SAChE Module 2 - ELA967: SAChE® - Atmospheric Dispersion

A correction factor may be needed when using a plume model (or other model with an inherently long averaging time) of the hazard time scale, th, is:

<t plume

A passive release refers to a release:

where the COTA cloud moves at the same speed and direction as the ambient wind

the US centers for disease control and prevention (CDC) developed IDLH to

(1) to ensure that the worker can escape from a given contaminated environment in the event of failure of the respiratory protection equipment and (2) to indicate a maximum level above which only a highly reliable breathing apparatus, providing maximum worker protection, is permitted.

the dry adiabatic lapse rate is approximately _____ per 100 meters (328 feet)

-1 C

Britter and mcQuaid report that the average time (tplume) for their plume correlation is:

10 minutes

The rate of heat transfer, Q, from a solid surface is expressed as:

NOT q/A

Regarding stability classes, what does the term, "3 D," refer to?

NOT wind speed is assumed to be 3 times that which typically occurs under D stability

Passive models were the first atmospheric dispersion models developed and were based on visual observations of:

smoke plumes

although flammable ignition will occur in milliseconds, for the purpose of atmospheric dispersion model calculations, the minimum relevant time scale, th, for flammability hazards is approximately

20 seconds

Rural conditions for briggs parameterization of passive plume dispersion coefficients reflects a surface roughness of approximately

3 cm

Despite decreased computational cost, _____ modules still require a significant investment for simulating a release scenario particularly of dimensions and locations of piping and equipment are included in the model

Computational Fluid Dynamics (CFD) models

if you have an answer i did not get you can edit it with the password:

Correction

T or F: in the briggs parameterization of passive plume dispersion coefficient, the predicted values of sigma y and sigma are independent of atmospheric stability classes

FALSE

T or F: the pasquill-gifford puff model predicts that if the wind speed is doubled, the COTA concentration at a fixed downwind distance is reduced by a factor of 2 provided that the change in wind speed does not alter the atmospheric stability.

FALSE

immediately dangerous to life and health (IDLH) criteria are based on exposure time of __________, but people should no longer be exposed to this concentration level as soon as possible

NOT 60 min

_____ models are generally considered to be incapable of simultaneously scaling mechanical turbulence and thermally induced turbulence, presenting a verification issue if both sources of turbulence are important aspects of the problem

NOT Computational fluid dynamics---should probably be wind tunnel model

Negative buoyancy of an airborne COTA can exist when:

NOT just COTA cloud denser than air

despite the fact that they are frequently used, passive dispersion coefficients are typically not provided for distances

NOT less than 10 meters

Which hazard should be considered for nitrogen when it is a component of COTA

Oxygen depletion

The pasquill-Gifford model is used for:

Passive COTAs

the time over which the cota becomes airborne is referred to as the

Source duration

T or F: Denser-than-air COTAs can significantly increase or decrease the downward distance to a fixed concentration level when compared with results from a passive atmospheric model

TRUE

T or F: ERPG concentration levels are determined by the chemical released

TRUE

T or F: The Britter-McQuaid plume model performance is expected to be less reliable as the wind speed approaches zero (for example, in scenarios involving light and variable winds).

TRUE

T or F: The Pasquill-Gifford puff model predicts that if the total airborne mass is doubled, the COTA concentration at a fixed downwind distance is doubled

TRUE

T or F: The britter-McQuaid puff model should not be used if the release is passive if the most conservative result is desired

TRUE

T or F: The lowest wind speed that can typically be measured with a modern cup anemometer is .5 m/s (1.6 ft/s)

TRUE

T or F: denser-than-air COTAs can fail to travel in the wind direction

TRUE

T or F: denser-than-air effects are most importantly influenced by wind speed

TRUE

T or F: the ALOHA hazard modeling program can model both plume and puff scenarios

TRUE

T or F: the predicted values of sigma y and sigma z puffs are sensitive to specification of atmospheric stability class

TRUE

what does B represent in the table of pasquill stability classes

The average behavior of B and C

Which of the parameters below is not included in the Britter-McQuaid correlations

all of the above

Theoretical analysis dictates that a dispersing plume that does not change the atmospheric flow field will have a gaussian spatial distribution in:

both the vertical and lateral direction

As the time required for mixing to the hazard concentration decreases, the hazard of a COTA cloud

decreases

for purposes of atmospheric dispersion modeling of flammable hazard, all pseudo-component properties should represent

depressurized properties of the airborne COTA

positive buoyancy of an airborne COTA exist when the ambient air density is ____ the density of the airborne COTA

greater than

when heat is transferred by forced convection, heat transfer coefficients ____

increase as fluid velocity increases

Denser-than-air effects are most important at

lower wind speeds, higher density difference, higher release rates

_____ models are typically easily solved on a computer with less user interaction than required for the solution of a partial differential equations (PDEs)

lumped parameter

Toxic Warning Levels are expressed in ___

ppm

the pasquill_gifford model and the britter-mcQuid model are examples of:

similarity models

1/sqrt f= 4 log(3.7 D/e) what is the e

surface roughness

equation: <C>tplume=E/pi σy σz u

the maximum (ensemble) average concentration for a continous passive plume from a point source at a given downwind distance

a person exposed to ERPG-2 concentration levels for 60 min can be expected to develop irreversible or other serious health effects

ERPG-2

T or F: Basic dispersion models include the ability to model the thermodynamic effect of mixing air with a suspended aerosol

FALSE

T or F: Inversions are accounted for in nearly all basic atmospheric dispersion models

FALSE

T or F: The Britter-McQuaid plume model allows for wind speeds of zero

FALSE

T or F: in the atmosphere, if the mean wind direction is constant, the wind direction must be zero

FALSE

T or F: Stability class G, when used, describes conditions that are less stable than F

FALSE

The ALOHA hazard modeling program can accommodate which of the following hazardous gas cloud sources

All of the above

---- is the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action

EPRG-2