Numerical analysis of laminar forced convection in concentric rotating cylinders: Entropy generation

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.

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Entropy generation analysis of laminar forced convection through uniformly heated helical coils considering effects of high length and heat flux and temperature dependence of thermophysical properties

Energy ◽

10.1016/j.energy.2015.01.041 ◽

2015 ◽

Vol 82 ◽

pp. 322-332 ◽

Cited By ~ 19

Author(s):

Mohammad Ahadi ◽

Abbas Abbassi

Keyword(s):

Heat Flux ◽

Temperature Dependence ◽

Forced Convection ◽

Entropy Generation ◽

Thermophysical Properties ◽

Helical Coils ◽

Laminar Forced Convection ◽

High Length

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Numerical Analysis of Laminar Forced Convection in Sinusoidal-Wavy-, Rounded-Ellipse-, and Rounded-Vee-Shaped Corrugated-Plate Channels

2010 14th International Heat Transfer Conference, Volume 2 ◽

10.1115/ihtc14-22082 ◽

2010 ◽

Author(s):

Dean Ferley ◽

Scott J. Ormiston

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Numerical Analysis ◽

Prandtl Number ◽

Friction Factor ◽

Forced Convection ◽

Reynolds Numbers ◽

Ansys Cfx ◽

Prandtl Numbers ◽

Laminar Forced Convection

Numerical analysis of steady, two-dimensional, laminar forced convection in corrugated-plate channels is performed using a commercial CFD code: ANSYS CFX. The flow domain consists of six modules in each of three wall corrugations: sinusoidal-wavy-shaped (SWS), rounded-ellipse-shaped (RES), and rounded-vee-shaped (RVS). One ratio of minimum-to-maximum plate spacings and one module length-to-height ratio is considered. Fluid flow and heat transfer are repeating in the modules and the results are examined in a typical module in the fully-developed region for Reynolds numbers in the range of 25 to 300 for Prandtl numbers of 0.7 (air), 2.29 (water), and 34.6 (ethylene glycol). The RES corrugation produced the highest peak value of local Nusselt number as well as the highest friction factor. The SWS corrugation produced the highest average Nusselt number, except at a Prandtl number of 34.6 at higher Reynolds number where the RES corrugation had the highest value. The RVS corrugation had the lowest friction factor for the geometric configuration considered. The highest heat transfer rate per unit pumping power was found at the highest Prandtl number for the RES corrugation.

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Entropy Generation in Thermally Developing Laminar Forced Convection Through a Slit Microchannel

ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels: Parts A and B ◽

10.1115/fedsm-icnmm2010-31070 ◽

2010 ◽

Author(s):

Arman Sadeghi ◽

Mostafa Baghani ◽

Mohammad Hassan Saidi

Keyword(s):

Forced Convection ◽

Entropy Generation ◽

Energy Equation ◽

Integral Transform ◽

Axial Coordinate ◽

Entropy Generation Number ◽

Group Parameter ◽

Laminar Forced Convection ◽

Thermal Entrance ◽

Increasing Function

The issue of entropy generation in laminar forced convection of a Newtonian fluid through a slit microchannel is analytically investigated by taking the viscous dissipation effect, the slip velocity and the temperature jump at the wall into account. Flow is considered to be hydrodynamically fully developed but thermally developing. The energy equation is solved by means of integral transform. The results demonstrate that to increase Knudsen number is to decrease entropy generation, while the effect of increasing values of Brinkman number and the group parameter is to increase entropy generation. Also it is disclosed that in the thermal entrance region the average entropy generation number over the cross section of channel is an increasing function of axial coordinate.

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