The effect of thermal processing with nanofluids on heat transfer, energy consumption (E), and the properties of pomegranate juice—including phenolic compounds, anthocyanins, and color indices—was investigated using standard methods, spectrophotometry, and image processing devices. For this purpose, three nanofluid velocities (Vnf) (0.52, 0.57, and 0.62 m/s), three pomegranate juice velocities (VPJ) (0.54, 0.61, and 0.68 m/s), and three nanoparticle concentrations (Cnp) (0 %, 1.5 %, and 3 %) were selected for the thermal processing of pomegranate juice in a shell and tube heat exchanger (STHX) using Central Composite Design (CCD). Optimal conditions were determined with Design-Expert software and the Response Surface Method (RSM), and the results for Copper (II) oxide (CuO) nanoparticles were compared with Aluminum oxide (Al2O3) and Titanium dioxide (TiO2) nanoparticles. The use of nanofluids containing CuO nanoparticles at concentrations of up to 3 % during the thermal processing of pomegranate juice improved heat transfer, reduced processing time by up to 48 %, and saved energy by up to 39 %. Thermal processing with nanofluids preserved color quality (Redness index, a* and Lightness index, L*), prevented anthocyanin degradation, reduced brown pigment formation, and maintained key phenolic compounds. Optimization using RSM revealed that the best operational conditions included 3 % CuO nanoparticles and flow rates of 0.62 and 0.67 m/s in the shell and tube sections, respectively, achieving a desirability index of 0.94. Furthermore, CuO nanofluids outperformed Al2O3 and TiO2 nanofluids in reducing processing time and preserving color and nutritional compounds.
