Jump to main content.

Module 2: Characteristics of Gases - Flow Rate - Practice Problems

Instructions:
Work these problems on a sheet of paper and check your answers against those provided below.

Helpful Calculators:
The following calculators may be useful in solving these problems. You can access them either from the "Calculators" button on the screen or from the links below.

Temperature Converter
Pressure Converter
Gas Flow Rate Converter (Actual Standard Conditions)

break line

Q icon #1
What form of gas flow rate data should be used to calculate the velocity of a gas stream through a duct?

  1. ACFM
  2. SCFM

A icon
Answer: a. ACFM

Solution:
ACFM is the correct form to use when evaluating gas flow characteristics, such as velocity, inside ductwork, equipment, and stacks.

break line

Q icon #2
What form of gas flow rate data should be used with the ideal gas law to determine the amount of gas that can participate in a chemical reaction?

  1. m3/min
  2. Nm3/min

A icon
Answer: b. Nm3/min

Solution:
Nm3/min is the correct form to use in this case because a specific quantity (number of moles) of gas is needed in the reaction.

break line

Q icon #3
What form(s) of gas flow rate data should be used when preparing a material balance concerning gas streams entering and leaving an air pollution control system?

  1. ACFM
  2. SCFM
  3. Nm3/min
  4. m3/min

A icon
Answer: b. SCFM and c. Nm3/min

Solution:
SCFM and Nm3/min are the correct forms to use in this case because material balance calculations deal with the quantities of gases (e.g. moles, mass).

break line

Q icon #4
What form(s) of gas flow rate data should be used when calculating the velocity of a gas stream exiting a stack?

  1. ACFM
  2. SCFM
  3. Nm3/min
  4. m3/min

A icon
Answer: a. ACFM and d. m3/min

Solution:
Gas flow rates must be expressed in ACFM or m3/min whenever gas velocity is calculated in air pollution control equipment, ductwork, and stacks. This is necessary to take into account the actual temperature and pressure of the gas stream. The change in the gas flow rate with the absolute temperature and pressure is indicated by Equations 4 and 5, which are modified forms of the ideal gas law.

break line

Q icon #5
What is the gas flow rate in SCFM if the measured gas flow rate is 26,456 ACFM, the gas temperature is 160°F, the relative pressure of the gas is -10 in. W.C., and the barometric pressure is 404 in. W.C.?

A icon
Answer: 21,811 SCFM

Solution:
  1. Calculate the absolute temperatures and pressures.
    equation 5(1)

  2. Convert from ACFM to SCFM.
    equation 5(2)

break line

Q icon #6
A flue gas stream moving through a baghouse has the characteristics provided below. How much air is infiltrating the baghouse and leaving in the exhaust gas stream? Assume a barometric pressure of 407 in. W.C.

Table 6

See Figure 4.
Figure 4

A icon
Answer: 1,527 SCFM

Solution:
  1. Convert the inlet and outlet gas flow rates to SCFM prior to checking for air infiltration.

    For the inlet gas stream,
    equation 6(1a)

    For the outlet gas stream,
    equation 6(1b)

  2. Calculate the air infiltration as follows:
    equation 6(2)

break line

Q icon #7
A flue gas stream moving through a fabric filter has the characteristics provided below. How much air is infiltrating the baghouse and leaving in the exhaust gas stream? Assume a barometric pressure of 101.325 kPa.

Table 7

See Figure 5.
Figure 5

Answer: 305.8 Nm3/min

Solution:
  1. Convert the inlet and outlet gas flow rates to Nm3/min prior to checking for air infiltration.

    For the inlet gas stream,
    equation 7(1a)

    For the outlet gas stream,
    equation 7(1b)

  2. Calculate the air infiltration as follows:
    equation 7(2)

break line

Q icon #8
A flue gas stream entering a carbon bed adsorber system has 2,000 m3/min at -4.5 kPa negative pressure and a temperature of 400°K. What is the gas flow rate expressed in ACFM?

Answer: 70,620 ACFM

Solution:
equation 8

break line

Return To Lesson
Flow Rate
Next Lesson
Concentrations

APTI Virtual Classroom

Local Navigation

Jump to main content.