An Experimental Study of Radiation Heat Transfer From Parallel Plates With Direction-Dependent Properties

1970 ◽  
Vol 92 (4) ◽  
pp. 610-615 ◽  
Author(s):  
W. Z. Black ◽  
R. J. Schoenhals
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Thermal Performance ◽  
Transfer Rate ◽  
Radiation Heat Transfer ◽  
Parallel Plates ◽  
Radiation Heat ◽  
Emission Pattern ◽  
Potential Value ◽  
Radiation Properties

An experimental study of radiation heat transfer from opposing parallel plates is described. Surfaces composed of many small grooves were used to fabricate plates having direction-dependent radiation properties. These plates possessed a collimated emission pattern which was found to influence significantly the heat transfer rate, the largest observed effects being approximately 40 percent. It appears that somewhat larger alterations could be achieved with further effort. The measurements obtained in this study establish the potential value of specially prepared surfaces for certain applications requiring improved thermal performance.

Heat Transfer Enhancement of Car Radiator Using Al₂ O₃ / Water Nanofluid in the Presence of Electric Field; an Experimental Study

2020 ◽  
pp. 15-24
Author(s):  
Koorosh Goudarzi ◽  
H. Jamali ◽  
V. Kalaei
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Electric Field ◽  
Heat Transfer Enhancement ◽  
Heat Transfer Rate ◽  
Thermal Performance ◽  
Transfer Rate ◽  
Pure Water ◽  
Transfer Enhancement ◽  
Fan Speed

In this experimental study, Aluminums Oxide (Al2O3) in Pure Water (PW) as nanofluid was used for heat transfer enhancement in car radiator together with electric field. Electric field with different voltage 8, 11, 14 kV and nanofluids with volume concentrations of 0.08%, 0.5% and 1% were investigated. From the experiments, it was found that the unit with electric field pronounced better heat transfer rate, especially at low fan speed. In addition heat transfer coefficient and heat transfer rate in engine cooling system increased with the usage of nanofluids Al2O3/PW compared to Pure Water alone. With the use of nanofluid with concentration of 1% and electric field for fan speed 600 and 1200 rpm, thermal performance factors were in a range between, 1.8–3.2 and 1.6–1.74, respectively. Thermal performance factor is more than 1 in all of cases, and it can be concluded that this technique can be used in car radiators to improve heat transfer.

scholarly journals Numerical Study of Entropy Generation due to Coupled Laminar and Turbulent Mixed Convection and Thermal Radiation in an Enclosure Filled with a Semitransparent Medium

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
M. Goodarzi ◽  
M. R. Safaei ◽  
Hakan F. Oztop ◽  
A. Karimipour ◽  
E. Sadeghinezhad ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Turbulent Flow ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Numerical Study ◽  
Radiation Heat Transfer ◽  
Radiation Heat ◽  
Semitransparent Medium

The effect of radiation on laminar and turbulent mixed convection heat transfer of a semitransparent medium in a square enclosure was studied numerically using the Finite Volume Method. A structured mesh and the SIMPLE algorithm were utilized to model the governing equations. Turbulence and radiation were modeled with the RNGk-εmodel and Discrete Ordinates (DO) model, respectively. For Richardson numbers ranging from 0.1 to 10, simulations were performed for Rayleigh numbers in laminar flow (104) and turbulent flow (108). The model predictions were validated against previous numerical studies and good agreement was observed. The simulated results indicate that for laminar and turbulent motion states, computing the radiation heat transfer significantly enhanced the Nusselt number (Nu) as well as the heat transfer coefficient. Higher Richardson numbers did not noticeably affect the average Nusselt number and corresponding heat transfer rate. Besides, as expected, the heat transfer rate for the turbulent flow regime surpassed that in the laminar regime. The simulations additionally demonstrated that for a constant Richardson number, computing the radiation heat transfer majorly affected the heat transfer structure in the enclosure; however, its impact on the fluid flow structure was negligible.

scholarly journals Effect of L-shaped heat source and magnetic field on heat transfer and irreversibilities in nanofluid-filled oblique complex enclosure

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Xiao-Hong Zhang ◽  
Tareq Saeed ◽  
Ebrahem A. Algehyne ◽  
M. A. El-Shorbagy ◽  
Adel M. El-Refaey ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Nusselt Number ◽  
Low Temperature ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Weak Magnetic Field ◽  
Radiation Heat Transfer ◽  
Bejan Number ◽  
Radiation Heat

AbstractIn this paper, the natural convection heat transfer of water/alumina nanofluid is investigated in a closed square cavity. An oblique magnetic field is applied on the cavity of angle $$\gamma$$ γ . There is also radiation heat transfer in the cavity. The cavity includes a high-temperature source of L-shape. A low-temperature source as a quadrant of a circle is placed at the corner of the cavity. All other walls are well insulated. The novelty of this work is a low-temperature obstacle embedded in the cavity. Simulations are conducted with a Fortran code based on the control volume method and simple algorithm. Entropy generation rate, Bejan number, and heat transfer are studied by changing different parameters. Results indicate that the highest rates of heat transfer and entropy generation have occurred for the perpendicular magnetic field at high values of the Rayleigh number. At these Rayleigh numbers, the minimum value of the Bejan number is obtained for 15° magnetic field. The magnetic field variation can lead to a change up to 53% in Nusselt number and up to 34% in generated entropy. In a weak magnetic field, the involvement of the radiation heat transfer mechanism leads to an increase in the heat transfer rate so that the Nusselt number can be increased by ten units considering the radiation heat transfer when there is no magnetic field. The maximum heat transfer rate occurs in the horizontal cavity and the minimum value in the cavity of 60° angle. For water, these values are 10.75 and 9.98 for 0 and 60 angles, respectively. Moreover, a weak magnetic field increases the heat transfer rate in the absence of the radiation mechanism, while it is reduced by considering a strong magnetic field.

Experimental study of radiation heat transfer coefficient of diffusion flames

2007 ◽  
Vol 29 (2) ◽  
pp. 98-104
Author(s):  
Bui Van Ga ◽  
Le Van Tuy ◽  
Huynh Ba Vang ◽  
Le Van Lu ◽  
Nguyen Ngoc Linh
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Transfer Coefficient ◽  
Diesel Engine ◽  
Transfer Coefficient ◽  
Combustion Chamber ◽  
Diffusion Flames ◽  
Radiation Heat Transfer ◽  
Radiation Heat ◽  
Coefficient Of Diffusion

Basing on analysis of flame pictures given by visioscope by two-color method, the paper presents evolution of radiation heat transfer coefficient \(\varepsilon_s\) of soot in diffusion flames in air, in furnace and in combustion chamber of Diesel engine. \(\varepsilon_s\) reaches respectively its maximal value of 0.15; 0.30 and 0.45 in regions of maximal soot fraction of the three above flames.

Application of Variational Methods to Radiation Heat-Transfer Calculations

1960 ◽  
Vol 82 (4) ◽  
pp. 375-380 ◽  
Author(s):  
E. M. Sparrow
Keyword(s):  
Heat Transfer ◽  
Variational Method ◽  
Integral Equations ◽  
Radiation Heat Transfer ◽  
General Description ◽  
Parallel Plates ◽  
Radiation Heat ◽  
Transfer Problems ◽  
Plate System ◽  
Good Agreement

A variational method is presented for solving a class of integral equations which arise in radiation heat-transfer problems. First, to demonstrate the formulation of radiation problems in terms of integral equations, consideration is given to a system consisting of two nonblack, finite, parallel plates. After a general description of the variational method, its use is illustrated by application to the parallel-plate system. Comparisons are made which show very good agreement with exact solutions.

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