Ventilation

Question 1

What is standard air temperature for ventilation problems?

Answer 1

70F

Question 2

What are the unit options for Q?

Answer 2

CFM or m3/s

Question 3

What is standard pressure for ventilation problems?

Answer 3

14.7 PSI = 101,325 PA = 407 inches of H2O

It’s the same standard pressure we use on in other problems. It’s on the equation sheet.

Question 4

Feet to miles conversion

Answer 4

5280 feet to 1 mile

Question 5

cm to inches

Answer 5

2.54 cm to 1 inch

Question 6

What is a density factor?

Answer 6

The ratio of density of air divided by the density of standard air

Question 7

What is the formula for density factor?

Answer 7

Df = (530 R / T)*(P/14.7 PSI)

Df = (294K / T)*(P/101325 Pa)

Question 8

What are the units in V = 4005 √VP/df

Answer 8

V = f/m
VP = in of H2O

Question 9

What are the units in V = 1.29√VP/df

Answer 9

V = m/s
VP = Pa

Question 10

Name two types of losses that can occur in a ventilation system

Answer 10

Static pressure losses and friction losses

Question 11

How is an elbow loss factor expressed in an equation

Answer 11

Fₕ

Question 12

Is a lower Fₕ better or worse?

Answer 12

Better

Question 13

Name 3 kinds of enclosing hoods

Answer 13

• Laboratory hood
• Glove box
• Paint booth

Question 14

Are hood energy losses directly proportional to velocity pressure?

Answer 14

Yes

Question 15

What is hood static pressure?

Answer 15

The total energy associated with accelerating air into the system (SPₕ)

Question 16

What is Cₑ?

Answer 16

Coefficient of entry

Question 17

What is SPₕ?

Answer 17

Hood static pressure

Question 18

What is the ideal Cₑ number?

Answer 18

The closer to 1, the better

Question 19

What does a pitot tube measure?

Answer 19

Static pressure

Question 20

What is the ideal pitot tube placement downstream of obstructions?

Answer 20

greater than or equal to 7 duct diameters

Question 21

What is the ideal pitot tube placement upstream obstructions?

Answer 21

3 duct diameters

Question 22

What is capture velocity?

Answer 22

The minimum hood induced air velocity necessary to capture and convey the contaminant into the hood

Question 23

Coefficient of entry definition

Answer 23

A measure of how efficient the hood is at accelerating the air

Question 24

Hood static pressure definition

Answer 24

The total energy associated with accelerating air into the system

Question 25

Ideal pitot tube placement downstream

Answer 25

> or equal to 7 duct diameters

Question 26

Ideal pitot tube placement upstream

Answer 26

> or equal to 3 duct diameters

Question 27

Circumference of circle

Answer 27

2πr