scholarly journals FREE CONVECTIVE HEAT TRANSFER FROM AN OBJECT AT LOW RAYLEIGH NUMBER

2013 ◽  
Vol 43 (1) ◽  
pp. 23-28
Author(s):  
Md. Golam Kader ◽  
Khandkar Aftab Hossain
Keyword(s):  
Heat Transfer ◽  
Rayleigh Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Difference Method ◽  
Vertical Direction ◽  
Large Enclosure ◽  
Uniform Grids ◽  
Heated Object ◽  
Free Convective Heat Transfer

Free convective heat transfer from a heated object in very large enclosure is investigated in thepresent work. Numerical investigation is conducted to explore the fluid flow and heat transfer behavior in thevery large enclosure with heated object at the bottom. Heat is released from the heated object by naturalconvection. Entrainment is coming from the surrounding. The two dimensional Continuity, Navier-Stokesequation and Energy equation have been solved by the finite difference method. Uniform grids are used in theaxial direction and non-uniform grids are specified in the vertical direction. The differential equations arediscretized using Central difference method and Forward difference method. The discritized equations withproper boundary conditions are sought by SUR method. It has been done on the basis of stream function andvorticity formulation. The flow field is investigated for fluid flowing with Rayleigh numbers in the range of 1.0 ?Ra ? 1.0×103 and Pr=0.71. It is observed that the distortion of flow started at Rayleigh number Ra=10. It isobserved that the average heat transfer remains constant for higher values of Reyleigh number and heatingefficiency varies with Ra upto the value of Ra=35 and beyond this value heating efficiency remains constant.DOI: http://dx.doi.org/10.3329/jme.v43i1.15775

Free Convection across Inclined Air Layers with One Surface V-Corrugated

1978 ◽  
Vol 100 (3) ◽  
pp. 410-415 ◽  
Author(s):  
S. M. ElSherbiny ◽  
K. G. T. Hollands ◽  
G. D. Raithby
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Rayleigh Number ◽  
Flat Plate ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Flat Plates ◽  
Plate Spacing ◽  
Air Layers ◽  
Free Convective Heat Transfer

Experimental measurements are presented for free convective heat transfer across inclined air layers, heated from below, and bounded by one V-corrugated plate and one flat plate. The measurements covered three values for the ratio, A, (average plate spacing to V-height), namely, A = 1, 2.5 and 4. It also covered angles of inclination with respect to the horizontal, θ, of 0, 30, 45 and 60 deg, and a range in Rayleigh number of 10 < Ra < 4 × 106. The study proves, both theoretically and experimentally, that the free convective heat transfer is essentially the same, regardless of whether the V-corrugated plate is above or below. It was found that for the same average plate spacing, L, the convective heat losses across air layers bounded by one V-corrugated and one flat plate are greater than those for two parallel flat plates by up to 50 percent for the range studied. Experimental results are given as plots of Nusselt number versus Rayleigh number. A correlation equation is given for Nusselt number, Nu, as a function of A, θ and Ra.

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