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    Wyświetlanie 1-4 z 4
    Tytuł:
    Prediction of flow boiling heat transfer coefficient for carbon dioxide in minichannels and conventional channels
    Autorzy:
    Mikielewicz, D.
    Jakubowska, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/240733.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    heat transfer coefficient
    flow boiling
    carbon dioxide
    minichannels
    współczynnik przewodnictwa cieplnego
    wrzenie w przepływie
    dwutlenek węgla
    minikanał
    Opis:
    In the paper presented are the results of calculations using authors own model to predict heat transfer coefficient during flow boiling of carbon dioxide. The experimental data from various researches were collected. Calculations were conducted for a full range of quality variation and a wide range of mass velocity. The aim of the study was to test the sensitivity of the in-house model. The results show the importance of taking into account the surface tension as the parameter exhibiting its importance in case of the flow in minichannels as well as the influence of reduced pressure. The calculations were accomplished to test the sensitivity of the heat transfer model with respect to selection of the appropriate two-phase flow multiplier, which is one of the elements of the heat transfer model. For that purpose correlations due to Müller-Steinhagen and Heck as well as the one due to Friedel were considered. Obtained results show a good consistency with experimental results, however the selection of two-phase flow multiplier does not significantly influence the consistency of calculations.
    Źródło:
    Archives of Thermodynamics; 2016, 37, 2; 89-106
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modeling the performance of water-zeolite 13X adsorption heat pump
    Autorzy:
    Kowalska, K.
    Ambrożek, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/240147.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    desorption
    adsorption
    mathematical simulation
    heat pump
    coefficient of performance
    desorpcja
    adsorpcja
    symulacja matematyczna
    pompa ciepła
    współczynnik wydajności
    Opis:
    The dynamic performance of cylindrical double-tube adsorption heat pump is numerically analysed using a non-equilibrium model, which takes into account both heat and mass transfer processes. The model includes conservation equations for: heat transfer in heating/cooling fluids, heat transfer in the metal tube, and heat and mass transfer in the adsorbent. The mathematical model is numerically solved using the method of lines. Numerical simulations are performed for the system water-zeolite 13X, chosen as the working pair. The effect of the evaporator and condenser temperatures on the adsorption and desorption kinetics is examined. The results of the numerical investigation show that both of these parameters have a significant effect on the adsorption heat pump performance. Based on computer simulation results, the values of the coefficients of performance for heating and cooling are calculated. The results show that adsorption heat pumps have relatively low efficiency compared to other heat pumps. The value of the coefficient of performance for heating is higher than for cooling
    Źródło:
    Archives of Thermodynamics; 2017, 38, 4; 191--207
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Application of the finite element method to the determining of boiling heat transfer coefficient for minichannel flow
    Autorzy:
    Piasecka, M.
    Maciejewska, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/240586.pdf
    Data publikacji:
    2013
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    heat transfer
    incipience of flow boiling
    finite element method
    przepływ ciepła
    przepływ wrzenia
    metoda elementów skończonych
    Opis:
    Miniature heat exchangers are used to provide higher cooling capacity for new technologies. This means a reduction in their size and cost but the identical power. The paper presents the method for determination of boiling heat transfer coefficient for a rectangular minichannel of 0.1 mm depth, 40 mm width and 360 mm length with asymmetric heating. Experimental research has focused on the transition from single phase forced convection to nucleate boiling, i.e., the zone of boiling incipience. The ‘boiling front’ location has been determined from the temperature distribution of the heated wall obtained from liquid crystal thermography. The experiment has been carried out with R-123, mass flux 220 kg/(m2s), pressure at the channel inlet 340 kPa. Local values of heat transfer coefficient were calculated on the basis of empirical data from the experiment following the solution of the two-dimensional inverse heat transfer problem. This problem has been solved with the use of the finite element method in combination with Trefftz functions. Temperature approximates (linear combinations of Trefftz functions) strictly fulfill the governing equations. In presented method the inverse problem is solved in the same way as the direct problem. The results confirmed that considerable heat transfer enhancement takes place at boiling incipience in the minichannel flow boiling. Moreover, under subcooling boiling, local heat coefficients exhibit relatively low values.
    Źródło:
    Archives of Thermodynamics; 2013, 34, 1; 55-69
    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
      Wyświetlanie 1-4 z 4

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