Tomatoes require immediate postharvest cooling due to higher perishability and associated losses. The situation becomes worsen in resource-constrained areas/farms as half of the tomatoes production may lost due to the losses. In this regard, a passive evaporative cooling-based tomato storage system (PEC-TSS) was developed and thermodynamically evaluated under different experimental conditions. Physicochemical analyses of tomatoes stored in PEC-TSS, outside, and room conditions were also performed to assess the comparative shelf-life. The PEC-TSS enabled a higher temperature drop about 11–14 °C, and maintained relative humidity above 85%. The corresponding average cooling efficiency, cooling capacity, exergy efficiency, temperature-humidity, and sustainability indices were determined as 80%, 2.1 kW, 26%, 31 °C, and 1.36, respectively. The titratable acidity and soluble solids of tomatoes retained 0.2 mg/g and 5°Brix, respectively, in the PEC-TSS. The physiological weight loss was measured about 20% for PEC-TSS-stored tomatoes compared to above 80% in other storage conditions. Therefore, the shelf-life of PEC-TSS stored tomatoes was extended to about 37 days under particular load conditions. The payback period of marginal-scale PEC-TSS was calculated about two years, with cost-benefit ratio greater than 1.0 from the second year to onwards.
The auto-ignition of cylinder lubricating oil droplets, which is primarily governed by the long physical ignition delay (evaporation phase), is the crucial inducement of pre-ignition in marine low-speed two-stroke hydrogen engines. To reveal the evaporation mechanisms of lubricating oil droplets, a two-dimensional model of C25H52-C30H62 binary surrogate droplets in nitrogen atmosphere is developed and validated against experiments covering stationary, forced convection, high-temperature and high-pressure conditions. Then the evaporation characteristics of oil droplets under high-temperature (700–1000 K), high-pressure (1–50 bar), and forced convection (0-4 m/s) conditions are illuminated. The results indicate that as ambient pressure increases from 1 bar to 50 bar, the normalized droplet lifetime decreases by 63.3% under forced convection conditions, which is opposite to the trend under stationary conditions. At high pressure, the increase of vapor phase density enhances convective heat transfer, while the decrease of vaporization latent heat lowers the energy required for phase transition. In the low inflow velocity range, the external shear forces and the Marangoni effect synergistically enhance the thermal and mass Peclet numbers, which accelerates droplet evaporation. However, when the inflow velocity exceeds 0.9 m/s, the competition between external shear and Marangoni convection suppresses the internal circulation, which prolongs the droplet lifetime. Under extremely high-pressure convective conditions, the oil droplet with large size exhibits higher heat transfer efficiency and shorter evaporation stage than that with small size. During the early and middle evaporation stages, the external shear forces dominate the internal circulation. Whereas, in the late stage, the Marangoni effect gradually overrides shear forces.
In this work, molecular dynamics simulations are conducted to investigate self-sustained transport within a sudden-expansion nanochannel with homogeneous surface energy. The microscopic mechanism of self-sustained transport is elucidated by calculating the thermo-osmotic force. The results indicate that the magnitude and direction of the volume flux within the channel can be effectively regulated by adjusting the intensity of the thermal sources on the channel walls. This is attributed to the sudden-expansion geometry, which induces thermo-osmotic forces in opposite directions but different magnitudes on the two sides. Specifically, the thermo-osmotic force in the narrow segment is stronger, resulting in a net flow due to force imbalance. Furthermore, the effects of averaged system temperature, channel segment length ratio, and the width difference between the two segments on the volume flux are systematically examined to determine the optimal flow control strategy. These findings provide valuable insights for the design of pump-free nanofluidic systems and promote advancements in emerging applications, such as low-grade thermal energy harvesting, energy-efficient water treatment, and high-efficiency energy conversion.
