Understanding Inconsistencies in Thermohydraulic Characteristics Between Experimental and Numerical Data for Di Water Flow Through a Rectangular Microchannel

Abstract

Facing discrepancies between numerical simulation, experimental measurement and theory is common in studies of fluid flow and heat transfer in microchannels. The cause of these discrepancies is often linked to the transition from the macro-scale to the micro-scale, where the flow dynamics might be expected to deviate due to possible change in dominant forces. In this work, an attempt is made to achieve agreement between experiment, numerical simulation and theoretical description within the usual framework of laminar flow theory. For this purpose, the pressure drop, friction factor, and Poiseuille number under isothermal conditions and the temperature profile, heat transfer coefficient, Nusselt number, and thermal performance index under diabatic conditions (heating power of 10 W) in a heat sink with a stainless steel microchannel with a hydraulic diameter of 850 µm were investigated numerically and experimentally for mass flow rates between 1 and 68 g/min. The source of inconsistencies in pressure drop characteristics is found to be linked to the geometrical details of the utilized microchannel, e.g. the design of inlet/outlet manifolds, the artefacts of manufacturing technique and other features of the experimental test rig. For the heat transfer characteristics, it is identified, that an appropriate estimation of the outer boundary condition for the numerical simulation remains the crucial challenge to obtain a reasonable agreement. The manuscript presents a detailed overview on how to consider these details to mitigate the discrepancies and to establish a handshake between experiments, numerical simulations and theory.