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Description:
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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 . The scalar and velocity variables were stored at staggered grid locations . Scalar variables (pressure and temperature ) and all thermophysical properties were stored at the main grid location and velocities were stored at the control volume faces . The solution to a one -dimensional convection diffusion equation was represented by the power law . The locations of grid points were generated by the algebraic grid generation technique . The curvilinear velocity and pressure fields were linked by the Semi -Implicit Method for Pressure Linked Equations (SIMPLE ) algorithm . The line -by -line method , which is a combination of the Tri -Diagonal Matrix Algorithm (TDMA ) and the Gauss -Seidel procedure , was used to solve the resulting set of discretization equations .
The result of the study established that the flow is observed to attain a periodically fully developed profile downstream of the fourth module . The strength increases and the size of the recirculation gets larger as the Reynolds number increases . As the height ratio increases , the strength and size of the recirculation decreases because the flow has enough space to expand through the tube passages . The increase in length ratio does not significantly impact the strength and size of the recirculation .
The non -dimesionalized pressure drop monotonically decreased 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 = 7 .0 indicate a significant increase in the computed module average Nusselt number when compared to those for Pr = 0 .7 . The overall performance of in -line configuration for lower height ratio (H /Da = 2 ) and higher length ratio (L /Da = 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 . |