scholarly journals ANALYSIS OF ENTROPY GENERATION FOR MIXED CONVECTION FLUID FLOW IN A TRAPEZOIDAL ENCLOSURE USING THE MODIFIED BLOCKED REGION METHOD

2020 ◽  
Vol 14 (2) ◽  
pp. 97-116
Author(s):  
Meysam Atashafrooz ◽  
Mohsen Shafie
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Mixed Convection ◽  
Entropy Generation ◽  
Inclination Angle ◽  
Computational Domain ◽  
Grashof Number ◽  
Region Method ◽  
Side Walls ◽  
Trapezoidal Enclosure

In this research, analysis of entropy generation for mixed convection fluid flow in a trapezoidal enclosure is numerically investigated. To achieve this goal, the influences of Grashof number, Reynolds number and inclination angle of enclosure side walls on the distributions of the velocity and temperature fields and the values of entropy generation and Bejan numbers are examined with full details. The Boussinesq approximation is used to calculate the buoyancy force. Also, the entropy generation numbers are calculated according to the second law of thermodynamics. In addition, the modified blocked region method is applied to accurately simulate the diagonal walls of the trapezoidal enclosure. The results of numerical solution show that the maximum values of the flow irreversibility in the whole computational domain of the enclosure are related to the case with the highest values of Grashof number, Reynolds number and inclination angle of side walls.

scholarly journals Entropy generation of a hybrid nanofluid on MHD mixed convection is a lid-driven cavity with partial heating having two rounded corners

2021 ◽  
Vol 321 ◽  
pp. 02004
Author(s):  
Zakaria Korei ◽  
Smail Benissaad
Keyword(s):  
Thermal Conductivity ◽  
Reynolds Number ◽  
Mixed Convection ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Object Oriented ◽  
Reynolds Numbers ◽  
Hybrid Nanofluid ◽  
Driven Cavity ◽  
Partial Heating

This research aims to investigate thermal and flow behaviors and entropy generation of magnetohydrodynamic Al2O3-Cu/water hybrid nanofluid in a lid-driven cavity having two rounded corners. A solver based on C ++ object-oriented language was developed where the finite volume was used. Parameter’s analysis is provided by varying Reynolds numbers (Re), Hartmann numbers (Ha), the volume fraction of hybrid nanofluid (ϕ), radii of the rounded corners. The findings show that reducing the radii of the rounded corners minimizes the irreversibility. Furthermore, the thermal conductivity and dynamic viscosity of hybrid nanofluid contribute to increasing the irreversibility. Finally, the entropy generation is decreased by increasing the Hartman number and increases by rising the Reynolds number.

Second Law Analysis of Magneto-Micropolar Fluid Flow Between Parallel Porous Plates

2018 ◽  
Vol 10 (4) ◽  
Author(s):  
Abbas Kosarineia ◽  
Sajad Sharhani
Keyword(s):  
Magnetic Field ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Entropy Generation ◽  
Hartmann Number ◽  
Second Law ◽  
Brinkman Number ◽  
Viscosity Parameter ◽  
Micropolar Fluid Flow ◽  
Second Law Analysis

In this study, the influence of the applied magnetic field is investigated for magneto-micropolar fluid flow through an inclined channel of parallel porous plates with constant pressure gradient. The lower plate is maintained at constant temperature and the upper plate at a constant heat flux. The governing motion and energy equations are coupled while the effect of the applied magnetic field is taken into account, adding complexity to the already highly correlated set of differential equations. The governing equations are solved numerically by explicit Runge–Kutta. The velocity, microrotation, and temperature results are used to evaluate second law analysis. The effects of characteristic and dominate parameters such as Brinkman number, Hartmann Number, Reynolds number, and micropolar viscosity parameter are discussed on velocity, temperature, microrotation, entropy generation, and Bejan number in different diagrams. The results depicted that the entropy generation number rises with the increase in Brinkman number and decays with the increase in Hartmann Number, Reynolds number, and micropolar viscosity parameter. The application of the magnetic field induces resistive force acting in the opposite direction of the flow, thus causing its deceleration. Moreover, the presence of magnetic field tends to increase the contribution of fluid friction entropy generation to the overall entropy generation; in other words, the irreversibilities caused by heat transfer reduced. Therefore, to minimize entropy, Brinkman number and Hartmann Number need to be controlled.

Thermofluid Characteristics on Natural and Mixed Convection Heat Transfer From a Vertical Rotating Hollow Cylinder Immersed in Air: A Numerical Exercise

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Basanta Kumar Rana ◽  
Bhajneet Singh ◽  
Jnana Ranjan Senapati
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Rayleigh Number ◽  
Aspect Ratio ◽  
Mixed Convection ◽  
Hollow Cylinder ◽  
Vertical Cylinder ◽  
Cylinder Wall ◽  
Flow And Heat Transfer

Abstract Numerical investigations are performed on natural and mixed convection around stationary and rotating vertical heated hollow cylinder with negligible wall thickness suspended in the air. The fluid flow and heat transfer characterization around the hollow cylinder are obtained by varying the following parameters, namely, Rayleigh number (Ra), Reynolds number (ReD), and cylindrical aspect ratio (L/D). The heat transfer quantities are estimated by varying the Rayleigh number (Ra) from 104 to 108 and aspect ratio (L/D) ranging from 1 to 20. Steady mixed convection with active rotation of hollow vertical cylinder is further studied by varying the Reynolds number (ReD) from 0 to 2100. The velocity vectors and temperature contours are shown in order to understand the fluid flow and heat transfer around the vertical hollow cylinder for both rotating and nonrotating cases. The surface average Nusselt number trends are presented for various instances of Ra, ReD, and L/D and found out that the higher rate of heat loss from the cylinder wall occurs at high Ra, low L/D (short cylinder) and high ReD.

Numerical study of magnetic field on mixed convection and entropy generation of nanofluid in a trapezoidal enclosure

2016 ◽  
Vol 403 ◽  
pp. 133-145 ◽  
Author(s):  
Alireza Aghaei ◽  
Hossein Khorasanizadeh ◽  
Ghanbarali Sheikhzadeh ◽  
Mahmoud Abbaszadeh
Keyword(s):  
Magnetic Field ◽  
Mixed Convection ◽  
Entropy Generation ◽  
Numerical Study ◽  
Trapezoidal Enclosure

Thermal Performance With Entropy Generation Analysis of Fluid Flow in a Heat Exchanger Pipe With Single and Double Strip Helical Screw Tape Inserts

2020 ◽  
Author(s):  
Shashank Ranjan Chaurasia ◽  
R. M. Sarviya
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Heat Exchanger ◽  
Entropy Generation ◽  
Thermal Performance ◽  
Twisted Tape ◽  
Maximum Enhancement ◽  
Twist Ratio ◽  
Single Strip

Abstract In heat exchangers, twisted tape insert is a technique to enhance heat transfer. In this paper, the experimental investigation is arranged to analyse thermal performance and entropy generation analysis on fluid flow in helical screw inserts with number of strips. The Nusselt number is achieved enhancement with double strip as compared to single strip helical screw inserts at decreased values of twist ratio and increased values of flow rates. The Nusselt number is achieved maximum enhancement of 112% with double strip helical screw insert than plain tube at 4000 of Reynolds number, whereas it is found higher value at Reynolds number of 16000. The common correlations of Nusselt number and friction factor with repect of Reynolds number, number of the strips and twist ratio are generated. The entropy generation analysis is also performed. The thermal performance factor is found increment with double strip than single strip helical screw inserts at twist ratio of 2.5 and 3, whereas, it is attained maximum value of 1.5 at twist ratio 2.5 and Reynolds number of 16000 with double strip helical screw insert. The double strip helical screw inserts are suitable for reducing the size of heat exchanger, which could dercrease the size of many thermal applications as solar water heater, radiator, electronic cooling systems.

Heat transfer and entropy generation analysis of Cu-water nanofluid in a vertical channel

2018 ◽  
Vol 15 (5) ◽  
pp. 604-613
Author(s):  
Essma Belahmadi ◽  
Rachid Bessaih
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Mixed Convection ◽  
Friction Factor ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Vertical Channel ◽  
Simple Algorithm ◽  
Content Type

Purpose The purpose of this study is to analyze heat transfer and entropy generation of a Cu-water nanofluid in a vertical channel. The channel walls are maintained at a hot temperature Tw. An up flow penetrates the channel at a uniform velocity v0 and a cold temperature T0 (T0 < Tw). The effects of Reynolds number Re, Grashof number Gr and solid volume fraction ϕ on streamlines, isotherms, entropy generation, friction factor, local and mean Nusselt numbers are evaluated. Design/methodology/approach The Cu-water nanofluid is used in this study. The software Ansys-fluent 14.5, based on the finite-volume method and SIMPLE algorithm, is used to simulate the mixed convection problem with entropy generation in a vertical channel. Findings The results show that the increase of Reynolds and Grashof numbers and solid volume fraction improves heat transfer and reduces entropy generation. Correlations for the mean Nusselt number and friction factor in terms of Reynolds number and solid volume fraction are obtained. The present results are compared with those found in the literature, which reveal a very good agreement. Originality/value The originality of this work is to understand the heat transfer and entropy generation for mixed convection of a Cu-water nanofluid in a vertical channel.

Investigation of Temperature Uniformity in an Open Cavity of Buoyancy Assisted Mixed Convection Heat Transfer With Multiple Discrete Inlet and Outlet Ports

2014 ◽  
Author(s):  
G. Yang ◽  
J. Y. Wu ◽  
Y. W. He ◽  
L. Yan
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Temperature Gradient ◽  
Mixed Convection ◽  
Convection Heat Transfer ◽  
Open Cavity ◽  
Temperature Uniformity ◽  
Convection Heat ◽  
Grashof Number ◽  
Mixed Convection Heat Transfer

Turbulent buoyancy assisted mixed convection heat transfer in an open cavity with multiple discrete inlet and outlet ports is investigated experimentally. The side walls of the rectangular cavity are symmetrically heated with constant and uniform temperature. The temperature distribution in the interior of the cavity is presented and discussed for the Reynolds numbers of 3919 ≤ Re ≤ 35405, the Grashof numbers of 1.56 × 107 ≤ Gr ≤ 3.45 × 107, the Prandtl number of Pr = 0.71 and for various quantities of inlet and outlet ports ranging from 1 × 1 to 5 × 5 with the same total opening area. Increasing Reynolds number and decreasing Grashof number can improve the temperature uniformity in the cavity. As the dispersion of the inlet ports increases, the maximum temperature gradient of the fluids in the cavity is decreased while the average temperature gradient is increased. The effect of inlet/outlet forms, Reynolds number and Grashof number on the Nusselt number is also investigated.

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