Analysis of natural convection in an enclosure with a heat-generating element

نوع: Type: thesis

مقطع: Segment: masters

عنوان: Title: Analysis of natural convection in an enclosure with a heat-generating element

ارائه دهنده: Provider: Ali Namdari

اساتید راهنما: Supervisors: Dr. Mohammad Saeed Aghighi

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: Dr. Mohsen Goodarzi- Dr.Habibollah Sayehvand

زمان و تاریخ ارائه: Time and date of presentation: 2024

مکان ارائه: Place of presentation: Faculty of Engineering

چکیده: Abstract: In this research, natural convection heat transfer inside a square chamber, containing a viscoplastic casson fluid and having a heat-generating element, has been investigated numerically the governing Partial differential equations describing the fluid flow and heat transfer, have been solved (using the Finite-Element Method based on coding in MATLAB environment) over wide ranges of the pertinent dimensionless parameters, including the Rayleigh number (〖10〗^4≥ Ra ≥〖10〗^6), Bingham number (Bn_max ≥ Bn≥ 0) and for Three different modes in terms of the location of the heat-generating element inside the chamber (y= -0.25 , 0 , +025), for a value of Prantel number (Pr = 100). The detailed temperature and flow fields inside the chamber are shown, respectively, by the figures related to the isotherm profiles and streamlines and the changes of the shear rate values in the flow domain, based on the corresponding figures. Also, the yielded and unyielded regions are identified in the flow domain. In addition, Further insights are provided by graphs showing the average Nusselt number in different states. It was found that the average Nusselt number decreases with the increase of Bingham number, and also the maximum Bingham number (Bn_max) and mean Nusselt number ((Nu) ̅), increases with increasing values of Rayleigh number. In addition, the effect of the location of the heat-generating element on the results of the average Nusselt number and the maximum Bingham number was investigated and It was found that at high Rayleigh values (Ra=〖10〗^6,〖10〗^5), that the convection’s power is high, As long as the Bingham number does not close to the limiting value of the Bingham number (Bn_max) and the convection heat transfer is dominant in the flow regime, the value of ((Nu) ̅) decreases with the going higher of location of the heat-generating element. But by approaching the maximum Bingham number or in the lower Rayleigh values (Ra=〖10〗^4), and the dominance of conductivity in the flow regime, the highest value of the (Nu) ̅ corresponds to the state where the heat-generating element is located at (y = 0). Also, the maximum Bingham number decreases with the going higher of location of the heat-generating element. In addition, owing to the presence of the fluid yield stress, the domain flow is covered by fluid-like (yielded) and solid-like (unyielded) regions, depending upon the prevailing stress levels vis-a-vis the value of the fluid yield stress. Furthermore, the yielded regions progressively diminish with the increasing value of the Bingham number or the decreasing value of the Rayleigh number or with the going higher of location of the heat-generating element as the buoyancy-induced flow weakens. and Finally, at the Bn_max number and the solid-like become of most of the flow domain, the heat transfer will reach its conductivity limit.

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