Techno-economic analysis of combined inverted Brayton – Organic Rankine cycle for high-temperature waste heat recovery

Many practical cases with waste heat recovery potential such as exhaust gases of reciprocating engines, cement kilns or heat-treating furnaces, are nowadays often integrated with organic Rankine cycle to convert waste heat to the mechanical power. However, when dealing with high-temperature waste heat, organic Rankine cycle faces efficiency limit due to the physical properties of the working and thermal fluids. That gives room for further enhancement of the waste heat recovery technologies via the investigation of different non-conventional schemes as one of the possible ways. In the present work, a system introducing the combined inverted Brayton plus organic Rankine cycle is under investigation. Aspen Hysys models of both conventional organic Rankine cycle and combined cycle were designed, orienting on waste heat recovery from the heavy-load gas-fueled reciprocating engine exhaust. In this way, the performance of the combined scheme was benchmarked versus the conventional organic Rankine cycle. An assessment of the organic Rankine cycle working fluids was provided, and pentane has shown the best thermodynamic performance. The study on inverted Brayton cycle defined the remarkable effect of the water condensation in the gas duct on the inverted Brayton cycle performance. Finally, both thermodynamic and economic optimizations of the models were conducted, setting the stage for the comparison of solutions. Results have shown the 10% advantage of the combined scheme over organic Rankine cycle in generated power and system efficiency. The levelized-cost-of-energy-based optimization for variable capacity factors has highlighted above 6% advantage of the investigated solution. The analysis of the sensitivity from machines' efficiencies and heat exchangers' pinches has shown that with some sets of parameters, the studied scheme may concede to the organic Rankine cycle. Keywords: Inverted Brayton cycle, Organic Rankine cycle, Waste heat recovery, High-temperature exhaust, Techno-economic analysi

La politique culturelle du prince-électeur Maximilien-Emmanuel de Bavière (1679-1726) et le « modèle français »

Les réflexions collectives sur le paradigme des transferts culturels ou de savoirs se sont jusqu’à présent penchées en priorité sur les échanges de type érudit ou savant. La présente contribution élargit la perspective aux transferts franco-allemands effectués dans le domaine des savoirs liés à l’État ou fonctionnels dans le cadre du pouvoir, subsumés dans le débat historique actuel sous le terme générique et théoriquement encore peu problématisé des savoirs d’État. La notion de savoirs d’Éta..

Effect of inlet air temperature and relative humidity on performance of pem fuel cell

Present paper investigates the influence of inlet air temperature and relative humidity on performance of a PEM Fuel Cell stack with maximum power of 175 W. In order to control the inlet air temperature, a cooling system was designed and implemented. Changing the inlet air temperature in the range between 15°C and 25°C, it was experimentally proved that the lower temperature results in better fuel cell performance. This dependence was found to be non-linear. Next step of the research was to take into account the air humidity and to analyze the cooling effect on membrane productivity. For this purpose, an air humidifier and a sensor were installed into the inlet channel. Experiments showed that the efficiency of the system is increasing with the growing relative humidity. CFD simulation of the reactants flow inside the FC stack was conducted, helping to analyze thermal regime, velocity distribution and migration of hydrogen ions through the membrane on a cathode side. Using experimental data, it was detected that temperature on cathode side exceeds operational limits already at 120W power load.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016

Techno-economic analysis of waste heat recovery by inverted Brayton cycle applied to an LNG-fuelled transport truck

Aiming for the better environmental and economic performance of traditional engines, waste heat recovery (WHR) technologies are actively studied to find their most beneficial applications. In this work, the inverted Brayton cycle (IBC) is investigated as a potential WHR solution for liquefied natural gas (LNG) fuelled transport truck. LNG being one of the less polluting fossil fuels is widely spreading nowadays in different industries due to the rapid development of the LNG supply chain in the world. LNG-fuelled cargo transportation follows this prevailing trend. Based on the overexpansion of flue gases to subatmospheric pressure, inverted Brayton cycle, in turn, is considered a prospective technology of WHR and techno-economic analysis of IBC in several configurations on-board of a heavy transport truck have been assessed. IBC is integrated into the engine cooling system in the basic layout, and additionally, it incorporates LNG regasification process in advanced configurations. Power balance based on Aspen Hysys model enables to perform system optimisation and gives preliminary design parameters of the system components. Cost function approach provides the basis for a preliminary economic assessment of the layouts. Although the system shows fuel economy of maximum about 2.1 %, analysis revealed the necessity to continue the search for better technical solutions in IBC-based systems to make them economically attractive due to high cost of installed equipment

Les échanges savants franco-allemands au xviiie siècle

Cet ouvrage applique pour la première fois de façon ample et réflexive la notion de transferts culturels créée par Michel Espagne et Michael Werner en 1985 au champ de l’histoire des savoirs entre aires francophones et germanophones au xviiie siècle. Si, en effet, dans son projet, la République des lettres s’étend à l’ensemble de l’Europe et fait fi des frontières politiques, elle est traversée de tensions notamment nationales. Or, les échanges savants mettent en relation des acteurs fortement mobiles et des aires linguistiques et culturelles autant ou plus que proprement politiques, si bien que les Cantons helvétiques et les Provinces-Unies sont inclus dans l’analyse. La complexité des frontières et l’emboîtement des espaces mènent à distinguer des échelles d’analyse fluctuantes selon les objets envisagés et dans le temps, et à insérer les transferts dans des ensembles de circulations et de réseaux. Seule une telle mise en contexte, qui réinterprète la notion de transferts, permet d’analyser les biais linguistiques et les clichés, de cerner le développement de médias particuliers (correspondances, périodiques savants, encyclopédies, littérature clandestine) ou de réseaux connexes (huguenots, francs-maçons, clandestins par exemple). On souligne à terme la porosité ou les hiatus entre types de savoirs (locaux et globaux, écrits et pratiques), la malléabilité des identités savantes et la complexité de ce que l’on résume habituellement sous le nom unifiant de Lumières