Performance Evaluation of Truck Equipped with the Evaporative Cooling System during Transportation of Vegetable

The research describes the development of an evaporative cooling system in a non-refrigerated truck for the short-term storage of vegetables during transportation. The system comprises an evaporative cooler, storage unit, power supply, control panel, and real-time data monitoring for temperature  and relative humidity. Computational fluid dynamic (CFD) simulation was conducted to investigate the temperature and airflow distributions in the evaporative-cooled storage unit for five different configurations of air inlet and outlet. The configuration of one air inlet (front — lower left) and two air outlets (top — front and back centre) of the storage unit was shown to provide  optimum temperature and airflow distributions and hence, was applied in the system modification. The functionality and performance of the modified system were then evaluated in terms of the cooling profile of the storage units and leafy vegetable quality for the fresh market. Three storage treatments for the selected vegetable were investigated, i.e., evaporative-cooled truck (T1), canvas truck (T2), and cold truck (T3) during a five-hour journey from Cameron Highlands to Serdang. The average temperature inside the storage units was T3 < T1 < T2. Evaporative-cooled truck exhibited an average temperature reduction (DT) of 10°C from the ambient condition. It also demonstrated a relative humidity of >90%, which was in agreement with the recommended relative humidity for leafy vegetable storage. Post-five-hour storage treatments, vegetable stored under T1 exhibited the least weight loss as compared to T2 and T3. The results indicated that the evaporative cooling system manages to preserve vegetable quality soon after harvesting, hence the potential to reduce postharvest loss during transportation.