numerical modeling of turbulence mixed convection heat transfer in air filled enclosures by finite...
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Int. Jnl. of Multiphysics Volume 5 · Number 4 · 2011 307
Numerical modeling of turbulence mixedconvection heat transfer in air filled enclosures by
finite volume methodMohammad Reza Safaei1*, Marjan goodarzi1 and
Mohammadali Mohammadi21Mashhad Branch, Islamic Azad University, Mashhad, Iran
2University Putra Malaysia, Serdang, Malaysia
ABSTRACT
In the present study, first the turbulent natural convection and then laminar
mixed convection of air flow was solved in a room and the calculated
outcomes are compared with results of other scientists and after showing
validation of calculations, aforementioned flow is solved as a turbulent
mixed convection flow, using the valid turbulence models Standard k−ε,
RNG k−ε and RSM.
To solve governing differential equations for this flow, finite volume
method was used. This method is a specific case of residual weighting
method. The results show that at high Richardson Numbers, the flow is
rather stationary at the center of the enclosure. Moreover, it is distinguished
that when Richardson Number increases the maximum of local Nusselt
decreases. Therefore, it can be said that less number of Richardson
Number, more rate of heat transfer.
Keywords: Mixed Convection Heat Transfer, Turbulence Models, Nusselt
Number, Turbulent Kinetic Energy, Reynolds Stress.
1. INTRODUCTIONMixed convection heat transfer is a phenomenon in which both natural and forcedconvections happen. Mixed convection heat transfer takes place either when buoyancy effectmatters in a forced flow or when there are sizable effects of forced flow in a buoyancy flow.Dimensionless numbers to determine this type of flow are as follows: Grashof Number(Gr = g.β.∆T.L3/v2), Reynolds Number (Re = ρ.v.l/µ), Rayleigh Number (Ra = Gr.Pr),Prandtl Number (Pr = Cp.µ/K), and Richardson Number (Ri). If you devide naturalconvection effect by forced convection effect, it yields to Richardson number and it is writtenas such: Ri = Gr/Re2. When it comes to limits and we have Ri→0 or Ri→∞, forcedconvection and natural convection become dominant heat transfers respectively [Bejan [1]].
Mixed convection heat transfer is a fundamentally significant heat transfer mechanismthat occurs in selection industrial and technological applications.
In the recent years, wide and practical usages of mixed convection heat transfer in areassuch as designing solar collectors, double-layer glasses, building insulations, coolingelectronic parts and have attracted many scientists in studying it.
*Corresponding author. Tel.: +989151022063; E-mail address: [email protected]