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Components of a CONTAM Project
Project Files
All data related to the characteristics of the projects you work with are stored in a "project" file having a "PRJ" extension. This is an ASCII file, which is intended to be "viewed" only by the CONTAM program. You should keep careful records of your project files and establish a naming convention that is meaningful to you for the various versions of a project that you may wish to save.
There are other files utilized by CONTAM including: simulation results files, weather files, library files, and the log file. Simulation results are stored in files created automatically by CONTAM with the same name as the PRJ file except that the "PRJ" extension is replaced by the "SIM," "SUM," "EXP," "CSM," "ACH" and "AGE" extensions depending on the type of results generated by the simulation (see Working with Simulation Results). Weather files and contaminant files, typically given the WTH and CTM extension, respectively, may contain up to a years worth of weather and outdoor contaminant data and are used when performing transient simulations (see Working with Weather). Weather and contaminant files are ASCII files, but the data is of a format unique to CONTAM. Library files are the means by which you can share various types of data between CONTAM projects. Each type of library data has a different extension: LB0 (contaminants and source/sinks), LB1 (schedules), LB2 (wind pressure profiles), LB3 (airflow elements), LB4 (duct flow elements) or LB5 (control super elements). You create libraries of data using ContamW (see Working with Data and Libraries). The log file, "CONTAMW2.LOG," is created in the directory in which the executable program resides each time you run the program. This file keeps track of operations that you perform during your session with ContamW and is a useful tool in the event that you require technical support from the program developers when working with the program (see Getting Help).
Building Components
Building components are the items that characterize the physical makeup of a building that you define using the CONTAM graphical user interface. This section briefly describes these components.
Levels
CONTAM represents buildings in terms of multiple levels, accounting for the communication of air and contaminants between these levels. Levels typically correspond to floors of a building, but a suspended ceiling acting as a return air plenum or a raised floor acting as a supply plenum may also be treated as a level.
Walls
Walls are used to designate zones which are regions surrounded by walls, floor and ceiling. These walls include the building envelope and internal partitions with a significant resistance to airflow.
Floors and Ceilings
Floors and ceilings are included implicitly by CONTAM for building zones. When you draw a zone on the SketchPad, CONTAM automatically includes the floor of the zone. To create a roof with penetrations into the floor below requires a blank level above the top floor. It is also possible to create a phantom zone with no floor or ceiling as might be required to create an atrium that spans multiple levels.
Zones
In CONTAM, a zone typically refers to a volume of air having a uniform temperature and contaminant concentration. However, beginning with version 2.4, zones can now be configured as one-dimensional convection/diffusion zones in which contaminant concentrations are allowed to vary along a user-specified axis.
There are three types of zones in CONTAM: normal, phantom and ambient. Normal zones are separated from the zone below by a floor. The ambient zone, which surrounds the building is implicitly defined and is identified by the symbol at the upper-left corner of the SketchPad. Any additional ambient zones must be connected to the default ambient zone. For example, you could use an ambient zone icon to define a courtyard. Phantom zones indicate that the area on the current level is actually part of the normal zone on the level immediately below. There is no floor between a phantom zone and the normal zone below. You could use phantom zones to define building features such as atriums. Only normal zones can be configured to be convection/diffusion zones, however, these zones can still be referenced by phantom zones.
Airflow Paths
An airflow path indicates some building feature by which air can move from one zone to another. Such features include cracks in the building envelope, open doorways, and fans. Path symbols placed on the walls are used to represent openings between zones or to ambient; any other placement represents an opening in the floor to the zone on the level below. CONTAMW can implement several different models or airflow elements to define airflow paths. The basic categories of airflow elements or models are as follows: small and large crack/openings represented by power-law and quadratic pressure relationships, small and large doorways elements, and fan/forced airflow elements.
Simple Air-handling Systems
The simple air-handling system (AHS) provides a simple means of introducing an air-handling system into a building without having to draw a duct system. It provides a reasonable model of an air-handling system that delivers user-specified flows where the system is properly balanced and the fan is not impacted by any other pressurizing effects in the building. The AHS consists of two implicit airflow nodes (return and supply), three implicit flow paths (recirculation, outdoor, and exhaust air), and multiple supply and return points that you place within the zones of the building. You can set the air flows of the AHS to vary according to a schedule.
Ducts
You can use ducts to implement a more detailed model of an air-handling system that handles a broader range of conditions. For example, when an air handler is off, the ductwork may provide flow paths between zones which are significant in relation to the normal construction cracks or openings. Ductwork consists of duct segments (paths) and junctions or terminal points (nodes). CONTAMW can implement several different duct segment models or duct flow elements to define duct segments. The basic categories of duct flow elements are as follows: resistance models, fan performance curves, and back-draft dampers.
Contaminants, Sources, Sinks and Filters
You can define an unlimited number of contaminants within a single project with a practically limitless number of sources associated with the contaminants. CONTAMW can simulate contaminant transport via airflow between zones, removal by filtration mechanisms associated with flow paths, and removal and addition by chemical reaction. CONTAMW can also implement several source and sink models to generate contaminants within or remove contaminants from a zone. These models include: constant generation, pressure driven, decaying source, cutoff concentration, reversible boundary layer diffusion, and burst models.
Schedules
Schedules are used to control or modify various properties of building components as a function of time. You can set schedules for airflow paths, duct flow paths; contaminant sources and sinks; and inlets, outlets and outdoor air delivery of simple air-handling systems. The effect of setting a schedule on a building component varies depending on the properties of the component. For example, you can set a schedule to adjust the airflow delivered to a zone by an inlet of a simple air-handling system.
Controls
Controls include sensors, actuators, modifiers and links. Control actuators can be used to modify various characteristics of building components based on control signals obtained from sensors and even modified by signal modifiers. For example, a sensor can be used to obtain a contaminant concentration within a zone, and a proportional control actuator can be used to adjust supply airflow into the zone based on the sensed concentration.
Occupants
Occupants can be used to determine the amount of contaminant exposure a person would be subjected to within a building. Occupants can also generate contaminants. You can set a schedule to establish each occupant's movement within a building. Occupant schedules can also be used to define periods of times when occupants are not in the building.
Weather
CONTAMW enables you to account for either steady-state or varying weather conditions. Weather conditions consist of ambient temperature, barometric pressure, wind speed and direction, as well as ambient contaminant concentrations.
Simulation
In CONTAMW, simulation is the process of forming a set of simultaneous equations based upon the information stored in the project file, performing the numerical analysis to solve the set of nodal equations according to user- defined specifications, and creating a simulation results file that can be viewed using the CONTAMW interface. There are three basic types of simulations that you can perform for airflow and contaminant analysis using CONTAMW: steady state, transient and cyclical.
