1. What is Mass Flow to Velocity Conversion?

Definition: This calculator converts mass flow rate (lb/hr) to velocity (ft/s) using fluid density and flow area.

Purpose: It helps engineers and technicians determine fluid velocity in pipes and ducts when only mass flow rate is known.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( V \) — Velocity (ft/s)
• \( W \) — Mass flow rate (lb/hr)
• \( \rho \) — Density (lb/ft³)
• \( A \) — Cross-sectional area (ft²)

Explanation: The formula converts mass flow to volumetric flow, then divides by area to get velocity. The 3600 converts hours to seconds.

3. Importance of Velocity Calculation

Details: Knowing fluid velocity is crucial for system design, ensuring proper flow rates, and avoiding issues like erosion or excessive pressure drop.

4. Using the Calculator

Tips: Enter mass flow rate in lb/hr, density (default 0.075 lb/ft³ for air at STP), and cross-sectional area. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why is density important in this calculation?
A: Density links mass flow to volumetric flow. Different fluids (air, water, steam) have different densities at various conditions.

Q2: What's a typical density for air?
A: Air at standard conditions is about 0.075 lb/ft³, but this changes with temperature and pressure.

Q3: How do I find the cross-sectional area?
A: For circular ducts, use \( A = \pi r^2 \) where r is the radius in feet.

Q4: What are typical velocity ranges in HVAC systems?
A: Usually 800-1200 ft/min (13-20 ft/s) for main ducts, 600-900 ft/min for branch ducts.

Q5: Can I use this for liquids as well as gases?
A: Yes, just use the appropriate density value for your liquid (water is ~62.4 lb/ft³ at room temp).