Mass Flux Density & Mass Velocity Calculator

Thermal-Hydraulics, Mass Transfer & Mass Velocity Metrology

Mass Flux Density is the mass flow rate passing through a unit cross-sectional area:

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• Universal Mass Flux Conversion Formulas (Perry's Handbook)**:

G_lb/(ft^2·s) = G_kg/(m^2·s)4.882428 = G_kg/(m^2·s) × 0.204816

G_lb/(ft^2·h) = G_kg/(m^2·s) × 737.3377 = G_lb/(ft^2·s) × 3,600

G_kg/(m^2·s) = G_lb/(ft^2·s) × 4.882428 = G_kg/(m^2·h)3,600

1 g/(cm^2·s) = 10.0 kg/(m^2·s)

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• Total Mass Flow & Linear Fluid Velocity Formulas**:

m = G × A

v = (G) / (ρ)

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• Standard Industrial Mass Flux Benchmarks**:

• RO Water Membrane: 30.0 kg/(m^2·h) 0.00833 kg/(m^2·s) 6.14 lb/(ft^2·h)

• Packed Distillation Tower (Vapor): 2.5 kg/(m^2·s) 0.512 lb/(ft^2·s) 1,843 lb/(ft^2·h)

• Nuclear PWR Reactor Core: 1,000 kg/(m^2·s) 204.82 lb/(ft^2·s) v = 1.33 m/s

• Supercritical Boiler Tube: 2,000 kg/(m^2·s) 409.63 lb/(ft^2·s) v = 4.00 m/s

How to Use This Calculator

Enter your Mass Flux Density Magnitude (G / ṁ'') (e.g. 1000 in G), From Mass Flux Unit — choose from kg/(m²·s) - SI Base Unit, Pounds per SqFt-Second (lb/(ft²·s) - Aerospace / Nuclear), Pounds per SqFt-Hour (lb/(ft²·h) - Chemical Process / Towers), To Mass Flux Unit — choose from Pounds per SqFt-Second (lb/(ft²·s)), Pounds per SqFt-Hour (lb/(ft²·h)), kg/(m²·s), Flow Channel Cross-Sectional Area (A in m²) (e.g. 0.50 in m²), Fluid Density (ρ in kg/m³) (e.g. 750 in kg/m³), and Nuclear & Chemical Process Benchmark — choose from Custom Mass Flux System, PWR Nuclear Reactor Core (1,000 kg/(m²·s), ρ=750) → 204.82 lb/(ft²·s) | 737,338 lb/(ft²·h) | ṁ = 500 kg/s | v = 1.33 m/s, Packed Distillation Column (2.5 kg/(m²·s), ρ=2.5) → 0.512 lb/(ft²·s) | 1,843 lb/(ft²·h) | v = 1.00 m/s. Results update instantly as you type — adjust any value to compare scenarios.

The Formula

Total Mass Flow Rate: m_dot = G * A (kg/s and lb/h)

Linear Fluid Velocity: v = G / rho (in m/s)

Worked Example

A nuclear thermal-hydraulics engineer evaluating a pressurized water reactor core with mass flux G = 1,000 kg/(m^2·s) across a 0.50 m^2 open core flow area calculates the total mass flow is 500.0 kg/s (3.97 million PPH) and coolant travels at 1.33 m/s through the fuel assemblies.

Understanding Your Result

Unit conversions are exact by definition within a given measurement system (e.g., 1 km = exactly 1,000 m). Cross-system conversions (metric to imperial) use defined exchange factors: 1 inch = exactly 2.54 cm; 1 pound = 0.45359237 kg. Round your converted result to match the precision of your original measurement — expressing more decimal places than your input justifies implies false accuracy. For regulatory, legal, or safety-critical applications, verify which measurement system is required by the applicable standard.