<p><i>The conservation of energy and the conservation of global resources are key elements of both physical and engineering processes. It means that available energy and available work are both recognized as valuable commodities and their destruction is considered with a renewed interest. According to the first law of thermodynamics, the design of heat and mass transfer equipment usually adopts magnitudes such as inlet and outlet temperatures, flow rates, and pressure drops. It allows for reaching minimal design objectives such as surfaces, flow configurations, and materials. Alternatively, the analysis according to the second law of thermodynamics could lead to entropy generation or exergy disruption minimization -for most or engineering systems- or maximization –usually, for living systems- depending on the considered system requirements. This second approach is based on thermodynamic irreversibility and allow determining the geometric and chemical parameters of the systems. A heat and mass transfer model and analysis for an innovative hybrid hot air balloon is assumed as the reference problem which has been adopted to understand the major behavioural elements. It is constituted by coupling a traditional hot air balloon with a helium inflatable balloon and this particular architecture, which has been used for altitude record flights is still far from an effective optimization. The dynamic equilibrium conditions with the surrounding atmosphere are considered. Both the first and the second law of thermodynamics are assumed to study the balloon envelope and porous mass losses, convection, that convection losses. A heating source and a buoyant gas source are included in the model and discussed. Photovoltaic generation is also considered and both propulsion and heating duty cycle to keep a constant altitude are considered. The system has been considered as a limited unsteady irreversible thermodynamic living system and has been optimized by coupling two different aerostatic systems: an open hot air volume heated by a combined hydrolysis/fuel-cell energy cycle. The mission is considered as an evolution of the system in equilibrium with the surrounding environment. Hence, the thermodynamic model based on irreversible thermodynamics.&nbsp;The model of minimum entropy generation is applied. The results according to both first and second law are produced and compared to actual flight data and they show very good agreement indicating that the major physical processes responsible for balloon performance aloft are accurately captured in the proposed coupled optimization process and demonstrate that the system could be optimized up to reach a very high stratospheric altitude. The model and the design is provided and discussed according to the constructal law as defined by Adrian Bejan.&nbsp;</i></p>

Irreversibility Analysis, Design, and Optimization of a Combined Hybrid Hot Air and Buoyant Gas Balloon for Stratospheric Persistence Analysis, Design and Optimization of a Combined Hybrid Hot Air and Buyant Gas Baloon for Stratopheric Persistence

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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