Table of Contents
Regular Original Research Article
| An Unifying Thermodynamic Framework for Nonlinear Macrokinetics in Reaction-Diffusion Systems |
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Stanislaw Sieniutycz |
115-125 |
Two competing directions in elementary chemical or transport steps are analyzed from the viewpoint of their contribution to the overall rates. Systems with nonlinear transport phenomena and chemical reactions are described by the equations of nonlinear kinetics of the Marcelin-Kohnstamm–de Donder type that contain terms exponential with respect to the Planck potentials and temperature reciprocal. Simultaneously these equations are analytical expressions characterizing the transport of the substance or energy through the energy barrier. They constitute potential representations of a generalized law of mass action that includes the effect of transfer phenomena and external fields. Important are the physical consequences of these kinetics near and far from equilibrium. In these developments nonlinear symmetries and generalized affinity are important. The affinity picture - new for transport phenomena - and the traditional Onsagerian picture are shown to constitute two equivalent representations for kinetics of chemical reactions and transfer processes. Correspondence with the Onsager’s theory is shown closely to the thermodynamic equilibrium. Yet, it can be shown that rates of transport processes and chemical reactions far-from-equilibrium cannot be determined uniquely in terms of their affinities since these rates depend on all state coordinates of the system. |
| Effects of Immersed Surfaces on the Combustor Efficiency of Small-Scale Fluidized Beds |
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Afsin Gungor, Nurdil Eskin |
127-136 |
In this study, effects of the different types of heat exchanger surfaces on the second law efficiency of a small-scale circulating fluidized bed (CFB) combustor are analyzed and the results are compared with the bubbling fluidized bed coal combustor effectiveness values. Using a previously developed simulation program, combustor efficiency and entropy generation values are obtained at different operation velocities at different height and volume ratios of the immersed surfaces, both for circulating and bubbling fluidized bed combustors. Besides that, the influence of the immersed surface types on the combustor efficiency was compared for different fluidized bed combustors. Through this analysis, the dimensions, arrangement and type of the immersed surfaces which achieve maximum efficiency are obtained. |
| Influence of Regenerative Feed Water Heaters on the Operational Costs of Steam Power Plants and HP Plants |
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Jan T. Szargut |
137-141 |
The influence of particular regenerative feed-water heaters on the operational costs of a steam power plant and HP plant has been determined by means of the incremental energy efficiency expressing the ratio of the increase of electricity production to the increase of the consumption of chemical energy of fuel, assuming a constant flow rate of steam at the outlet of the turbine (power plant) or a given production rate of useful heat (HP plant). Exemplary calculations are included. |
| Procedures for the Search of the Optimal Configuration of District Heating Networks |
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Vittorio Verda, Chiara Ciano |
143-153 |
This paper deals with the choice of the optimal configuration of the district heating network to be built in an urban area. The users to be connected with the network are determined so that an economic objective function is optimized. In this approach, the average unit cost of heat is considered as the function to be minimized. An alternative heating system is considered for the users not connected with the network. In this work, three different iterative procedures are presented. All these procedures start with an initial superstructure connecting the possible users. The initial structure is progressively simplified by disconnecting one user at each iteration. The three procedures differ in the algorithm for the network simplification: the first procedure is deterministic, while the others use probabilistic approaches derived from the simulated annealing technique. The procedures are applied to a small portion of the urban tissue of Turin and their effectiveness is compared. |
| Technical Note: Zero Emissions Power Generation with CO2 Reduction by Fayalite |
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Nikolay Akinfiev, James McGovern, Evgeny Yantovski |
155-157 |
In this paper a new ‘fuel’, fayalite Fe2SiO4, is proposed tentatively and a new concept involving the convergence of a power plant and its fuel source is described. The CO2 from the power plant would be injected underground where it would be reduced to methane. The methane would then serve as the ‘derived fuel’ of the power plant having been produced by the reaction of fayalite with the CO2. One of the possible chemical reactions of CO2 with rock is indicated, along with properties of the mineral fayalite. Calculations of the Gibbs free energy and enthalpy show that the reaction of carbon dioxide with fayalite is exothermic and might be self-sustaining. |
ISSN: 2146-1511
