Numerical Investigation Of Entropy Generation Research Articles

Numerical investigation of entropy generation in laminar forced convection flow over inclined backward and forward facing steps in a duct under bleeding condition

A numerical investigation of entropy generation in laminar forced convection of gas flow over a recess including two inclined backward and forward facing steps in a horizontal duct under bleeding condition is presented. For calculation of entropy generation from the second law of thermodynamics in a forced convection flow, the velocity and temperature distributions are primary needed. For this purpose, the two-dimensional Cartesian coordinate system is used to solve the governing equations which are conservations of mass, momentum and energy. These equations are solved numerically using the computational fluid dynamic techniques to obtain the temperature and velocity fields, while the blocked region method is employed to simulate the inclined surface. Discretized forms of these equations are obtained by the finite volume method and solved using the SIMPLE algorithm. The numerical results are presented graphically and the effects of bleeding coefficient and recess length as the main parameters on the distributions of entropy generation number and Bejan number are investigated. Also, the effect of Reynolds number and bleeding coefficient on total entropy generation which shows the amount of flow irreversibilities is presented for two recess length. The use of present results in the design process of such thermal system would help the system attain the high performance during exploitation. Comparison of numerical results with the available data published in open literature shows a good consistency.

Numerical investigation of entropy generation in a parabolic trough receiver at different concentration ratios

This paper presents results of a numerical analysis of entropy generation in a parabolic trough receiver at different concentration ratios, inlet temperatures and flow rates. Using temperature dependent thermal properties of the heat transfer fluid, the entropy generation due to heat transfer across a finite temperature difference and entropy generation due to fluid friction in the receiver has been determined. Results show a reduction in the entropy generation rate as the inlet temperature increases and an increase in the entropy generation rate as the concentration ratio increases. Results further show that, there is an optimal flow rate at which the entropy generated is a minimum, for every combination of concentration ratio and inlet temperature. The optimal flow rates at which the entropy generated is minimum are presented for different flow rate and concentration ratio, and the results are the same irrespective of the inlet temperature considered. For the range of inlet temperatures, flow rates and concentration ratios considered, the Bejan number, which measures the contribution of entropy generation due to heat transfer irreversibility to the total entropy generation rate is about 1 at low flow rates and is between 0 and 0.24 at the highest flow rate.

Numerical Investigation of Entropy Generation in Unsteady MHD Generalized Couette Flow with Variable Electrical Conductivity

The thermodynamic second law analysis is utilized to investigate the inherent irreversibility in an unsteady hydromagnetic generalized Couette flow with variable electrical conductivity in the presence of induced electric field. Based on some simplified assumption, the model nonlinear governing equations are obtained and solved numerically using semidiscretization finite difference techniques. Effects of various thermophysical parameters on the fluid velocity, temperature, current density, skin friction, the Nusselt number, entropy generation number, and the Bejan number are presented graphically and discussed quantitatively.

Numerical investigation of entropy generation in an unsteady flow through a porous pipe with suction

This paper investigates the entropy generation rates in an unsteady flow of a variable viscosity incompressible fluid through a porous pipe with uniform suction at the surface. The nonlinear governing equations for momentum and energy balance are derived and solved numerically using a semi–implicit finite difference scheme in order to obtain the fluid velocity and temperature profiles. Numerical results for volumetric entropy generation numbers, irreversibility distribution ratio and the Bejan number are presented graphically and discussed quantitatively for various values of the embedded parameters.

Ivestigation of Entropy Generation in 3-D Laminar Forced Convection Flow over a Backward Facing Step with Bleeding

A numerical investigation of entropy generation in laminar forced convection of gas flow over a backward facing step in a horizontal duct under bleeding condition is presented. For calculation of entropy generation from the second law of thermodynamics in a forced convection flow, the velocity and temperature distributions are primary needed. For this purpose, the three-dimensional Cartesian coordinate system is used to solve the Navier-Stokes and energy equations by the computational fluid dynamic techniques. Discretized forms of these equations are obtained by the finite volume method and solved using the SIMPLE algorithm. The numerical results are presented graphically and the effects of bleeding coefficient on the distributions of entropy generation and Nusselt numbers along the duct’s wall and also on total entropy generation are presented. The numerical results can be used in design of such thermal system with high performance. Comparison of numerical results with the available data published in open literature shows a good consistency.

Analysis of Entropy Generation Due to Natural Convection in Tilted Square Cavities

In this article, the numerical investigation of entropy generation due to heat transfer irreversibility and fluid friction irreversibility during natural convection within tilted square cavity with hot wall AB, cold side walls (DA and BC), and top insulated wall (CD) has been performed. The numerical simulation has been carried out for various fluids of industrial importance (Pr = 0.015, 0.7, and 1000), Rayleigh numbers (103 ≤ Ra ≤ 105), and different inclination angles (φ = 15°, 45°, and 75°). The results are presented in terms of isotherms (θ), streamlines (ψ), entropy generation maps due to heat transfer (Sθ), and fluid friction (Sψ). The total entropy generation (Stotal), average Bejan number (Beav), and average heat transfer rate (Nu̅AB) are plotted for Rayleigh number 103 ≤ Ra ≤ 105. The maximum values of Sθ occur near the corner regions of wall AB due to a junction of hot and cold walls. On the other hand, maximum values of Sψ are found near the walls of the cavity due to friction between the circulation cells and walls of the cavity. It is found that minimum entropy generation occurs for φ ≥ 45° at convection dominant mode (Ra = 105) for lower Pr (Pr = 0.015 and 0.7). The inclined cavity with φ = 45° may be an alternative optimal inclination angle in optimal thermal processing of high Pr (Pr = 1000).

Numerical Investigation of Entropy Generation and Optimization on a Centrifugal Fan

Numerical Investigation of Entropy Generation and Optimization on a Centrifugal Fan

A numerical investigation of entropy generation in the entrance region of curved pipes at constant wall temperature

In this study, developing incompressible viscous flow and heat transfer in the curved pipes are studied numerically to analyze the entropy generation and thermodynamic optimization in the entrance region at a constant wall temperature. The governing equations including continuity, momentum and energy equations are solved using a second order finite difference method based on the projection algorithm. Entropy generation and optimal Reynolds number calculation based on the entropy generation minimization are carried out for two cases considering the two groups of non-dimensional parameters both numerically and analytically. The comparison of the numerical results in the entrance region with the analytical ones in the fully developed region indicates that both solutions predict nearly the same optimal Reynolds numbers, specially, for the first group of the non-dimensional parameters.