Load & DesignQuestion 16 of 110
Air velocity in a duct is calculated by dividing airflow (CFM) by what?
a.The duct length
b.The cross-sectional area of the duct in square feet
c.The static pressure
d.The temperature difference
Explanation
Velocity in feet per minute equals CFM divided by the duct cross-sectional area in square feet. Excessive velocity causes noise and high friction losses, while too little velocity can reduce throw and mixing. Designers balance velocity against static pressure limits.
Practice all 110 questions free — no signup required.
Related questions on this topic
- What is the primary purpose of a Manual J block load versus a room-by-room load?
- If a home has a calculated cooling load of 30,000 BTU/hr, what nominal equipment size is the closest match?
- Friction rate in duct design is typically expressed in which units?
- A branch duct must deliver 200 CFM at a velocity of about 600 feet per minute. Approximately what free area is required?
- Under California energy standards, duct leakage in many new and altered systems must be verified by which method?
- Which condition would a technician correct by performing an accurate load calculation instead of using a rule of thumb like square footage per ton?
Last reviewed: · editorial process
PrepPass Editorial Team · Verified against California CSLB C-20 Warm-Air HVAC Trade Exam · How we review