Fluid flow and heat transfer in microchannels with rectangular cross section

Abstract

Forced convective heat transfer coefficients and friction factors for flow of water in microchannels with a rectangular cross section were measured. An integrated microsystem consisting of five microchannels on one side and a localized heater and seven polysilicon temperature sensors along the selected channels on the other side was fabricated using a double-polished-prime silicon wafer. For the microchannels tested, the friction factor constant $\user2{C} = \user2{f}Re_{{D_{h} }}$ obtained are values between 53.7 and 60.4, which are close to the theoretical value from a correlation for macroscopic dimension, 56.9 for D _h  = 100 μm. The heat transfer coefficients obtained by measuring the wall temperature along the micro channels were linearly dependent on the wall temperature, in turn, the heat transfer mechanism is strongly dependent on the fluid properties such as viscosity. The measured Nusselt number in the laminar flow regime tested could be correlated by $Nu = 0.00058{\text{ }}Re_{{D_{h} }} ^{{1.15}} {\text{ }}Pr^{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-\nulldelimiterspace} 3}} {\left( {{{\mu} {\left( \user2{T} \right)}} \mathord{\left/ {\vphantom {{{\mu} {\left(\user2{T} \right)}} {{\mu} {\left( {\user2{T}_{\infty } } \right)}}}} \right. \kern-\nulldelimiterspace} {{\mu} {\left( {\user2{T}_{\infty } } \right)}}} \right)}^{{2.76}} {\left( {\user2{W} \mathord{\left/ {\vphantom { \user2{{W H}}}} \right. \kern-\nulldelimiterspace} \user2{H}} \right)}^{{0.3}} ,$ which is quite different from the constant value obtained in macrochannels.