OCTOBER 19-20, 2012 - YMCA University of Science & Technology

Proceedings of the National Conference on
Trends and Advances in Mechanical Engineering,
YMCA University of Science & Technology, Faridabad, Haryana, Oct 19-20, 2012
Figure 1: The physical parameter set includes information about the physical geometry of the
problem. The computational parameters concern the numerical simulation of the model.
The power of CFD is not purely quantitative. The graphical depictions of air movement and comfort within a
space are a powerful communication tool for engineers, architects, and developers. These vivid depictions of the
building operation can speed the acceptance of low-energy, passive design elements and allay the fears of some
members of the design team[3].A commercial CFD package ANSYS Fluent 12.1 has been applied to simulated
the model, thus the numerical technique used including geometry, numerical grids, boundary conditions and
turbulence models. The ventilation of passive room had been simulated.
2. 0 3-D CFD simulation
2.1 Turbulent model
The ventilation flow usually related with turbulent flow the standard k- turbulence model is based on transport
equations for turbulence kinetic energy, k, and its rate of dissipation, , are obtained from the [5]:
Following transport equations::
And
In these equations, G k represents the generation of turbulence kinetic energy due to the mean velocity gradients,
G b is the generation of turbulence kinetic energy due to buoyancy. Y M represents the contribution of the
fluctuating dilatation in compressible turbulence to the overall dissipation rate, C 1 ,C 2 , and C 3 are constants.
σ k and σ are the turbulent Prandtl numbers for k and , respectively. S k and S are userdefined source terms
2.2 Radiation model
The surface-to-surface radiation model can be used to account for the radiation exchange in an enclosure of graydiffuse
surfaces. The energy exchange between two surfaces depends in part on their size, separation distance,
and orientation. These parameters are accounted for by a geometric function called a “view factor”. The energy
reflected from surface k is
(1)
(2)
where q out,k is the energy flux leaving the surface, ε k is the emissivity, σ is Boltzmann’s
constant, and q in,k is the energy flux incident on the surface from the surroundings[5],
the incident energy flux q in,k can be expressed in terms of the energy flux leaving all other surfaces as
(3)
where A k is the area of surface k and F jk is the view factor between surface k and surface
j. For N surfaces, using the view factor reciprocity relationship gives the view factor f jk is the fraction of energy
leaving surface k that is incident on surface j
(4)
(5)
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