From Macro to Micro Scales: Identifying and Measuring Scaling Effects

Scaling effects in continuum flows can be identified that characterize flow and heat transfer in small, micro-sized devices compared to the same geometries but on a macro-sized scale, when the underlying continuum equations (Navier-Stokes and first law of thermodynamics) are subject to a dimensional analysis. In order to identify micro scaling effects experimentally, measured flow quantities are compared to numerically calculated results, based on a theoretical model that is appropriate for macro scale channels (no scaling effects, continuum approach). They have to be interpreted carefully, including a thorough error analysis of experiments as well as the theoretical model. Instead of trying to experimentally identify scaling effects in fixed geometries we suggest to combine macro parts in a way that micro channels emerge. Then, continuously adjustable sizes of the channels can be realized that go from macro to micro dimensions. Equally important, the surfaces of the channels are freely accessible when the macro parts are disjoined. Two such facilities are shown and discussed.