scholarly journals Effect of wall proximity in fluid flow and heat transfer from a square prism placed inside a wind tunnel

2007 ◽  
Vol 11 (4) ◽  
pp. 65-78 ◽  
Author(s):  
Dipes Chakrabarty ◽  
Ranajit Brahma
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Drag Coefficient ◽  
Average Nusselt Number ◽  
Pressure Coefficient ◽  
Angle Of Attack ◽  
Height Ratio ◽  
Flow And Heat Transfer ◽  
Square Prism ◽  
Wall Proximity

Experimental investigations in fluid flow and heat transfer have been carried out to study the effect of wall proximity due to flow separation around square prisms. Experiments have been carried out for the Reynolds number 4.9?104, blockage ratios are 0.1, 0.2, 0.3 and 0.4, different height-ratios, and various angles of attack. The static pressure distribution has been measured on all faces of the square prisms. The results have been presented in the form of pressure coefficient, drag coefficient for various height-ratios and blockage ratios. The pressure distribution shows positive values on the front face whereas on the rear face negative values of the pressure coefficient have been observed. The positive pressure coefficient for different height-ratios does not vary too much but the negative values of pressure coefficient are higher for all points on the surface as the bluff body approaches towards the upper wall of the wind tunnel. The drag coefficient decreases with the increase in angle of attack as the height-ratio decreases. The maximum value of drag coefficient has been observed at an angle of attack nearly 50? for square prism at all height-ratios. The heat transfer experiments have been carried out under constant heat flux condition. Heat transfer coefficients are determined from the measured wall temperature and ambient temperature, and presented in the form of Nusselt number. Both local and average Nusselt numbers have been presented for various height-ratios. The variation of local Nusselt number has been shown with non-dimensional distance for different angles of attack and blockage ratios. The variation of average Nusselt number has also been shown with different angles of attack for blockage ratios. The local as well as average Nusselt number decreases as the height-ratio decreases for all non-dimensional distance and angle of attack for square prisms. The average Nusselt number for square prisms of different blockage ratio varies with the angle of attack. But there is no definite angle of attack at different block- age ratio at which the value of average Nusselt number is either maximum or minimum.

scholarly journals Mixed convection heat transfer from a heated circular cylinder

2019 ◽  
Vol 54 (1) ◽  
pp. 83-88
Author(s):  
H Laidoudi ◽  
M Bouzit
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Drag Coefficient ◽  
Average Nusselt Number ◽  
Convection Heat Transfer ◽  
Circular Cylinders ◽  
Governing Equations ◽  
Thermal Buoyancy ◽  
Flow And Heat Transfer ◽  
Mixed Convection Heat Transfer

This paper performs the effects of thermal buoyancy and the triangular arrangement of circular cylinders on fluid flow and heat transfer within a horizontal channel, the governing equations involving continuity; momentum and energy are solved in two-dimensional, laminar and steady flow regime. The average Nusselt number and drag coefficient are computed for the range of these conditions: Ri = 0 to 2 at fixed value of Pr = 1, Reynolds number Re = 30 and geometrical configurations (blockage ratio of β = 0.1). In order to observe the flow structure and temperature field under the gradual effect of thermal buoyancy, the streamlines and isotherm contours are illustrated. It is found that, a gradual increase in the value of buoyancy strength creates an asymmetrical flow around the cylinders. Interesting variations of drag coefficient and average Nusselt number are plotted with respect to Richardson number for each cylinder. Bangladesh J. Sci. Ind. Res.54(1), 83-88, 2019

Forced convection heat transfer study of a blunt-headed cylinder in non-Newtonian power-law fluids

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jaspinder Kaur ◽  
Roderick Melnik ◽  
Anurag Kumar Tiwari
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Drag Coefficient ◽  
Power Law ◽  
Average Nusselt Number ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Total Drag ◽  
Shear Thinning Fluids ◽  
Power Law Fluids

Abstract In this present work, forced convection heat transfer from a heated blunt-headed cylinder in power-law fluids has been investigated numerically over the range of parameters, namely, Reynolds number (Re): 1–40, Prandtl number (Pr): 10–100 and power-law index (n): 0.3–1.8. The results are expressed in terms of local parameters, like streamline, isotherm, pressure coefficient, and local Nusselt number and global parameters, like wake length, drag coefficient, and average Nusselt number. The length of the recirculation zone on the rear side of the cylinder increases with the increasing value of Re and n. The effect of the total drag coefficient acting on the cylinder is seen to be higher at the low value of Re and its effect significant in shear-thinning fluids (n < 1). On the heat transfer aspect, the rate of heat transfer in fluids is increased by increasing the value of Re and Pr. The effect of heat transfer is enhanced in shear-thinning fluids up to ∼ 40% and it impedes it’s to ∼20% shear-thickening fluids. In the end, the numerical results of the total drag coefficient and average Nusselt number (in terms of J H −factor) have been correlated by simple expression to estimate the intermediate value for the new application.

Heat Transfer, Fluid Flow, and Pressure Measurements Inside a Rotating Two-Pass Duct With Detached 90-Deg Ribs

2003 ◽  
Vol 125 (3) ◽  
pp. 565-574 ◽  
Author(s):  
Tong-Miin Liou ◽  
Meng-Yu Chen ◽  
Yu-Ming Wang
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Rotation Number ◽  
Pressure Coefficient ◽  
Heat Transfer Fluid ◽  
Laser Doppler Velocimeter ◽  
Height Ratio ◽  
Mean Velocity ◽  
Transfer Velocity

Transient thermochromic liquid crystal thermography, a laser-Doppler velocimeter, and pressure transducers have been used to measure the local heat transfer, velocity, and wall static-pressure distributions, respectively, in a rotating two-pass square duct with 90-deg ribs detached from the leading and trailing walls. The ribs were square in cross-section and their detached-distance/height ratio was 0.38. The rib-height/duct-height ratio and the pitch/rib-height ratio were 0.136 and 10, respectively. The duct Reynolds number was 1×104 and rotation number ranged from 0 to 0.2. Results are compared with attached rib cases in terms of regional averaged Nusselt number, transverse mean velocity component, pressure coefficient distributions and variation of friction factor with rotation number. The competition between convection effect of the wall jet and downwash effect of the rib-top separated shear layer on the heat transfer augmentation is addressed in detail. Discussion on local Nusselt number distribution, mean velocity components, and turbulent kinetic energy is included. Simple expressions are obtained to correlate friction factor with rotation number. Rib detachment is found to enhance heat transfer on the leading wall of the first outward pass and on the trailing wall of the second inward pass over as compared to the attached rib case. The trend is reversed on the other two walls. Nevertheless, detached ribs create more uniform heat transfer distributions on the leading and trailing walls than attached ribs.

Numerical investigation of heat transfer and hydrodynamics for in-line drop-shaped tubes bundle

2020 ◽  
pp. 42-59
Author(s):  
R. Deeb ◽  
◽  
A.V. Kolotvin ◽  
Keyword(s):  
Heat Transfer ◽  
Software Package ◽  
Average Nusselt Number ◽  
Numerical Study ◽  
Pressure Coefficient ◽  
Equivalent Diameter ◽  
Heat Transfer Characteristics ◽  
Circular Tubes ◽  
The Third ◽  
Flow And Heat Transfer

A numerical study using the software package ANSYS has been conducted to investigate fluid flow and heat transfer characteristics for in-line drop-shaped and circular tubes bundles in crossflow. Reynolds number based on equivalent diameter varied in range of 3x103 ≤ Re ≤ 18.7x103. The longitudinal spacing SL= 37, 46.25 mm, while the transversal spacing ST =37 mm. A mathematical and numerical model has been developed for numerical evaluation of heat transfer and hydrodynamic of a studied bundles. The distribution of the pressure coefficient over a half surface of the circular and drop-shaped tubes of the third row was obtained. Correlations of the average Nusselt number and the friction coefficient for the studied bundles in terms of Re were presented. Results showed that pressure coefficient and heat transfer of drop-shaped tubes depend on position of tubes in tubes bundle. The thermal–hydraulic performance of the drop-shaped tubes bundle is about 1,45~ 2,01 и 1,45~ 2,01 times greater than the circular one for SL= 37, 46.25 mm, respectively.

Buoyancy Driven Flow, Heat Transfer and Entropy Generation Characteristics for Different Heater Geometries Placed in Cryogenic Liquid: A CFD Study

2021 ◽  
pp. 1-20
Author(s):  
Someshwar Ade ◽  
Sushil Rathore
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Entropy Generation ◽  
Heat Generation ◽  
Average Nusselt Number ◽  
Cryogenic Liquid ◽  
Heat Generation Rate ◽  
Heat Transfer Characteristics ◽  
Flow And Heat Transfer

Abstract The present work reports 3D computational study of buoyancy driven flow and heat transfer characteristics for a localized heater (analogous to superconductor) submerged in cryogenic liquid nitrogen in an enclosure. Seven different heater geometries are considered and the effect of heater geometry on flow and heat transfer characteristics are illustrated. The heater is generating heat at a constant rate (W/m3). Continuity, momentum and energy equations are solved using finite volume method. Liquid flow and heat transfer features are demonstrated with the help of velocity vector and temperature contours. Rayleigh number, average Nusselt number, maximum vertical velocity of fluid flow, average velocity of fluid flow are the parameters which are considered for comparing seven different geometries of heater. Additionally, an analysis of the entropy generation owing to transfer of heat and friction due to fluid flow are reported. Furthermore, the dependency of average Nusselt number, maximum velocity of fluid, entropy generation owing to transfer of heat and fluid friction as a function of heat generation rate is illustrated graphically. The results of this study indicate that heater geometry can considerably affect the transfer of heat, fluid flow features and entropy generation under same heat generation rate in the heater. Highest average Nusselt number on heater surface is obtained when heater geometry is circular; whereas lowest value of total entropy generation in the domain is obtained when heater geometry is equilateral triangle.

scholarly journals Free convection of a nanofluid in a square cavity with a heat source on the bottom wall and partially cooled from sides

2014 ◽  
Vol 18 (suppl.2) ◽  
pp. 283-300 ◽  
Author(s):  
Mostafa Mahmoodi ◽  
Arani Abbasian ◽  
Sebdani Mazrouei ◽  
Saeed Nazari ◽  
Mohammad Akbari
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Rayleigh Number ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Heat Sinks ◽  
Square Cavity ◽  
Flow And Heat Transfer ◽  
Rayleigh Numbers

The problem of free convection fluid flow and heat transfer in a square cavity with a flush mounted heat source on its bottom wall and two heat sinks on its vertical side walls has been investigated numerically. Via changing the location of the heat sinks, six different arrangements have been generated. The cavity was filled with Cu-water nanofluid. The governing equations were discretized using the finite volume method and SIMPLER algorithm. Using the developed code, a parametric study was undertaken, and effects of Rayleigh number, arrangements of the heat sinks and volume fraction of the nanoparticles on fluid flow and heat transfer inside the cavity were investigated. Also for the middle-middle heat sinks arrangement, capability of five different water based nanofluids on enhancement of the rate of heat transfer was examined and compared. From the obtained results it was found that the average Nusselt number, for all six different arrangements of the heat sinks, was an increasing function of the Rayleigh number and the volume fraction of the nanoparticles. Also it was found that at high Rayleigh numbers, maximum and minimum average Nusselt number occurred for middle-middle and top-bottom arrangement, respectively. Moreover it was found that for the middle-middle arrangement, at high Rayleigh numbers, maximum and minimum rate of heat transfer was obtained by Cu-water and TiO2-water nanofluids respectively.

scholarly journals Mixed convection inside nanofluid filled rectangular enclosures with moving bottom wall

2011 ◽  
Vol 15 (3) ◽  
pp. 889-903 ◽  
Author(s):  
Mostafa Mahmoodi
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Mixed Convection ◽  
Richardson Number ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Flow And Heat Transfer ◽  
Simpler Algorithm ◽  
Horizontal Wall

The mixed convection fluid flow and heat transfer in lid-driven rectangular enclosures filled with the Al2O3-water nanofluid is investigated numerically. The left and the right vertical walls as well as the top horizontal wall of the enclosure are maintained at a constant cold temperature Tc. The bottom horizontal wall of the enclosure, which moves from left to right, is kept at a constant hot temperature Th, with Th>Tc. The governing equations written in terms of the primitive variables are solved using the finite volume method and the SIMPLER algorithm. Using the developed code, a parametric study is performed and the effects of the Richardson number, the aspect ratio of the enclosure and the volume fraction of the nanoparticles on the fluid flow and heat transfer inside the enclosure are investigated. The results show that at low Richardson numbers, a primary counterclockwise vortex is formed inside the enclosure. More over it is found that for the range of the Richardson number considered, 10-1-101, the average Nusselt number of the hot wall, increases with increasing the volume fraction of the nanoparticles. Also it is observed that the average Nusselt number of the hot wall of tall enclosures is more that to that of the shallow enclosures.

Heat Transfer, Fluid Flow, and Pressure Measurements Inside a Rotating Two-Pass Duct With Detached 90° Ribs

2002 ◽  
Author(s):  
Tong-Miin Liou ◽  
Meng-Yu Chen ◽  
Yu-Ming Wang
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Rotation Number ◽  
Pressure Coefficient ◽  
Heat Transfer Fluid ◽  
Laser Doppler Velocimeter ◽  
Height Ratio ◽  
Mean Velocity ◽  
Transfer Velocity

Transient thermochromic liquid crystal thermography, a laser-Doppler velocimeter, and pressure transducers have been used to measure the local heat transfer, velocity, and wall static-pressure distributions, respectively, in a rotating two-pass square duct with 90° ribs detached from the leading and trailing walls. The ribs were square in cross-section and their detached-distance/height ratio was 0.38. The rib-height/duct-height ratio and the pitch/rib-height ratio were 0.136 and 10, respectively. The duct Reynolds number was 1×104 and rotation number ranged from 0 to 0.2. Results are compared with attached rib cases in terms of regional averaged Nusselt number, transverse mean velocity component, pressure coefficient distributions and variation of friction factor with rotation number. The competition between convection effect of the wall jet and downwash effect of the rib-top separated shear layer on the heat transfer augmentation is addressed in detail. Discussion on local Nusselt number distribution, mean velocity components, and turbulent kinetic energy is included. Simple expressions are obtained to correlate friction factor with rotation number. Rib detachment is found to enhance heat transfer on the leading wall of the first outward pass and on the trailing wall of the second inward pass over as compared to the attached rib case. The trend is reversed on the other two walls. Nevertheless, detached ribs create more uniform heat transfer distributions on the leading and trailing walls than attached ribs.

scholarly journals Numerical Investigation of Flow and Heat Transfer over a Shallow Cavity: Effect of Cavity Height Ratio

Fluids ◽  
2021 ◽  
Vol 6 (7) ◽  
pp. 244
Author(s):  
Salem S. Abdel Aziz ◽  
Abdel-Halim Saber Salem Said
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Average Nusselt Number ◽  
Flow Behavior ◽  
Cavity Flow ◽  
Bottom Wall ◽  
Recirculation Region ◽  
Height Ratio ◽  
Shallow Cavities ◽  
Shallow Cavity

Flow over shallow cavities is used to model the flow field and heat transfer in a solar collector and a variety of engineering applications. Many studies have been conducted to demonstrate the effect of cavity aspect ratio (AR), but very few studies have been carried out to investigate the effect of cavity height ratio (HR) on shallow cavity flow behavior. In this paper, flow field structure and heat transfer within the 3-D shallow cavity are obtained numerically for two height ratio categories: HR = 0.0, 0.25, 0.5, 0.75, and 1.0 and HR = 1.25, 1.5, 1.75, 2.0, 2.25, and 2.5. The governing equations, continuity, momentum, and energy are solved numerically and using the standard (K-ε) turbulence model. ANSYS FLUENT 14 CFD code is used to perform the numerical simulation based on the finite volume method. In this study, the cavity aspect ratio, AR = 5.0, and Reynolds number, Re = 3 × 105, parameters are fixed. The cavity’s bottom wall is heated with a constant and uniform heat flux (q = 740 W/m2), while the other walls are assumed to be adiabatic. For the current Reynolds number and cavity geometry, a single vortex structure (recirculation region) is formed and occupies most of the cavity volume. The shape and location of the vortex differ according to the height ratio. A reverse velocity profile across the recirculation region near the cavity’s bottom wall is shown at all cavity height ratios. Streamlines and temperature contours on the plane of symmetry and cavity bottom wall are displayed. Local static pressure coefficient and Nusselt number profiles are obtained along the cavity’s bottom wall, and the average Nusselt number for various height ratios is established. The cavity height ratio (HR) is an important geometry parameter in shallow cavities, and it plays a significant role in the cavity flow behavior and heat transfer characteristics. The results indicate interesting flow dynamics based on height ratio (HR), which includes a minimal value in average Nusselt number for HR ≈ 1.75 and spatial transitions in local Nusselt number distribution along the bottom wall for different HRs.

scholarly journals Numerical study of flow and heat transfer in differentially heated enclosures

2014 ◽  
Vol 18 (2) ◽  
pp. 451-463 ◽  
Author(s):  
Byong-Hoon Chang
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Average Nusselt Number ◽  
Numerical Study ◽  
Two Dimensional ◽  
Flow And Heat Transfer ◽  
Aspect Ratios ◽  
Heated Air ◽  
Side Walls ◽  
Laminar Natural Convection

Two-dimensional laminar natural convection is studied numerically for differentially heated air-filled rectangular enclosures with adiabatic side walls and aspect ratios of 1, 2, 4 and 8. The inclination angle of the enclosure was varied from 0? to 180?, and the effect of inclination on flow field and heat transfer was investigated over the range 103 ? Ra ? 106. Correlations of average Nusselt number based on the present results are presented for horizontal and vertical cases. Large discrepancies were found among published results.

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