ANALYSIS OF HEAT-TRANSFER AND FLUID-FLOW THROUGH A SPIRALLY FLUTED TUBE USING A POROUS SUBSTRATE APPROACH

An innovative approach was opted for modeling the flow and heat transf er through spirally fluted tubes. The model divided the flow domain in to two regions. The flutes were modeled as a porous substrate with dir ection-dependent permeabilities. This enabled modeling the swirl compo nent in the fluted tube. The properties of the porous substrate such a s its thickness, porosity, and ratio of the direction-dependent permea bilities were obtained from the geometry of the fluted tube. Experimen tal data on laminar Nusselt numbers and friction factors for different types of fluted tubes representing a broad range of flute geometry we re available. Experimental data from a few of the tubes tested were us ed to propose a relationship between the permeability of the porous su bstrate and the flute parameters, particularly the flute spacing. The governing equations were discretized using the Finite Element Method. The model was verified and applied to the other tubes in the test matr ix. Very good agreement was found between the numerical predictions an d the experimental data.