Iskanje po katalogu digitalne knjižnice

Opis: In this article, the mechanism and functioning of a refrigeration system based on the magnetic system and the magnetocaloric effect are examined. Magnetic refrigeration plants operate based on a state-of-the-art technology that does not contain any toxic refrigerant that is harmful to the environment and the ozone layer. The magnetocaloric effect is created by a rare earth metal called gadolinium. We have studied the benefits of using this type of mechanism for both domestic and industrial needs. High efficiency, net energy consumption lower than the classic, silent systems, and a lack of typical refrigerant characterize this type of installation. The following layout describes the initial prototype for AMR in magnetocaloric refrigeration.
Ključne besede: energy efficiency, gadolinium material, magnetocaloric effect, alternative technology, AMR
Objavljeno v DKUM: 01.12.2023; Ogledov: 20; Prenosov: 0
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Opis: The vast majority of steam power plants in the world are based on the Rankine cycle. It is a wellknown, trustworthy process that uses water or water vapour as a working medium, which supplies heat from various primary energy sources: fossil fuels, renewable energy sources (solar energy, energy from wood biomass, etc.) or a combination of both. With the Rankine cycle, energy sources other than electricity can be produced, which can be used as the primary energy source for various applications. The present article focuses on the production of hydrogen in addition to electricity; therefore, two energy sources are obtained from the same system with a few modifications of the existing power plant for further exploitation. There are several processes for hydrogen production using the Rankine cycle; in the present article, two processes are focused on: using part of the electricity produced and obtaining hydrogen by electrolysis of water or using part of high quality steam (basically heat energy) in combination with electricity and obtaining hydrogen by a thermochemical copper-chlorine process. Each of these processes has its advantages and disadvantages, which are presented in the present article with an example model of a power plant.
Ključne besede: Rankine cycle, hydrogen production, electrolysis, thermochemical process
Objavljeno v DKUM: 01.12.2023; Ogledov: 19; Prenosov: 0
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Opis: In this article, a brief introduction of conventional refrigeration is given, followed by a description and history of magnetic refrigeration. The active magnetic regenerator comprises 12 parallel plates of magnetocaloric material (gadolinium (Gd)), through which circulates the heat transfer fluid (water, in this case). At both ends of the regenerator are the heat exchangers. The hot heat exchanger (HHEX) and the cold heat exchanger (CHEX) connects the fluid to the heat sources. The principle of operation of a magnetic refrigeration installation is based on exploiting the magnetocaloric effect from the materials that possess these properties (in this case, Gd).
Ključne besede: magnetic refrigeration, active magnetic regenerator, magnetocaloric material
Objavljeno v DKUM: 10.11.2023; Ogledov: 57; Prenosov: 2
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Opis: In this paper, we will calculate the needs for hydrogen if all traffic in Croatia was driven by hydrogen. In the article, we will determine the required amount in several ways. First, we will briefly describe fuel cell cars and the extent to which the amount of exhaust gases would be reduced. We will then explain the ways of obtaining hydrogen, its transport and what the purchase costs would be. Finally, we will compare the results and draw some conclusions.
Ključne besede: hydrogen, hydrogen technologies, hydrogen acquisition, transport
Objavljeno v DKUM: 30.10.2023; Ogledov: 120; Prenosov: 7
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Opis: This paper presents the concept of reconstruction of the existing coal-fired combined heat and power plant to comply with new European environmental policies. The existing coal-fired boiler will be replaced by two new dual pressure heat recovery steam generators, which will utilize the exhaust gas heat from two new gas turbines. The steam from the heat recovery steam generators will be fed to the existing steam turbine. After the reconstruction, the nominal turbine inlet steam mass-flow of 40 kg/s will be reduced to 30 kg/s. During periods of low heat demand, only one gas turbine and one heat recovery steam generator will be in operation and the live steam mass-flow may drop even to 12 kg/s. Prior to the reconstruction, dedicated tests of the existing steam turbine were carried out using the steam from the existing coal-fired boiler. The goal of the test was to verify the viability of operation with such an extremely low mass-flow. The results of tests show that such operation is possible but inefficient from a power generation point of view. Besides this, the turbine control algorithm needs to be accommodated to this extreme operating regime and additional measures like displacement of the extraction points and steam cooling will be required to control the temperature of the steam extractions. The novelty of this paper is using real prereconstruction process data for the assessment of feasibility and efficiency of the post-reconstruction operation of a combined heat and power turbine.
Ključne besede: cogeneration, control valves, exhaust gas, heat recovery, steam turbine
Objavljeno v DKUM: 30.10.2023; Ogledov: 48; Prenosov: 3
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