Akın Burak Etemoglu

Numerical Investigation of Turbulent Impinging Jet Cooling of a Constant Heat Flux Surface

In this study, heat transfer characteristics in the single slot jet impinging cooling process of constant heat flux surface are numerically investigated. It is assumed that the flow is turbulent, two-dimensional and in steady state. Governing equations are solved by using Galerkin finite element method by employing five two-equation turbulence models based on Reynolds-averaged Navier-Stokes (RANS) approach. Although the most satisfactory results are obtained with nonlinear algebraic stress model of Shih-Zhu-Lumley in stagnation region, overall performance of RNG and standard k − ϵ models are better in comparison with other models by considering entire region. Subsequent computations are performed with RNG and standard k − ϵ models for nozzle to plate spacing and Reynolds numbers in the ranges of 4 ≤ z/D h ≤ 10 and 4000 ≤ Re ≤ 12000, respectively. Also, inlet turbulence intensity and heat flux boundary conditions effects on heat transfer are investigated. Property variation and buoyancy effects are considered to decrease possible discrepancy with experimental results and capture the turbulence intensity effects more accurately. Acceptable agreement with the measured values in published literature are obtained and discussed.

A theoretical approach to the drying process of thin film layers

In this study, the process of drying of thin films on a continuously moving flat plate which occurs in ink and coating solvents is examined theoretically. For simplicity, it is assumed that during the drying period the solvent has porous media and on the drying surface the vapour pressure of the evaporating liquid remains at a quasi-saturated value corresponding to the temperature of the liquid. Under these assumptions, two relationships which give the time rate of both the solvent temperature and the drying rate are obtained, depending on the drying air, surface, and solvent properties. The theoretical results are compared with some experimental data and found to be satisfactory particularly for the total drying time.

Effect of Turbulence Models and Near-Wall Modeling Approaches on Numerical Results in Impingement Heat Transfer

In this study, turbulence models and near-wall modeling approaches were compared in impingement heat transfer. The Reynolds-averaged Navier-Stokes (RANS) turbulence models were compared using three near-wall modeling approaches. Moreover, the effect of near-wall modeling approaches on heat transfer was investigated and the predictions were compared with experiments. All computations were performed with the FLUENT code by considering two-dimensional, steady, and incompressible flow. Wall functions (WF) should be used carefully in conjunction with turbulence models, and the enhanced wall treatment (WT) is suggested for practical applications. The standard k–ϵ model showed the best agreement with the experimental data among the models used under the considered conditions.