Development and Validation of a Thermally Stable Small-Scale Cold Storage System for Enhanced Post-Harvest Preservation of Tomatoes – Experimental and Numerical Approach

Resumen

Perishable agricultural commodities, which are subject to post-harvest depreciation, are a chronic problem in developing areas, which can be explained by the lack of cold-storage facilities, spatial variability of temperature patterns, and frequent power outages. The current study aims to design, optimize and experimentally test an improved small scale cold-storage facility that will improve uniformity of airflow, maintain thermal conditions and increase shelf life of tomatoes in decentralized rural environment. To make a comparison between conventional and curvature-modified cold-storage geometry, a three-dimensional Computational Fluid Dynamics (CFD) model was carried out based on the use of the SST k-ω turbulence model. The optimized design was installed in a cold-storage chamber of 8.42m³ with a 0.6TR vapor-compression refrigerator unit and 500-liter, water based thermal reserve. The results of CFD indicated an increase in penetration of airflow, a reduction in stagnant areas and a drop in local hot-spots temperature of 25-27°C to 22-25°C, accompanied by a reduction in precooling time of approximately 40 minutes. Conditions in experiments were also supported by experimental validation that kept temperatures at 11 ± 2°C, with relative humidity at 80-90% during a 28-day time interval. The stored tomatoes recorded the least weight loss of only 5.2% in the physiological weight and retained a pH between 4.3 and 5.9; whereas the tomatoes not stored withered after 12-13 days. The combined device was able to provide 15-20 hours of thermal reserve when the power went off. The current work validates that the application of CFD-based geometric optimization, coupled with thermal-back up, significantly improves cooling efficiency, stability in operation, and shelf-life conservation in a small-scale cold-storage facility.