The European Physical Journal Applied Physics

Physics and Mechanics of Fluids, Microfluidics

On Reynolds number and scaling effects in microchannel flows

J. Yaoa1, Y. F. Yaoa1, M. K. Patela2 and P. J. Masona1

Faculty of Engineering, Kingston University, Roehampton Vale, Friars Avenue, London SW15 3DW, UK

School of Computing & Mathematical Sciences, University of Greenwich, 30 Park Row, London SE10 9LS, UK


This paper presents a numerical study of the Reynolds number and scaling effects in microchannel flows. The configuration includes a rectangular, high-aspect ratio microchannel with heat sinks, similar to an experimental setup. Water at ambient temperature is used as a coolant fluid and the source of heating is introduced via electronic cartridges in the solids. Two channel heights, measuring 0.3 mm and 1 mm are considered at first. The Reynolds number varies in a range of 500–2200, based on the hydraulic diameter. Simulations are focused on the Reynolds number and channel height effects on the Nusselt number. It is found that the Reynolds number has noticeable influences on the local Nusselt number distributions, which are in agreement with other studies. The numerical predictions of the dimensionless temperature of the fluid agree fairly well with experimental measurements; however the dimensionless temperature of the solid does exhibit a significant discrepancy near the channel exit, similar to those reported by other researchers. The present study demonstrates that there is a significant scaling effect at small channel height, typically 0.3 mm, in agreement with experimental observations. This scaling effect has been confirmed by three additional simulations being carried out at channel heights of 0.24 mm, 0.14 mm and 0.1 mm, respectively. A correlation between the channel height and the normalized Nusselt number is thus proposed, which agrees well with results presented.

(Received March 27 2006)

(Revised October 3 2006)

(Accepted November 8 2006)

(Online publication January 17 2007)


  • 47.61.-k – Micro- and nano- scale flow phenomena;
  • 47.61.Fg – Flows in micro-electromechanical systems (MEMS) and nano-electromechanical systems (NEMS)