• Passive cooling blanket (PCB) reduced temperature by a maximum of up to 20 °C. • PCB shows consistent performance across diverse climatic conditions and crop types, maintaining high humidity and stable temperatures. • PCB extended fresh produce shelf life and significantly reduced postharvest losses. • PCB reduced vendor tomato losses by approximately 92% in Uganda. • 97% of Kenyan farmers showed interest in adopting the PCB for improved storage. This study evaluates the effectiveness of evaporative passive cooling blankets (PCBs) in reducing postharvest losses and extending the shelf life of fruits and vegetables in Kenya, Uganda, and Nigeria. Using locally available natural materials such as sawdust and charcoal, PCBs were deployed under diverse climatic conditions to assess their capacity for temperature reduction and humidity control. In Kenya, PCBs achieved temperature reductions of up to 10 °C and maintained relative humidity near 95 %, reducing postharvest losses of vegetables by up to 45 % and extending shelf life by 3–4 days. In Uganda, PCB application along the local tomato supply chain lowered average air temperatures by up to 2 °C, with peak reductions of up to 20 °C. This intervention extended tomato shelf life by 2 days and improved market outcomes, although performance was moderated by rainy-season conditions. In Nigeria, PCBs reduced average air temperature by 5 °C, increased relative humidity by 25 %, and decreased tomato weight loss and rot by 32 % and 20 %, respectively. Overall, the use of PCBs reduced postharvest losses by approximately 30 % across the three countries. These findings demonstrate a scalable, low-cost, electricity-free cooling solution suitable for smallholder farmers in Sub-Saharan Africa. By validating PCB performance under real field conditions, this study highlights the potential of passive evaporative cooling technologies to enhance food preservation, reduce waste, and improve food security in resource-limited settings.

This study proposes an innovative nonuniformly twisted elliptical tube heat exchanger (NTETHEX) with unequal twist pitches to address the inadequacy of uniformly twisted tube designs in double-tube heat exchanger system. A numerical investigation was conducted in the laminar regime, evaluating nine CFD cases with twist ratios ranging from 1.0 to 2.0. The optimal configuration featuring an outer tube combination of (400-800-1400) achieved the highest Nusselt number ( Nu ) and thermal performance. Further, the numerical solutions are optimized by integrating Box-Behnken Design, Response Surface Methodology, NSGA-II and a weighted factor scalarization technique. The critical design variables such as Reynolds number ( Re ), twist pitch ( P ), and surface temperature ( T s ) were analyzed to enhance the Nusselt number ( Nu ), minimizing the friction factor ( f ), and improving the PEC . Also, Quadratic polynomial regression models are developed, and their significance are evaluated through analysis of variance (ANOVA). The objective functions fitted via RSM are processed with NSGA-II to identify the set of Pareto optimal solutions. The outcomes of this multi objective optimization study compared with uniformly twisted tube and the Nu increased by 52 % and frictional coefficient is reduced by 200 % . It is evident that raising Re markedly enhances Nu . The best-performing NTETHEX configuration was found at Re = 3940.54, T s = 365 K , and P = 1.90 demonstrates the potential of nonuniformly twisted tube for highly efficient heat exchangers in critical energy applications.