M!Zare 48,037 اشتراک گذاری ارسال شده در 4 تیر، ۱۳۹۱ [TABLE=class: tocArticle, width: 100%] [TR] [TD=class: tocTitle] برای مشاهده این محتوا لطفاً ثبت نام کنید یا وارد شوید. ورود یا ثبت نام [/TD] [TD=class: tocGalleys] برای مشاهده این محتوا لطفاً ثبت نام کنید یا وارد شوید. ورود یا ثبت نام [/TD] [/TR] [TR] [TD=class: tocAuthors] Alicia Boyano, Ana-Maria Blanco-Marigorta, Tatiana Morosuk, George Tsatsaronis [/TD] [TD=class: tocPages]1-9[/TD] [/TR] [TR] [TD=class: tocAbstract, width: 90%] Steam methane reforming (SMR) is one of the most promising processes for the production of hydrogen. Therefore, the overall thermodynamic efficiency of this process is of particular importance. The thermodynamic inefficiencies in a thermal system are related to exergy destruction and exergy loss. However, a conventional exergetic analysis cannot evaluate the mutual interdependencies among the system components nor the real potential for improving the energy conversion system being considered. One of the tools under development for the improvement of energy conversion systems from the thermodynamic viewpoint is the advanced exergetic analysis. In this paper, the avoidable part of the exergy destruction is estimated and the interactions among components of the overall system are evaluated in terms of endogenous and exogenous exergy destruction. The assumptions required for these calculations are discussed in detail, especially for those components that are typically used in chemical processes. Results of this paper suggest options for increasing the thermodynamic efficiency of hydrogen production by steam-methane reforming.[/TD] [/TR] [/TABLE] 1 نقل قول لینک به دیدگاه
M!Zare 48,037 مالک اشتراک گذاری ارسال شده در 4 تیر، ۱۳۹۱ [TABLE=class: tocArticle, width: 100%] [TR] [TD=class: tocTitle] برای مشاهده این محتوا لطفاً ثبت نام کنید یا وارد شوید. ورود یا ثبت نام [/TD] [TD=class: tocGalleys] برای مشاهده این محتوا لطفاً ثبت نام کنید یا وارد شوید. ورود یا ثبت نام [/TD] [/TR] [TR] [TD=class: tocAuthors] Wojciech Stanek [/TD] [TD=class: tocPages]11-16[/TD] [/TR] [TR] [TD=class: tocAbstract, width: 90%]Unfavourable influence of human activity on the natural environment can be divided into two groups: depletion of limited non-renewable resources and rejection of harmful substances. The depletion of non-renewable resources should be minimized to keep them for future mankind (sustainable development). Exergy can be applied as measure of the quality of natural resources. The influence of human activities on the depletion of natural resources can be evaluated by means of the calculus of cumulative consumption of exergy of non-renewable natural resources (thermo-ecological cost). The paper presents selected applications of the theory of thermo-ecological cost developed by Szargut.[/TD] [/TR] [/TABLE] 1 نقل قول لینک به دیدگاه
M!Zare 48,037 مالک اشتراک گذاری ارسال شده در 4 تیر، ۱۳۹۱ [TABLE=class: tocArticle] [TR] [TD=class: tocTitle] برای مشاهده این محتوا لطفاً ثبت نام کنید یا وارد شوید. ورود یا ثبت نام [/TD] [TD=class: tocGalleys] برای مشاهده این محتوا لطفاً ثبت نام کنید یا وارد شوید. ورود یا ثبت نام [/TD] [/TR] [TR] [TD=class: tocAuthors] Amaya Martínez-Gracia, Antonio Valero, Javier Uche [/TD] [TD=class: tocPages]17-25[/TD] [/TR] [TR] [TD=class: tocAbstract, width: 90%]The hydroelectricity potential of rivers is a very well-know parameter used to characterize the availability of a river as a function of its flow and its altitude. However, the chemical potential of water flowing through the rivers is commonly ignored. In its source, water presents high quality and, therefore, it owns an important availability that can be expressed through its chemical exergy value. On the opposite, when it flows into the sea and reaches the thermodynamic equilibrium, it can not be further used and it is converted into a null exergy value. Within these two limit values, the exergy state of the river at its different stages can be assessed. On the other hand, water availability for specific uses depends on its quality. In this way, the almost always hidden value of water, its chemical potential, is highlighted and can be compared to the potential component, since they are expressed in the same units (energy units). In this paper, it is shown that potential and chemical exergy values of rivers rise up with values with the same order of magnitude. That is, the chemical value of a river is, from a thermodynamic perspective, as much as its potential value. The main difference lies in the current available technologies to take advantage of those physical disequilibrium: while hydro-power turbines are a completely proved technology, there are not yet commercial devices to take advantage of the hydro-chemical potential. Results of those estimations for a small Spanish river, the Muga river, are presented in this paper in order to prove the accuracy of the methodology. It is shown that the potential exergy of that river ranges from 2.37 to 7.15 MW, while its chemical exergy is comprised between 2.30 and 8.78 MW for the present state of the river. In addition, several exergy indexes are defined as basic parameters to provide information about the advantage taken from the river, that is, about the water uses within the watershed. [/TD] [/TR] [/TABLE] 1 نقل قول لینک به دیدگاه
M!Zare 48,037 مالک اشتراک گذاری ارسال شده در 4 تیر، ۱۳۹۱ [TABLE=class: tocArticle] [TR] [TD=class: tocTitle] برای مشاهده این محتوا لطفاً ثبت نام کنید یا وارد شوید. ورود یا ثبت نام [/TD] [TD=class: tocGalleys] برای مشاهده این محتوا لطفاً ثبت نام کنید یا وارد شوید. ورود یا ثبت نام [/TD] [/TR] [TR] [TD=class: tocAuthors] Jan Gorski, Slawomir Rabczak [/TD] [TD=class: tocPages]27-33[/TD] [/TR] [TR] [TD=class: tocAbstract, width: 90%] The critical mass flow of dense gases strongly depends on real gas effects. In the present work the detailed assessment of the critical flow conditions and the limiting mass velocity in the flow of refrigerants has been experimentally verified. Critical flow function C* data for R-410A and R-507A have been predicted based on Martin–Hou equation of state. The computational study was assured by implementation of theoretical model [1] for one dimensional (1D) and non-linear gas dynamic problems. This model, with the corrections for the boundary layer (BL) displacement thickness, gives a better prediction of the critical flow function than classical approach. Appropriate sonic flow conditions have been executed in the pressurized closed loop system by using ISO 9300 critical Venturi nozzle. Measurements of critical mass flow for dense superheated vapour of R-410A and R-507A carried out on laboratory test stand have confirmed the accuracy of the model and its physical significance. A main result of the investigations is a set of graphs C*(T0, p0) and tablesfor an assumed range of stagnation temperature T0 and pressure p0 at the upstream flow.[/TD] [/TR] [/TABLE] 1 نقل قول لینک به دیدگاه
M!Zare 48,037 مالک اشتراک گذاری ارسال شده در 4 تیر، ۱۳۹۱ [TABLE=class: tocArticle] [TR] [TD=class: tocTitle] برای مشاهده این محتوا لطفاً ثبت نام کنید یا وارد شوید. ورود یا ثبت نام [/TD] [TD=class: tocGalleys] برای مشاهده این محتوا لطفاً ثبت نام کنید یا وارد شوید. ورود یا ثبت نام [/TD] [/TR] [TR] [TD=class: tocAuthors] Grzegorz Brus, Yosuke Komatsu, Shinji Kimijima, Janusz Szmyd [/TD] [TD=class: tocPages]43-51[/TD] [/TR] [TR] [TD=class: tocAbstract, width: 90%]The conversion of biogas to electricity presents an attractive niche application for fuel cells. Thus attempts have been made to use biogas as a fuel for high temperature fuel cell systems such as SOFC. Biogas can be converted to hydrogen-rich fuel in a reforming process. For hydrocarbon-based fuel, three types of fuel conversion can be considered in reforming reactions: an external reforming system, an indirect internal reforming system and a direct internal reforming system. High-temperature SOFC eliminates the need for an expensive external reforming system. The possibility of using internal reforming is one of the characteristics of high temperature fuel cells like SOFC. However, for high-temperature operation, thermal management of the SOFC system becomes an important issue. To properly carry out thermal management, both detailed modeling and numerical analyses of the phenomena occurring inside the SOFC system is required. In the present work, the process of reforming biogas on a Ni/YSZ and a Ni/SDC catalyst has been numerically and experimentally investigated. Measurements including different thermal boundary conditions, steam-to-carbon ratios and several different fuel compositions were taken. A numerical model containing methane/steam reforming reaction, dry reforming reaction and shift reaction has been proposed to predict the gas mixture composition at the outlet of the reformer. The results of the numerical computation were compared with experimental data and good agreement has been found. The results indicate the importance of combined, numerical and experimental studies in the design of SOFC reformers. The combined approach used leads to the successful prediction of the outlet gas composition for different modelling conditions.[/TD] [/TR] [/TABLE] 1 نقل قول لینک به دیدگاه
M!Zare 48,037 مالک اشتراک گذاری ارسال شده در 4 تیر، ۱۳۹۱ [TABLE=class: tocArticle] [TR] [TD=class: tocTitle] برای مشاهده این محتوا لطفاً ثبت نام کنید یا وارد شوید. ورود یا ثبت نام [/TD] [TD=class: tocGalleys] برای مشاهده این محتوا لطفاً ثبت نام کنید یا وارد شوید. ورود یا ثبت نام [/TD] [/TR] [TR] [TD=class: tocAuthors] Norman Poboss, Karolina Swiecki, Alexander Charitos, Craig Hawthorne, Mariusz Zieba, Günter Scheffknecht [/TD] [TD=class: tocPages]53-59[/TD] [/TR] [TR] [TD=class: tocAbstract, width: 90%]A gasification product gas with a hydrogen content over 75 vol-%db and a heating value of 15 MJ/m³STP,db has been obtained through the absorption enhanced reforming of biomass. The Absorption Enhanced Reforming (AER) process involves a Dual Fluidized Bed (DFB) system consisting of a gasifier and a regenerator (calciner). In the DFB system, the Ca - looping ratio is an important parameter defined as the ratio of the molar flow rate of regenerated sorbent (FCa) and carbon (Fc) which enters the gasifier as fuel. A special feature of the 20 kWth DFB test facility at IFK is the Ca - looping rate control through a cone valve. Therefore, the Ca - looping ratio (FCa/FC) was varied between a value of 2 and 12 molCaO/molC to investigate its influence on the cold gas efficiency, product gas yield, yield of gas components and gravimetric tar concentration during the AER of biomass. The experiments were carried out with wood pellets and a Greek limestone as CO2 sorbent. The experimental work shows a clear influence of the Ca - looping ratio on the AER process. It shows also that beyond a certain value of this parameter, the tar and gas composition is stabilized. [/TD] [/TR] [/TABLE] 1 نقل قول لینک به دیدگاه
M!Zare 48,037 مالک اشتراک گذاری ارسال شده در 4 تیر، ۱۳۹۱ [TABLE=class: tocArticle] [TR] [TD=class: tocTitle] برای مشاهده این محتوا لطفاً ثبت نام کنید یا وارد شوید. ورود یا ثبت نام [/TD] [TD=class: tocGalleys] برای مشاهده این محتوا لطفاً ثبت نام کنید یا وارد شوید. ورود یا ثبت نام [/TD] [/TR] [TR] [TD=class: tocAuthors] Mariusz Zieba, Mathias Fink, Anja Schuster, Günther Scheffknecht, Roland Berger [/TD] [TD=class: tocPages]35-41[/TD] [/TR] [TR] [TD=class: tocAbstract, width: 90%]In this paper, a review of the experimental investigations on the fuel-NOx formation during flameless combustion is presented. The first series of experiments described in the paper were conducted using ammonia doped synthetic gases with different compositions. During these experiments, the influence of gas composition on the conversion of ammonia (NH3) to NOx is investigated. The second series of experiments were conducted using product gas generated in a fluidized bed gasifier. These results show the dependencies between the gasifier operating parameters, product gas composition and final NOx emissions. Moreover, the concentrations of the ammonia and hydrogen cyanide (HCN) in the product gas were measured in order to calculate the conversion ratios of these compounds to NOx. The results show the significant influence of the gas composition and the gasifier process parameters on the final NOx emissions. In particular, the hydrocarbon content influences the ammonia to NOx conversion. The lowest NOx emissions and therefore the lowest conversion ratios were measured while burning gases with a low hydrocarbon content. An increase of the hydrocarbon concentration in the gas corresponded to a rapid increase in the conversion ratios.[/TD] [/TR] [/TABLE] 1 نقل قول لینک به دیدگاه
ارسال های توصیه شده
به گفتگو بپیوندید
هم اکنون می توانید مطلب خود را ارسال نمایید و بعداً ثبت نام کنید. اگر حساب کاربری دارید، برای ارسال با حساب کاربری خود اکنون وارد شوید .