Browsing by Author "Marwa, Vicent"

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    Design and performance analysis of portable solar powered cooler for vaccine storage
    (SCI, 2024-10-31) Marwa, Vicent; Kivevele, Thomas; Kichonge, Baraka; Selemani, Juma
    The efficacy of vaccine storage is significantly impacted by temperature fluc- tuations within the cooler, often exacerbated by using phase change materials in existing cooler designs for remote areas. These materials can undergo uneven melting and phase separation, leading to temperature instability and vaccine potency loss. In response to this challenge, the present study intro- duces a novel design of a portable, locally‐made solar‐powered cooler opti- mized for longer storage periods. The cooler's performance in terms of tem- perature distribution, airflow dynamics, and the coefficient of performance (COP) is meticulously examined through computational fluid dynamics (CFD) simulations. The simulated results were validated using experimental data from the open literature, ensuring accuracy and reliability. The findings indicate that the developed cooler achieves significant improvements over traditional models. For instance, the current model reaches a temperature of +12°C in just 84 min, compared to 208 min, as reported in the literature results. Moreover, the current model reaches a temperature of −12°C in 195 min and it has energy efficient with a COP of 4.5. Statistical analysis further confirms the reliability of the simulation results, with root mean square and mean absolute percentage errors of 6.587 and 24.2%, respectively. Additionally, a comparative study of five insulative materials highlights polyurethane (Po) as the top performer, with a heat transfer performance of 14.3%, followed by feather fiber (Fe) (18.7%), fly ash (Fl) (19.8%), fiberglass (Fi) (21.9%), and coconut fiber (Co) (25.9%). Notably, net present value (NPV) of $689.336 and $448.01 was obtained for economic analysis of the current model over the existing model, showing the feasibility of the study. Hence, the cooler's effectiveness in storing vaccines in isolated regions exceeds that of conventional models, providing a hopeful solution to tackle vital challenges in vaccine distribution and preservation.
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    Simulation and Experimental Performance Analysis of Portable Locally-Made Solar-Powered Cooler for Vaccine Storage
    (Trans Tech Publications Ltd, 2025-02) Marwa, Vicent; Kichonge, Baraka; Selemani, Juma; Kivevele, Thomas
    Poor storage conditions, particularly exposure to extreme temperatures, can significantly compromise vaccine efficacy, making them ineffective or harmful. This highlights the urgent need for adequate storage infrastructure and monitoring systems, especially in remote areas with limited healthcare resources. This study evaluates the performance of a locally-made solar-powered cooler designed for vaccine storage in such environments. A digital AKO thermostat was integrated to control the compressor according to specified temperature limits, alongside a data logger for continuous temperature monitoring and a fluke device for DC and voltage measurements. The experimental results, validated against existing literature, were reliable and accurate. Key findings reveal that the cooler can reduce temperature to -14.9°C within 180 minutes, surpassing the performance of previous models that attained a temperature of -10°C after 144 minutes. The optimal insulation thickness for maintaining a cooling temperature of -15°C was determined to be 0.07 m using polyurethane insulation material, compared to 0.129 m with Feather Fiber, reflecting a 45.7% increase in efficiency at an ambient temperature of 42°C. Similar results were observed at an ambient temperature of 32°C. Modeling outcomes provided valuable guidance for the experimental design and comparative analysis.