Effects of Circular Cylindrical Block On Heat Flow For MHD Free Convection In A Non-Uniformly Heated Trapezoidal Enclosure

The problem of laminar free convection in a trapezoidal enclosure, filled with a fluidsaturated porous medium and with internal heat generation has been investigated using a penalty finite element analysis. The enclosure bottom wall is heated at a constant temperature and the top wall is subjected to a constant cold temperature whereas the left inclined wall is considered to be non-isothermal and the right inclined wall is isothermally cooled. The effects of the porosity of the medium and heat generation on the isotherms and streamlinesare investigated. The rate of heat transfer from the walls of the cavity is examined as well. The Prandtl number of the fluid is chosen to be 0.7 (air) whereas the value of the Rayleigh number is selected to be 105.

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Computational study of laminar free convection inside tilting irregular cavity of a batch-type solar collector

Thermal Science ◽

10.2298/tsci200521078b ◽

2021 ◽

pp. 78-78

Author(s):

Fahad Butt ◽

Abdul Badar ◽

Ajaz Janjua ◽

Salman Siddiqui

Keyword(s):

Free Convection ◽

Tilt Angle ◽

Solar Collector ◽

Computational Study ◽

Batch Type ◽

Side Walls ◽

Trapezoidal Enclosure ◽

Correlation Trend ◽

Solar Thermal System ◽

Rayleigh Numbers

Batch-type solar collector is a tilt-able water-heating solar-thermal system comprising an isosceles-trapezoidal enclosure housing a circular-cylinder absorber at the bottom wall, insulated side-walls, and flat-top glazing. Free convection of air inside such trapezoidal enclosure is studied numerically by varying the tilt angle of the whole enclosure from 0o-70o. The influence of tilt on the flow field has been demonstrated by plotting the streamlines and isotherms. The present study successfully identifies the importance of enclosure-tilt in quantifying heat-loss between absorber and glazing by developing a computational correlation between Nusselt and Rayleigh as a function of tilt. The correlation trend is non-monotonic over the range of angular Rayleigh numbers numerically experimented with having a peak around angular Rayleigh number 3?105 corresponding to the tilt-angle 30 degrees. The irregular-shaped cavity implies that the heat-transfer correlations already existing for regular-shaped cavities may not be used otherwise they will draw implausible conclusions and this argument identifies the novelty of the present study.

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Analysis of The Rayleigh Number in the Area of Steel Rectangular Sections in the Conditions of Stedy and Unstedy Heat Flow/ Analiza Liczby Rayleigha W Obszarze Stalowych Profili Prostokątnych W Warunkach Ustalonego I Nieustalonego Przepływu Ciepła

Civil and Environmental Engineering Reports ◽

10.1515/ceer-2014-0029 ◽

2014 ◽

Vol 14 (3) ◽

pp. 107-118 ◽

Cited By ~ 2

Author(s):

Rafał Wyczółkowski

Keyword(s):

Heat Transfer ◽

Heat Treatment ◽

Rayleigh Number ◽

Heat Flow ◽

Free Convection ◽

Mathematical Description ◽

Experimental Measurements ◽

Heat Transfer Phenomenon ◽

Steel Sections ◽

Criterial Dependence

Abstract The paper presents the experimental measurements dedicated to the research for the Rayleigh number (Ra) in the area of rectangular steel sections. This problem is associated with the analysis of the free convection which takes place in the heating of sections bundles during the heat treatment. The study was conducted for both steady and transient heat transfer. The values of the Ra number obtained for the tested sections allow to describe the phenomenon of convection on the basis of a very simple criterial dependence. It greatly simplifies the mathematical description of the heat transfer phenomenon in the concerned charges.

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