Convective Heat Transfer in a Liquid Saturated Porous Layer

1976 ◽  
Vol 43 (2) ◽  
pp. 249-253 ◽  
Author(s):  
R. J. Buretta ◽  
A. S. Berman
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Upper Bound ◽  
Heat Sources ◽  
Onset Of Convection ◽  
Saturated Porous Layer ◽  
Rayleigh Numbers ◽  
Heating From Below ◽  
Good Agreement

The convective heat transfer in fluid saturated porous beds either heated from below or heated by distributed sources is investigated for several bed thicknesses and permeabilities. For the case of heating from below Rayleigh numbers range from about 10–10,000. For distributed heat sources Rayleigh numbers range from about 10–1000. Critical Rayleigh numbers for the onset of convection are estimated as 38 for heating from below and 31.8 for distributed heat sources. Heat transfer results for convection induced by heating from below are in good agreement with analytical upper bound estimates obtained by Gupta and Joseph.

An Experimental and Numerical Analysis of Natural Convective Heat Transfer in a Square Cavity With Five Discrete Heat Sources

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Giorgia Nardini ◽  
Massimo Paroncini ◽  
Raffaella Vitali
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Cavity Wall ◽  
Heat Sources ◽  
Square Cavity ◽  
Bottom Cavity ◽  
Vertical Walls ◽  
Rayleigh Numbers ◽  
Vertical Cavity

This paper provides an experimental and numerical investigation of natural convection in a square cavity. The square cavity is full of air (Pr = 0.71) and contains four heat sources of height hW, positioned symmetrically on the vertical walls of the cavity with a fifth heat source of height hB, located in the center of the bottom cavity wall. Two configurations are analyzed for Rayleigh numbers ranging from 1.00 × 104 to 1.00 × 105: configuration 1 has four cold sources located on the vertical cavity wall and configuration 2 has two hot and two cold sources located on the vertical cavity walls. An analysis of the holographic interferograms, numerical isotherms, streamlines, and velocity maps obtained demonstrates an increased development of natural convective heat transfer in configuration 1.

scholarly journals The Natural Convective Heat Transfer in a Partially Divided Enclosure: A Study on the Influence of the Source Position

2009 ◽  
Vol 2009 ◽  
pp. 1-10 ◽  
Author(s):  
Francesco Corvaro ◽  
Massimo Paroncini
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Dynamic Behaviour ◽  
Velocity Fields ◽  
Source Position ◽  
Square Enclosure ◽  
Nusselt Numbers ◽  
First Case ◽  
Rayleigh Numbers

The aim of this paper is to analyse the natural convective heat transfer generated by a source with a height of located in two different positions inside a square enclosure of side . In the first case, is 0.5 of while in the second case it is 0.4. The comparison is based both on the evaluation of the local and average Nusselt numbers at different Rayleigh numbers and on the study of the velocity fields at the same Rayleigh numbers in the two different configurations. The experimental analysis was carried out through a holographic interferometry, to study the heat transfer, and through a 2D-PIV system, to analyse the dynamic behaviour of the phenomenon. Finally, for = 0.5 we compared the experimental results with those obtained through the volume finite software Fluent 6.3.26. In the analysis, it is possible to see that the position of the source influences both the average Nusselt numbers on the hot surfaces and the development of a small bubble on the upper surface.

scholarly journals An interferometric study of free convective heat transfer at an indoor glazing with an insect screen attachment

2021 ◽  
Author(s):  
Daniel Zalcman
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Flow Simulation ◽  
Cfd Models ◽  
Interferometric Study ◽  
Set Up ◽  
Screen Temperature ◽  
Good Agreement ◽  
Free Convective Heat Transfer

Free convective heat transfer from an idealized window with an insect screen attachment was studied using a Mach-Zehnder interferometer. An experimental model was set up with an isothermal plate, two commercially available screens (KHP=8.74×10-9 m2, tHP=0.29 mm and KLP=3.40×10-9 m2, tLP=0.65 mm) and window to screen spacings of b=2 cm and b=1 cm. Heat transfer measurements using finite fringe interferograms were taken at a Rayleigh number of Ra=5.30×107 based on window height. Infinite fringe interferograms were taken for temperature field visualization. Screen temperature was also measured. Experimental results were compared to a preliminary CFD model developed with SolidWorks Flow Simulation and show good agreement. The results show that an insect screen produces a reduction in the convective heat transfer from the indoor glazing. The current measurements show that the effect of window to screen spacing is small. Results from this study are expected to be used for the validation of CFD models and for the development of correlations.

Natural Convective Heat Transfer Through a Liquid Between a Heated Horizontal Surface and a Vertical Fin Attached to a Cooled Surface

1999 ◽  
Author(s):  
Patrick H. Oosthuizen
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Prandtl Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Lower Surface ◽  
Horizontal Surface ◽  
Finite Element Procedure ◽  
Liquid Depth ◽  
Rayleigh Numbers

Abstract Natural convective heat transfer from a heated horizontal surface directly exposed to a liquid into which vertical fins, attached to a cooled horizontal surface, project vertically downwards has been numerically studied. It has been assumed that the flow is steady, laminar and two-dimensional. The governing equations have been written in terms of dimensionless variables and have been solved using the finite element procedure. The solution has the following parameters: the Rayleigh number, the Prandtl number, the dimensionless half-width i.e. the ratio of the half-distance between the fins to the liquid depth, the dimensionless gap between the bottom of the fin and the lower surface, and the ratio of the thermal conductivity of the fin material to that of the liquid. Because of the application being considered, the Prandtl number has been taken as 5. Solutions have been obtained for Rayleigh numbers of between 10 and 1,000,000 for dimensionless half-widths of between 1 and 0.2 for thermal conductivity ratios of 20, 10 and 4 for a range of dimensionless fin gaps and widths.

Mixed Convection Heat Transfer From Thermal Sources Mounted on Horizontal and Vertical Surfaces

1990 ◽  
Vol 112 (4) ◽  
pp. 975-987 ◽  
Author(s):  
S. S. Tewari ◽  
Y. Jaluria
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Source ◽  
Mixed Convection ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Finite Width ◽  
Heat Sources ◽  
Wide Range ◽  
Thermal Sources

An experimental study is carried out on the fundamental aspects of the conjugate, mixed convective heat transfer from two finite width heat sources, which are of negligible thickness, have a uniform heat flux input at the surface, and are located on a flat plate in the horizontal or the vertical orientation. The heat sources are wide in the transverse direction and, therefore, a two-dimensional flow circumstance is simulated. The mixed convection parameter is varied over a fairly wide range to include the buoyancy-dominated and the mixed convection regimes. The circumstances of pure natural convection are also investigated. The convective mechanisms have been studied in detail by measuring the surface temperatures and determining the heat transfer coefficients for the two heated strips, which represent isolated thermal sources. Experimental results indicate that a stronger upstream heat source causes an increase in the surface temperature of a relatively weaker heat source, located downstream, by reducing its convective heat transfer coefficient. The influence of the upstream source is found to be strongly dependent on the surface orientation, especially in the pure natural convection and the buoyancy dominated regimes. The two heat sources are found to be essentially independent of each other, in terms of thermal effects, at a separation distance of more than about three strip widths for both the orientations. The results obtained are relevant to many engineering applications, such as the cooling of electronic systems, positioning of heating elements in furnaces, and safety considerations in enclosure fires.

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