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Macroscopic modeling of hydrodynamic and thermal behavior of nanofluid flows at the entry region of uniformly heated pipe is studied. Single-phase models with and without thermal dispersion effect, Eulerian-Eulerian, and Eulerian-Mixture two-phase models are evaluated by comparing predicted convective heat transfer coefficients and friction factors with experimental results from literature. Solutions with two different velocity pressure coupling algorithms, Full Multiphase Coupled, and Phase Coupled Semi-Implicit Method for Pressure Linked Equations are also compared in terms of accuracy and computational cost. Dispersion model that uses velocity gradient to define dispersion conductivity is found to be more effective at entry region compared to other single-phase models. However, two-phase models predict convective heat transfer coefficient and friction factor more accurately at the entry region. Moreover, computational cost of Eulerian-Eulerian two-phase model can be reduced up to 50% by implementing Full Multiphase Coupled scheme. (C) 2014 Elsevier Masson SAS. All rights reserved.

Thermal interfaces are encountered in many thermal management applications and interface materials are used to minimize thermal contact resistance resulting from solid–solid contact. For opto-electronic devices the quality of the thermal interface is critical for removing the generated heat for proper thermal management. Defects in the thermal interface introduce additional thermal resistance in the thermal path, and must be prevented. Detection of defects in the thermal interfaces becomes critical during the assembly process development. Imaging techniques such as X-ray computerized tomography, or scanning acoustic microscopy that require expensive equipment and significant processing time is necessary. Thermal tomography in conjunction to IR thermometry can be used as a lower cost alternative to these techniques. The feasibility of thermal tomography for non-destructive characterization of thermal interfaces is presented by considering different image reconstruction algorithms. The algorithms considered are the iterative perturbation algorithm, Levenberg–Marquardt algorithm and the regularized Newton–Gauss algorithm, and they were found to be capable of characterizing the thermal interface layer.