differs at the microscale compared to the macroscale.

Keywords:

• friction factor
• pressure drop
• microscale
• property variations

The authors thank the Industrial Research & Consultancy Centre, Indian Institute of Technology Bombay, India, for sponsoring this research through project code 10IRAWD005. The authors thank Government Polytechnic, Thane, Directorate of Technical Education, Mumbai, and Professor C. M. Sevatkar, Government College of Engineering, Pune, for the support. The authors also thank the Priority Research Centers Program, National Research Foundation of Korea (NRF), grant no. 2009-0094016, for encouraging this investigation. The authors are grateful to the A. von Humboldt Foundation, Germany, grant no. INI/1104249, for the rich exposure to research methodology.