Forced Convection in a Uniformly Heated Enclosure: Effect of the Inlet and Two Outlet Port Locations

2007 ◽  
Author(s):  
A. I. Botello-Arredondo ◽  
A. Hernandez-Guerrero ◽  
C. Rubio-Arana ◽  
M. Picon-Nun˜ez
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Temperature Fields ◽  
Transfer Enhancement ◽  
Square Cavity ◽  
Maximum Heat ◽  
Number Range ◽  
Outlet Port ◽  
Maximum Heat Transfer ◽  
Effective Design

In an earlier study, Saeidi and Khodadadi presented results on forced convection inside a square cavity with one inlet and one outlet ports. Their most effective design showed maximum heat transfer and minimum pressure drop for a particular location of the ports. In the present study a cavity with one inlet and two outlet ports is considered, and different conditions and geometric arrays for the position of the ports are analyzed. The cold incoming fluid is heated by the isothermal hot walls. The outlet ports are positioned at forty-five different locations on the walls. A Reynolds number range of 10 < Re < 500 is considered, clearly within the laminar regimen. The flow and temperature fields are obtained as part of the solution. As expected, an increment of vorticity brought a heat transfer enhancement. The effect of the outlet ports and their location is discussed.

Forced Convection in a Uniformly Heated Enclosure With Different Aspect Ratios: Effect of the Inlet and Two Outlet Port Locations

2008 ◽  
Author(s):  
A. I. Botello-Arredondo ◽  
A. Hernandez-Guerrero ◽  
C. Rubio-Arana ◽  
M. Pen˜a-Taveras
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Forced Convection ◽  
Flow Behavior ◽  
Temperature Fields ◽  
Transfer Enhancement ◽  
Number Range ◽  
Outlet Port ◽  
Aspect Ratios

This paper presents a numerical investigation on forced convection in a cavity with one inlet and two outlet ports. For the present study three different aspect ratios between height (H) and length (L), (H ≠ L)were considered (AR = H/L), AR = 1, 1.3 and 2.5. Different conditions and geometric arrays for the position of the ports are analyzed. The walls of the cavity are considered to be isothermal warming-up the incoming cold fluid. A Reynolds number range of 10 < Re < 500 is considered, clearly within the laminar regimen. The flow and temperature fields are obtained as part of the solution. As expected, the aspect ratio affects the flow behavior in the cavity. An increment of vorticity leads to a heat transfer enhancement. The different aspect ratios of the cavity and the effect of the outlet ports and their location are discussed.

scholarly journals Development of Forced Convection Heat Transfer Enhancement System by using Mesh Inserts in a Circular Tube

2021 ◽  
Author(s):  
Avinash D. Sapkal ◽  
Akash A Pawar ◽  
Shridhar V Kulkarni ◽  
Umesh B Andh ◽  
Digambar T Kashid ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Flow Rate ◽  
Test Section ◽  
Circular Tube ◽  
Convection Heat Transfer ◽  
Transfer Enhancement ◽  
Measure Flow Rate ◽  
Maximum Heat ◽  
Maximum Heat Transfer

In the present work, aluminium mesh type inserts flow has been developed. The aluminium meshes are arranged on spokes at the angle of 00, 450, 900 concerning horizontal are inserted in the test section to create turbulence. To carry out an experimental investigation using this mesh inserts, we have developed a forced convection system. In this system, we have wounded three 200 Volt heaters over a 500 mm test section of 25 mm diameter respectively. The input to the heater is controlled by a variable dimmer stat, and the mass flow rate is controlled by an orifice meter with a diameter of 25 mm across which the manometer is connected to measure flow rate. Experiments were carried out at Reynolds number greater than 4000. The experimental setup was validated first and readings with different inserts were taken. This led to the conclusion that the rate of heat transfer was improved by using mesh inserts inclined at an angle 00, 450, and 900. Among these, the inserts inclined at 450 angles showed maximum heat transfer rate i.e., 37.44%, 29.95%, and 38.40% for the manometric reading of 5 mm, 4 mm, and 3 mm respectively.

Forced Convection in a Square Cavity With Inlet and Outlet Ports

2004 ◽  
Author(s):  
S. M. Saeidi ◽  
J. M. Khodadadi
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Forced Convection ◽  
Computational Study ◽  
Temperature Fields ◽  
Primary Vortex ◽  
Square Cavity ◽  
Outlet Port ◽  
Nusselt Numbers ◽  
The Right

A finite-volume-based computational study of steady laminar forced convection inside a square cavity with inlet and outlet ports is presented. Given a fixed position of the inlet port, the location of outlet port is varied along the four walls of the cavity. The widths of the ports are equal to 5, 15 and 25 percent of the side. By positioning the outlet ports at 9 locations on the walls for Re = 10, 40, 100 and 500 and Pr = 5, a total of 101 cases were studied. For high Re and with the shortest distance between the inlet and outlet ports along the top wall, a primary CW rotating vortex that covers about 70 to 80 percent of the cavity is observed. Similar cases with smaller Re exhibit identical flow patterns but with weaker vortices as Re is lowered. As the outlet ports is lowered along the right wall, the CW primary vortex diminishes its strength; however a CCW vortex that is present next to the top right corner covers a greater portion of the cavity. With the outlet port moving left along the bottom wall, the CW primary vortex is weakened further and the CCW vortex occupies nearly the right half of the cavity. The temperature fields are directly related to the presence of the multiple vortices in the cavity. Regions of high temperature gradient are consistently observed at the interface of the throughflow and next to the solid walls on both sides of the outlet port. Local Nusselt numbers are low at 3 corners when no outlet port is present in their vicinity, whereas intense heat transfer rate is observed on the two sides of the outlet port. Between these minima and maxima, the local Nusselt number can vary drastically depending on the flow and temperature fields. By placing the outlet port with one end at the 3 corners, maximum total Nusselt number of the cavity can be achieved. Minimum total heat transfer of the cavity is achieved with the outlet port located at the middle of the walls.

Enhancement of Natural Convection Heat Transfer by a Staggered Array of Discrete Vertical Plates

1980 ◽  
Vol 102 (2) ◽  
pp. 215-220 ◽  
Author(s):  
E. M. Sparrow ◽  
C. Prakash
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Transfer Enhancement ◽  
Parallel Plate ◽  
Convection Heat Transfer ◽  
Transfer Enhancement ◽  
Enhanced Heat Transfer ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Parameter Ranges

An analysis has been performed to determine whether, in natural convection, a staggered array of discrete vertical plates yields enhanced heat transfer compared with an array of continuous parallel vertical plates having the same surface area. The heat transfer results were obtained by numerically solving the equations of mass, momentum, and energy for the two types of configurations. It was found that the use of discrete plates gives rise to heat transfer enhancement when the parameter (Dh/H)Ra > ∼2 × 103 (Dh = hydraulic diameter of flow passage, H = overall system height). The extent of the enhancement is increased by use of numerous shorter plates, by larger transverse interplate spacing, and by relatively short system heights. For the parameter ranges investigated, the maximum heat transfer enhancement, relative to the parallel plate case, was a factor of two. The general degree of enhancement compares favorably with that which has been obtained in forced convection systems.

A Numerical Study of Heat Transfer Enhancement by a Rectangular Cylinder Placed Parallel to the Heated Wall

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
J. F. Derakhshandeh ◽  
Md. Mahbub Alam
Keyword(s):  
Heat Transfer ◽  
Vortex Dynamics ◽  
Numerical Study ◽  
Vortex Street ◽  
Heated Wall ◽  
Transfer Enhancement ◽  
Maximum Heat ◽  
Single Row ◽  
Rectangular Cylinder ◽  
Maximum Heat Transfer

The flow around a rectangular cylinder mounted in the vicinity of a hot wall is numerically studied at a Reynolds number of 200. While the cylinder chord-to-height ratio C/W is varied from 2 to 10, the gap distance G from the wall to the cylinder is changed from 0.25 to 6.25. The focus of this study is given on the dependence of G/W and C/W on the heat transfer from the wall and associated physics. The variation in the Strouhal number is presented as a function of C/W. It is observed that the effect of G/W on the vortex dynamics and heat transfer is much more than that of C/W. Based on the dependence of the vortex dynamics and heat transfer on G/W, we have identified four distinct flows: no vortex street flow (G/W < 0.75), single-row vortex street flow (0.75 ≤ G/W ≤ 1.25), inverted two-row vortex street flow (1.25 < G/W ≤ 2.5), and two-row vortex street flow (G/W > 2.5). At the single-row vortex street flow, the two opposite-sign vortices appearing in a jetlike flow carry heat from the wall to the wake and then to the freestream. The maximum heat transfer is achieved at the single-row vortex street flow and 8% increase occurs at C/W = 2, G/W = 0.75–1.25.

Study of Flow and Convective Heat Transfer in a Simulated Scaled Up Low Emission Annular Combustor

2011 ◽  
Vol 3 (3) ◽  
Author(s):  
Sunil Patil ◽  
Teddy Sedalor ◽  
Danesh Tafti ◽  
Srinath Ekkad ◽  
Yong Kim ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convective Heat ◽  
Swirling Flow ◽  
Numerical Study ◽  
Swirl Number ◽  
Maximum Heat ◽  
Number Range ◽  
Maximum Heat Transfer ◽  
Annular Combustor

Modern dry low emissions (DLE) combustors are characterized by highly swirling and expanding flows that makes the convective heat load on the gas side difficult to predict and estimate. A coupled experimental–numerical study of swirling flow inside a DLE annular combustor model is used to determine the distribution of heat transfer on the liner walls. Three different Reynolds numbers are investigated in the range of 210,000–840,000 with a characteristic swirl number of 0.98. The maximum heat transfer coefficient enhancement ratio decreased from 6 to 3.6 as the flow Reynolds number increased from 210,000 to 840,000. This is attributed to a reduction in the normalized turbulent kinetic energy in the impinging shear layer, which is strongly dependent on the swirl number that remains constant at 0.98 for the Reynolds number range investigated. The location of peak heat transfer did not change with the increase in Reynolds number since the flow structures in the combustors did not change with Reynolds number. Results also showed that the heat transfer distributions in the annulus have slightly different characteristics for the concave and convex walls. A modified swirl number accounting for the step expansion ratio is defined to facilitate comparison between the heat transfer characteristics in the annular combustor with previous work in a can combustor. A higher modified swirl number in the annular combustor resulted in higher heat transfer augmentation and a slower decay with Reynolds number.

scholarly journals Investigation of the novelty of latent functionally thermal fluids as alternative to nanofluids in natural convective flows

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Zoubida Haddad ◽  
Farida Iachachene ◽  
Eiyad Abu-Nada ◽  
Ioan Pop
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Enhancement ◽  
Volume Fraction ◽  
Heat Of Fusion ◽  
Transfer Enhancement ◽  
Maximum Heat ◽  
Thermal Fluids ◽  
Maximum Heat Transfer ◽  
Wide Range

AbstractThis paper presents a detailed comparison between the latent functionally thermal fluids (LFTFs) and nanofluids in terms of heat transfer enhancement. The problem used to carry the comparison is natural convection in a differentially heated cavity where LFTFs and nanofluids are considered the working fluids. The nanofluid mixture consists of Al2O3 nanoparticles and water, whereas the LFTF mixture consists of a suspension of nanoencapsulated phase change material (NEPCMs) in water. The thermophysical properties of the LFTFs are derived from available experimental data in literature. The NEPCMs consist of n-nonadecane as PCM and poly(styrene-co-methacrylic acid) as shell material for the encapsulation. Finite volume method is used to solve the governing equations of the LFTFs and the nanofluid. The computations covered a wide range of Rayleigh number, 104 ≤ Ra ≤ 107, and nanoparticle volume fraction ranging between 0 and 1.69%. It was found that the LFTFs give substantial heat transfer enhancement compared to nanofluids, where the maximum heat transfer enhancement of 13% was observed over nanofluids. Though the thermal conductivity of LFTFs was 15 times smaller than that of the base fluid, a significant enhancement in thermal conductivity was observed. This enhancement was attributed to the high latent heat of fusion of the LFTFs which increased the energy transport within the cavity and accordingly the thermal conductivity of the LFTFs.

Numerical Prediction of Fluid Flow and Heat Transfer in the Target System of an Axisymmetric Accelerator-Driven Subcritical System

2006 ◽  
Vol 129 (4) ◽  
pp. 582-588 ◽  
Author(s):  
K. Arul Prakash ◽  
G. Biswas ◽  
B. V. Rathish Kumar
Keyword(s):  
Heat Transfer ◽  
Turbulent Flows ◽  
Thermal Conditions ◽  
Temperature Fields ◽  
Target System ◽  
Fe Method ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Target Module ◽  
Subcritical System

Thermal hydraulics related to the design of the spallation target module of an accelerator-driven subcritical system (ADSS) was investigated numerically using a streamline upwind Petrov-Galerkin (SUPG) finite element (FE) method. A large amount of heat is deposited on the window and in the target during the course of nuclear reaction between the proton beam and the molten lead-bismuth eutectic (LBE) target. Simulations were carried out to predict the characteristics of the flow and temperature fields in the target module with a funnel-shaped flow guide and spherical bottom of the container. The beam window was kept under various thermal conditions. The analysis was extended to the case of heat generation in the LBE. The principal purpose of the analysis was to trace the temperature distribution on the beam window and in the LBE. In the case of turbulent flows, the number of recirculation regions is decreased and the maximum heat transfer was found to take place downstream of the stagnation zone on the window.

An Experimental Investigation of Heat Transfer Enhancement by Pulsating Laminar Flow in a Triangular Grooved Channel

2012 ◽  
Vol 516-517 ◽  
pp. 249-252 ◽  
Author(s):  
Bing Chang Yang ◽  
Dong Xu Jin
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Strouhal Number ◽  
Enhancement Factor ◽  
Pulsating Flow ◽  
Transfer Enhancement ◽  
Maximum Heat ◽  
Pulsation Amplitude ◽  
Maximum Heat Transfer

Heat transfer enhancement by pulsating flow in a triangular grooved channel has been experimentally investigated. Effects of Reynolds number Re, Strouhal number St, pulsation amplitude A on the heat transfer enhancement were studied. The experimental results show that, the pulsating flow can significantly enhance heat transfer compared to the steady flow case, for instance, an enhancement of 115% is achieved at Re=400, A=0.5 and St=0.3. There exists an optimal Strouhal number corresponding to the maximum heat transfer enhancement factor. The heat transfer enhancement factor increases with the increase of Reynolds number and pulsation amplitude.

Heat Transfer Enhancement in Turbulent Ribbed-Pipe Flow

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Changwoo Kang ◽  
Kyung-Soo Yang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Pipe Flow ◽  
Joint Probability ◽  
Turbulent Heat Transfer ◽  
Immersed Boundary ◽  
Turbulent Heat ◽  
Transfer Enhancement ◽  
Maximum Heat ◽  
Maximum Heat Transfer

The present study aims at explaining why heat transfer is enhanced in turbulent ribbed-pipe flow, based on our previous large eddy simulation (LES) database (Kang and Yang, 2016, “Characterization of Turbulent Heat Transfer in Ribbed Pipe Flow,” ASME J. Heat Transfer, 138(4), p. 041901) obtained for Re = 24,000, Pr = 0.71, pitch ratio (PR) = 2, 4, 6, 8, 10, and 18, and blockage ratio (BR) = 0.0625. Here, the bulk velocity and the pipe diameter were used as the velocity and length scales, respectively. The ribs were implemented in the cylindrical coordinate system by means of an immersed boundary method. In particular, we focus on the cases of PR ≥ 4 for which heat transfer turns out to be significantly enhanced. Instantaneous flow fields reveal that the vortices shed from the ribs are entrained into the main recirculating region behind the ribs, inducing velocity fluctuations in the vicinity of the pipe wall. In order to identify the turbulence structures responsible for heat transfer enhancement in turbulent ribbed-pipe flow, various correlations among the fluctuations of temperature and velocity components have been computed and analyzed. The cross-correlation coefficient and joint probability density distributions of velocity and temperature fluctuations, obtained for PR = 10, confirm that temperature fluctuation is highly correlated with velocity-component fluctuation, but which component depends upon the axial location of interest between two neighboring ribs. Furthermore, it was found via the octant analysis performed for the same PR that at the axial point of the maximum heat transfer rate, O3 (cold wallward interaction) and O5 (hot outward interaction) events most contribute to turbulent heat flux and most frequently occur.

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