scholarly journals Natural Convection Heat Transfer From Arrays of Isothermal Triangular Fins in Air

1994 ◽  
Vol 116 (1) ◽  
pp. 105-111 ◽  
Author(s):  
A. Karagiozis ◽  
G. D. Raithby ◽  
K. G. T. Hollands
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Transfer Performance ◽  
Large Range ◽  
Convection Heat Transfer ◽  
Base Plate ◽  
Single Equation ◽  
Vertical Orientation ◽  
Nusselt Numbers ◽  
Vertical Base

Measurements of the heat transfer to air by natural convection from arrays of isothermal triangular fins on a vertical base plate are reported for several array geometries, for a large range of Rayleigh number, and for two orientations (vertical fins and horizontal fins). The data are believed to be the first available for this important geometry. A single equation is provided that correlates the measured Nusselt numbers for the vertical orientation with an rms error of 4.8 percent. The horizontal fin orientation was shown to have inferior heat transfer performance.

Numerical Studies on Natural Convection Heat Transfer – Fins with Closed Top

2014 ◽  
Vol 592-594 ◽  
pp. 1682-1686 ◽  
Author(s):  
C. Balachandar ◽  
S. Arunkumar ◽  
M. Venkatesan
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Convection Heat Transfer ◽  
Base Plate ◽  
Plate Temperature ◽  
Ansys Fluent ◽  
Numerical Studies ◽  
Vertical Base

Fins are extended surfaces provided to enhance the heat transfer rate of a system. Several attempts have been made in the past to augment the heat transfer rate by using fins of various geometries. In the present study an array of rectangular fins with closed top, standing on a vertical base is analysed under natural convection conditions using commercial CFD code ANSYS FLUENT©. The numerical model is validated with the available experimental results for fins with open top under natural convection conditions. The plate fin heat sink is analysed for a constant heat duty of 60 W. The height, thickness and length of the fins are taken to be constant throughout the analysis. A detailed study is carried out to examine the dependency of the base plate temperature on the thickness of the closed top and on the number of fins. It is concluded based on the analysis that heat fins with closed top are found to have a decreased base plate temperature compared to the conventional rectangular fins.

scholarly journals Effect of an axial hole on natural convection heat transfer from a cylindrical pin fin attached to a horizontal plate

2018 ◽  
Vol 22 (6 Part A) ◽  
pp. 2493-2502
Author(s):  
Saurav Manna ◽  
Subhas Haldar ◽  
Subrata Ghosh
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Convection Heat Transfer ◽  
Base Plate ◽  
Hole Diameter ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Horizontal Plate ◽  
Pin Fin ◽  
Laminar Natural Convection

Heat transfer under laminar natural convection from a hollow cylindrical fin mounted on a horizontal base plate has been numerically studied. The flow outside the fin is much stronger than that inside the hole and as a consequence the rate of heat transfer from a hollow fin is primarily due to the contribution by the outer surface of the fin. Fortunately, the rate of heat transfer is not negatively affected by the presence of the hole at the fin centre. On the contrary, when the Grashof number is higher or the hole diameter is bigger, the inside surface contributes marginally to the heat transfer. A hollow fin saves material and weighs less compared to a solid fin. So, this feature may be exploited.

scholarly journals Heat Transfer Performance of Different Fluids During Natural Convection in Enclosures with Varying Aspect Ratios

2021 ◽  
Vol 287 ◽  
pp. 03010
Author(s):  
Rajashekhar Pendyala ◽  
Suhaib Umer Ilyas ◽  
Yean Sang Wong
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Heat Transfer Performance ◽  
Convection Heat Transfer ◽  
Heat Transfer Process ◽  
Natural Convection Heat Transfer ◽  
Transfer Performance ◽  
Convection Heat ◽  
Aspect Ratios

The heat transfer process takes place in numerous applications through the natural convection of fluids. Investigations of the natural convection heat transfer in enclosures have gained vital importance in the last decade for the improvement in thermal performance and design of the heating/cooling systems. Aspect ratios (AR=height/length) of the enclosures are one of the crucial factors during the natural convection heat transfer process. The investigated fluids consisting of air, water, engine oil, mercury, and glycerine have numerous engineering applications. Heat transfer and fluid flow characteristics are studied in 3-dimensional rectangular enclosures with varying aspect ratios (0.125 to 150) using computational fluid dynamics (CFD) simulations. Studies are carried out using the five different fluids having Prandtl number range 0.01 to 4500 in rectangular enclosures with the hot and cold surface with varying temperature difference 20K to 100K. The Nusselt number and heat transfer coefficients are estimated at all conditions to understand the dependency of ARs on the heat transfer performance of selected fluids. Temperature and velocity profiles are compared to study the flow pattern of different fluids during natural convection. The Nusselt number correlations are developed in terms of aspect ratio and Rayleigh number to signify the natural convection heat transfer performance.

scholarly journals Experimental Observation of Natural Convection Heat Transfer Performance of a Rectangular Thermosyphon

Energies ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1702 ◽  
Author(s):  
C. S. Huang ◽  
Chia-Wang Yu ◽  
R. H. Chen ◽  
Chun-Ta Tzeng ◽  
Chi-Ming Lai
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Transfer Performance ◽  
Thermal Power ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Transfer Performance ◽  
Convection Heat ◽  
Heating Section ◽  
Cooling Section

This study experimentally investigates the natural convection heat transfer performance of a rectangular thermosyphon with an aspect ratio of 3.5. The experimental model is divided into a loop body, a heating section, a cooling section, and two adiabatic sections. The heating section and the cooling section are located in the vertical legs of the rectangular loop. The length of the vertical heating section and the length of the upper and lower horizontal insulation sections are 700 mm and 200 mm, respectively, and the inner diameter of the loop is 11 mm. The relevant parameters and their ranges are as follows: the input thermal power is 30–60 W (with a heat flux in the range of 60–3800 W/m2); the temperature in the cooling section is 30, 40, or 50 °C; and the potential difference between the hot and cold sections is 5, 11, or 18 for the cooling section lengths of 60, 45, and 30 cm, respectively. The results indicate that the value of the dimensionless heat transfer coefficient, the Nusselt number, is generally between 5 and 10. The heating power is the main factor affecting the natural convection intensity of the thermosyphon.

An Experimental Study of Natural Convection in a Vertical Cavity With Discrete Heat Sources

1988 ◽  
Vol 110 (3) ◽  
pp. 616-624 ◽  
Author(s):  
M. Keyhani ◽  
V. Prasad ◽  
R. Cox
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Flow Visualization ◽  
Vertical Wall ◽  
Convection Heat Transfer ◽  
Cold Wall ◽  
Onset Of Convection ◽  
Flow Cells ◽  
Nusselt Numbers ◽  
Vertical Cavity

Natural convection heat transfer in a tall vertical cavity (aspect ratio = 16.5), with one isothermal vertical cold wall, and eleven alternately unheated and flush-heated sections of equal height on the opposing vertical wall, is experimentally investigated. The flow visualization pictures for the ethylene glycol–filled cavity reveal a flow pattern consisting of primary, secondary, and tertiary flows. The heat transfer data and the flow visualization photographs indicate that the stratification is the primary factor influencing the temperature of the heated sections. This behavior persists for all the runs where the secondary flow cells cover a large vertical extend of the cavity. Based on the analysis of the photographs it is suggested that the turbulent flow should be expected when the local modified Rayleigh number is in the range of 9.3×1011 to 1.9×1012. It is found that discrete flush-mounted heating in the enclosure results in local Nusselt numbers that are nearly the same as those reported for a wide flush-mounted heater on a vertical plate. This is believed to be due to the fact that the present problem is inherently unstable, and the smallest temperature difference between a heated section and the cold wall results in the onset of convection motion.

A Study on Improving in Natural Convection Heat Transfer for Heat Sink of High Power LEDs

2011 ◽  
Vol 383-390 ◽  
pp. 6834-6839 ◽  
Author(s):  
Xiang Rui Meng ◽  
Xin Ling Ma ◽  
Ji Fu Lu ◽  
Xin Li Wei
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Sink ◽  
Heat Transfer Performance ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Transfer Performance ◽  
Stagnation Zone ◽  
Convection Heat ◽  
Symmetry Center

In this paper the natural convection heat transfer performance of horizontal heat sink was studied by numerical simulation and experiment. The numerical simulation results show that there are some interesting features in the flow field of heat sink model. 1) Among the fins, the air vertically flows only through the fins in the symmetry center of heat sink while it horizontally flows through the fins in other area. 2) There is an air stagnation zone located at the fin root in the symmetry center of heat sink. These features both caused the decrease in heat transfer temperature difference and heat transfer area in fact. The natural convection heat transfer performance of heat sink is affected at last. In order to eliminate the air stagnation zone and change in the flow way of air, some holes were perforated at the fin root. These holes play its role. In this test, the heat transfer power of heat sink with seven holes has increased by 16.7% compared with the prototype.With the increase in the number of holes, the natural convection heat transfer power of heat sink also increases. But when the number of holes reaches to a value, the increase in the number of holes will not function properly.

Effect of Surface Radiation on Conjugate Natural Convection in a Square Enclosure with a Tube at Different Locations

2013 ◽  
Vol 281 ◽  
pp. 190-196 ◽  
Author(s):  
Jian Sheng Wang ◽  
Yong Xu
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Transfer Performance ◽  
Convection Heat Transfer ◽  
Surface Radiation ◽  
Square Enclosure ◽  
Conjugate Natural Convection ◽  
Different Temperatures ◽  
Vertical Walls ◽  
Effect Of Surface

The conjugate natural convection heat transfer with and without the interaction of the surface radiation in a square enclosure was carried out by numerical simulation. The vertical walls of the square enclosure were heated with different temperatures, and the others were adiabatic. A circular tube was inserted into the square enclosure. It was observed that varied location of the tube center can lead to different motion and heat transfer intensities. In addition, surface radiation reduces the convective heat transfer in the square enclosure compared to the pure natural convection case and enhances the overall heat transfer performance.

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