A computational study of enhanced heat transfer in laminar flows of non-newtonian fluids in corrugated-plate channels

摘要

The enhanced heat transfer behavior of laminar shear-thinning, power-law fluid flows in sinusoidal corrugated-plate channels is investigated. With duct plates at uniform wall temperature, periodically developed flows are considered for a wide range of channel corrugation aspect ratio (0 <=gamma<=1), flow rates (10<=Re_g<=1500), and pseudo-plastic flow behavior indices (n = 0.5, 0.8, and 1.0). Typical velocity and temperature distributions, along with extended results for isothermal friction factor f and Collburn factor j are presented. The enhanced forced convection is found to be strongly influenced by gamma, and the flow field displays two distinct regimes: undisturbed laminar or no swirl, and swirl flow regimes. In the no-swirl regime, behavior similar to that in fully developed straight duct flows with no crossstream disturbance is obtained. The shear-thinning nature of the fluid, however, decreases f and enhances j. In the swirl regime, flow separation and reattachement in the corrugation troughs generates transverse vortices that grow with Re_g and gamma. The transition to this regime is also seen to depend on Re_g, gamma, and n, and in shear-thinning flows, it occurs at a lower Re_g. The combined effects of corrugated plate geometry and non-Newtonian fluid rheology produce a heat transfer enhancement, as measured by the factor j/f, of over 3.3 times that in a flat-plate channel depending upon gamma, n, and Re_g.