Three-dimensional natural convection in finned cubical enclosures (original) (raw)
Related papers
Heat transfer enhancement in cubical enclosures with vertical fins
Applied Thermal Engineering, 2007
Natural convection of air in a cubical enclosure with a thick partition fitted vertically on the hot wall is numerically investigated for Rayleigh numbers of 10 3-10 6. A three dimensional convective circulation is generated, in which the cold flow sweeps the fin faces and the hot wall, with low flow blockage. The combined contributions of these faces cause heat transfer enhancements over 40% at high Rayleigh numbers and thermal conductivity ratios (R k). These enhancements significantly exceed the ones obtained with horizontal fins. Even low R k values cause heat transfer enhancements, except at Ra = 10 4 .
CFD Analysis of Heat Transfer and Flow Characteristics in A 3D Cubic Enclosure
IJMER
Flow arising “naturally” from the effect of density difference, resulting from temperature or concentration difference in a body force field such as gravity, the process is termed as natural convection. There has been growing interest in buoyancy-induced flows and the associated heat and mass transfer over the past three decades, because of the importance of these flows in many different areas such as cooling of electronic equipment, pollution, materials processing, energy systems and safety in thermal processes. Steady state laminar natural convection in a cubic enclosure with a cold vertical wall and two square heaters with constant temperature on the opposite wall is studied numerically. The enclosure is fitted with various liquids. Three-dimensional Navier Stokes equations are solved by employing SIMPLE algorithm. Computations are performed for a range of Rayleigh number from 104 to 107 while enclosure aspect ratio varies from 0.1 to 1.25. The effects of Rayleigh number, enclosure aspect ratio, and Prandtl number on heat transfer characteristics are studied in detail. The results show that the flow field is very complex and heat transfer from the two heaters is not the same. The effect of Prandtl number is negligible in the range 5 to 100 with other parameters kept constant. This allows the use of liquids such as water for studying other dielectric liquids, provided the flow geometry and other non-dimensional parameters are similar. The overall Nusselt number increased markedly with Rayleigh Number. It is also affected by enclosure aspect ratio.
Thermal Science, 2014
In the present paper, natural convection fluid flow and heat transfer in a square cavity heated from below and cooled from sides and the ceiling with a thin fin attached to its hot bottom wall is investigated numerically. The right and the left walls of the cavity, as well as its horizontal top wall are maintained at a constant temperature T c , while the bottom wall is kept at a constant temperature T h ,with T h > T c. The governing equations are solved numerically using the finite volume method and the couple between the velocity and pressure fields is done using the SIMPLER algorithm. A parametric study is performed and the effects of the Rayleigh number and the length of the fin on the flow pattern and heat transfer inside the cavity are investigated. Two competing mechanisms that are responsible for the flow and thermal modifications are observed. One is the resistance effect of the fin due to the friction losses which directly depends on the length of the fin, whereas the other is due to the extra heating of the fluid that is offered by the fin. It is shown that for high Rayleigh numbers, placing a hot fin at the middle of the bottom wall has more remarkable effect on the flow field and heat transfer inside the cavity.
Challenges in Nano and Micro Scale Science and Technology, 2019
This investigation is a three dimensional comprehensive heat transfer analysis for partially differentially heated enclosure with the vertical fin mounted on the hot wall. The thermal lattice Boltzmann based on D3Q19 method is utilized to illustrate the effects of vertical fins and nanoparticles on the flow and thermal fields. The effects of Rayleigh number and different arrangement of fins on the fluid flow and heat transfer have been scrutinized. The streamlines and isotherms and Nusselt number along the hot wall are illustrated for 104<Ra<108 and nanoparticles volume fraction 0.01<φ6 and two fins in Ra =104), the average Nu could be increased by more than 60%, but the effect of using the nanofluids (φ=0.03, Cuo/Water) is less than 30%. So arrangement of fins and nanofluids (φ=0.03, Cuo/Water) effects improve the heat transfer mechanism in the cubical enclosure.
Heat transfer increase with thin fins in three dimensional enclosures
WIT Transactions on Engineering Sciences, 2010
Heat transfer enhancement with highly conductive, thin vertical fins attached to the hot wall of a differentially heated cubical enclosure is numerically investigated. Two such fins attached to the hot wall were found to promote heat transfer enhancements of over 40% with respect to the unfinned case at Ra = 10 5-10 7. This is one of the highest enhancements found to date in cavities of low aspect ratio. At a Rayleigh number of 10 8 , enhancements were lower, suggesting that this Rayleigh number marks the upper utilization limit of fins in enclosures to promote heat transfer. Results show that for further heat transfer optimization, sensitivity to variables as the fin thickness and length should be studied.
Natural Convection at Different Prandtl Numbers in Rectangular Cavities with a Fin on the Cold Wall
The natural convection in differentially heated rectangular cavities with a fin attached to the cold wall was investigated numerically. The top and the bottom horizontal walls of the cavities were insulated while their left and the right vertical walls were maintained at a constant temperature Th and Tc, respectively with Th > Tc. The governing equations written in terms of the primitive variables were solved numerically using the finite volume method while the velocity and pressure fields were coupled using the SIMPLER algorithm. Using the developed code effects of pertinent parameters such as length and location of fin, aspect ratio of the enclosure, Rayleigh number, and Prandtl number on heat transfer and fluid flow in the enclosure were investigated. The results showed that for the cavity filled with water, at high Rayleigh numbers, a longer fin placing at the middle of the right wall has more remarkable effect on the heat transfer inside the cavity. Also, it was observed tha...
2014
In this article an experimental investigation is made to predict the performance of heated triangular fin array within a vertically oriented and air filled rectangular enclosure. The experimental analysis is done to analyze the effects of several influencing parameters for their wide ranges; Rayleigh number 295214 ≤ Ra ≤ 773410, fin spacing 25 mm ≤ S ≤ 100 mm and fin height 12.5 mm ≤ L ≤ 37.5 mm for constant heat flux boundary conditions at the heated and cooled walls of the enclosure. An empirical correlation is also developed relating Nusselt number to several influencing parameters.
Effect of length and inclination of a thin fin on natural convection in a square enclosure
2006
A numerical investigation of steady, laminar, natural convective fluid flow in a square enclosure with an inclined heated thin fin of arbitrary length attached to the hot wall is considered. A transverse temperature gradient is applied on two opposing walls of the enclosure, while the other two walls are adiabatic. Attachment of highly conductive inclined thin fins with lengths equal to 20%, 35%, and 50% of the side, positioned in the middle of the hot left wall of the enclosure, is examined. The problem is formulated in terms of the vorticity-stream function procedure. A numerical solution based on the finite-volume method is obtained. Representative results illustrating the effects of the thin-fin inclination angle and length on the streamlines and temperature contours within the enclosure are reported. In addition, results for the local and average Nusselt numbers at the heated wall of the enclosure are presented and discussed for various parametric conditions. It is found that the Rayleigh number and the thin-fin inclination angle and length have significant effects on the average Nusselt number of the heated wall including the fin of the enclosure.
Heat Transfer Research, 2011
Fluid flow and natural convection heat transfer in a differentially heated square cavity with a fin attached to its cold wall is investigated numerically. The top and the bottom horizontal walls of the cavity are insulated while the left and right vertical walls of the cavity are maintained at a constant temperature T h and T c , with T h > T c , respectively. The governing equations written in terms of the primitive variables are solved numerically using the finite volume method and the SIMPLER algorithm. Using the developed code, a parametric study is performed, and the effects of the Rayleigh number, length of the fin and its position on the flow pattern and heat transfer inside the enclosure are investigated. The results show that for high Rayleigh numbers, a longer fin placing at the middle of the right wall has a more remarkable effect on the flow field and heat transfer inside the cavity.
Effects of fin on mixed convection heat transfer in a vented square cavity: A numerical study
Mağallaẗ al-qādisiyyaẗ li-l-ʻulūm al-handasiyyaẗ, 2023
Numerical investigation of mixed convective in a vented square cavity with fin. The horizontal walls are adiabatic, while the left and right walls are hot (ℎ) and cold () temperatures, respectively. The fluid inlet to the cavity from the lower left open area(), and exits from the upper right open area (). In this study, a finite element scheme is employed. The analysis is done for specific Prandtl number (= 7), Reynolds number (50 ≤ ≤ 200), fin length (0.2 ≤ ≤ 0.6), Richardson number (0.1 ≤ ≤ 1), and the location of the fin (0.2 ≤ ℎ ≤ 0.6). The finding indicates that the increases when high the location of the fin increases at the maximum height of this fin location is estimated to be 17% due to an increase in the fluid flow area on the hot wall caused by rising convective. The highest heat transfer occurs when the fin length equals 0.6 at the location(ℎ = 0.2).