A Numerical Study of Fluid Flow and Heat Transfer over a Bank of Flat Tubes

The present study considers steady laminar two-dimensional incompressible flow over both in-line and staggered flat tube bundles used in heat exchanger applications. The effects of various independent parameters, such as Reynolds number (Re), Prandtl number (Pr), length ratio (L=Da), and height ratio (H=Da), on the pressure drop and heat transfer were studied. A finite-volume-based FORTRAN code was developed to solve the governing equations. In all, 10 modules were considered in this study. The flow is observed to attain a periodically fully developed condition downstream of the fourth module. The nondimensionalized pressure drop decreases monotonically with an increase in the Reynolds number. In general, the module average Nusselt number increases with an increase in the Reynolds number. The results at Pr 1⁄4 7.0 indicate a significant increase in the computed module average Nusselt number when compared to those for Pr 1⁄4 0.7. The overall performance of the in-line configuration for lower height ratio (H=Da 1⁄4 2) and higher length ratio (L=Da 1⁄4 6) is preferable since it provides higher heat transfer rate for all Reynolds numbers except for the lowest Re value of 25. As expected, the staggered configurations perform better than the in-line configuration from the heat transfer point of view. Also from the heat transfer point of view, equivalent circular tubes perform better than flat tube banks. However, the heat transfer performance ratio was always greater than 1, signifying that from the pressure-drop point of view the flat tube banks perform better than a tube bank with equivalent circular tubes.