1. What Is the Flow Coefficient Cv?

Definition: The flow coefficient (Cv) is a dimensionless number that represents the flow capacity of a valve or other flow component.

Purpose: It defines the number of gallons per minute (GPM) of water at 60°F that will flow through a valve with a 1 psi pressure drop.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( C_v \) — Flow coefficient (dimensionless)
• \( Q \) — Flow rate (GPM)
• \( \Delta P \) — Pressure drop across the valve (psi)
• \( SG \) — Specific gravity of the fluid (relative to water)

Explanation: The formula relates the flow rate through a valve to the pressure drop and fluid properties.

3. Importance of Flow Coefficient

Details: Cv is critical for valve sizing, system design, and ensuring proper flow control in piping systems.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What does a higher Cv value mean?
A: A higher Cv indicates a greater flow capacity - more fluid can pass through with the same pressure drop.

Q2: How does specific gravity affect Cv?
A: Heavier fluids (higher SG) require more pressure to achieve the same flow rate, resulting in lower Cv values.

Q3: What's a typical Cv range for valves?
A: Cv values range from <1 for small valves to >1000 for large industrial valves.

Q4: Can Cv be used for gases?
A: Yes, but additional corrections are needed for compressible flow calculations.

Q5: How is Cv related to Kv?
A: Kv is the metric equivalent (m³/h at 1 bar drop), where Cv = 1.156 Kv.