Laminar convection behaviour in microchannels in conventional thermal entry length and beyond

Previously reported and present experimental data are processed to give the Nusselt number (Nu) along the flow in microchannels, which is segregated based on the conventional thermal entry length into thermally-developing and thermally-developed modes. The Nu is also found to reduce in the thermally-developed regime, thereby confirming that the unusual behaviour of Nu receding with increasing Reynolds number (Re) is not due to the characteristic of a thermally-developing flow. The experimental data is processed to obtain wall and coolant temperatures along the flow. The differential form of the steady-flow energy equation is derived for heat transfer in microchannels from first principles, which, upon integration, features the dependence of Nu on the Brinkman number (Br)