Coffee bean particle motion in a rotating drum measured using Positron Emission Particle Tracking (PEPT)

Area of Science:

• Food Science and Technology
• Chemical Engineering
• Physics

Background:

• Coffee roasting involves complex physicochemical transformations.
• Heat transfer during roasting is significantly influenced by the time-temperature profile and particle dynamics.
• Understanding granular flow is crucial for optimizing roasting processes.

Purpose of the Study:

• To characterize the granular flow of coffee beans in a pilot-scale rotating drum roaster using Positron Emission Particle Tracking (PEPT).
• To investigate the impact of operational parameters (drum speed, batch size, bean density) on coffee particle dynamics.
• To correlate particle dynamics with heat transfer phenomena for improved coffee roasting.

Main Methods:

• Utilized Positron Emission Particle Tracking (PEPT), a non-invasive imaging technique, to track coffee bean movement.
• Conducted experiments in a pilot-scale rotating drum roaster.
• Analyzed particle motion data to identify distinct flow regions (in-flight and bean bed).

Main Results:

• Identified two primary regions of particle motion: a disperse phase of in-flight particles and a dense bean bed.
• Demonstrated that drum speed, batch size, and bean density significantly affect particle dynamics.
• Established a link between particle dynamics and heat transfer efficiency.

Conclusions:

• Particle dynamics in coffee roasting are controllable via drum speed, batch size, and bean density.
• Optimizing drum speed for different coffee densities can modulate conductive heat transfer.
• Findings support the development of physics-driven models for coffee roasting and inform best practices.