CFD Study of Heat Transfer in Power-law Fluids over Multiple Corrugated Circular Cylinders in a Heat Exchanger

The heat transfer in power-law fluids across three corrugated circular cylinders placed in triangular pitch arrangement is studied computationally in a confined channel. Continuity, momentum and energy balance equations were solved using ANSYS FLUENT (Version 18.0). The flow is assumed to be steady, incompressible, 2D and laminar. A square domain of side 300 D is selected after detailed domain study. An optimized grid with 98187 cells is used in the study. The convergence criteria of 10 for the continuity, x-momentum and y-momentum balances and 10 for energy equation were used. Constant density and non-Newtonian power-law viscosity modules were used. Diffusive term is discretized using central difference scheme. Convective terms are discretized using Second Order Upwind (SOU) scheme. Pressure-velocity coupling between continuity and momentum equations was implemented using the SIMPLE (Semi-Implicit Method for Pressure Linked Equation) scheme. Streamlines show wake development behind the cylinders, which is much dominant at large Re and n . Isotherm contours are cramped at higher values of Re and Pr , implying higher heat transfer. Global parameters like C and Nu are computed for the wide ranges of controlling dimensionless parameters, such as power-law index (0.3 ≤ n ≤ 1.5), Reynolds (0.1 ≤ Re ≤ 40) and Prandtl numbers (0.72 ≤ Pr ≤ 500). The Nu plot attains a pitch near corrugation of surface due to abrupt change in velocity and temperature gradients. Nu increases with Re and/or Pr and decreases with n under otherwise identical situations. Nu is correlated with pertinent parameters, namely, Re Pr and n .