Phase-segmented analysis of blackberry pomace convective drying: Mass transfer dynamics, exergy efficiency, and staged temperature guidelines

Valorizing high-moisture blackberry pomace is constrained by convective drying analyses that mask evolving behavior and hinder rational design. This study applied a phase-segmented framework to convective drying at 50–90 °C, integrating kinetics, mass transfer, exergy, sustainability, and techno-economics. Five semi-empirical models were assessed; the Page model best described kinetics (R 2 = 0.9964–0.9992). Phase segmentation captured shifting controls, with Biot number (Bi), mass transfer coefficient ( h m ), and effective diffusivity ( D eff ) evolving, and activation energy rising from 19.22 kJ mol −1 in phase 1 to 60.87 kJ mol −1 in phase 3. Exergy analysis identified early efficiency peaks and late irreversibilities; peak η ex reached ∼13–16 % at 50–80 °C and ∼9 % at 90 °C, then fell below 1 % near completion, revealing recoverable outlet-air potential. Specific energy consumption decreased from 210.24 to 59.18 MJ kg −1 . Phase-resolved indicators yielded staged guidelines: 70–80 °C (phase 1), 60–70 °C (phase 2), and 50–60 °C (phase 3) to limit losses and preserve efficiency. Sustainability improved with temperature (sustainability index ( SI ) 1.15–1.99; CO 2 9.00–3.89 kg CO 2 kg −1 H 2 O). Techno-economic scenarios informed by energy savings and cost reductions suggested pay-back near 1.2 years under reduced demand. The framework clarifies mass- and energy-transfer mechanisms and delivers guidelines warranting validation via staged-temperature runs, supporting process refinement and control. • Page model accurately described blackberry pomace drying kinetics ( R 2 > 0.99) • Phase-segmented analysis revealed distinct D eff , E a , h m and Bi dynamics. • E a for diffusion dramatically increased in final phase (61 kJ mol −1 ) • Staged temperature profile (70–80 °C→60–70 °C→50–60 °C) proposed via exergy analysis • Efficiency gains via optimization shown economically viable by TEA for valorization