Mass Transfer Coefficient Calculator

Mass Transfer Coefficient Calculator

Wiratama

11/16/20252 min read

1. Definition

The mass transfer coefficient (k) quantifies how fast a chemical species moves from one phase to another due to concentration gradients. It is a key parameter in equipment such as:

  • Absorbers

  • Strippers

  • Distillation columns

  • Dryers

  • Packed towers

  • Reactors with gas–liquid interfaces

Mass transfer coefficients describe the rate of diffusion across the boundary layer on each side of the interface and are essential for designing separation and reaction processes.

2. Background Theory

Mass transfer in fluids is often described using film theory, which assumes a thin stagnant film near the interface controls mass flux. The flux is given by:

Where:

  • k = mass transfer coefficient (m/s)

  • C,A,b = bulk concentration

  • CA,i = interface concentration

To estimate kkk, engineers often use dimensionless correlations involving:

Reynolds Number

Represents the ratio of inertial to viscous forces.
Higher Re → more turbulence → higher mass transfer.

Schmidt Number

Represents the ratio of momentum diffusivity to mass diffusivity.

Sherwood Number

A dimensionless group that directly relates to the mass transfer coefficient.

General Film Theory Correlation

The calculator uses a commonly applied empirical relation for external flow:

These exponents are widely used for pipes, tubes, and external flows where convection enhances diffusion.

3. How the Calculator Works

Step 1 — User Inputs

The calculator requires:

  • Diffusivity D

  • Fluid velocity u

  • Characteristic length L

  • Fluid density ρ

  • Dynamic viscosity μ

Step 2 — Compute Non-Dimensional Numbers

The calculator computes Re and Sc

Step 3 — Compute Sherwood Number

Step 4 — Compute the Mass Transfer Coefficient

Step 5 — Output Results

The calculator displays:

  • Reynolds number

  • Schmidt number

  • Sherwood number

  • Mass transfer coefficient kkk

4. Applications

This calculator is useful for quick calculations in:

  • Gas absorption & stripping

  • Liquid–liquid extraction

  • Drying operations

  • Evaporation

  • Bubble columns & stirred tanks

  • Packed tower mass transfer design (with extension)

It is ideal for:

  • Early-stage equipment sizing

  • Educational use

  • Quick engineering estimates