CHAPTER 4 - SOURCE MODEL

Question 1

These are selected to describe how materials are discharged from the process

Answer 1

Source Models

Question 2

This pertains when the material is ejected from holes and cracks in tanks and
pipes, leaks in flanges, valves and pumps, and severed or ruptured pipes.

Answer 2

Limited aperture release

Question 2

It is subsequently used to describe how the material is transported downwind and dispersed to some concentration levels.

Answer 2

Dispersion Models

Question 3

This model converts the incident-specific results into effects on people, such as injury or death, and structures.

Answer 3

Effects Models

Question 4

This pertains to large holes developed in the process unit, releasing a substantial
amount of material in a short time.

Answer 4

Wide aperture release

Question 5

This is designed to prevent the overpressuring of tanks and process vessels.

Answer 5

Relief Systems

Question 5

What will happen if the liquid is stored under pressure above its atmospheric
boiling point and the leak is below the liquid level?

Answer 5

It will result in a stream of liquid flashing partially into vapor

Question 6

What will happen if the leak is located in the vapor space above the liquid inside a
tank?

Answer 6

It will result in either a vapor stream or a two-phase stream composed of
vapor and liquid, depending on the physical properties of the material.

Question 7

This force between the moving liquid and the wall of the leak converts some of
the kinetic energy of the liquid into thermal energy, resulting in a reduced
velocity.

Answer 7

Frictional Forces

Question 8

This is the complicated function of Reynolds number of the fluid escaping
through the leak and the diameter of the hole.

Answer 8

Discharge Coefficient

Question 9

Frictional forces between a liquid and the wall of a pipe convert kinetic energy
into

Answer 9

Thermal Energy

Question 10

What is the driving force for the movement of a liquid in the pipe?

Answer 10

The pressure difference across the pipe

Question 11

A type of flow that is characterized by smooth, layered fluid movement is known
as

Answer 11

Laminar Flow

Question 12

The Reynolds number is a dimensionless quantity used to predict the onset of
turbulence. A low Reynolds number indicates:

Answer 12

Laminar Flow

Question 13

Which of the following factors contributes to turbulence in fluid flow?

Answer 13

High Reynolds Number

Question 14

In a pipe system, what happens to the pressure as the pipe diameter decreases?

Answer 14

Decreases

Question 15

What is the primary function of a valve in a piping system?

Answer 15

Control fluid flow

Question 16

A Function of the Reynolds number and the roughness of the pipe ε.

Answer 16

Fanning friction factor

Question 16

A method that defines the excess head loss in terms of two constants (reynolds
number and pipe internal diameter)

Answer 16

2-K Method

Question 16

It is the maximum downstream pressure resulting in maximum flow through a
hole or pipe.

Answer 16

Choked pressure

Question 16

This is characterized by releasing the gas through a small crack with large
frictional losses.

Answer 16

Throttling

Question 16

Which of the following statements is valid for downstream pressures less than
𝑃choked ?

Answer 16

The velocity of the fluid at the throat of the leak is the velocity of sound at the
prevailing conditions.

Question 16

For sharp-edged orifices with a Reynolds number greater than 30,000 and not choked,
what is the constant discharge coefficient?

Answer 16

0.61

Question 17

For choked flows, the discharge coefficient __________ as the downstream pressure
decreases.

Answer 17

Increases

Question 18

# 1. For this type of discharge, most of the pressure energy is converted into kinetic energy, source models require only the diameter of the leak

Answer 18

Free Expansion

Question 19

In the context of modeling vapor flow through pipes, which of the following best describes adiabatic flow?

Answer 19

Rapid vapor flows through insulated pipes without heat exchange with surroundings.

Question 20

The phenomenon where a liquid rapidly evaporates due to a leak in a pressurized container, causing some of the liquid to turn into vapor explosively, is known as?

Answer 20

Flashing

Question 21

The type of vapor flow that occurs through an insulated pipe with no heat exchange is called?

Answer 21

Adiabatic Flow

Question 22

What happens to the temperature of a superheated liquid during flashing?

Answer 22

It decreases to the new boiling point as vaporization occurs.

Question 23

Why are numerical models required for real vapor flow through pipes?

Answer 23

Because no generalized accurately capture the intermediate behavior

Question 24

For flashing liquids composed of multiple miscible substances, the flash calculation becomes more complex because?

Answer 24

The more volatile components flash preferentially.

Question 25

In isothermal flow of gas in a pipe with friction, the gas velocity is assumed to be?

Answer 25

Below sonic velocity

Question 26

Which of the following must be considered when a flashing liquid escapes through pipes or holes?

Answer 26

Two-phase flow conditions.

Question 27

What provides the driving force for gas transport in the isothermal flow through the pipe?

Answer 27

Pressure gradient across the pipe

Question 28

Who identified that the expansion factor reaches a maximum 𝑌g in both adiabatic and isothermal gas flow scenarios?

Answer 28

Keith and Crowl

Question 29

In isothermal flow conditions, the temperature of the gas is?

Answer 29

Constant across the entire pipe length

Question 30

In the adiabatic choked flow of gas through a pipe, the maximum velocity is typically reached at?

Answer 30

The end of the pipe

Question 31

What is a distinguishing feature of the adiabatic flow case compared to the isothermal case?

Answer 31

There is no heat exchange with the surroundings in adiabatic flow

Question 32

# 1. At the end of the pipe in isothermal flow, the pressure is?

Answer 32

Equal to the pressure of the surroundings

Question 33

In the modeling of vapor flow through pipes, which two special cases are primarily considered?

Answer 33

Adiabatic and isothermal flow behavior

Question 34

The initial stage of boiling is usually controlled by the heat transfer from _____?

Answer 34

Ground

Question 35

The realistic releases represent the incident outcomes with a low probability of occurring. Worst-case releases are those that assume almost catastrophic failure of the process.

Answer 35

The first statement is true

Question 36

All the models, including consequence models, have uncertainties. These uncertainties arise because of

Answer 36

An incomplete understanding of the geometry of the release, unknown or poorly characterized physical properties, a poor understanding of the chemical or release process, and unknown or poorly understood mixture behavior.

Question 37

How is heat transferred to a liquid boiling from a pool?

Answer 37

From the ground by conduction and convection, and by radiation from the sun or other sources

Question 38

# 1. Realistic release incident for process pipes smaller than 2 inches.

Answer 38

Assume a full bore rupture

Question 39

How are uncertainties treated in consequence modeling?

Answer 39

By dispersion modeling to obtain conservative estimates

Question 40

If an internal company study is being completed to determine the actual consequences of plant releases, then the realistic cases would be selected. However, if a study is being completed to meet the requirements of the EPA Risk Management Plan, then the worst case releases must be used.

Answer 40

Both statements are true

Question 41

The method for liquid pool evaporation or boiling works adequately for,

Answer 41

Liquefied natural gas (LNG) and perhaps for ethane and ethylene

Question 42

For any particular modeling study several receptors might be present that require the same decisions for conservative design. For example, dispersion modeling based on a ground-level release will minimize the consequence for the surrounding community but will not minimize the consequence for plant workers at the top of a process structure.

Answer 42

Both statements are false

Question 43

Guidelines for selection process for worst-case incidents, except one;

Answer 43

Use calculated total release rate at set pressure; assume all material released is airborne.