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# OSCILLATIONS OF HEAT TRANSFER AND LARGE-SCALE CIRCULATION IN TURBULENT MIXED CONVECTION

Westhoff, Andreas and Schmeling, Daniel and Bosbach, Johannes and Claus, Wagner (2010) OSCILLATIONS OF HEAT TRANSFER AND LARGE-SCALE CIRCULATION IN TURBULENT MIXED CONVECTION. In: Third Int. Symposium on Bifurcations and Instabilities in Fluid Dynamics, p. 34. The Univercity Nottingham. Third Int. Symposium on Bifurcations and instabilities in fluid dynamics, 10.-13. Aug. 2009, Nottingham (UK).

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## Abstract

Mixed convection (MC) describes the transport of heat in fluids when forced convection (FC) and thermal convection (TC) coexists. It is a very often occurring flow condition e.g. in the oceans, the atmosphere, indoor climatisation or in many industrial processes and applications. MC can be characterised by the dimensionless parameters Rayleigh number $Ra \equiv \Delta T \beta g H^3 / \kappa \nu$, Reynolds number $Re \equiv U H / \nu$, Prandtl number $Pr \equiv \nu / \kappa$ and Archimedes number $Ar = Ra / (Re^2 \times Pr)$ which is the ratio of buoyancy to inertia forces. In this study we investigated the influence of torsional oscilations of the large-scale circulations (LSC) on the heat transfer at MC in a rectangular cavity. To cover a large range of $600 < Re < 3 \times 10^6$ and $1 \times 10^5 < Ra < 1 \times 10^{11}$ two convection cells with an aspect ratio of 1:1:5 (height:width:length) have been constructed using air as working fluid. As a characteristic length the height $H$ of the cell is chosen and the spatially averaged inflow velocity as characteristic velocity $U$. The convection cells consist of a rectangular container with an air inlet at the top and an air outlet at the bottom. Inlet and outlet are located at the same side of the cell. They span the whole length of the cell and are constituted by rectangular channels. The bottom is equipped with a heated copper plate and the top with an aluminium heat exchanger with cooling fins. The small cell with the dimensions $H = 100$ mm, $W = 100$ mm and $L = 500$ mm was designed to be operated under high pressure conditions up to 100 bar. The large convection cell has been designed to work under ambient pressure with the same aspect ratio. However, its dimensions are scaled by a factor of 5.

Item URL in elib:https://elib.dlr.de/66605/
Document Type:Conference or Workshop Item (Speech, Paper)
Title:OSCILLATIONS OF HEAT TRANSFER AND LARGE-SCALE CIRCULATION IN TURBULENT MIXED CONVECTION
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Westhoff, Andreasandreas.westhoff (at) dlr.deUNSPECIFIED
Schmeling, Danieldaniel.schmeling (at) dlr.deUNSPECIFIED
Bosbach, Johannesjohannes.bosbach (at) dlr.deUNSPECIFIED
Claus, Wagnerclaus.wagner (at) dlr.deUNSPECIFIED
Date:August 2010
Journal or Publication Title:Third Int. Symposium on Bifurcations and Instabilities in Fluid Dynamics
Open Access:Yes
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Page Range:p. 34
Publisher:The Univercity Nottingham
Status:Published
Keywords:mixed convection, turbulence, heat transfer, large-scale circulations, flow structure formation
Event Title:Third Int. Symposium on Bifurcations and instabilities in fluid dynamics
Event Location:Nottingham (UK)
Event Type:international Conference
Event Dates:10.-13. Aug. 2009
Organizer:School of mathematical sciences University of Nottingham
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:Aircraft Research (old)
DLR - Research area:Aeronautics
DLR - Program:L AR - Aircraft Research
DLR - Research theme (Project):L - Systems & Cabin (old)
Location: Göttingen
Institutes and Institutions:Institute of Aerodynamics and Flow Technology > Fluid Systems
Deposited By: Westhoff, Andreas
Deposited On:26 Nov 2010 09:58