A new method for heat transfer coefficient measurements of single-phase fluids during laminar flow in microchannels.

• This paper proposes a new method for heat transfer coefficient measurement. • The wall temperatures on the microchannel before and after the heater measured. • The temperature profile simulated with consideration of the axial conduction. • The measured wall temperatures compared to the simulated wall temperatures. • The Nu number in the laminar flow for a microchannel is independent of Re number. The measurement of heat transfer coefficients in microchannels is complicated due to the small sizes involved. Moreover, a heat transfer mechanism which is not usually considered, the axial conduction effect in the channel wall, must also be evaluated in micro-scale measurements. Previous heat transfer coefficient measurements have not accounted for the axial conduction effect, and those measurements showed the inconsistent result with the theory. In this paper, a new measurement method is developed to validate the theory that predicts a Nusselt number independent of Reynolds number in the laminar flow regime for microchannels. A numerical model is used to simulate heat transfer characteristics in a microchannel with wall conduction, and to predict the wall temperature difference between a location at the end of the heater and a location 3 mm away from the heater on the microchannel. The temperature difference is experimentally measured on a 160 μ m hydraulic diameter microchannel and compared with the numerical model. The comparison shows that the Nusselt number in the laminar flow regime for the microchannel is independent of Reynolds number at least down to Re=300. [ABSTRACT FROM AUTHOR]