Pressure Drop vs Flow Rate Formula

Pressure Drop Formula:

\[ \Delta P = \frac{V^2 \times \rho}{2 \times 144} \] \[ V = \frac{Q}{A \times 448.83} \]

Velocity (V): ft/s

Pressure Drop (ΔP): psi

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1. What is the Pressure Drop vs Flow Rate Formula?

Definition: This calculator determines the pressure drop in a pipe system based on flow rate, pipe cross-sectional area, and fluid density.

Purpose: It helps engineers and technicians analyze fluid flow systems and predict pressure losses in piping networks.

2. How Does the Calculator Work?

The calculator uses two key formulas:

\[ V = \frac{Q}{A \times 448.83} \] \[ \Delta P = \frac{V^2 \times \rho}{2 \times 144} \]

Where:

\( \Delta P \) — Pressure drop (psi)
\( V \) — Fluid velocity (ft/s)
\( \rho \) — Fluid density (lb/ft³)
\( Q \) — Flow rate (GPM)
\( A \) — Cross-sectional area (ft²)

Explanation: First calculates velocity from flow rate, then uses velocity to determine pressure drop based on kinetic energy.

3. Importance of Pressure Drop Calculation

Details: Proper pressure drop estimation ensures adequate pump sizing, system efficiency, and prevents flow-related issues in piping systems.

4. Using the Calculator

Tips: Enter the flow rate in GPM, pipe cross-sectional area in ft², and fluid density (default 62.4 lb/ft³ for water). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's the 448.83 conversion factor?
A: This converts GPM to ft³/s (1 GPM = 0.002228 ft³/s) and accounts for unit consistency in the equation.

Q2: What's a typical fluid density for water?
A: Water at 60°F has a density of 62.4 lb/ft³, but this varies with temperature and dissolved solids.

Q3: Does this account for pipe friction?
A: No, this is the dynamic pressure component only. For complete pressure drop, include friction losses using Darcy-Weisbach.

Q4: How do I find cross-sectional area?
A: For circular pipes: \( A = \pi \times (D/2)^2 \) where D is diameter in feet.

Q5: What's a reasonable velocity range?
A: Typically 3-10 ft/s for water systems to balance pressure drop and erosion concerns.