ANSYS Airpak Solutions

Analyzing Carbon Monoxide Levels in a Parking Structure

In this example, computer simulation helped ensure low carbon monoxide levels in a new parking structure by making it possible to evaluate the performance of different ventilation system designs without the expense of actually building and testing them. The main concern in the design was ensuring that carbon monoxide would remain below specified levels even when 125 cars were waiting to exit the garage with their engines running for a long period of time. Engineers at Dunham Associates evaluated the performance of the ventilation system diffuser using Airpak. Five different diffuser configurations were evaluated while the total capacity of the ventilation system was maintained at a constant level. Engineers used the simulation to select the most efficient diffuser configuration, making it possible to build a cost-effective ventilation system that met all performance requirements without any modifications.

Overall geometry

Car group modeling: 125 cars emitting heat and CO

Airpak image showing one case of D Floor (36 ft. above G Floor) CO distribution

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Building Air Intake and Exhaust Design: Plumes from Stacks in a City Block

Proper design of building air intake and exhaust systems requires understanding of the complex behavior that plumes from stacks can exhibit when the building exhausts are located within the midst of several other nearby buildings, structures, or terrain. To meet the needs for accurate predictions of exhaust dilution and airflow patterns between buildings, Airpak provides physical modeling as the economical alternative to full-scale field evaluations.

Plume particle traces colored by concentration level show the dilution and trajectory of the contaminants while surfaces are colored by surface pressure magnitude

Velocity vectors on a horizontal cross-section show the complex airflow patterns that develop between buildings

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Canopy Local Exhaust Design

Industrial manufacturing facilities may have welding stations that generate large amounts of heat and harmful toxins, which must be contained to ensure a safe workplace. This example shows how Airpak can be used to help design a canopy local exhaust system where the main design question was whether or not the inclusion of an internal hood air supply would degrade the performance of the hood. If internal air supply was not detrimental to the operation of the hood, the facility owner could reduce the amount of conditioned air delivered to the space.

Canopy hood geometry

Vertical plane cuts showing the airflow patterns and temperature contours in the vicinity of the welding station give an indication of the flow about the welding station and worker as well as the strong thermal plume due to radiation heating the floor.

Airflow patterns

Air temperature contours

By looking at contours of vertical velocity magnitude at the hood opening, engineers can better see the reasons why a particular design is better.

Vertical velocity contours at hood opening

After the simulation of an isolated canopy hood is completed, one can easily build a larger model of the entire facility including over 40 square 4-way ceiling diffusers and look for system-wide effects that may arise from having several canopy hoods in close proximity to other canopy hoods or potential problems due to ventilations system design.

Temperature contours on a vertical plane for a large facility simulation

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Cleanroom and Minienviroment Design

Use Airpak to help determine: airflow patterns, air turbulence, contaminant transport, equipment effects, room pressurization, temperature and humidity, process exhaust.

Cleanroom and minienviroment design

Cooling of an Exhibit Space

Circular ceiling diffuser supplies cool air for occupant comfort in a large 60' x 54' x 60' section of an exhibit space.

Model includesheat loads from overhead lighting as well as the occupants
(click to view animation)

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Cooling Ventilation: Negatively Buoyant Jet

A frequently encountered phenomena in cold air distribution applications involves the interaction of buoyant forces with the inertial forces of the jet. The behavior of a cold air jet entering a typically-sized room at a ventilation rate of 15 air changes per hour (ACH) was modeled using Airpak. The deflection of the non-isothermal jet is readily apparent from the series of computed results that are presented here: particle traces, velocity vectors, and temperature contours.

Particle traces colored by velocity magnitude show supply jet deflection due to negatively buoyant forces

Velocity vectors on a cross-sectional plane confirm the jet deflection as well as identify relatively stagnant regions that develop near the ceiling

The amount of jet deflection relative to a path in the direction normal to the supply diffuser depends on several factors including the geometry and thermal boundary conditions of the room as well as the temperature and flow conditions of the ventilation supply. In addition to accurate predictions of velocity and temperature distributions, Airpak provides the designer with information pertaining to Indoor Air Quality (IAQ) and thermal comfort considerations.

Temperature contours show the jet deflection and the thermal stratification that maintains relatively warmer air near the ceiling

Predicted mean vote (PMV) contours show that occupants located in the immediate vicinity of the supply discharge will feel cold while the majority of occupants elsewhere in the room would feel slightly cool

The freshness of the air can be visualized by looking at contours of the mean age of air and an assessment of the expected level of thermal comfort can be estimated by looking at contours of predicted mean vote (PMV) and or predicted percent dissatisfied (PPD).

Mean age of air contours show that the air in the room is not well mixed with significant difference in air freshness

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Displacement Ventilation of an Auditorium

Modeling airflow patterns and predicting thermal comfort with Airpak helps architects and engineers to explore new ventilation approaches.

Velocity vectors on a vertical plane cutting through the middle of a high school auditorium

Particle traces from displacement ventilation inlet diffusers colored by temperature rise to the ceiling mounted exhausts due to the heat generated by the audience

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Five-Story Parking Garage Ventilation

Airpak can be used to simulate the airflow in a parking garage. In this application, the five-story parking garage, planned by Mechanical Design Studio of Concord, CA, was designed to fit within the perimeter of an apartment building complex. In order to minimize ducting, it was decided that the ground floor automobile access should be used as the source of fresh-air entrainment for the garage. It was proposed that air-moving devices be placed on each level to enhance the movement of air in a spiral motion throughout the facility.

Airpak model of the parking garage

A three-dimensional model of the garage was created using Airpak. On each floor, recirculating fans were used to draw the air in a spiral motion through the floor and up the ramps, while a centrifugal blower was used to draw exhaust air out a common stack that originates on the second floor. CFD modeling using Airpak was used to determine the effectiveness of this ventilation strategy.

Velocity vectors illustrating the flow paths and speeds

The project provided invaluable information that confirmed the effectiveness of the ventilation design. By performing the analysis prior to construction, there will be a significantly reduced risk of retrofit once the building construction has been completed.

Isosurface where the mean age of air is 400 seconds (6.7 minutes)

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IAQ and Comfort: Conference Room

Airpak can also model conference room ventilation scenarios with several people created using Airpak's powerful person object. This application concerns cooling ventilation from a circular ceiling diffuser for a conference room with seven people in the room where one of the occupants is delivering a presentation from a screen projector. The heat sources in the room include the seven people and the screen projector.

Mean age of air contours shown on surfaces in the conference room as well as on a cross-sectional plane at table level indicate that the fresh supply air (at this particular ventilation flow rate) tends to move across the ceiling before descending down the walls resulting in relatively stale air in the vicinity of the conference room table

Flow patterns within the room at table level contain several low-velocity swirling eddies as shown by the velocity vectors

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Industrial Ventilation: Paint Spray Booth

Workers involved in the spray painting of automobiles or other large equipment frequently work inside spray booths equipped with ventilation systems to protect them from harmful fumes. Airpak was used in this example to evaluate the ability of a particular ventilation system design to allow the painter to work without a protective mask as well as evaluate the safety margins present in regards to fire hazard potential.

Velocity vectors colored by paint fume concentration level in a cross-sectional plane show airflow patterns within the spray booth equipped with an overhead supply and central floor exhaust

The body-fitted mesh necessary to accurately resolve the airflow around a complex shape, such as an automobile, is not available in other software claiming to be accurate ventilation design tools

Spray-paint fume concentration level contours give the designer information on the spread of harmful paint fumes