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CFM worksheet

Grades 6–7 · CCSS 6.G.A.2, 6.RP.A.3.d, 6.EE.A.2.c

Solve each problem and show your work. Round answers to 2 decimal places where needed.

1.
Problem 1.
- Work out CFM from: Heat load and temperature difference
- Sensible heat load: 25,000 Btu/h
- Temperature difference (ΔT): 18 °F
- Sensible heat factor: 1.2
Find: Airflow
Answer
2.
Problem 2.
- Work out CFM from: Room size and air changes
- Room length: 10 ft
- Room width: 7 ft
- Ceiling height: 7 ft
- Air changes per hour: 6 ACH
Find: Airflow
Answer
3.
Problem 3.
- Work out CFM from: Heat load and temperature difference
- Sensible heat load: 22,500 Btu/h
- Temperature difference (ΔT): 20 °F
- Sensible heat factor: 1.2
Find: Airflow
Answer
4.
Problem 4.
- Work out CFM from: Heat load and temperature difference
- Sensible heat load: 29,000 Btu/h
- Temperature difference (ΔT): 18 °F
- Sensible heat factor: 0.8
Find: Airflow
Answer
5.
Problem 5.
- Work out CFM from: Heat load and temperature difference
- Sensible heat load: 16,000 Btu/h
- Temperature difference (ΔT): 60 °F
- Sensible heat factor: 1.25
Find: Airflow
Answer
6.
Problem 6.
- Work out CFM from: Room size and air changes
- Room length: 18 ft
- Room width: 15 ft
- Ceiling height: 7 ft
- Air changes per hour: 6 ACH
Find: Airflow
Answer
7.
Problem 7.
- Work out CFM from: Heat load and temperature difference
- Sensible heat load: 25,000 Btu/h
- Temperature difference (ΔT): 15 °F
- Sensible heat factor: 1.1
Find: Airflow
Answer
8.
Problem 8.
- Work out CFM from: Room size and air changes
- Room length: 12 ft
- Room width: 11 ft
- Ceiling height: 8 ft
- Air changes per hour: 1 ACH
Find: Airflow
Answer
9.
Problem 9.
- Work out CFM from: Heat load and temperature difference
- Sensible heat load: 20,000 Btu/h
- Temperature difference (ΔT): 15 °F
- Sensible heat factor: 1.15
Find: Airflow
Answer
10.
Problem 10.
- Work out CFM from: Heat load and temperature difference
- Sensible heat load: 24,000 Btu/h
- Temperature difference (ΔT): 60 °F
- Sensible heat factor: 1.2
Find: Airflow
Answer

Answer key: CFM worksheet

1. Airflow: 1,157.41 CFM
1. Find the airflow. The heat the air carries is 1.2 × CFM × the temperature difference, so divide the load by 1.2 × the difference
  $\frac{25,000}{1.2 \times 18}$ $= 1,157.407407 CFM$
2. Airflow: 49 CFM
1. Find the room's volume: length × width × height
  $10 \times 7 \times 7$ $= 490 ft³$
2. Multiply the volume by the air changes per hour, then divide by 60 to turn 'per hour' into 'per minute'
  $\frac{490 \times 6}{60}$ $= 49 CFM$
3. Airflow: 937.5 CFM
1. Find the airflow. The heat the air carries is 1.2 × CFM × the temperature difference, so divide the load by 1.2 × the difference
  $\frac{22,500}{1.2 \times 20}$ $= 937.5 CFM$
4. Airflow: 2,013.89 CFM
1. Find the airflow. The heat the air carries is 0.8 × CFM × the temperature difference, so divide the load by 0.8 × the difference
  $\frac{29,000}{0.8 \times 18}$ $= 2,013.888889 CFM$
5. Airflow: 213.33 CFM
1. Find the airflow. The heat the air carries is 1.25 × CFM × the temperature difference, so divide the load by 1.25 × the difference
  $\frac{16,000}{1.25 \times 60}$ $= 213.333333 CFM$
6. Airflow: 189 CFM
1. Find the room's volume: length × width × height
  $18 \times 15 \times 7$ $= 1,890 ft³$
2. Multiply the volume by the air changes per hour, then divide by 60 to turn 'per hour' into 'per minute'
  $\frac{1,890 \times 6}{60}$ $= 189 CFM$
7. Airflow: 1,515.15 CFM
1. Find the airflow. The heat the air carries is 1.1 × CFM × the temperature difference, so divide the load by 1.1 × the difference
  $\frac{25,000}{1.1 \times 15}$ $= 1,515.151515 CFM$
8. Airflow: 17.6 CFM
1. Find the room's volume: length × width × height
  $12 \times 11 \times 8$ $= 1,056 ft³$
2. Multiply the volume by the air changes per hour, then divide by 60 to turn 'per hour' into 'per minute'
  $\frac{1,056 \times 1}{60}$ $= 17.6 CFM$
9. Airflow: 1,159.42 CFM
1. Find the airflow. The heat the air carries is 1.15 × CFM × the temperature difference, so divide the load by 1.15 × the difference
  $\frac{20,000}{1.15 \times 15}$ $= 1,159.42029 CFM$
10. Airflow: 333.33 CFM
1. Find the airflow. The heat the air carries is 1.2 × CFM × the temperature difference, so divide the load by 1.2 × the difference
  $\frac{24,000}{1.2 \times 60}$ $= 333.333333 CFM$