1. COMSOL Simulation of Air Pollutant Particle Transmission in a Building
Manquan Fang, Advisor: Prof.Jani Pallis, Prof. Xingguo Xiong
Department of Electrical Engineering, University of Bridgeport, Bridgeport, CT 06604
Abstract
Here one original model are defined as a reference, in order to observe different results due to different parameters.
Indoor and outdoor air pollution is linked to many chronical respiratory diseases and may even cause premature deaths. In order to control the air pollution to protect human health, it is important to understand the pattern of air pollution propagation. In this poster, COMSOL simulation is used to simulate the air pollutant particle transmission process inside a building. COMSOL model of a building with windows and doors is developed. COMSOL Multiphysics simulation is used to show how the air pollutants diffuse from the origin to the other parts of the building. The influence of windows and doors to the particle transmission process is also studied. It compares different conditions when the doors/windows are opened, closed and with/without wind. The simulation results can be used to guide the design optimization of the building for better ventilation of pollutant particles. It gives good understanding about the particle transmission behavior of air pollutants in a building.
Contamination Material
(gas)
Degree o Freedom
211735
Computational Time
450 s
Temperature K
Air Velocity
8 m/s
Inward Flux
= 64.2 mol/
Input Pressure
= 10 pa
Static Pressure
= 100 pa
Diffusion coefficient
= ( )
Windows
Close
Changing Variates
Study
Model 1
New
Computational time T 1 K
300 k
449 s 2
8 m/s
10 m/s
845 s
Contamination Material 3 ,
636 s
Windows 4
Close
Open
5623 s 5
10 pa
50 pa
389 s 6
9.08 10
340 s
Table-1.
Parameters of Model #1
and
Changing Variate
Introduction
Indoor air pollutant is associated with the emission and accumulation of pollutants which generally attributed to poor ventilation and air exchange. With studying the indoor air pollutant, the results can also be used to analyze outdoor pollutant, since outdoor air pollution is one of the most popular concerns of society. This simulation helps to understand the transportation and diffusion of contamination particles, and predict its future movement. COMSOL Multiphysics Software will be used to simulate this condition. COMSOL is a general-purpose platform software for modeling engineering applications.
3D Plot Groups are powerful Comsol tools, different groups such as surfaces, isosurfaces, arrows and slices can be displayed different parameters, such as concentration, speed or pressure. The results of each studies can be shown graphically. The error of time of stable step size is around 130%, depends on different conditions. Typically, study 4 and 6 are not appliable.
Chapman–Enskog Theory for the Dependence of the Diffusion Coefficient of Gases
Modeling
Modelling process in COMSOL software consists of building up or importing space geometry, selection of physics module, assigning values and defining boundaries, and meshing (MODELLING OF PARTICLE TRANSMISSION IN LAMINAR FLOW USING COMSOL MULTIPHYSICS).
Using 3-D Space Dimension, Transport of Diluted Species and Laminar Flow as physics module, and Time Dependent as study module, then we finish the preparation.
Since COMSOL nowdays is already a popular software, there are tons of open-sourced model of building with doors and windows provided for all the COMSOL users. Since they are open-sourced and need no authorization, all these models are ready to be used.
Fig. 3. Result of Original Model
Study 4 is totally different from all the other studies, where all these other studies will get a set of similar results which are totally predictable. The key point of study 4 is that if these windows are open or not. The reason why this study 4 is important is that open-windowed building can be extremely valuable for studying the outdoor contamination. Walls, doors, windows and roofs here are nothing but diversion. These surfaces do diverse the air and pollution but do not block them in a restricted area.
Figure 1. 3D view of the structure of Geometry Building
Defining the material studied in this simulation. Specifically, Carbon Dioxide and Sulfur Dioxide is the one used in this study (also the most common contamination in atmosphere). All the other materials, includes mixing gases, can be used in simulation. Laminar Flow, or SPF, defined the inlets, outlets and fans, which provides the ability for gases to ventilate in this building. In this simulation, three inlets are defined on the wall, and three outlets are defined on all these windows. Furthermore, the speed of fan, or in other word, the speed of wind in this building, is defined as well, since it plays a significant role to interface the diffusion of the gases.
Fig. 4. Air Circulation for Study 4
Figure 2. 3D view of the Surface for the Fan
Fig. 5. Concentration for Study 4
Transport of Diluted Species, or TDS, defines the inflows, outflows and fluxes. This one provides the possibility that the Carbon Dioxide (or any contamination sources) to be transferred or moved with wind. Outflows will be corresponding to the outlets defined in SPF. There are two alternatives available to define the rest. Either simply defining the fan plate as the inflow plate, or defining the fan plate as the flux plate. It is unnecessary to define both of inflows and fluxes, or they will be overwritten. The property of flux, or the concentration of contamination is also defined here. All these numbers or types can be changed to apply to different situations. Two objects are said to be coupled when they are interacting with each other (Wikipedia). Flow Coupling, also couples two physics here, TDS and LPF, in order to compute them simultaneously. Two alternatives can be used to mesh this building. This building can be either meshed by User- Controlled or Physics- Controlled. Physics- controlled should be easier, since the software itself can automatically mesh it according to different element sizes. Coarser element size reduces the computation complexity and time, finer increases it.
Fig. 6. Velocity and Pressure
Conclusions and Future Work
All these studies show that different temperature, pressure, components, ventilation, wind velocity will have different influence on it. Typically, higher temperature/altitude/pressure will have higher velocity and larger area of diffusion. Open windowed will have higher degree of freedom. With this study, precaution can be made to prevent further contamination, or recursion can be made to track the pollution source.
COMSOL Simulation
The Control Variates method will be applied to different study in order to compare different situations. Typically, different ventilation, in/outlets, temperature will be the one discussed.
The fan in SPF and the flux in TDS can be user defined to simulate the ventilation systems; the inlets outlets can be activated or deactivated to simulate the open or close of windows; the temperature in SPF, TDS and Global Definition,the General Inward Flux and Static Pressure at no Flow can be user assigned.
References
[1] Ismail A. Rahman, [2] J. C. P., [3] A. A. "Modelling of Particle Transmission in Laminar Flow Using Comsol Multiphysics", ARPN Journal of Engineering and Applied Sciences, VOL. 11, NO. 10, MAY 2016.