1. What is the Hagen-Poiseuille Equation?

The Hagen-Poiseuille equation describes the relationship between pressure difference, flow rate, and resistance in laminar flow through a cylindrical pipe. It's particularly useful in chromatography systems and other fluid dynamics applications.

2. How Does the Calculator Work?

The calculator uses the Hagen-Poiseuille equation:

Where:

• \( Pressure \) — Pressure difference (psi)
• \( r \) — Radius of the tube (mm)
• \( Viscosity \) — Dynamic viscosity (cP)
• \( L \) — Length of the tube (m)

Explanation: The equation shows that flow is directly proportional to the pressure gradient and the fourth power of the radius, and inversely proportional to viscosity and length.

3. Importance of Flow Calculation

Details: Accurate flow calculation is essential for designing chromatography systems, optimizing separation conditions, and ensuring proper system performance in GC applications.

4. Using the Calculator

Tips: Enter pressure in psi, radius in mm, viscosity in cP, and length in meters. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What are typical viscosity values for GC carrier gases?
A: Hydrogen: ~0.009 cP, Helium: ~0.019 cP, Nitrogen: ~0.017 cP at room temperature.

Q2: How does temperature affect the calculation?
A: Viscosity changes with temperature. For accurate results, use viscosity values at your operating temperature.

Q3: What is the range of validity for this equation?
A: The equation is valid for laminar flow (Re < 2100) in straight, rigid tubes with Newtonian fluids.

Q4: How does column diameter affect flow rate?
A: Flow rate is proportional to the fourth power of radius, so small diameter changes have large effects on flow.

Q5: Can this be used for packed columns?
A: No, packed columns require more complex calculations accounting for particle size and porosity.