Numerical study of compressible convective heat transfer with variations in all fluid properties

The effects of property variations in single-phase laminar forced micro-convection with constant wall heat flux boundary condition are investigated in this work. The fully-developed flow through micro-sized circular (axisymmetric) geometry is numerically studied using two-dimensional continuum-based conservation equations. The non-dimensional governing equations show significance of momentum transport in radial direction due to mu(T) variation and energy transport by fluid conduction due to k(T) variation. For the case of heated air, variation in C-p(T) and k(T) causes increase in Nu. This is owing to: (i) reduction in T-w (T-w-T-m), and (delta T/delta r)(w) and (ii) change in delta T-m/delta z results in axial conduction along the flow. The effects of rho(p,T) and mu(T) variation on convective-flow are indirect and lead to: (i) induce radial velocity which alters u(r) profile significantly and (ii) change in (delta u/delta r)(w) along the flow. It is proposed that the deviation in convection with C-p(T), k(T) variation is significant through temperature field than rho(p,T), mu(T) variation on velocity field. It is noted that Nu due to variation in properties differ from invariant properties (Nu = 48/11) for low subsonic flow. (C) 2009 Elsevier Masson SAS. All rights reserved.