'Car cabin air flow analysis' simulation project by Ali_Arafat


#1

I created a new simulation project called 'Car cabin air flow analysis':

This project simulates the flow inside a car cabin.


More of my public projects can be found here.


#2

Description


 
With the discovery of the internal combustion engine, the automotive industry has observed an exponential rise in the number of cars on the streets, worldwide. As is evident from global warming and climate change, unsurprisingly, automobiles are responsible for the largest share of air pollution. The pollutants are not only released due to fuel combustion but also due to other processing occurring in the car system.
 
For instance, the cool blast of air from the Air Conditioner (AC) may be a cooling effect for us, but it actually is hot air with hot gases being removed during a multi-step process. Interestingly, the refrigeration cycle is an application of the Second Law of Thermodynamics. But unfortunately, it is a law and there are no exceptions to it. The amount of heat that is captured from a certain space or body (to be cooled) is always less than the amount of heat that is released to the atmosphere.
 
So what can we do about it? We could make sure that the car cabin is designed such that there is lesser energy consumption (lesser heat released).
 

Project Goals


 

 
The following project intends to simulate the airflow inside the cabin of a car, using the SimScale platform. Computational Fluid Dynamics (CFD) is an important tool used to conduct an analysis, whose results are employed in order to make/modify such a design. Furthermore, a better cabin design will ensure the thermal comfort of the driver as well as the passengers.
 
Our eventual goal is to observe the velocity and temperature contours to study the airflow pattern as well as regions of heating and cooling. We will also look for areas of recirculation with the aim of eliminating or minimizing them.
 

Geometry


 
The geometry is that of a standard wagon type 4-door car. The source geometry (entire car) was provided by GrabCAD user Joerg Schmit . Engineers at SimScale have modified it in order to enable it for internal flow analysis.
 
image
 
image
 
For the sake of simplicity and to save computational resources, only the car cabin is considered for the meshing and CFD simulation.The cabin interior has 4 inlet air conditioning ducts (2 in center and 2 at the sides) and one outlet as shown in the figure below.
 
image
 

Meshes


 
The complete modified car geometry was imported and the interior car domain was meshed using the hex-dominant parametric (only CFD) mesh is generated with 16 Computing Cores and multiple mesh refinements. These refinements are made on the surfaces where we require a better accuracy of the results.
The mesh along with the refinements can be observed in the image below:
 
image
 
Resultant mesh
 
The final mesh consists of approximately 2.7 million cells.
 

Simulation


 
The project simulates internal air flow of the car cabin modeled via steady state convective heat transfer with the K-Omega SST turbulence model.
 
The boundary conditions are set as follows:
 

  1. Initial temperature: The car cabin is at an initial temperature of 30 degrees Celsius.
  2. Inlet: Air at a fixed mass flow rate of 0.02 kg/s and a temperature of 10 degrees Celsius is taken
  3. Outlet: A pressure boundary condition is set at the outlet.
  4. Walls: The windows, considered to be walls, are kept at a fixed temperature of 30 degrees Celsius.
     
    The job was run on 8 computing cores and took around 12.5 hours.
     

Results and Conclusion


The simulation analyzes the mean flow field and temperature distribution inside the cabin. The results below have been processed on ParaView, an open-source scientific visualization software. They provide a good insight into how flow and temperatures vary at different sections inside the cabin.
 


 
Velocity Contours
 

 
Temperature Contours
 
Shown below are the velocity streamlines colored by temperature.
 

 
Velocity Streamlines
 
From the images above, we can see that cold air adequately reaches the passengers seated at the back of the car as well as those in the front.