Abstract

Heat transfer modeling plays a major role in design and optimization of modern and efficient thermal-fluid systems. Further, turbulent flows are thermodynamic processes, and thus, the second law of thermodynamics can be used for critical evaluations of such heat transfer models. However, currently available heat transfer models suffer from a fundamental shortcoming: their development is based on the general notion that accurate prediction of the flow field will guarantee an appropriate prediction of the thermal field, known as the. In this work, an assessment of the capability of the in predicting turbulent heat transfer when applied to shear flows of fluids of different Prandtl numbers will be given. Towards this, a detailed analysis of the predictive capabilities of the concerning entropy generation is presented for steady and unsteady state simulations. It turns out that the provides acceptable results only for mean entropy generation, while fails to predict entropy generation at small/sub-grid scales.

Highlights

  • There are various systems where turbulent heat transfer plays an important role in development and optimization

  • The current study aims to provide a comprehensive assessment of the prediction capabilities of the Reynolds Analogy for entropy production when applied to turbulent, attached, wall-bounded shear flows of fluids with different Pr numbers

  • This covers a wide range of Pr numbers, i.e., Pr = 0.025, 0.71, and 200, to study capabilities of the Reynolds Analogy when dynamics of heat transfer are significantly different

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Summary

Introduction

There are various systems where turbulent heat transfer plays an important role in development and optimization. Various investigations using the entropy concept including different configurations and physical processes with a variety of numerical and analytical approaches to better understanding the process can be found in References [7,12,13,14,15] Based on this concept, only a few Direct Numerical Simulation (DNS) can be found in the literature [16,17,18,19,20,21], which are restricted to simple geometries and low-to-medium Reynolds numbers due to the high computational cost.

Governing Equations
Turbulence Models
Energy Equation and Heat Transfer Model
Temperature Variance Equation
Entropy Equation
Entropy Production—Steady-State calculations
Entropy Production—Unsteady calculations
Flow Configuration
Code Description
Results and Discussion
Steady-State Simulations
Unsteady Simulations
Conclusions and Outlook
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