RT Journal Article ID 447dcde35c81bc1e A1 Srinivasan, Vijayaraghavan A1 Vafai, Kambiz A1 Christensen, Richard N. T1 Experimental Investigation, Modeling and Prediction of Friction Factors and Friction Increase Ratio for Flow Through Spirally Fluted Tubes JF Journal of Enhanced Heat Transfer JO JEH(T) YR 1994 FD 1994-12-01 VO 1 IS 4 SP 337 OP 350 AB The friction characteristics of internal laminar flow through spirally fluted tubes was investigated both experimentally and numerically. The friction factor in the laminar flow regime was experimentally obtained for twelve different spirally fluted tubes with a broad range of geometrical variation of the flutes. The fluted tubes were modeled by dividing the flow domain into two regions. The flutes were modeled as a porous substrate with direction dependent permeabilities. This enabled modeling the swirl component in the fluted tube. The properties of the porous substrate such as its thickness, porosity and ratio of the direction dependent permeabilities were obtained from the geometry of the fluted tube. The governing equations were discretized and solved using the Finite Element Method. The friction factors at a selected Reynolds number from three of the tested tubes were used to propose a relationship between the permeability of the porous substrate and the flute parameters, particularly the flute spacing. The model was verified at other Reynolds number and excellent agreement was found between the model predictions and the experimental data. The application of the permeability correlation was also applied to the other tube in the test matrix and once again the model predictions closely matched the experimental data. PB Begell House LK https://www.dl.begellhouse.com/journals/4c8f5faa331b09ea,7ff6015202d77804,447dcde35c81bc1e.html