How to search?
advanced search

Search results

Filters

  • Journals
  • Authors
  • Keywords
  • Date
  • Type

Search results

Number of results: 6
items per page: 25 50 75
Sort by:

CFD simulation of DEBORA boiling experiments

Roland Rzehak Eckhard Krepper
Archives of Thermodynamics | 2012 | No 1 August | 107-122 | DOI: 10.2478/v10173-012-0005-0
Keywords Subcooled flow boiling Computational fluid dynamics simulation Heat flux partitioning Two-fluid model
Download PDF Download RIS Download Bibtex

Abstract

In this work we investigate the present capabilities of computational fluid dynamics for wall boiling. The computational model used combines the Euler/Euler two-phase flow description with heat flux partitioning. This kind of modeling was previously applied to boiling water under high pressure conditions relevant to nuclear power systems. Similar conditions in terms of the relevant non-dimensional numbers have been realized in the DEBORA tests using dichlorodifluoromethane (R12) as the working fluid. This facilitated measurements of radial profiles for gas volume fraction, gas velocity, bubble size and liquid temperature as well as axial profiles of wall temperature. After reviewing the theoretical and experimental basis of correlations used in the ANSYS CFX model used for the calculations, we give a careful assessment of the necessary recalibrations to describe the DEBORA tests. The basic CFX model is validated by a detailed comparison to the experimental data for two selected test cases. Simulations with a single set of calibrated parameters are found to give reasonable quantitative agreement with the data for several tests within a certain range of conditions and reproduce the observed tendencies correctly. Several model refinements are then presented each of which is designed to improve one of the remaining deviations between simulation and measurements. Specifically we consider a homogeneous MUSIG model for the bubble size, modified bubble forces, a wall function for turbulent boiling flow and a partial slip boundary condition for the liquid phase. Finally, needs for further model developments are identified and promising directions discussed.
Go to article

Authors and Affiliations

Roland Rzehak
Eckhard Krepper

Exergy analysis of operation of two-phase ejector in compression refrigeration systems

Jarosław Karwacki Adam Dudar Dariusz Butrymowicz Kamil Śmierciew
Archives of Thermodynamics | 2013 | No 4 December | 107-122 | DOI: 10.2478/aoter-2013-0032
Keywords Two-phase ejector Compression refrigeration system COP Exergy
Download PDF Download RIS Download Bibtex

Abstract

Paper deals with theoretical analysis of possible efficiency increase of compression refrigeration cycles by means of application of a twophase ejector. Application of the two phase ejector in subcritical refrigeration system as a booster compressor is discussed in the paper. Results of exergy analysis of the system operating with various working fluids for various operating conditions have been shown. Analysis showed possible exergy efficiency increase of refrigeration compression cycle.

Go to article

Authors and Affiliations

Jarosław Karwacki
Adam Dudar
Dariusz Butrymowicz
Kamil Śmierciew

Contradiction in the eyes of Gaston Milhaud

Anna Jedynak
Przegląd Filozoficzny. Nowa Seria | 2019 | No 3 | 107-122 | DOI: 10.24425/pfns.2019.129763
Keywords contradiction convention G. Milhaud objectivity reality subjectivity
Download PDF Download RIS Download Bibtex

Abstract

Gaston Milhaud rejects the principle of contradiction if it is conceived as an absolute and universal rule. He claims that it only holds in some narrowly defined circumstances. According to him, the greater is mental contribution to an act of cognition the more appropriate is the application of the principle of contradiction. My analysis of his views shows that he wanted to emphasize the differences between the objective reality and its mental or linguistic representations rather than undermine the logical principle of contradiction. Parallels can be noted between Milhaud’s views on contradiction and Leon Chwistek’s theory of the multiplicity of realities, as well as Kazimierz Ajdukiewicz’s concept of the cognitive role of language.

Go to article

Authors and Affiliations

Anna Jedynak

Less means more, or less for more. Spatial, social and psychological approach to the issue of micro-apartments

Agata Twardoch
Teka Komisji Urbanistyki i Architektury Oddziału Polskiej Akademii Nauk w Krakowie | 2017 | vol. XLV | 107-122
Keywords demographic trends micro-apartment micro-flat housing normative
Download PDF Download RIS Download Bibtex

Abstract

The article presents the problem of micro-apartments. The issue is presented in a cross-sectional view, covering both the historical overview and current trends. The problem has been discussed against the background of demographic factors that justify the trend of minimizing living space. In addition to spatial issues, the paper presents the social and psychological issues related to small-scale inhabitation, as well as legal frames concerning minimal size of the flats.

Go to article

Authors and Affiliations

Agata Twardoch

The optimization of cut-off grades by means of memetic algorithms

Erhan Cetin Abdurrahman Dalgic
Gospodarka Surowcami Mineralnymi - Mineral Resources Management | 2022 | vol. 38 | No 1 | 107-122 | DOI: 10.24425/gsm.2022.140607
Keywords memetic algorithms optimization cut-off grades depletion rate rehabilitation cost
Download PDF Download RIS Download Bibtex

Abstract

Cut-off grades optimization is a fundamental issue for mineral deposits. A cut-off grade is any grade that is used to separate two courses of action; to mine or not to mine, to process or to dump. In order to achieve the maximum discounted cash flow, generally a decreasing order of cut-off grades schedule takes place. Variable mining costs are applied to the extracted material, not to all of the depletion rate as some of the depletion can be left in-situ. B ecause of access constraints, some of the blocks that have an average grade less than the determined cut-off grade are left in-situ, some of them are excavated and dumped as waste material. The probability density function of an exponential distribution is used to find the portion of the material below the cut-off used that is left in situ. The parts of a mineral deposit that are excavated but will be dumped as waste material and tailings of ore incur some additional cost of rehabilitation. The method of memetic algorithms is a very robust optimization tool. It is a step further from the genetic algorithms. The crossover, mutation and natural selection behavior of the method ensures it escape from a local optimum point, and a further local search improves the optimum further. This paper describes the general problem of cut-off grades optimization, outlines the use of memetic algorithms in cut-off grades optimization and further extension of the method including partial depletion rates and variable rehabilitation cost. This paper is the first application of memetic algorithms to cut-off grades optimization in this context.
Go to article

Bibliography

Cetin, E . 2016. Cut-off grades optimization by means of memetic algorithms with uncertain market conditions. Middle East Journal of Technic 1(1).
Cetin, E . and Dowd, P. A. 2002. The use of genetic algorithms for multiple cut-off grade optimisation. Proceedings of the 30th International Symposium on the Application of Computers and Operations Research in the Minerals Industries, Littleton, Colorado, USA.
Cetin, E . and Dowd, P.A. 2016. M ultiple cut-off grade optimization by genetic algorithms and comparison with grid search method and dynamic programming. The Journal of the South African Institute of Mining and Metallurgy 116(7), pp. 681–688, DOI: 10.17159/2411-9717/2016/v116n7a10.
Dowd, P.A. 1976. Application of dynamic and stochastic programming to optimise cut-off grades and production rates. Transactions of the Institution of Mining and Metallurgy Section A: Mining Industry 81. pp. 160–179.
Dawkins, R. 1976. The Selfish Gene, Oxford University Press.
Garg, P. 2009. A Comparison between Memetic algorithm and Genetic algorithm for the Cryptanalysis of Simplified Data Encryption Standard Algorithm. International Journal of Network Security & Its Applications (IJNSA), 1(1), pp. 34–42.
Gholamnejad, J. 2008. Determination of the optimum cutoff grade considering environmental cost. Journal of International Environmental Application and Science 3(3), pp. 186-194.
Gholamnejad, J. 2009. Incorporation of rehabilitation cost into the optimum cut-off grade determination. The Journal of the South African Institute of Mining and Metallurgy 109(2), pp. 89–94.
Holland, J.H. 1975. Adaptation in N atural and Artificial Systems. University of Michigan Press, USA.
Lane, K.F. 1964. Choosing the optimum cutoff grade. Colorado School of Mines Quarterly 59(4), pp. 811–829.
Lane, K.F. 1988. The Economic Definition of Ore. Mining Journals Books Ltd., L ondon, UK.
Go to article

Authors and Affiliations

Erhan Cetin
1
ORCID: ORCID
Abdurrahman Dalgic
2
  1. Dicle University, Diyarbakır, Turkey
  2. Alanya Alaaddin Keykubat University, Alanya, Turkey

Geochemistry of the carboniferous coal-bearing series and the miocene cover within the Upper Silesian Coal Basin – a case study

Ewa Krzeszowska
Gospodarka Surowcami Mineralnymi - Mineral Resources Management | 2023 | vol. 39 | No 4 | 107-122 | DOI: 10.24425/gsm.2023.148166
Keywords Miocene Carboniferous USCB chemostratigraphy
Download PDF Download RIS Download Bibtex

Abstract

This paper presents geochemical data for 171 core samples of the Carboniferous coal-bearing series and the Miocene cove from the central part of the Upper Silesian Coal Basin. Major oxide concentrations (Al 2O 3, SiO 2, Fe 2O 3, P 2O 5, K 2O, MgO, CaO, Na 2O, K 2O, MnO, TiO 2, and Cr 2O 3) were obtained using XRF. Trace and major elements (Mo, Cu, Pb, Zn, Ni, Co, U, Cr, V, Mn, As, Th, Sr, Cd, Sb, Bi, Ba, Ti, W, Zr, Ce, Nb, Ta, Be Sc) were analysed ICP-MS. The main goals of this study were to demonstrate the distribution, as well as the stratigraphical variability, of the selected elements and to determine whether chemostratigraphy tools could be effectively applied to analyze Carboniferous and Miocene deposits of the USCB. Geochemical studies have shown showed different geochemical features of the samples from the Carboniferous and the Miocene. The diversity is mainly expressed in the enrichment of Miocene sediments in Ca and Sr related to biogenic carbonate material. It was also stated that the concentrations of trace elements associated with the detrital fraction, such as Zn, Cr, Co, Ba, Ti, Zr, Nb, and Sc show slightly higher values in Carboniferous sediments. On the basis of the content of Ti, Zr, and Nb, as well as ratios such as Th/U, Zr/Th, Ti/Zr, and TiO 2/K 2O, units with different inputs of the terrigenous fraction can be identified in both Carboniferous and Miocene formations. The paper shows that chemostratigraphy can be used as a stratigraphic and correlation tool for the Carboniferous and the Miocene deposits of the USCB.
Go to article

Authors and Affiliations

Ewa Krzeszowska
1
ORCID: ORCID
  1. Silesian University of Technology, Poland

This page uses 'cookies'. Learn more