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Number of results: 49
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Abstract

The engine simulations have become an integral part of engine design and development. They are based on approximations and assumptions. The precision of the results depends on the accuracy of these hypotheses. The simplified models of frozen composition, chemical equilibrium and chemical kinetics provide the compositions of combustion products for engine cycle simulations. This paper evaluates the effects of different operating conditions and hypotheses on the exergetic analysis of a spark-ignition engine. The Brazilian automotive market has the highest number of flex-fuel vehicles. Therefore, a flex-fuel engine is considered for simulations in order to demonstrate the effects of these different hypotheses. The stroke length and bore diameter have the same value of 80 mm. The in-cylinder irreversibility is calculated for each case at the closed part of the engine cycle. A comparative analysis of these hypotheses provides a comprehensive evaluation of their effects on exergetic analysis. Higher values of accumulated irreversibility are observed for the oversimplified hypothesis.
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Abstract

The main goal of the considered work is to adjust mathematical modeling for mass transfer, to specific conditions resulting from presence of chemical surface reactions in the flow of the mixture consisting of helium and methanol. The thermocatalytic devices used for decomposition of organic compounds incorporate microchannels coupled at the ends and heated to 500 ◦C at the walls regions. The experiment data were compared with computational fluid dynamics results to calibrate the constants of the model’s user defined functions. These extensions allow to transform the calculations mechanisms and algorithms of commercial codes adapting them for the microflows cases and increased chemical reactions rate on the interphase between fluid and solid, specific for catalytic reactions. Results obtained on the way of numerical calculations have been calibrated and compared with the experimental data to receive satisfactory compliance. The model has been verified and the performance of the thermocatalytic reactor with microchannels under hydrogen production regime has been investigated.
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Abstract

The paper presents the results of simulation tests of hydraulic resistance and temperature distribution of the prototype Stirling alpha engine supplied with waste heat. The following elements were analyzed: heater, regenerator and cooler. The engine uses compressed air as a working gas. Analyses were carried out for three working pressure values and different engine speeds. The work was carried out in order to optimize the configuration of the engine due to the minimization of hydraulic resistance, while maintaining the required thermal capacity of the device. Preliminary tests carried out on the real object allowed to determine boundary and initial conditions for simulation purposes. The simulation assumes that there is no heat exchange between the regenerator and the environment. The solid model used in simulation tests includes the following elements: supply channel, heater, regenerator, cooler, discharge channel. Due to the symmetrical structure of the analyzed elements, simulation tests were carried out using 1/6 of the volume of the system.
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Abstract

Turbine stages can be divided into two types: impulse stages and reaction stages. The advantages of one type over the second one are generally known based on the basic physics of turbine stage. In this paper these differences between mentioned two types of turbines were indicated on the example of single stage turbines dedicated to work in organic Rankine cycle (ORC) power systems. The turbines for two ORC cases were analysed: the plant generating up to 30 kW and up to 300 kW of net electric power, respectively. Mentioned ORC systems operate with different working fluids: DMC (dimethyl carbonate) for the 30 kW power plant and MM (hexamethyldisiloxane) for the 300 kW power plant. The turbines were compared according to three major issues: thermodynamic and aerodynamic performance, mechanical and manufacturing aspects. The analysis was performed by means of the 0D turbomachinery theory and 3D computational aerodynamic calculations. As a result of this analysis, the paper indicates conclusions which type of turbine is a recommended choice to use in ORC systems taking into account the features of these systems.
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Abstract

The paper illustrates a case study of fluid selection for an internal combustion engine heat recovery organic Rankine cycle (ORC) system having the net power of about 30 kW. Various criteria of fluid selection are discussed. Particular attention is paid to thermodynamic performance of the system and human safety. The selection of working fluid for the ORC system has a large impact on the next steps of the design process, i.e., the working substance affects the turbine design and the size and type of heat exchangers. The final choice is usually a compromise between thermodynamic performance, safety and impact on natural environment. The most important parameters in thermodynamic analysis include calculations of net generated power and ORC cycle efficiency. Some level of toxicity and flammability can be accepted only if the leakages are very low. The fluid thermal stability level has to be taken into account too. The economy is a key aspect from the commercial point of view and that includes not only the fluid cost but also other costs which are the consequence of particular fluid selection. The paper discusses various configurations of the ORC system – with and without a regenerator and with direct or indirect evaporation. The selected working fluids for the considered particular power plant include toluene, DMC (dimethyl carbonate) and MM (hexamethyldisiloxane). Their advantages and disadvantages are outlined.
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Abstract

This paper presents the origins of marine steam turbine application on liquefied natural gas carriers. An analysis of alternative propulsion plant trends has been made. The more efficient ones with marine diesel engines gradually began to replace the less efficient plants. However, because of many advantages of the steam turbine, further development research is in progress in order to achieve comparable thermal efficiency. Research has been carried out in order to achieve higher thermal efficiency throughout increasing operational parameters of superheated steam before the turbine unit; improving its efficiency to bring it nearer to the ideal Carnot cycle by applying a reheating system of steam and multi stage regenerative boiler feed water heating. Furthermore, heat losses of the system are reduced by: improving the design of turbine blades, application of turbine casing and bearing cooling, as well as reduction in steam flow resistance in pipe work and maneuvering valves. The article identifies waste energy sources using the energy balance of a steam turbine propulsion plant applied on the liquefied natural gas carrier which was made out basing on results of a passive operation experiment, using the measured and calculated values from behavioral equations for the zero-dimensional model. Thermodynamic functions of state of waste heat fluxes have been identified in terms of their capability to be converted into usable energy fluxes. Thus, new ways of increasing the efficiency of energy conversion of a steam turbine propulsion plant have been addressed.
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Abstract

Effective use of energy in various branches of economy is one of world trends in development of power engineering. Relevant energy consumption occurs during exploitation of buildings, so there is still potential to diminish it as far as heating, ventilation, and air conditioning are concerned. Particularly in summer season, the choice of respective roofing colour can play a decisive role for the heat flux transferred to the inside of the object. Decrease of heat flux causes a lower heat burden to the building and lower power consumption by the air conditioning systems. In winter, on the contrary, heat flux transferred to building’s interior should be higher, as a result, demand of energy for heating will be lower. However, calculations of the heat flux require that energy balance must be made for the object. Unfortunately, not all producers of roofing covers inform about the values of reflectivity and thermal emissivity of their products, which is, in turn, necessary for calculations. In the present paper, research methodology elaborated by authors is proposed for determination of thermal emissivity of roofing covers. The paper presents test stand, methodology, and research results for roofing paper in blue colour (as an example) for which the thermal emissivity is an unknown parameter.
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Abstract

The authors present a numerical study of a start-up of a boiler with a thick-walled element subjected to thermomechanical loading. The significance of calculations of real heat transfer coefficients has been demonstrated. Fluid dynamics, mechanical transient thermal and static structural calculations have been conducted in both separate and coupled modes. Strain-stress analyses prove that the effect of the heat transfer coefficient changing in time and place in comparison with a constant one as recommended by standards is the key factor of fatigue calculations.
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Abstract

Geometry of plate heat exchangers (PHE) is characterized by a complex net of narrow channels. It enhances turbulence and results in better heat transfer performance. Theoretically, larger number of channels (plates) should proportionally increase the PHE heat power capacity. In practice a nonuniform massflow distribution in consecutive flow channels can significantly deteriorate the overall heat exchange performance. The flow maldistribution is one of the most commonly reported exploitation problems and is present in PHE with and without phase-change flows. The presented paper investigates numerically a flow pattern in PHE with evaporation of R410A refrigerant. Various sizes of PHE are considered. The paper introduces a robust methodology to transform the complicated geometry of a real 3D PHE to its 2D representation. It results in orders of magnitude faster calculations and allows for fast evaluation of different geometrical changes of PHE and their effect on flow maldistribution.
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Abstract

The purpose of the work was to experimentally determine the characteristics of the prototype of a Roto-Jet pump (the Pitot tube pump) during its operation under conditions typical for the domestic micro power plant. The low-boiling fluid, sold under the trade name of HFE7100 and characterised by a zero ozone depletion potential (ODP) coefficient, was used as a working medium in the organic Rankine cycle (ORC). An electric thermal oil heater with a maximum power of 2×24 kWe was used as a heat source. The pump of Roto-Jet type was specially designed for the operation with the following rated parameters of the thermodynamic cycle: nominal flow rate of the working fluid 0.17 kg/s, operating pressure 1.2 MPa. The pump was put under load using an expansion valve that simulated the operation of an expansion machine. The article discusses thermodynamic and flow conditions to be met by the pumping engine as well as results of the experimental research. Moreover, the article includes the operational characteristics of the ORC installation and the Roto-Jet pump obtained during the operation with the target working medium – HFE7100. The engineering problems the authors of this article faced when designing and testing the pumping engine prototype are also presented.
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Abstract

The article concerns computer modelling of processes in cooling systems of internal combustion engines. Modelling objectives and existing commercial programs are presented. It also describes Author’s own method of binding graphs used to describe phenomena in the cooling system of a spark ignition engine. The own model has been verified by tests on the engine dynamometer. An example of using a commercial program for experimental modelling of an installation containing a heat accumulator is presented.
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Abstract

The application of waste heat from exhaust gas of ship’s main engines has become widely practiced as early as in the 1930s. Thus the increase of ship’s overall efficiency was improved. Nowadays all newly built ships of the 400 gross tonnage and above must have specified energy efficiency design index, which is a measure for CO2 emissions of the ship and its impact on the environment. Therefore, the design of waste heat recovery systems requires special attention. The use of these systems is one of the basic ways to reduce CO2 emissions and to improve the ship’s energy efficiency. The paper describes the ship’s heating systems designed for the use of waste heat contained in the exhaust gas of self-ignition engines, in which the heat carriers are respectively water vapor, water or thermal oil. Selected results of comparative exergy analysis of simplified steam, water and oil heating systems have been presented. The results indicate that the oil heating system is comparable to the water system in terms of internal exergy losses. However, larger losses of exergy occur in the case of a steam system. In the steam system, a significant loss is caused by the need to cool the condensate to avoid cavitation in boiler feed pumps. This loss can in many cases cause the negative heat balance of ship during sea voyage while using only the exhaust gas boilers.
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Abstract

The Stirling engine type alpha is composed of two cylinders (expansion space E and compression space C), regenerator that forms the space between the cylinders and the buffer space (under the pistons). Before the start-up and as a result of long-term operation, the average pressure in the working space (above the pistons) and in the buffer space is the same. However, in the initial phase of operation, the average pressure in the working space is different then the average pressure in the buffer space depending on the crankshaft starting position (starting angle). This, in turn, causes a large variation in the starting torque. An additional unfavorable factor caused by a large variation in the course of the indicated torque is the rotational speed variation and the formation of torsional vibrations in the drive system. After some time, depending on the quality of the engine piston sealing, the average pressure in the working and buffer space will equalize. The occurrence of the above-described phenomenon affects the selection of the starting electric motor, which can be significantly reduced, when the crankshaft starting position is optimized (the starting torque is several times greater than the average torque occurring in the generator operation mode). This paper presents the analysis of the impact of the crankshaft starting position on the course of the indicated torque and the resulting start-up energy. Starting the engine at an unfavorable position of the crankshaft may, in extreme cases, increase the starting torque even three times.
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Abstract

The policy of sustainable development seeks to improve energy efficiency of industrial equipment. Efforts to improve energy efficiency also apply to the paint shops, where the recovery of waste heat is sought. The main source of a large amount of low-temperature waste heat in the paint shop is the spray booth. The second place where a large amount of low temperature waste heat is released is the room where the compressed air is prepared. Low energy efficiency of air compressors requires a large electric power supply. As a result, the emitted large heat fluxes become waste energy of the technological process. Heat is equivalent to up to 93% of the electric power supplied in the air compression process. There are solutions for recovering heat from compressors coming from the oil cooling water, but then the waste heat from the cooling of the compressed air and from the electric motor is released into air in the room. A method for recovering low-temperature waste heat from the air preparation room by means of an air-source heat pump has been proposed. An energy balance of the air compression and dehumidification process for the paint shop was made. A Matlab’s built-in numerical model includes air compressor and dehumidifier, heat recovery and accumulation for the purposes of use in the spray booth. A simulation experiment was carried out on the effectiveness of heat recovery from the air preparation room. The use of combined energy management in paint shops was proposed.
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Abstract

Contemporary world brings along a continuing interpenetration of cultures strengthened by the migration revolution. The social space created by multiplicity of ethnic groups is very often a result of migration processes which totally formed such states as Canada or Australia. The sources of the European multiculturalism were, on the one hand, the officially accepted workforce, on the other hand – immigration being the effect of the colonial past of such states as France, Great Britain or Germany
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Abstract

The article presents the author’s considerations relating to the current and common problem of multiculturalism. Nowadays “multiculturalism” can be defined as co-existence – in the determined physical, social and political sphere as well as in a concrete historical period of time – of many ethnic groups representing different axiological and normative systems. The social created by multiplicity of ethnic groups is very often a result of migration processes which totally formed such states as Canada or Australia. The sources of the European multiculturalism were, on the one hand, the officially accepted workforce as Federal Republic of Germany, on the other one – immigration being the effect of the colonial past of such states as France, Holland or Britain. All these countries took up more or less advanced actions towards being able to deal with the deepening ethnic diversification. There appeared political project – multiculturalism.
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Abstract

In the last decades borderlands studies have been rapidly developing in various disciplines. Within the changing function of European borders (from separating line between two souvereign states to borderscapes of intercultural flows and fluid identity) the focus of border scholars moved towards social relations and bottom-up perspective. Thus, borderlands are perceived as laboratories of European integration and multicultural spaces. For the aim of this article, borderlands are defined as spaces located on the geographical border between different states, nations and cultures that are objects of European Union cohesion policy. By analysing the Eurobarometer survey on cross-border cooperation I try to demonstrate differences between border regions covered by the Interreg cross-border cooperation programmes in terms of cross-border practices, general trust in others and attitudes towards citizens of neighbouring countries.
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Abstract

In the article, the author presents the basic relations between a nation state and a multicultural society. According to the author, the attitude of the nation state and the dominant nation in the state to the phenomenon of cultural diversity of society is a key phenomenon in the theory and practice of multiculturalism. Namely, the nation state is characterized by two strategies defining the attitude to the cultural diversity of society. It is a strategy of cultural homogenization and a pluralistic. The emergence of a pluralistic strategy begins with the occurrence and eventual growth of phenomena and processes referred to as multiculturalism and multicultural society.
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Abstract

The aim of the presented paper is to show the history of the development of research on social minorities in the environment of Bialystok sociologists. This research center, located on the north-eastern borderland of Poland, was one of the first in Poland to develop research in the field of borderland sociology. With time, the research subject has been expanded, from the analysis of the assimilation of the Belarusian minority to the contemporary face of the idea of a multicultural society, discussing not only nationality, religiosity, but also non-heteronormities.
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Abstract

The main object of this article is to present the history of the establishing legal regulations in Poland concerning additional place names and other official signs in the languages of national minorities. This process has been always very difficult, because as it teaches the experience of many European countries, it affects issues related the national identity, the role of the national language in the state and the tradition of recognizing linguistic diversity in a given country. In the article, I will try to show that the introduction of such regulations in Poland has been with the one hand an important, perhaps even historical, change in the functioning of the Polish society and administration which consisted of official admission of other languages into the public sphere thus violating the dominant tradition of Polish language dominance in the country. From the other hand, the presence of a minority place-names indicates a change in the way in which minority groups publicly present their ethnic identities. It takes place not only through maintaining national cultures and learning the mother tongue but also through increased visual presence in the public sphere.
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Abstract

The research task of the essay is to answer the question of what is the face of the nation in the ethnic enclaves situated at the peripheries of national states. The subject of the analyses is the local population of the village Jaworzynka. In 1922, the settlement Herczawa was founded as a local unit independent from Jaworzynka. Since then Herczawa began to belong to Czechoslovakia. The state-owned status of Jaworzynka, which started to be a part of the Republic of Poland, was recognized after the World War I. The author takes into account the longue durre of folk and national culture generated in the Silesian Beskidy in the second half of the 18th century. The national culture is the main term applied to the investigations of the borderland regions. According to the ethno-symbolic approaches (Anthony D. Smith) and culturalism methods in sociology (Antonina Kłoskowska), the author analyses in his research: 1) language, 2) religion, 3) folkways and mores 4) arts, 5) local knowledge and literature. These elements delineate the sphere of symbolic culture. Based on the common folk culture, two national cultures have been formed nowadays – the Polish and Czech ones. Both Polish and Czech Census Bureau data and objective elements of national culture discussed in the essay indicate the process of national revival. The local people of Jaworzynka identify themselves as Poles and the population of Herczawa define themselves as Czechs. The content and the form of the local culture are visible in Jaworzyna, but they seem to be latent or diminishing in Herczawa.
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Abstract

Some consider the multiculturality of Wrocław to be its obvious and socially legitimised “property”, whereas others view it as controversial and refutable construct. In the paper, we would like to investigate the multiculturality of the Lower Silesia’s capital taking into account its internal differentiation, which is mostly due to the adjudicating authorities – city authorities, its citizens and researchers — as well as observable dynamics. Hence, we propose to inspect the following: firstly, the real differentiation of the social structure of Wrocław’s inhabitants and its transformations related mostly to the influx of Ukrainians, who change the ethnic cityscape; secondly, the politics of municipal authorities regarding the promotion and strengthening of the city’s image as the multicultural, open and tolerant “meeting place”, as well as initiatives inscribed therein and other observable, contradictory events; thirdly, the evaluation of Wrocław’s multiculturality and its selected aspects performed by the city’s inhabitants and revealed in the research on this phenomenon in 2011 and in two editions of Social Diagnosis of Wrocław (2014 and 2017).
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Abstract

Professor Jacek Fisiak’s outstanding achievements are well known in the scholarly community in Poland and abroad. He was an excellent and widely recognizable scholar, an exceptional teacher and talent-detector, an ingenious science manager, and he was so likeable and cordial! Professor Jacek Fisiak directed the Institute of English at Adam Mickiewicz University in Poznań for 40 years. Thanks to his management, English studies in Poznań obtained a leading position among such institutions in Poland and in the world. Professor Fisiak also cared about other English departments in Poland. On the one hand, he supervised 61 (!) PhD students who continued their academic careers throughout Poland, on the other, he supported English studies as well as the humanities and research in general as Minister of National Education and member of numerous influential bodies. I am grateful to Professor Fisiak for his guidance in my academic work, starting with my M.A., through the doctoral and post-doctoral degrees and the professorial title, my function as his deputy director for 3 terms, up to the ‘take-over of the command’ of the Institute and the creation of the Faculty of English. His opus survives and will last.
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