Effect of temperature-dependent viscosity variation on fully developed laminar microconvective flow

The effects of temperature-dependent viscosity variation on fully developed flow through a microchannel are numerically investigated in this work. The effects of A(T) variation are able to couple the velocity and temperature fields. Therefore, the velocity and temperature profiles vary qualitatively along the micro-flow. Due to mu(T) variation, the concept of flow undevelopment (the reverse process of flow development) is observed in the flow regime. Four different flow regions have been observed in the flow regime and possible path is, developed undeveloping undeveloped developing. In the vicinity of the inlet, the hydrodynamic undevelopment of flow (the reverse process of hydrodynamic development of flow) is represented by the distortion in axial velocity profile which is confirmed from partial derivative/partial derivative(z) over bar(partial derivative(u) over bar/partial derivative(r) over bar)(W) > 0. The thermal undevelopment of flow (the reverse process of thermal development of flow).is expressed by the rapid enhancement in the convective heat transfer coefficient (h) along the flow due to significant flattening of the axial velocity profile. This study also investigates the Chilton-Colburn analogy for variable viscosity fluid at different mean velocities. The direct proportionality between the Chilton-Colburn j-factor for heat transfer, j(H)(=St.Pr-2/3) and the skin friction coefficient (C-f) is studied which shows the validity of the Chilton-Colbum analogy for variable viscosity fluid. It is observed that the Chilton-Colburn analogy is largely valid for lower values of mean velocity, but progressively fails as the mean velocity of the fluid increases. Additionally, the role of a modified non-dimensional parameter "IIS mu T" in flow friction is also investigated in this research. (C) 2015 Elsevier Masson SAS. All rights reserved.