Natural Convection Heat Transfer From an Array of Rectangular Protrusions in an Enclosure Filled With Dielectric Liquid

1994 ◽  
Vol 116 (2) ◽  
pp. 138-147 ◽  
Author(s):  
Y. Joshi ◽  
M. D. Kelleher ◽  
M. Powell ◽  
E. I. Torres
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Vertical Wall ◽  
Convection Heat Transfer ◽  
Dielectric Liquid ◽  
Bottom Surface ◽  
Surface Boundary ◽  
Electronic Packages ◽  
Number Range ◽  
Surface Boundary Conditions

An experimental investigation of natural convection liquid immersion cooling of a three by three array of rectangular protrusions in an enclosure is presented. The heated elements geometrically simulated 20 pin dual-inline electronic packages and were mounted on a plexiglass substrate, which formed one vertical wall of a dielectric liquid filled rectangular enclosure. The remaining vertical boundaries of the enclosure were insulated, while the top and bottom were maintained at prescribed temperatures using individual heat exchanger plates. Protrusion surface temperatures in steady state are reported for a range of power dissipation levels for three fluorinert liquids spanning a Prandtl number range from about 20 to 1400. The influence of enclosure top and bottom surface boundary conditions and its width on element temperatures is investigated. Non-dimensional heat transfer results are empirically correlated. Changes in component temperatures due to partial powering of the array are also measured.

Natural Convection Heat Transfer in a Rectangular Liquid Metal Pool With Bottom Heating and Top Cooling

2006 ◽  
Author(s):  
Il S. Lee ◽  
Yong H. Yu ◽  
Hyoung M. Son ◽  
Jin S. Hwang ◽  
Kune Y. Suh
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Liquid Metal ◽  
Convection Heat Transfer ◽  
Bottom Surface ◽  
Natural Convection Heat Transfer ◽  
Metal Pool ◽  
Convection Heat ◽  
Integral System ◽  
Bottom Heating

An experimental study is performed to investigate the natural convection heat transfer characteristics with subcooled coolant to create engineering database for basic applications in a lead alloy cooled reactor. Tests are performed in the ALTOS (Applied Liquid-metal Thermal Operation Study) apparatus as part of MITHOS (Metal Integrated Thermo Hydrodynamic Operation System). A relationship is determined between the Nusselt number Nu and the Rayleigh number Ra in the liquid metal rectangular pool. Results are compared with correlations and experimental data in the literature. Given the similar Ra condition, the present test results for Nu of the liquid metal pool with top subcooling are found to be similar to those predicted by the existing correlations or experiments. The current test results are utilized to develop natural convection heat transfer correlations applicable to low Prandtl number Pr fluids that are heated from below and cooled by the external coolant above. Results from this study are slated to be used in designing BORIS (Battery Optimized Reactor Integral System), a small lead cooled modular fast reactor for deployment at remote sites cycled with MOBIS (Modular Optimized Brayton Integral System) for electricity generation, tied with NAVIS (Naval Application Vessel Integral System) for ship propulsion, joined with THAIS (Thermochemical Hydrogen Acquisition Integral System) for hydrogen production, and coupled with DORIS (Desalination Optimized Reactor Integral System) for seawater desalination. Tests are performed with Wood’s metal (Pb-Bi-Sn-Cd) filling a rectangular pool whose lower surface is heated and upper surface cooled by forced convection of water. The test section is 20 cm long, 11.3 cm high and 15 cm wide. The simulant has a melting temperature of 78°C. The constant temperature and heat flux condition was realized for the bottom heating once the steady state had been met. The test parameters include the heated bottom surface temperature of the liquid metal pool, the input power to the bottom surface of the section, and the coolant temperature.

Natural Convection Heat Transfer Characteristics of Flat Plate Enclosures

1979 ◽  
Vol 101 (1) ◽  
pp. 120-125 ◽  
Author(s):  
K. R. Randall ◽  
J. W. Mitchell ◽  
M. M. El-Wakil
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Aspect Ratio ◽  
Tilt Angle ◽  
Convection Heat Transfer ◽  
Transfer Coefficients ◽  
Number Range ◽  
Grashof Number ◽  
Average Heat ◽  
Plate Spacing

Heat transfer by natural convection in rectangular enclosures has been experimentally studied using interferometric techniques. The effects of Grashof number, tilt angle, and aspect ratio on both the local and average heat transfer coefficients have been determined. The Grashof number range tested was 4 × 103 to 3.1 × 105, and the aspect ratio (ratio of enclosure length to plate spacing) varied between 9 and 36. The angles of tilt of the enclosure with respect to the horizontal were 45, 60, 75 and 90 deg. Correlations are developed for both local and average Nusselt number over the range of test variables. The effect of tilt angle is found to reduce the average heat transfer by about 18 percent from the value of 45 deg to that at 90 deg. No significant effect of aspect ratio over the range tested was found. A method for characterizing the flow regimes that is based on heat transfer mechanisms is proposed.

Natural Convection Heat Transfer From a Plate in a Semicircular Enclosure

1992 ◽  
Vol 114 (1) ◽  
pp. 121-126 ◽  
Author(s):  
G. A. Moore ◽  
K. G. T. Hollands
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Plate Thickness ◽  
Fluid Motion ◽  
Convection Heat Transfer ◽  
Bulk Fluid ◽  
Number Range ◽  
Balance Technique ◽  
Conductive Component

In the subject geometry, a long thin plate at uniform temperature is contained coaxially and symmetrically in a long semicircular trough closed at the top and having a uniform but different temperature. Heat flows across the air-filled region between the two by both natural convection and gaseous conduction. The problem of characterizing the free convective component of this heat transfer—that is, the component caused by bulk fluid motion—is treated experimentally by using a heat balance technique, with the measurements being repeated at different pressures, in order to cover a wide Rayleigh number range, from Ra ≈ 10 to Ra ≈ 108. Nusselt number versus Rayleigh number plots are presented for each of several combinations of plate-to-trough spacing and tilt angle, and the plots are correlated by equations. The problem of characterizing the conductive component is treated by numerically solving the steady diffusion equation in the air-filled region, and the results are correlated as a function of the spacing and the plate thickness.

scholarly journals Simulation of Natural Convection Heat Transfer in a 2-D Trapezoidal Enclosure

2019 ◽  
Vol 16 (4) ◽  
pp. 7375-7390 ◽  
Author(s):  
K. Venkatadri ◽  
S. Abdul Gaffar ◽  
Ramachandra Prasad V. ◽  
B. Md. Hidayathulla Khan ◽  
O. Anwar Beg
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Prandtl Number ◽  
Vertical Wall ◽  
Convection Heat Transfer ◽  
Side Wall ◽  
Practical Applications ◽  
Wide Range ◽  
Trapezoidal Enclosure

Natural convection within trapezoidal enclosures finds significant practical applications. The natural convection flows play a prominent role in the transport of energy in energyrelated applications, in case of proper design of enclosures to achieve higher heat transfer rates. In the present study, a two-dimensional cavity with adiabatic right side wall is studied. The left side vertical wall is maintained at the constant hot temperature and the top slat wall is maintained at cold temperature. The dimensionless governing partial differential equations for vorticity-stream function are solved using the finite difference method with incremental time steps. The parametric study involves a wide range of Rayleigh number, Ra, 103 ≤ Ra ≤ 105 and Prandtl number (Pr = 0.025, 0.71 and 10). The fluid flow within the enclosure is formed with different shapes for different Pr values. The flow rate is increased by enhancing the Rayleigh number (Ra = 104 ). The numerical results are validated with previous results. The governing parameters in the present article, namely Rayleigh number and Prandtl number on flow patterns, isotherms as well as local Nusselt number are reported. 

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.

Experiments and Theory on Natural Convection Heat Transfer From Bodies of Complex Shape

1985 ◽  
Vol 107 (3) ◽  
pp. 624-629 ◽  
Author(s):  
M. J. Chamberlain ◽  
K. G. T. Hollands ◽  
G. D. Raithby
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Complex Shape ◽  
Convection Heat Transfer ◽  
Average Error ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Transient Method ◽  
Number Range

Measurements of the heat transfer by natural convection from isothermal bodies to air are reported and compared to the predictions of the method proposed by Raithby and Hollands [7, 8]. The bodies tested were the cube in various orientations and a body consisting of two touching spheres (a bisphere). The experimental Rayleigh number range extended from 10 to 107. The experimental method incorporated measuring the heat transfer by the transient method and varying the Rayleigh number by varying the pressure. The predictions agreed with the measurements to within an average error of about 3 percent. The results are correlated by single equations, which can be extended to fluids other than air.

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