Modeling of cross-flow heat exchangers with viscoelastic fluids

The conduction–convection heat loss from a viscoelastic liquid, subjected to two-dimensional flow within the core of a cross-flow heat exchanger arrangement with a mixed or unmixed external fluid, is investigated with direct numerical simulations. A numerical algorithm based on the finite difference method is implemented in time and space with the Giesekus constitutive model for the viscoelastic liquids. The core-fluid is subjected to an initial Poiseuille flow, driven by an adverse pressure gradient and its temperature varies in both the longitudinal and transverse directions. The results show that a viscoelastic core-fluid choice leads to slightly higher temperature losses within the core-fluid stream as compared to a corresponding Newtonian fluid. As is expected, we also observe significantly higher temperature drops within the core-fluid for the case of unmixed ambient fluids as opposed to the mixed external fluid.