Variable Property Effects in Single-Phase Incompressible Flows Through Micro Tubes

In a systematic approach we address the question of how important variable property effects are for flows in micro-sized channels. Due to heat transfer, the temperature dependence of fluid properties like viscosity and thermal conductivity results in deviations in a solution that accounts for that dependence compared to a solution for constant fluid properties. Compared to flows through macro-sized geometries it turns out that two distinct scaling effects lead to a strong influence of variable fluid properties in micro-sized channels. Examples are given in which Nusselt numbers differ by up to 30% depending on how the property behaviour is accounted for.