101,354 research outputs found
Dynamic Modeling of Organic Rankine Cycle Power Systems
No full textNew promising applications of organic Rankine cycle (ORC) technology, e.g., concentrated solar power, automotive heat recovery and off-grid distributed electricity generation, demand for more dynamic operation of ORC systems. Accurate physically-based dynamic modeling plays an important role in the development of such systems, both during the preliminary design as an aid for configuration and equipment selection, and for
control design and optimization purposes. A software library of modular reusable dynamic models of ORC components has been developed in the MODELICA language and is documented in the paper. The model of an exemplary ORC system, namely the 150
kW e Tri-O-Gen ORC turbogenerator is validated using few carefully conceived experiments. The simulations are able to reproduce steady-state and dynamic measurements of
key variables, both in nominal and in off-design operating conditions. The validation of the library opens doors to control-related studies, and to the development of more challenging dynamic applications of ORC power plants
Notes on the evolution of cemetery areas in Italy
No full textRecent changing in funerary architecture in Ital
The flexible asymmetric shock tube (FAST): A Ludwieg tube facility for wave propagation measurements in high-temperature vapours of organic fluids
No full textThis paper describes the commissioning of the flexible asymmetric shock tube (FAST), a novel Ludwieg tube-type facility designed and built at Delft University of Technology, together with the results of preliminary experiments. The FAST is conceived to measure the velocity of waves propagating in dense vapours of organic fluids, in the so-called non-ideal compressible fluid dynamics (NICFD) regime, and can operate at pressures and temperatures as high as 21 bar and 400 ?C, respectively. The set-up is equipped with a special fast-opening valve, separating the high-pressure charge tube from the low-pressure plenum. When the valve is opened, a wave propagates into the charge tube. The wave speed is measured using a time-of-flight technique employing four pressure transducers placed at known distances from each other. The first tests led to the following results: (1) the leakage rate of 5×10?4mbarl s?1 for subatmospheric and 5×10?2mbarl s?1 for a superatmospheric pressure is compatible with the purpose of the conceived experiments, (2) the process start-up time of the valve has been found to be between 2.1 and 9.0 ms, (3) preliminary rarefaction wave experiments in the dense vapour of siloxane D6 (dodecamethylcyclohexasiloxane, an organic fluid) were successfully accomplished up to temperatures of 300?C, and (4) a method for the estimation of the speed of sound from wave propagation experiments is proposed. Results are found to be within 2.1 % of accurate model predictions for various gases. The method is then applied to estimate the speed of sound of D6 in the NICFD regime.Aerodynamics, Wind Energy & PropulsionAerospace Engineerin
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
Working Fluid Design for Organic Rankine Cycle (ORC) Systems
No full textThe Organic Rankine Cycle is an energy conversion cycle similar to the conventional Rankine cycle which runs on a working fluid other than water. The selection of a working fluid is a critical part of designing an Organic Rankine Cycle (ORC) system. The number of fluid types actually used in commercial ORC power plants do not justify the number of fluid selection studies present in scientific literature. Hence the objective of this work is to develop a tool which simultaneously optimizes the energy conversion process and selects the optimum working fluid for a given heat source. It is based on a framework that uses a continuous-molecular targeting approach which allows for an integrated working fluid and system design. The process is modeled in Cycle Tempo, a modern graphical tool for thermodynamic analysis and optimization of systems for the production of electricity, heat and refrigeration. The system is simultaneously optimized with the pure component parameters of PCP-SAFT equation of state using a state-of-the-art optimization suite. The working fluid is selected by comparison of the pure component parameters of the PCP-SAFT equation of state with real fluids. A preliminary turbine model implemented directs the tool to generate suitable fluids for practically realistic systems. The tool has been tested for a waste heat recovery system for heavy-duty truck engines based on an ORC turbogenerator. The choice of working fluid is restricted to only the siloxane class which not only adheres to the technical, environmental, and toxicological requirements typical of the automotive sector but also allows for the implementation of a preliminary radial turbine model, whose shaft can be lubricated by the working fluid itself. The turbine has been modeled by applying the methodology of using non-dimensional parameters. Future work will be devoted to implement detailed component models and extending the scope of fluid selection to other organic fluid classes.Energy TechnologyProcess and EnergyMechanical, Maritime and Materials Engineerin
Working fluid design for organic rankine cycle systems (ORC)
No full textThe Organic Rankine Cycle is an energy conversion cycle similar to the conventional Rankine cycle which runs on a working fluid other than water. The selection of a working fluid is a critical part of designing an Organic Rankine Cycle (ORC) system. The number of fluid types actually used in commercial ORC power plants do not justify the number of fluid selection studies present in scientific literature. Hence the objective of this work is to develop a tool which simultaneously optimizes the energy conversion process and selects the optimum working fluid for a given heat source. It is based on a framework that uses a continuous-molecular targeting approach which allows for an integrated working fluid and system design. The process is modeled in Cycle Tempo, a modern graphical tool for thermodynamic analysis and optimization of systems for the production of electricity, heat and refrigeration. The system is simultaneously optimized with the pure component parameters of PCP-SAFT equation of state using a state-of-the-art optimization suite. The working fluid is selected by comparison of the pure component parameters of the PCP-SAFT equation of state with real fluids. A preliminary turbine model implemented directs the tool to generate suitable fluids for practically realistic systems. The tool has been tested for a waste heat recovery system for heavy-duty truck engines based on an ORC turbogenerator. The choice of working fluid is restricted to only the siloxane class which not only adheres to the technical, environmental, and toxicological requirements typical of the automotive sector but also allows for the implementation of a preliminary radial turbine model, whose shaft can be lubricated by the working fluid itself. The turbine has been modeled by applying the methodology of using non-dimensional parameters. Future work will be devoted to implement detailed component models and extending the scope of fluid selection to other organic fluid classes.Energy TechnologyProcess & EnergyMechanical, Maritime and Materials Engineerin
Experimental Observation of Non-Ideal Compressible Fluid Dynamics: with Application in Organic Rankine Cycle Power Systems
No full textFlight Performance and PropulsionEnergy Technolog
Collective Entrainment and Confinement Amplify Transport by Schooling Microswimmers
No full textMicroswimmers can serve as cargo carriers that move deep inside complex flow networks. When a school collectively entrains the surrounding fluid, their transport capacity can be enhanced. This effect is quantified with good agreement between experiments with self-propelled droplets and a confined Brinkman squirmer model. The volume of liquid entrained can be much larger than the droplet itself, amplifying the effective cargo capacity over an order of magnitude, even for dilute schools. Hence, biological and engineered swimmers can efficiently transport materials into confined environments
Handwritten biographical information on Paulina T. McClung Merritt
No full textA handwritten biography of Paulina T. McClung Merritt by an unknown author, 1892.
Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.
No full textIFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells
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