Heat Transfer In Rectangular Duct Research Articles

The effect of variable viscosity on laminar flow and heat transfer in rectangular ducts.

Numerical solutions are presented for the flow and heat transfer problems of laminar forced convection for liquids in rectangular ducts by use of several correlative equations for viscosity-temperature as used in the studies of the circular tube, where the fully developed velocity and temperature fields, under the boundary conditions of axially uniform wall heat flux and peripherally uniform wall temperature, are assumed. The effects of viscosity variations on the profiles of velocity and temperature, the friction factor and the Nusselt number are summarized as follows: i) the velocity profile is strongly affected by the viscosity ratio based on the wall and cup mixing temperature (μw/μm), whereas the temperature profile is affected weakly, and ii) the relationship of f/fcp vs. μw/μm for various aspect ratios is in good agreement with that of the circular tube as reported by Shannon et al. and Deissler, in the region of μw/μm<10 where fcp is the friction factor for the case of constant viscosity. On the other hand, the relationship of Nu/Nucp vs. μw/μm is different from that of the circular tube, except in the region where μw/μm is closer to unity, and its difference is remarkable in a larger aspect ratio.

Heat Transfer in Rectangular Ducts with Fins from Opposite Walls

AbstractThe paper deals with the heat transfer performance of an internally finned rectangular duct in the case of combined free and forced convection by fully developed laminar flow of a single phase fluid with or without heat generation. It is found that continuous straight fins of rather large fin length give the best heat transfer performance.