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Abstract
Developing mixed convection flow in internally finned tubes with variable viscosity was numerically investigated for a fin geometry range of 8 ≤ N≤24, 0.1 ≤ H ≤ 0.3 and an operating condition range of 50 ≤ Prin ≤ 1250, 0 ≤ Rain ≤ 107, and 0 ≤ qwd/kin ≤ 2000. The numerical model was validated by comparison with existing numerical and experimental data. Internal finning was found to produce a complex two-cell, buoyancy-induced vortex structure. The results show that coring (retarded velocity in the interfin region) leads to poor heat transfer performance of tubes with large numbers of fins or with tall fins. The overall results indicated that large enhancement in the heat transfer can be obtained in the entrance region. Furthermore, variable viscosity effects are seen to have a pronounced effect on the friction factor and Nusselt number predictions.
Notes
Address correspondence to Dr. Biswadip Shome, Fiber Glass Research Center, PPG Industries, Inc., 201 Zeta Drive, Pittsburgh, PA 15238, USA. E-mail: [email protected]
