Symmetric Sink Flow and Heat Transfer Between Two Parallel Disks

2003 ◽  
Author(s):  
Marco Aure´lio dos Santos Bernardes
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Friction Factor ◽  
Volumetric Flow Rate ◽  
Internal Boundary ◽  
External Boundary ◽  
Radial Coordinate ◽  
Flow And Heat Transfer ◽  
Disk Spacing

The k-ε model are performed to investigate numerically the steady, turbulent, incompressible flow and heat transfer converging radially between two stationary disks, which is as a continuously developing flow problem under the internal boundary layer approximations. The effect of relaminarization was considered. This present study has presented a good agreement with the laminar investigation of Murphy et al [1], where no heat transfer was considered. At large values of the dimensionless radii (>> 1) the velocity profile becomes parabolic and invariant and the friction factor approaches the classic value obtained for fully developed flow between infinite plates, 24/Re0, where Re0 is an overall Reynolds number based on the volumetric flow rate and the disk spacing and is independent of radius. At radii less than one a typical external boundary layer evolves close to the wall with an approximately uniform core region, the boundary layer thickness decreases from one-half the disk spacing to values proportional to the local radii as the flow accelerates and the friction factor approaches the constant 2.17/Re0. A local Nusselt number, Nu = 230(r/R)0.650(1 − r/R)−0.386, where r is radial coordinate and R the radius of the disk, was estimated. A large overall Reynolds number was imposed and a relaminarization of the flow was observed. It was suggested that these results can be applicable for laminar and turbulent flow under Re0 = 106.

Symmetric Sink Flow Between Parallel Plates

1978 ◽  
Vol 100 (4) ◽  
pp. 477-484 ◽  
Author(s):  
H. D. Murphy ◽  
M. Coxon ◽  
D. M. McEligot
Keyword(s):  
Boundary Layer ◽  
Volumetric Flow Rate ◽  
Internal Boundary Layer ◽  
Internal Boundary ◽  
External Boundary ◽  
Parallel Plates ◽  
Fully Developed Flow ◽  
Developing Flow ◽  
Steady Laminar ◽  
Disk Spacing

Steady, laminar, incompressible flow converging radially between two stationary disks is investigated numerically as a continuously developing flow problem under the internal boundary layer approximations. At dimensionless radii much greater than one the velocity profile becomes parabolic and invariant, but at radii less than one a typical external boundary layer evolves close to the wall with an approximately uniform core region; and the boundary layer thickness decreases from one-half the disk spacing to values proportional to the local radii as the flow accelerates. At large radii the friction factor approaches the classic value obtained for fully developed flow between infinite plates, 6ν/Vt, but at small radii it approaches the constant 2.17/R0, where R0 is an overall Reynolds number based on the volumetric flow rate and the disk spacing and is independent of radius. Tabular and graphical results are provided for the intermediate range of radii, where both viscous and inertial effects are important and exact analyses are not available.

Local Flow and Heat Transfer Behavior in Convex-Louver Fin Arrays

1999 ◽  
Vol 121 (1) ◽  
pp. 136-141 ◽  
Author(s):  
N. C. DeJong ◽  
A. M. Jacobi
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Shear Layer ◽  
Local Flow ◽  
Number Range ◽  
Flow And Heat Transfer ◽  
Transfer Behavior ◽  
Strip Geometry

Local and surface-averaged measurements of convection coefficients and core pressure-drop data are provided for an array of convex-louver fins. For a Reynolds number range from 200 to 5400, these data are complemented with a flow visualization study and contrasted with new measurements from a similar offset-strip geometry. The results clarify the effects of boundary layer restarting, shear-layer unsteadiness, spanwise vortices, and separation, reattachment, and recirculation on heat transfer in the convex-louver geometry.

scholarly journals Periodically fully developed laminar flow and heat transfer in a two-dimensional horizontal channel with staggered fins

2017 ◽  
Vol 21 (6 Part A) ◽  
pp. 2443-2455 ◽  
Author(s):  
Oğuz Turgut ◽  
Kamil Arslan
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Laminar Flow ◽  
Prandtl Number ◽  
Friction Factor ◽  
Horizontal Channel ◽  
Flux Boundary Condition ◽  
Working Fluids ◽  
Flow And Heat Transfer ◽  
Smooth Channel

The 2-D periodically fully developed laminar forced convection fluid flow and heat transfer characteristics in a horizontal channel with staggered fins are investigated numerically under constant wall heat flux boundary condition. Study is performed using ANSYS Fluent 6.3.26 which uses finite volume method. Air (Pr @ 0.7) and Freon-12 (Pr @ 3.5) are used as working fluids. Effects of Reynolds number, Prandtl number, fin height, and distances between two fins on heat transfer and friction factor are examined. Results are given in the form of non-dimensional average Nusselt number and average Darcy friction factor as a function of Reynolds number for different fin distances and Prandtl numbers. The velocity and temperature profiles are also obtained. It is seen that as the fin distance increases, behavior approaches the finless channel, as expected. Also, thermal enhancement factors are given graphically for working fluids. It is seen that heat transfer dominates the friction as both the distance between two fins and Prandtl number increase. It is also seen that fins having blockage ratio of 0.10 in 2-D periodically fully developed laminar flow is not advantageous in comparison to smooth channel without fins.

Effect of Entrance Condition on Frictional Losses and Transition to Turbulence in Minichannel Flows

2004 ◽  
Author(s):  
Levi A. Campbell ◽  
Satish Kandlikar
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Friction Factor ◽  
Reynolds Numbers ◽  
Transition To Turbulence ◽  
Second Step ◽  
Flow And Heat Transfer ◽  
Small Channels

In studying the fluid flow and heat transfer in microchannels and minichannels, various claims have been made regarding transition at Reynolds numbers significantly below 2300. As a first step in identifying the reasons for such reports on early transition, the effect of entrance geometry on the pressure drop and transition to turbulence was studied in a conventional channel of 19 mm inside diameter (Kandlikar and Campbell [1]). As a second step, the effect of entrance condition on pressure drop and transition to turbulence is studied in small channels with diameters of 1.067 mm and 0.457 mm. The two entrance conditions employed for both channels are re-entrant and smooth. The experimental results show the effect of entrance condition on local friction factor, transition Reynolds number, and Hagenbach’s factor.

Single-phase fluid flow and heat transfer characteristics of nanofluid in a circular microchannel: Development of flow and heat transfer correlations

2020 ◽  
Vol 234 (18) ◽  
pp. 3689-3708 ◽  
Author(s):  
Mangal Singh Lodhi ◽  
Tanuja Sheorey ◽  
Goutam Dutta
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Friction Factor ◽  
Nanoparticle Concentration ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Circular Microchannel

The convective heat transfer in microchannels with the use of nanofluids has proved to be a potential candidate for cooling of micro-electromechanical system devices. The current research article presents the experimental study on fluid flow and heat transfer characteristics of [Formula: see text]/water nanofluid in a microchannel under thermally developing laminar flow at Reynolds number ranging from 300 to 1000. The experimental set-up of a circular microchannel test section with an inner diameter of [Formula: see text] and length of [Formula: see text] is fabricated to conduct the experimental study. The effect of nanoparticle concentration ([Formula: see text]), Reynolds number ([Formula: see text]) on fluid flow and heat transfer characteristics of [Formula: see text]/water nanofluid have been measured and compared with that of distilled water (DW). The results indicate that the maximum enhancement in local heat transfer coefficient is achieved up to [Formula: see text], while friction factor is achieved up to [Formula: see text] for [Formula: see text]/water nanofluid with nanoparticle concentration of [Formula: see text] as compared to DW. The results showed that the performance evaluation criterion of [Formula: see text]/water nanofluid is greater than unity ([Formula: see text]), implying the benefits of nanofluids as compared to DW. Moreover, the predicted data obtained by the present proposed correlations for friction factor and local Nusselt number using [Formula: see text]/water nanofluid show reasonably good agreement with the deviations of [Formula: see text] and [Formula: see text], respectively, with the numerical data as compared to the predicted data obtained by the existing correlations available in the literature.

Three-Dimensional Flow and Heat Transfer Calculations in Micro-Channel Heat Exchangers

2001 ◽  
Author(s):  
A. K. Saha ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Friction Factor ◽  
Critical Reynolds Number ◽  
Numerical Study ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Plane Channel ◽  
Micro Channel ◽  
Flow And Heat Transfer

Abstract A three-dimensional numerical study has been carried out to analyze the unsteady flow and heat transfer in a micro-channel with an array of periodically mounted square cylinders. The current geometry represents a micro-heat exchanger and has potential applications in the cooling of turbine blades and electronic cooling. The cylinder dimensions are of the order of few microns. The three-dimensional unsteady Navier-Stokes and energy equations are solved using higher order temporal and spatial discretizations. The simulations have been carried out for a range of Reynolds number based on cylinder width (180–600) and a Prandtl number of 6.99. Conjugate heat transfer calculations have been employed to account for the conduction in the solid cylinder and convection in the fluid. The flow is found to become unsteady at a critical Reynolds number that falls between 250 and 400. The flow shows quasi-periodic behavior with multiple frequencies at a Reynolds number of 400. The heat transfer enhancement compared to a plane channel is marginal (1.1–1.4 times) for the steady flow cases whereas it is significant (12–15 times) when the flow is unsteady. The friction factor was found to decrease with Reynolds number in both the steady and unsteady regimes. However, the friction factor increases at the critical Reynolds number where it becomes unsteady in nature.

scholarly journals Effects of Reynolds number, baffle angle, and baffle distance on three-dimensional turbulent flow and heat transfer in a circular pipe

2015 ◽  
Vol 19 (5) ◽  
pp. 1633-1648 ◽  
Author(s):  
Oguz Turgut ◽  
Erkan Kizilirmak
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Friction Factor ◽  
Thermal Performance ◽  
Three Dimensional ◽  
Circular Pipe ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

In this study, steady-state three-dimensional turbulent forced convection flow and heat transfer characteristics in a circular pipe with baffles attached inside pipe have been numerically investigated under constant wall heat flux boundary condition. Numerical study has been carried out for Reynolds number Re of 3000-50,000, Prandtl number Pr of 0.71, baffle distances s/D of 1, 2, and 3, and baffle angle a of 30o-150o. Ansys Fluent 12.0.1 software has been used to solve the flow field. It is observed that circular pipe having baffles has a higher Nusselt number and friction factor compared to the smooth circular pipe without baffles. Maximum Nusselt number and friction factor are obtained for the baffle angle of 90o. Nusselt number increases while baffle distance increases in the range of studied; however, friction factor decreases. Periodically fully developed conditions are obtained after a certain module. Thermal performance factor increases with increasing baffle distance in the rage of studied but decreases with increasing Reynolds number; maximum thermal performance factor is obtained for the baffle angle of 150?. Results show that baffle distance, baffle angle, and Reynolds number play important role on both flow and heat transfer characteristics. The accuracy of the results obtained in this study is verified by comparing the results with those available in the literature for smooth circular pipes. All the numerical results are correlated within accuracy of ?10 and ?15% for average Nusselt number and Darcy friction factor, respectively.

Flow and Heat Transfer in Microchannels of the MTPV Systems

2012 ◽  
Vol 614-615 ◽  
pp. 181-185
Author(s):  
Ge Ping Wu ◽  
Ping Lu
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
Flow Characteristics ◽  
Rod Bundles ◽  
Flow And Heat Transfer ◽  
Microchannel Cooling ◽  
Volume Method

Heat transfer and flow characteristics in the microchannel cooling passages with three different types of the MTPV systems are numerically investigated. This investigation covers Reynolds number in the range of 100 to 1000 and heat flux ranged from 50kW/m2 to 150kW/m2. The steady, laminar flow and heat transfer equations are solved in a finite-volume method. Results such as temperature distribution, heat transfer coefficient, pressure drop and friction factor are reported. A comparison of the heat transfer coefficient and friction factor of the different microchannels are also presented. The heat transfer performance of the rod bundles microchannel is found to be much better than others. Both friction factor and heat transfer coefficient are increased as the Reynolds number increased.

Effect of Entrance Condition on Frictional Losses and Transition to Turbulence

2002 ◽  
Author(s):  
Satish G. Kandlikar ◽  
Levi A. Campbell
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Friction Factor ◽  
Closed Loop ◽  
Reynolds Numbers ◽  
Transition To Turbulence ◽  
Flow And Heat Transfer ◽  
Inner Diameter

In studying the fluid flow and heat transfer in microchannels, various claims have been made regarding transition at Reynolds numbers significantly below 2300. As a first step in identifying the reasons for such early transition, the effect of entrance geometry on the pressure drop and transition to turbulence is studied experimentally in a conventional channel of 1.9 cm inner diameter. Four types of entrance conditions have been studied with flow of oil in a closed loop. The experimental results show the effect of entrance conditions on local friction factor, hydrodynamic developing length, and transition Reynolds number. The study will be extended to microchannels in the future.

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