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    Wyświetlanie 1-4 z 4
    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:
    Comparative study of heat transfer and pressure drop during flow boiling and flow condensation in minichannels
    Autorzy:
    Mikielewicz, D.
    Andrzejczyk, R.
    Jakubowska, B.
    Mikielewicz, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/240815.pdf
    Data publikacji:
    2014
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    two-phase pressure drops
    heat transfer coefficient
    boiling
    condensation
    dwufazowy spadek ciśnienia
    współczynnik przenikania ciepła
    wrzenie
    kondensacja
    Opis:
    In the paper a method developed earlier by authors is applied to calculations of pressure drop and heat transfer coefficient for flow boiling and also flow condensation for some recent data collected from literature for such fluids as R404a, R600a, R290, R32,R134a, R1234yf and other. The modification of interface shear stresses between flow boiling and flow condensation in annular flow structure are considered through incorporation of the so called blowing parameter. The shear stress between vapor phase and liquid phase is generally a function of nonisothermal effects. The mechanism of modification of shear stresses at the vapor-liquid interface has been presented in detail. In case of annular flow it contributes to thickening and thinning of the liquid film, which corresponds to condensation and boiling respectively. There is also a different influence of heat flux on the modification of shear stress in the bubbly flow structure, where it affects bubble nucleation. In that case the effect of applied heat flux is considered. As a result a modified form of the two-phase flow multiplier is obtained, in which the nonadiabatic effect is clearly pronounced.
    Źródło:
    Archives of Thermodynamics; 2014, 35, 3; 17-37
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    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:
    Heat transfer in helical coil heat exchanger:An experimental parametric study
    Autorzy:
    Kowalski, Krzysztof
    Downarowicz, Dorota
    Powiązania:
    https://bibliotekanauki.pl/articles/185443.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    helical coil
    heat exchanger
    condensation
    Wilson method
    laminar flow
    pressure drop
    wymiennik ciepła
    kondensacja
    Metoda Wilsona
    przepływ laminarny
    Spadek ciśnienia
    Opis:
    Helical coil heat exchangers are widely used in a variety of industry applications such as refrigerationsystems, process plants and heat recovery. In this study, the effect of Reynolds number and theoperating temperature on heat transfer coefficients and pressure drop for laminar flow conditions wasinvestigated. Experiments were carried out in a shell and tube heat exchanger with a copper coiledpipe (4 mm ID, length of 1.7 m and coil pitch of 7.5 mm) in the temperature range from 243 to 273 K.Air – propan-2-ol vapor mixture and coolant (methylsilicone oil) flowed inside and around the coil,respectively. The fluid flow in the shell-side was kept constant, while in the coil it was varied from 6.6to 26.6 m/s (the Reynolds number below the critical value of 7600). Results showed that the helicalpipe provided higher heat transfer performance than a straight pipe with the same dimensions. Theconvective coefficients were determined using the Wilson method. The values for the coiled pipe werein the range of 3–40 W/m2·K. They increased with increasing the gas flow rate and decreasing thecoolant temperature.
    Źródło:
    Chemical and Process Engineering; 2019, 40, 1; 101--114
    0208-6425
    2300-1925
    Pojawia się w:
    Chemical and Process Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-4 z 4

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