Assessing hygrothermal effects on the evaporative cooling of fruits with waste palm fruit fibre pads

This study explores using recycled waste palm fruit fibres as wetting pads in evaporative cooling (EVC) systems. The goal is to analyze how this wetting pad, influences the drivers of the EVC process and the effects on the quality of pre-cooled orange and papaya. The collected data is a foundation for analyzing transient heat responses during the pre-cooling process. To achieve this, we conducted cooling experiments using direct evaporative cooling (EVC) systems at a constant air delivery velocity of 4 m/s. The air delivery temperature for cooled fruits ranged from 25.8 °C to 20.2 °C at an air relative humidity range of 85.6 – 96.8 %. We develop heat transfer models to understand the cooling mechanism using established methods. Our results revealed that our active EVC reduced inlet temperature by ∼10 °C, with air delivery speed at 4 m s⁻¹. Our cooling efficiency ranged from 77% to 98.8%, and cooling capacity (CP) varied within 0.73 ≤ CP ≤ 2.52 kW. For orange and papaya, core temperatures reached 21.38 °C and 21.14 °C, respectively, in 16 hours from a peak of about 25.81 °C. Papaya exhibited a higher moisture loss per unit area and moisture flux of (1.03×10⁻⁵ kg/m².s) compared to orange (1.501×10⁻⁷ kg/m².s),. Fruit quality index analysis indicated low-quality loss (< 1%) for both fruits. Thus, orange lost approximately 0.00257% of its quality, while papaya lost 0.63% during cooling. The evaporative flux increased with temperature with Papaya having a higher evaporative flux than orange with a maximum value of 8.75 W while orange exhibited a maximum value of 0.0424 W.