A Study on Turbulent Flow and Heat Transfer Characteristics in Ducts of Relevance for Heat Exchangers

The performance of an explicit algebraic stress model with a cubic equation for closure constants is assessed in predicting the turbulent flow dynamics of ducts relevant for heat exchangers. The use of a cubic equation allows elimination of any damping functions in the tensor representation for the Reynolds stresses and thereby improves prediction of turbulent stresses theoretically. The methodology used here allows for prediction of Cm in any spatial points and eliminates the use of damping functions in the turbulent viscosity. A flow parameter, which characterizes the flow type from plane strain and plane shear to elliptical flows, is used to prescribe the flow type in the ducts under consideration. In all cases, isothermal conditions are imposed on the duct walls, and the turbulent heat fluxes are modeled using a new bounded quadratic generalized gradient-diffusion type model. In addition, the calculated results are compared with existing experimental data and satisfactory results are obtained. A comparison of velocity and temperature contours is shown in order to study the effect of waviness on flow/heat dynamics.