Facade CFD Simulation Considering Radiation, ANSYS Fluent HVAC Training

Facade Project Description

The present problem simulates the airflow through the space between the two walls of the double façade of the building. To move the airflow upwards in this space based on the density changes caused by the pressure and temperature changes, the boundary condition of the pressure equal to the atmospheric pressure at the inlet and outlet of this space has been used. The main cause of temperature changes is the presence of solar energy on the plates of these shells; therefore, the radiation energy model of Discrete Ordinates (DO) and the solar ray tracing model have been used.

It is also assumed that the ambient airflow around the shells has a temperature of 300 K and a heat transfer coefficient of 10 W.m-2.K-1. Also, in the space between these two walls, a shutter-shaped shading is used, which helps the ventilation process in the system. The purpose of this study is to investigate the behavior of fluid flow in an upward motion and heat transfer in space between two shells and between shading plates.

Geometry & Mesh

The geometry of the present model is three-dimensional and is drawn using Design Modeler software. The geometry consists of a rectangular cube chamber and several rows of shutter-like plates called shading. The compartment has dimensions of 3 meters, 1.5 meters, and 0.2 meters. Shading plates also have a thin thickness with a slope of 45 degrees and are located in 120 rows. The figure below shows an overview of the model’s geometry.

The meshing of the present model has been done using ANSYS Meshing software. The mesh type is unstructured and the element number is 4264442. The figure below shows a view of the mesh.

CFD Simulation

To simulate the present model, several assumptions are considered, which are:

• The simulation is based on the Pressure-Based solver.
• Simulation has studied fluid behavior and heat transfer.
• The simulation is Steady-State.
• The effect of gravity on the flow is considered equal to -9.81 m/s2.

The following is a summary of the steps for defining the problem and its solution:

Models (facade)
k-epsilon	Viscous model
standard	k-epsilon model
standard wall function	near-wall treatment
on		Energy
Boundary conditions (facade)
pressure-inlet		Inlet
0 pascal	gauge pressure
1	Internal emissivity
active	participate s in solar ray tracing
Pressure outlet	(facade)	Outlet
0 pascal	gauge pressure
1	Internal emissivity
active	participate s in solar ray tracing
wall		Outer walls
stationary wall	wall motion
1	Internal emissivity
300 K	free stream temperature for convection
10 W.m-2.K-1	heat transfer coefficient for convection
semi-transparent	BC type	(facade)
active	participate s in solar ray tracing
wall		slat walls
stationary wall	wall motion
1	Internal emissivity
0 W.m-2	heat flux
active	participate s in solar ray tracing
Solution Methods (facade)
SIMPLE		Pressure-velocity coupling
Second-order	pressure	Spatial discretization
first-order upwind	momentum
second upwind	turbulent dissipation rate
second-order upwind	turbulent kinetic energy
first-order upwind	energy
first-order upwind	discrete ordinates
Initialization (facade)
Standard	Initialization method
0 m.s-1	velocity (x,y,z)
0 pascal	gauge pressure
300 K	temperature

Facade Results

At the end of the solution process, two-dimensional and three-dimensional contours related to pressure and velocity and temperature, as well as two-dimensional and three-dimensional pathlines were obtained. The two-dimensional contours are drawn in the XY section and in the middle of the space between the two shells.

Analysis

The diagram of the velocity distribution in the XZ section of the model is plotted at a height of 2 m from the floor of the model in the line passing through the center of the geometry and in line with the x-axis between -0.1 and +0.1. The geometric model has an angle of 45 degrees.

 

You can obtain Geometry & Mesh file, and a comprehensive Training Movie which presents how to solve the problem and extract all desired results.