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    Wyświetlanie 1-8 z 8
    Tytuł:
    Flow structures during refrigerants condensation
    Autorzy:
    Sikora, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/95199.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Koszalińska. Wydawnictwo Uczelniane
    Tematy:
    condensation
    refrigerant
    minichannel
    flow pattern
    kondensacja
    czynnik chłodniczy
    minikanał
    model przepływu
    Opis:
    For several years, in the world are carried out studies on the refrigerants condensation in minichannels. These studies are aimed at understanding the condensation process and facilitate the design of mini heat exchangers. It is very important to optimize heat transfer and drive power consumption of the is the knowledge of the processes occurring during refrigerants condensation in pipe minichannels. It is important in this case to make a individual flow structures maps for the refrigerants, due to the significant effect of flow structured formed in the minichannel on the heat transfer and flow resistance. Unfortunately, in relation to the number of publications about condensation in minichannels, the number of published flow maps is relatively small. Due to the fact that the condensation process takes place differently in the minichannels and conventional channels, there is no possibility of using the flow maps for conventional channels to identification flow patterns in minichannels. One of the most popular flow maps for the condensation in minichannels is the map created by Colleman and Garimella, which was made for the R134a refrigerant. The authors conducted their own experimental studies of refrigerants R134a, R404A and R407C condensation in pipe minichannels with an internal diameter d = 3.3 - 0.31 mm. These studies results were subjected to calculation identification of flow structures using the map of Colleman and Garimella. These results are compared with the criteria published on Thome and Cavallini flow maps.
    Źródło:
    Journal of Mechanical and Energy Engineering; 2017, 1, 1; 101-106
    2544-0780
    2544-1671
    Pojawia się w:
    Journal of Mechanical and Energy Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Pomiar parametrów geometrycznych i przepływowych struktur przepływu dwufazowego w minikanałach
    Measurements of geometrical and flow parameters of two-phase flow structures in minichannels
    Autorzy:
    Sikora, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/152930.pdf
    Data publikacji:
    2014
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    skraplanie
    struktury przepływu dwufazowego
    minikanały
    czynnik chłodniczy HFE-7100
    condensation
    flow patterns
    two-phase flow structures
    minichannel
    HFE-7100 refrigerant
    Opis:
    Przeprowadzono badania eksperymentalne skraplania czynnika chłodniczego HFE7100 w minikanale rurowym o średnicy wewnętrznej d = 2 mm. Podczas badań wykonano wizualizację występujących podczas procesu skraplania struktur przepływu. Dokonano pomiaru parametrów geometrycznych i przepływowych w celu identyfikacji struktur przepływu dwufazowego skraplania w minikanale. Przeprowadzono identyfikację zakresu występowania poszczególnych struktur przepływu podczas skraplania niskociśnieniowego czynnika chłodniczego HFE7100. Badania wykonano w całym zakresie procesu skraplania (x = 0 – 1).
    Identification of flow patterns can be made by two methods. The first one is a calculation method consisting in calculating flow parameters and comparing their values with the ranges given by other authors or flow maps. This method has a number of limitations associated with a small amount of existing flow patterns maps, and many restrictions on their use. The second method visualizes the flow and identifies it from photos. This method is more accurate. This paper presents a methodology and results of experimental identification of the two-phase flow structure by measurement of flow and geometrical parameters. The test stand was designed and built. An optical measurement system was used for recording, processing and image analysis. Preliminary measurements were made for a two-phase flow mixture of HFE – 7100 refrigerant. The results of visualization and measurement of parameters are shown in the figures presented in the paper.
    Źródło:
    Pomiary Automatyka Kontrola; 2014, R. 60, nr 10, 10; 872-875
    0032-4140
    Pojawia się w:
    Pomiary Automatyka Kontrola
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Pomiary oporów przepływu podczas skraplania w minikanałach rurowych
    Measures of pressure drops during condensation in tulbar minichannels
    Autorzy:
    Sikora, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/153482.pdf
    Data publikacji:
    2012
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    skraplanie
    opory przepływu
    pomiary
    minikanały
    czynnik chłodniczy
    condensation
    flow resistance
    measures
    minichannel
    refrigerant
    Opis:
    Badanie i analiza oporów przepływu podczas skraplania czynników chłodniczych w minikanałach rurowych ma duże znaczenie dla poznania procesu skraplania. W artykule tym przedstawiono wyniki przeprowadzonych badań, które mają na celu ułatwienie projektowania, konstrukcji i eksploatacji kompaktowych wymienników ciepła. W wyniku analizy rezultatów badań autorka proponuje własną zależność pozwalającą na wyznaczenie średnich i lokalnych oporów przepływu w minikanałach.
    Nowadays, much attention is paid to miniaturization of devices while increasing their efficiency. The same is with heat exchangers which have to exchange a lot of heat from a small area. By using minichannels and phase transitions, miniaturization of heat exchangers with intensification of heat exchange is possible. Unfortunately, the decrease in internal diameter creates problems associated with an increased flow resistance, which is a negative phenomenon because it causes increases in energy consumption for refrigerant transportation. The understanding of the dependence between the flow resistance and the flow parameters, refrigerant properties as well as internal diameter of a minichannel can improve design, construction and exploitation of compact heat exchangers. It will also enable optimization of the heat transfer coefficient α and flow resistance (Δp/L) growth. For this purpose, investigations were performed on three different refrigerants: R134a, R404A, R407C in minichannels with an internal diameter of the range dw = 0.31 mm - 3.3 mm. Miniaturization of compact heat exchangers and use of environmentally friendly CFC substitutes also help to reduce harmful effects on the environment and costs due to the absorptivity of material decrease. Based on the analysis of the investigation results the author has developed own correlation describing change of the pressure drop on the minichannel length, depending on its internal diameter, flow parameters and refrigerant properties.
    Źródło:
    Pomiary Automatyka Kontrola; 2012, R. 58, nr 6, 6; 559-562
    0032-4140
    Pojawia się w:
    Pomiary Automatyka Kontrola
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modeling of pressure drop during refrigerant condensation in pipe minichannels
    Autorzy:
    Sikora, M.
    Bohdal, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/240860.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    minichannels
    pressure drop
    refrigerant
    condensation
    minikanał
    spadek ciśnienia
    chłodziwo
    kondensacja
    Opis:
    Investigations of refrigerant condensation in pipe minichannels are very challenging and complicated issue. Due to the multitude of influences very important is mathematical and computer modeling. Its allows for performing calculations for many different refrigerants under different flow conditions. A large number of experimental results published in the literature allows for experimental verification of correctness of the models. In this work is presented a mathematical model for calculation of flow resistance during condensation of refrigerants in the pipe minichannel. The model was developed in environment based on conservation equations. The results of calculations were verified by authors own experimental investigations results.
    Źródło:
    Archives of Thermodynamics; 2017, 38, 4; 15--28
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An investigation of the thermal characteristics of the refrigerants zeotropic mixtures condensation in minichannels
    Autorzy:
    Bohdal, T.
    Sikora, M.
    Widomska, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/175244.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    condensation
    heat transfer coefficient
    mass flux density
    minichannels
    vapor quality
    zeotropic mixture
    Opis:
    This paper describes the results of experimental investigations of heat transfer during the condensation of the homogenous R134a refrigerant and zeotropic mixtures R404A, R407C and R410A in pipe minichannels with internal diameters 0.31–3.30 mm. The values of the local and average heat transfer coefficient throughout the range of changes in the vapor quality 1–0 were determined. Based on the obtained results, the effect of vapor quality, mass flux density and channel diameter changes on heat transfer coefficient was illustrated. a pronounced effect of the refrigerant properties at the heat exchange efficiency during the condensation process in pipe minichannels was indicated. The results were compared with calculations according to the correlations proposed by other authors. On the basis of the experimental investigations, the authors proposed their own correlation for the calculation of local heat transfer coefficient, obtaining the results of compatibility tests in the range of ±20%.
    Źródło:
    Transactions of the Institute of Fluid-Flow Machinery; 2015, 128; 43-57
    0079-3205
    Pojawia się w:
    Transactions of the Institute of Fluid-Flow Machinery
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The analysis of thermal and flow characteristics of the condensation of refrigerant zeotropic mixtures in minichannels
    Autorzy:
    Bohdal, T.
    Widomska, K.
    Sikora, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/240470.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    minichannels
    condensation
    zeotropic mixture
    heat transfer coefficient
    pressure drop
    minikanał
    kondensacja
    mieszanina zeotropowa
    współczynnik przewodnictwa cieplnego
    spadek ciśnienia
    Opis:
    The paper presents the results of experimental heat transfer and pressure drop during condensation of the single component refrigerant R134a and zeotropic mixtures R404A, R407C, and R410A in tube minichannels of internal diameter from the range 0.31–3.30 mm. The local values and the average of heat transfer coefficient and pressure drop in the whole range of the change in mass quality were measured. On the basis of the obtained test results there was illustrated the influence of the change of mass vapor quality, the mass flux density, and the inner diameter of channel on the studied parameters. These results were compared with the calculation results based on the relations postulated by other authors. The discrepancy range was ± 50%. On the basis of given test results own correlation was developed to calculate the heat transfer coefficient and pressure drop of tested refrigerants which presents the obtained results in a range of discrepancy of ±25%.
    Źródło:
    Archives of Thermodynamics; 2016, 37, 2; 41-69
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Condensation of refrigerant R407C in multiport minichannel section
    Autorzy:
    Bohdal, T.
    Charun, H.
    Sikora, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/240486.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    condensation
    minichannels
    R407C refrigerant
    heat exchanger
    kondensacja
    minikanały
    czynnik chłodniczy R407C
    wymiennik ciepła
    Opis:
    Analysis of the state of-the-art in research of refrigerant condensation in miniature heat exchangers, so-called multiports, was made. Results of refrigerant R407C condensation in a mini condenser made in the form of two bundles of tubular minichannels from stainless steel with an inside diameter 0.64 mm and length 100 mm have been presented. Two exchangers consisted of four minichannels and 8 minichannels have been investigated. The values of average heat transfer coefficient and frictional pressure drops throughout the condensation process were designated. The impact of the vapor quality of refrigerant and the mass flux density on the intensity of heat transfer and flow resistance were illustrated. A comparative analysis of test results for various refrigerants in both mini heat exchangers were made.
    Źródło:
    Archives of Thermodynamics; 2016, 37, 4; 3-18
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Investigation of flow structures during HFE-7100 refrigerant condensation
    Autorzy:
    Bohdal, T.
    Sikora, M.
    Widomska, K.
    Radchenko, A. M.
    Powiązania:
    https://bibliotekanauki.pl/articles/240718.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    condensation
    minichannels
    flow structures
    refrigerant
    kondensacja
    minikanał
    struktura przepływu
    czynnik chłodniczy
    Opis:
    The experimental research of environmentally friendly refrigerant HFE-7100 condensation in pipe minichannels was conducted. During the investigations of HFE-7100 condensation in a minichannel with internal diameter 2 mm together with visualization of flow patterns was made. Visualization results were compared with existing flow structure maps. The identification of the range of flow patterns occurrence during the condensation process of low-pressure refrigerant HFE-7100 was made. The tests were performed throughout the whole range of condensation process.
    Źródło:
    Archives of Thermodynamics; 2015, 36, 4; 25-34
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-8 z 8

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