Wyniki wyszukiwania - Biblioteka Nauki

1

Modeling the dynamic operation of a small fin plate heat exchanger – parametric analysis

100%

Motyliński K. , Kupecki J.

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tom Vol. 36, no. 3

85--103

EN

Given its high efficiency, low emissions and multiple fuelling options, the solid oxide fuel cells (SOFC) offer a promising alternative for stationary power generators, especially while engaged in micro-combined heat and power (μ-CHP) units. Despite the fact that the fuel cells are a key component in such power systems, other auxiliaries of the system can play a critical role and therefore require a significant attention. Since SOFC uses a ceramic material as an electrolyte, the high operating temperature (typically of the order of 700–900°C) is required to achieve sufficient performance. For that reason both the fuel and the oxidant have to be preheated before entering the SOFC stack. Hot gases exiting the fuel cell stack transport substantial amount of energy which has to be partly recovered for preheating streams entering the stack and for heating purposes. Effective thermal integration of the μ-CHP can be achieved only when proper technical measures are used. The ability of efficiently preheating the streams of oxidant and fuel relies on heat exchangers which are present in all possible configurations of power system with solid oxide fuel cells. In this work a compact, fin plate heat exchanger operating in the high temperature regime was under consideration. Dynamic model was proposed for investigation of its performance under the transitional states of the fuel cell system. Heat exchanger was simulated using commercial modeling software. The model includes key geometrical and functional parameters. The working conditions of the power unit with SOFC vary due to the several factors, such as load changes, heating and cooling procedures of the stack and others. These issues affect parameters of the incoming streams to the heat exchanger. The mathematical model of the heat exchanger is based on a set of equations which are simultaneously solved in the iterative process. It enables to define conditions in the outlets of both the hot and the cold sides. Additionally, model can be used for simulating the stand-alone heat exchanger or for investigations of a semiadiabatic unit located in the hotbox of the μ-CHP unit.

2

Sensitivity analysis of reacting two-phase flow in nuclear heat-based gasification process

80%

Kupecki J. , Badyda K. , Anglart H.

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tom Vol. 91, nr 2

54-62

EN

Current work investigates influence of operating parameters on chemical reactions occuring within two-phase reacting flow. This particular flow analysed, corresponds to processes in coal gasifier unit supplied in heat by a high temperature gas cooled nuclear reactor (HTGR). Due to the fact that gasification is a complex process, in which multiphase mixture undergoes chemical reactions, it crucial to answer questions about sensitivity to parameters changes. Performed analysis was dedicated to answer question about the optimal flow parameters. Controll of flow patern, namely the swirl of coal-oxygen mixture traversing the gasifier domain, allowed creating efficiency curve, relating gas composition with non-axial component of the velocity vector. Using numerical model of the process, numbers of simulations were run in order to determine operation point yielding the highest efficiency, defined as a ratio of higher heating values of a syngas product of gasification process and coal feed into the unit. Obtained results concerning the most favorable operating parameters can be valuable information of evaluation of such gasification system from the economical point of view. Created tool can be used to study the system performance for various types of coal-fed.

3

Postępy w rozwoju układów μ-CHP z ogniwami paliwowymi

80%

Jewulski J. , Kupecki J. , Błesznowski M.

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tom nr 1

11--15

PL

Technologia ogniw paliwowych umożliwia zmniejszenie emisji zanieczyszczeń oraz oszczędności energii i kosztów eksploatacji. Układy μ-CHP oparte na technologii ogniw paliwowych zaczynają stanowić, w chwili obecnej, w postaci instalacji demonstracyjnych, jeden z elementów składowych europejskiego systemu energetycznego. Obecnie, w trakcie realizacji jest kilkanaście europejskich programów badawczo-rozwojowych poświęconych technologii μ-CHP z ogniwami paliwowymi. Układy te charakteryzują się sprawnością elektryczną do 60% (LHV), już w zakresie mocy pojedynczych kilowatów (1-5 kW). Osiągi układów opartych na technologii ogniw paliwowych są konkurencyjne w stosunku do pozostałych technologii, np. opartych na silnikach wewnętrznego spalania lub silnikach Stirlinga. Jednostki z ogniwami stałotlenkowymi są przy tym układami wielopaliwowymi. Biorąc pod uwagę straty przesyłu energii, oszczędności paliwa w przypadku energetyki rozproszonej są znaczące w stosunku do rozwiązań konwencjonalnych. Możliwe są działania prosumenckie, w których z wykorzystaniem inteligentnego licznika, możliwy jest dwukierunkowy przesył energii elektrycznej. W analizie porównawczej typoszeregu układów μ-CHP szczególne znaczenie odgrywa jednostka μ-CHP/SOFC zasilana paliwem otrzymanym z reformingu parowego gazu ziemnego. Przeprowadzone analizy wskazują, iż właściwie zintegrowany cieplnie układ μ-CHP pokrywa zapotrzebowanie domu jednorodzinnego na energię elektryczną oraz ciepłą wodę użytkową. Prace w kierunku rozwoju wysokosprawnych jednostek kogeneracyjnych z ogniwami SOFC prowadzone są również w Instytucie Energetyki. Działania w tym zakresie skoncentrowane są na optymalizacji osiągów wybranych elementów konstrukcyjnych układu μ-CHP/SOFC, badaniach symulacyjnych i eksperymentalnych oraz wspłówdziale w instalacjach demonstracyjnych.

EN

Fuel cell technology enables energy savings, reduction of emissions and decrease in operating costs. The micro-CHP systems based on fuel cell technology are becoming, for now in the form of demonstration installations, one of the components of the European energy supply system At present, there are numerous European research and development projects targeting micro-CHP and fuel cell systems. These systems are characterised with high electrical LHV efficiency of up to 60%, already in the range of single kilowatts (1-5 kW). Performance of systems based on fuel cells is competitive with performance offered by other potential technologies such as Stirling engines and internal combustion engines. Demonstrated high efficiency of μ-CHP/SOFC units fuels interest in their implementation in distributed power generation. There are meaningful fuel savings realized, relative to traditional power generation, when transmission losses are taken into account. In addition, prosumer solutions are possible with the use of intelligent meters enabling bidirectional transmission of electricity. In the comparative analysis of μ-CHP system, particular attention is drawn by μ-CHP/SOFC system fuelled with steam reformed natural gas. The results of analysis indicate that properly integrated μ-CHP system covers demand of a single family house for electric power and hot utility water. Research and development in high efficiency solid oxide fuel cell based cogeneration systems is also carried at the Instytut Energetyki. In particular, work is concentrated on performance optimization of the μ-CHP/SOFC system components, numerical simulations, experimental studies and participation in demonstration installations.

4

Selected aspects of the design and operation of the first Polish residential micro-CHP unit based on solid oxide fuel cells

61%

Kupecki J. , Skrzypkiewicz M. , Stefański M. , Stępień M. , Wierzbicki M. , Golec T.

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tom Vol. 96, nr 4

270--275

EN

The first Polish micro-combined heat and power unit (micro-CHP) with solid oxide fuel cells (SOFC) was designed and constructed in the facilities of the Institute of Power Engineering in Warsaw. The system was launched in September 2015 and is under investigation. At the current stage the unit is customized to operate on a pre-treated biogas. Adaptation of the fuel processing system, which is based on a steam reformer, makes it possible to utilize other gaseous and liquid fuels, including natural gas. The electric and thermal output of the system, up to 2 kW and about 2 kW, respectively, corresponds to the typical requirements of a detached dwelling or a small commercial site. Functionality of the system was increased by engaging two separate start-up modules, which are used for preheating the system from a cold state to the nominal working conditions. The first module is based on a set of electric heaters, while the second module relies on an additional start-up burner. The startup of the system from ambient conditions up to a thermally self-sufficient stage takes about 7 hours using the electric preheaters mode. Output residual heat was used to heat water to a temperature of about 50°C. The temperature of the flue gases at the inlet to the hot water tank was measured at approximately 300°C. Steam reforming of the biogas was performed by delivering deionized water to the steam reformer in order to maintain the S/C ratio at a range of 2–3.5. Selected aspects of the design and construction as well the first operational experiences are presented and discussed. The numerical modeling methodology is presented as a complimentary tool for system design and optimization.

5

Magazynowanie energii superkondensatory i cewki nadprzewodzące

51%

Chmielewski A. , Kupecki J. , Szablowski Ł. , Fjałkowski K. J. , Zawieska J. , Bogdziński K. , Kulik O. , Adamczewski T.

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tom nr 10

42--43

PL

Popularnymi technikami magazynowania energii elektrycznej są superkondensatory i cewki nadprzewodzące. Techniki te są łatwo skalowalne i pozbawione barier technologicznych. Są dojrzałymi i perspektywicznymi technikami krótkoterminowego magazynowania energii.