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Optimisation of tree path pipe network with nonlinear optimisation method
Danijela Urbancl, Darko Goričanec, 2009, izvirni znanstveni članek

Opis: In this paper, the optimisation of pipe network with hot water is presented. The mathematical model, consisting of the nonlinear objective function and system of nonlinear equations for the hydraulics limitations is developed. On its basis, the computer program for determination optimal tree path with the use of simplex method was solved. For economic estimation the capitalised value method, which consider all costs of investment and operation was used. The results are presented for real case study network with 24 nodes and 33 pipe sectors.
Ključne besede: district heating, pipe network, optimisation, non-linear programming, simplex method
Objavljeno: 01.06.2012; Ogledov: 1501; Prenosov: 76
URL Povezava na celotno besedilo

5.
Long-term performance of central heat pumps in Slovenian homes
Milan Marčič, 2004, izvirni znanstveni članek

Opis: Due to limited availability of natural resources exploited for heating and in order to reduce the environmental impact, people should strive to use renewable energy sources. Heat pumps allow the conversion of ambient heat, available in almost unlimited quantities, to heating energy. The paper describes an energy-saving house provided with good thermal insulation and heated by an air-to-water split-type heat pump. The condenser is located in the attic and the evaporator in the boiler room of the house. The house heating up to the ambient temperature of 0 °C was provided by an air-to-water heat pump and a condensing oil heating furnace if the ambient temperature dropped to below 0 °C. The results of the nine-year testing showed that the heat pump was used during most of the heating season. The average coefficient of performance (COP) of the air-to-water heat pump in nine heating seasons was3.16, indicating that over 68% of the heat was obtained from the ambient air. The comparison between COP of air-to-water heat pumps in energy-saving house and of water-to-water heat pumps fitted in houses dealt with under otherprojects indicates that water-to-water heat pumps have higher COPs. The heat pumps obtain heat from groundwater, hence they are capable of operating throughout the heating season, and possess the highest COP. The advantage of an air-to-water heat pump, however, lies in its simple design and a wide rangeof applications. Due to limited availability of natural resources exploited for heating and in order to reduce the environmental impact, people should strive to use renewable energy sources. Heat pumps allow the conversionof ambient heat, available in almost unlimited quantities, to heating energy. The paper describes an energy-saving house provided with good thermal insulation and heated by an air-to-water split-type heat pump. The condenser is located in the attic and the evaporator in the boiler room of thehouse. The house heating up to the ambient temperature of 0 °C was providedby an air-to-water heat pump and a condensing oil heating furnace if the ambient temperature dropped to below 0 °C. The results of the nine-year testing showed that the heat pump was used during most of the heating season. The average coefficient of performance (COP) of the air-to-water heat pump in nine heating seasons was 3.16, indicating that over 68% of the heat was obtained from the ambient air. The comparison between COP of air-to-water heatpumps in energy-saving house and of water-to-water heat pumps fitted in houses dealt with under other projects indicates that water-to-water heat pumps have higher COPs. The heat pumps obtain heat from groundwater, hence they are capable of operating throughout the heating season, and possess the highest COP. The advantage of an air-to-water heat pump, however, lies in its simple design and a wide range of applications. In comparison to the furnace, the heat pump yielded considerable saving in fuel and monry, which justifies its home heating application in the Central European climatic area. The analys
Ključne besede: heating, energy saving houses, heat pumps, therodynamics, refrigeration
Objavljeno: 01.06.2012; Ogledov: 1368; Prenosov: 85
URL Povezava na celotno besedilo

6.
Nanocomposite foams from iron oxide stabilized dicyclopentadiene high internal phase emulsions
Sebastijan Kovačič, Christian Slugovc, Gregor Ferk, Nadejda B. Matsko, 2014, strokovni članek

Opis: Nanocomposite polyHIPE foams with open-cellular morphology were obtained using nanoparticles ($γFe_2O_3/Fe_3O_4$), surfactant (Pluronic L121) or nanoparticle/surfactant stabilized dicyclopentadiene high internal phase emulsions (DCPD HIPEs). Upon curing, cavity sizes were found to vary drastically between 950 ± 360 µm down to 7 ±3 µm de- pending on the HIPE formulations. As-obtained nanocomposite polyHIPE foams were functionalized using elemental bromine in THF. Upon bromination the nanoparticles are moved from the cavities surfaces into the bulk phase of the polymer scaffold, which affects the inductive-heating capability of the magnetic nanocomposite foams decreasing it by the factor of 2.
Ključne besede: chemical technology, nanocomposites, bromination, microstructure, pickering HIPEs, $γFe_2O_3/Fe_3O_4$ nanoparticles, Ring Opening Metathesis Polymerization (ROMP), dicyclopentadiene, inductive heating
Objavljeno: 24.08.2017; Ogledov: 370; Prenosov: 58
.pdf Celotno besedilo (967,87 KB)
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7.
Characterization of Slovenian coal and estimation of coal heating value based on proximate analysis using regression and artificial neural networks
Darja Kavšek, Adriána Bednárová, Miša Biro, Roman Kranvogl, Darinka Brodnjak-Vončina, Ernest Beinrohr, 2013, izvirni znanstveni članek

Opis: Chemical composition of Slovenian coal has been characterised in terms of proximate and ultimate analyses and the relations among the chemical descriptors and the higher heating value (HHV) examined using correlation analysis and multivariate data analysis methods. The proximate analysis descriptors were used to predict HHV using multiple linear regression (MLR) and artificial neural network (ANN) methods. An attempt has been made to select the model with the optimal number of predictor variables. According to the adjusted multiple coefficient of determination in the MLR model, and alternatively, according to sensitivity analysis in ANN developing, two descriptors were evaluated by both methods as optimal predictors: fixed carbonand volatile matter. The performances of MLR and ANN when modelling HHV were comparable; the mean relative difference between the actual and calculated HHV values in the training data was 1.11% for MLR and 0.91% for ANN. The predictive ability of the models was evaluated by an external validation data set; the mean relative difference between the actual and predicted HHV values was 1.39% in MLR and 1.47% in ANN. Thus, the developed models could be appropriately used to calculate HHV.
Ključne besede: Slovenian coal, higher heating value, HHV, regression, artificial neural network
Objavljeno: 03.04.2017; Ogledov: 679; Prenosov: 234
.pdf Celotno besedilo (749,77 KB)
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8.
The influence of electric arc activation on the speed of heating and the structure of metal in welds
Oleksandr Savytsky, Mychailo Savytsky, Darko Bajić, Yuriy Shkrabalyuk, Tomaž Vuherer, 2016, izvirni znanstveni članek

Opis: This paper presents the results of a research related to the impact of electric arc activation onto drive welding energy and metal weld heating speed. It is confirmed that ATIG and AMIG methods, depending on metal thickness, single pass weldability and chemical composition of activating flux, enable the reduction of welding energy by 2-6 times when compared to conventional welding methods. Additionally, these procedures create conditions to increase metal weld heating speed up to 1,500-5,500 °C/s-1. Steel which can be rapidly heated, allows for a hardened structure to form (with carbon content up to 0.4%), together with a released martensitic structure or a mixture of bainitic-martensitic structures. Results of the research of effectiveness of ATIG and AMIG welding showed that increase in the penetration capability of electric arc, which increases welding productivity, is the visible side of ATIG and AMIG welding capabilities.
Ključne besede: arc welding, active flux, penetration, heating speed, driving energy
Objavljeno: 07.07.2017; Ogledov: 341; Prenosov: 218
.pdf Celotno besedilo (592,40 KB)
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9.
Ground-sourced energy wells for heating and cooling of buildings
Heinz Brandl, Dietmar Adam, Roman Markiewicz, 2006, izvirni znanstveni članek

Opis: Energy wells are thermo-active elements for an economical extraction or storage of ground energy, similar to energy piles and other deep foundation elements also used as heat exchangers. Heating and/or cooling of buildings requires a primary and secondary thermo-active circuit, commonly connected by a heat pump. The paper gives several design aspects of energy wells which can be also used for the design of deep energy foundations. Thermal response tests have proved suitable for the in-situ determination of thermal ground properties required for an optimised design. Moreover, different systems of energy wells are discussed, and a comprehensive pilot research project is described.
Ključne besede: energy wells, energy foundations, geothermal geotechnics, geothermal heating/cooling, thermo-active structures, thermal ground properties, field testing
Objavljeno: 17.05.2018; Ogledov: 219; Prenosov: 75
.pdf Celotno besedilo (4,24 MB)
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