Moving Drying Fronts: Locate the Evaporating Boundary before Choosing a Model

Define the Material or Thermodynamic Model

The Torabi–Mehrafarin drying model treats the evaporation boundary as a moving interface between wet and dry regions. In its falling-rate description, the interface recedes inside a porous medium. Front position is a spatial model variable distinct from a total water-loss curve.

Review a Hypothetical Comparison

Imagine a 5 mm slab with an assigned front 1.0 mm below the exposed face at time A and 1.5 mm at time B. The modelled dry-layer thickness increases by 0.5 mm while wet material remains deeper inside. An observation that the face looks dry at both times cannot distinguish those two interface positions.

Keep the Evidence with the Decision

Record the assumed geometry, front definition and independent observation used to estimate position. Check whether a sharp interface is defensible or whether the material instead has a broad moisture profile.

The fictional positions are not measurements and give no front velocity without a time interval. A receding-interface model is one representation of porous drying, not a universal mechanism for every solid or solvent system.

Does evaporation occur at an exposed surface or at a receding internal interface?

This blank worksheet is for your own project. It contains no H M machine trial result.

Customer Questions

Primary References

These references support the technical principles discussed in this guide. The worked examples and review questions are educational.

• Torabi–Mehrafarin drying model
• Reference from hmpharmamachines.com