1. What is Flow Coefficient Cv?

Definition: The Cv value represents the flow capacity of a valve, defined as the number of US gallons per minute of water that will flow through the valve with a pressure drop of 1 psi.

Purpose: It helps engineers select and size valves properly for fluid control applications.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( C_v \) — Flow coefficient (dimensionless)
• \( Q \) — Flow rate (gallons per minute)
• \( \Delta P \) — Pressure drop (pounds per square inch)
• \( SG \) — Specific gravity of fluid (dimensionless)

Explanation: The flow rate is divided by the square root of the pressure drop divided by specific gravity to determine the valve's flow capacity.

3. Importance of Cv Calculation

Details: Proper Cv calculation ensures correct valve sizing, preventing issues like cavitation, excessive pressure drop, or insufficient flow capacity.

4. Using the Calculator

Tips: Enter the flow rate in GPM, pressure drop in psi, and fluid specific gravity (default 1.0 for water). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical Cv value range?
A: Cv values range from <1 for small valves to >1000 for large valves, depending on valve type and size.

Q2: How does specific gravity affect Cv?
A: Higher specific gravity fluids require larger Cv valves for the same flow rate and pressure drop.

Q3: Can this be used for gases?
A: This formula is primarily for liquids. Gas flow calculations require additional factors.

Q4: What's the relationship between Cv and Kv?
A: Kv is the metric equivalent: 1 Cv ≈ 1.156 Kv.

Q5: How accurate is this calculation?
A: It provides theoretical Cv. Actual performance may vary based on valve design and flow conditions.