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

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 macroscale to the microscale, where the flow dynamics might be expected to deviate due to possible changes 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 mu m were investigated numerically and experimentally for mass flow rates between 1 and 68 gmin(-1). The source of inconsistencies in pressure drop characteristics is found to be linked to the geometrical details of the utilized microchannel, for example, the design of inlet/outlet manifolds, the artifacts 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 paper provides a detailed overview of how to account for these details to mitigate the discrepancies and to establish a handshake between experiments, numerical simulations, and theory.