Numerical Study of Entropy Generation in Fully Developed Turbulent Circular Tube Flow Using an Elliptic Blending Turbulence Model

Abstract

As computational fluid dynamics (CFD) advances, entropy generation minimization based on CFD becomes attractive for optimizing complex heat-transfer systems. This optimization depends on the accuracy of CFD results, such that accurate turbulence models, such as elliptic relaxation or elliptic blending turbulence models, become important. The performance of a previously developed elliptic blending turbulence model (the model) to predict the rate of entropy generation in the fully developed turbulent circular tube flow with constant heat flux was studied to provide some guidelines for using this class of turbulence model to calculate entropy generation in complex systems. The flow and temperature fields were simulated by using a CFD package, and then the rate of entropy generation was calculated in post-processing. The analytical correlations and results of two popular turbulence models (the realizable k–ε and the shear stress transport (SST) k–ω models) were used as references to demonstrate the accuracy of the model. The findings indicate that the turbulent Prandtl number (Prt) influences the entropy generation rate due to heat-transfer irreversibility. Prt = 0.85 produces the best results for the model. For the realizable k–ε and SST k–ω models, Prt = 0.85 and Prt = 0.92 produce the best results, respectively. For the realizable k–ε and the SST k–ω models, the two methods used to predict the rate of entropy generation due to friction irreversibility produce the same results. However, for the model, the rates of entropy generation due to friction irreversibility predicted by the two methods are different. The difference at a Reynolds number of 100,000 is about 14%. The method that incorporates the effective turbulent viscosity should be used to predict the rate of entropy generation due to friction irreversibility for the model. Furthermore, when the temperature in the flow field changes dramatically, the temperature-dependent fluid properties must be considered.

Impact of a closed-space rectangular heated source on MHD mixed convection flows into a lid-driven cavity with a heated wavy bottom surface in presence of internal heat generation or absorption.

“…Quyyumet al [28] studied magneto-hydrodynamic combined convection and heat-generating tangent hyperbolic nanofluid with Newtonian heat transfer. And other similarities can be found Johnson et al [29], Yang et al [30],Bouterra et al [31], and Laurel et al [32].In addition, the finite element (FE) method, magnetic field, mixed/hybrid convection, and heat source are more detailed [33][34][35].…”

“…Overall,all of the above research can be classified into three categories. The first set focuses on MHD mixed and natural convection [9][10][11][12][13][14][15][16][17][18][19] within a square wavy cavity, the second set deals with MHD mixed and natural convection within a square wavy cavity having fins [20][21][22][23][24], and the third on MHD mixed and natural convection with heat generation or absorption [25][26][27][28][29][30][31][32]. Effects of Electromagnetic fields on plasma and Hall currents on viscoelastic fluid have been studied [40][41][42] with nonlinear heat and mass transfer.…”

Thermohydraulic and Irreversibility Analyses of Swirl Flows Utilizing Distorted Radial Fins: Entropy Generation and Entransy Dissipation Evaluation

“…Thus, incorporation of entransy evaluation is critical to minimize losses for heat transfer systems, providing quantified statistics on the practicality of various fluid phenomena for heat transfer enhancement. Reduction of entransy due to entransy dissipation and thermal resistances can be obtained utilizing Equation (32) and Equation (33), respectively, which expresses EDR and ETR for turbulent convective heat transfer. Figure 15 shows the effect of incremental Reynolds number with EDR for various DRF angles.…”

“…Subsequently, entropy generation minimization (EGM) emerged as an approach for optimal thermal system designs. Numerous investigations have been conducted on second law analysis and EGM, to optimize thermal system performances [31][32][33][34][35]. Mwesigye et al numerically analysed the effects of longitudinal vortices generated by surface-detached twisted tapes [36].…”

Heat Transfer and Entropy Generation of Turbulent Flow in Corrugated Channel using Nanofluid

“…In addition, when increasing the volume fraction of the nanoparticles (Al2O3 and CuO), an increase in the average Nusselt number and friction factor compared to a decrease in the coefficient of performance (PEC) were observed [5]. In Yang and Yang [6], the study is devoted to numerical simulation of fully developed turbulent flow with constant heat flux imposed in a circular tube. The temperature and flux fields were simulated by CFD, but the rate of entropy generation was calculated in postprocessing.…”