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Wyszukujesz frazę "boiling heat transfer" wg kryterium: Temat

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    Wyświetlanie 1-10 z 10
    Tytuł:
    Nucleate pool boiling heat transfer from small horizontal smooth tube bundles
    Autorzy:
    Krasowski, K.
    Cieśliński, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/175416.pdf
    Data publikacji:
    2011
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    boiling heat transfer
    smooth tube bundle
    Opis:
    Measurements of boiling heat transfer coefficients in water, methanol and refrigerant R141b are reported for the bundles of smooth tubes that represent a portion of a flooded-type evaporator. Each bundle contained 19 instrumented, electrically heated tubes in a staggered triangular-pitch layout. The effect of heat flux, tube pitch and operating pressure is studied in the paper. Bundle factor and bundle effect are discussed as well. A correlation for prediction of a bundle average heat transfer coefficient is proposed.
    Źródło:
    Transactions of the Institute of Fluid-Flow Machinery; 2011, 123; 85-97
    0079-3205
    Pojawia się w:
    Transactions of the Institute of Fluid-Flow Machinery
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A study of flow boiling heat transfer in a rectangular minichannel using liquid crystal and infrared thermography
    Autorzy:
    Strąk, K.
    Piasecka, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/175560.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    flow boiling heat transfer
    rectangular minichannel
    enhanced foil surface
    liquid crystal thermography
    infrared thermography
    Opis:
    This paper presents results of flow boiling heat transfer in two parallel asymmetrically heated vertical minichannels. The heating element for Fluorinert FC-72 flowing in the minichannels was a thin foil with an enhanced surface on the side in contact with the fluid. The channels were observed from both sides through glass panes. Two of the panes allowed us to observe the two phase flow patterns on the enhanced surface of the foil, while the other two panes were used for simultaneous measurement of temperature on the smooth side of the foil. The temperature was measured by applying two contactless methods. One was liquid crystal thermography (LCT), which required treating the foil surface with thermochromic liquid crystals (TLCs), and the other was infrared thermography (IRT), which required coating the foil surface with black paint. Calculations were performed on the basis ofa one-dimensional model to determine the heat transfer coefficient at the foil-fluid interface from the Robin boundary condition. The experimental results were graphically represented as the foil temperature and the heat transfer coefficient against the distance from the minichannel inlet and as LCT and IRT images obtained for saturated boiling.
    Źródło:
    Transactions of the Institute of Fluid-Flow Machinery; 2015, 128; 97-118
    0079-3205
    Pojawia się w:
    Transactions of the Institute of Fluid-Flow Machinery
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Experimental investigation and characteristics of multiwalled carbon nanotube aqua nanofluids from a flat plate heater surface in a pool
    Autorzy:
    Vasudevan, D.
    Senthil Kumar, D.
    Murugesan, A.
    Vijayakumar, C.
    Powiązania:
    https://bibliotekanauki.pl/articles/201185.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    nanofluids
    critical heat flux
    heat transfer coefficient
    boiling
    heat transfer enhancement
    Opis:
    In this experimental investigation, the critical heat flux (CHF) of aqua-based multiwalled carbon nanotube (MWCNT) nanofluids at three different volumetric concentrations 0.2%, 0.6%, and 0.8% were prepared, and the test results were compared with deionized water. Different characterization techniques, including X-ray diffraction, scanning electron microscopy and Fourier transform infrared, were used to estimate the size, surface morphology, agglomeration size and chemical nature of MWCNT. The thermal conductivity and viscosity of the MWCNT at three different volumetric concentrations was measured at a different temperature, and results were compared with deionized water. Although, MWCNT-deionized water nanofluid showed superior performance in heat transfer coefficient as compared to the base fluid. However, the results proved that the critical heat flux is increased with an increase in concentrations of nanofluids.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2020, 68, 3; 547-554
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Boiling in micro-channels
    Autorzy:
    Hetsroni, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/199886.pdf
    Data publikacji:
    2010
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    micro-channel
    boiling
    pressure drop
    heat transfer
    fluctuation
    Opis:
    Boiling heat transfer in micro-channels is a subject of intense academic and practical interest. Though many heat transfer correlations have been proposed, most were empirically formulated from experimental data. However, hydrodynamic and thermal aspects of boiling in micro-channels are not well understood. Moreover, there are only a few theoretical models that link the heat transfer mechanism with flow regimes in micro-channels. Also, there are discrepancies between different sets of published results, and heat transfer coefficients have either well exceeded, or fallen far below, those predicted for conventional channels. Here we consider these problems with regard to micro-channels with hydraulic diameters ranging roughly from 5 ěm to 500 ěm, to gain a better understanding of the distinct properties of the measurement techniques and uncertainties, the conditions under which the experimental results should be compared to analytical or numerical predictions, boiling phenomenon, as well as different types of micro-channel heat sinks. Two-phase flow maps and heat transfer prediction methods for vaporization in macro-channels are not applicable in micro-channels, because surface tension dominates the phenomena, rather than gravity forces. The models of convection boiling should correlate the frequencies, sizes and velocities of the bubbles and the coalescence processes, which control the flow pattern transitions, together with the heat flux and the mass flux. Therefore, the vapour bubble size distribution must be taken into account. The flow pattern in parallel micro-channels is quite different from that in a single micro-channel. At same values of heat and mass flux, different, time dependent, flow regimes occur in a given micro-channel. At low vapour quality, heat flux causes a sudden release of energy into the vapour bubble, which grows rapidly and occupies the entire channel cross section. The rapid bubble growth pushes the liquid-vapour interface on both caps of the vapour bubble, at the upstream and the downstream ends, and leads to a reverse flow. We term this phenomenon as explosive boiling. One of the limiting operating conditions with flow boiling is the critical heat flux (CHF). The CHF phenomenon is different from that observed in conventional size channels.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2010, 58, 1; 155-163
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An investigation into the influence of different parameters on the onset of boiling in minichannels
    Autorzy:
    Piasecka, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/240757.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    inicjacja wrzenia
    przepływ wrzenia
    wymiana ciepła
    flow boiling
    heat transfer
    Incipience (onset) of boiling
    Opis:
    The paper presents experimental studies on boiling heat transfer in rectangular minichannels. The investigations focus on the transition from single phase forced convection to nucleate boiling, i.e., in the zone of boiling incipience. The experiment has been carried out with FC-72, R-123 and R-11 at the Reynolds number below 4700, corresponding to mass flow rate range 95-710 kg/(m s). The main part of the test section is a minichannel of pre-set depth from 0.7 to 2 mm and width (20, 40 and 60 mm), with different spatial orientations from vertical to horizontal and 30% inclination angle adjustment. The objective of the paper includes the impact of selected parameters (liquid flow velocity, pressure and inlet liquid subcooling, channel dimensions and spatial orientation) on the boiling incipience in minichannels. The investigations are intended to develop a correlation for the calculations of the Nusselt number under the conditions of boiling incipience in the minichannel as a function of changeable parameters.
    Źródło:
    Archives of Thermodynamics; 2012, 33, 4; 67-90
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Study of heat transfer during pool boiling on minifins surface coated with carbon nanotubes
    Autorzy:
    Strąk, E.
    Pastuszko, R.
    Kłosowiak, R.
    Urbaniak, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/175588.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    pool boiling
    carbon nanotube
    heat transfer coefficient
    power
    electronic cooling
    Opis:
    The article describes the study of heat transfer during pool boiling on minifins surface coated with nanostructure. This is a molecular level technology used in engineering or mechanical factory. A surface with carbon nanotubes (CNTs) is highly effective in reducing the superheat incipience and enhancing both the heat flux and heat transfer coefficient. The paper focuses on the comparison of the surfaces, on which pool boiling heat transfer occurs, i.e., on minifins coated with carbon nanotubes (MF+N) with surfaces formed by sintering the woven copper wire mesh to the minifins tips (MF+M) and with plain minifins surface (MF). The experiments were carried out for two boiling fluids: water and ethyl alcohol. The purpose of the presented study was to find out which of those tested surfaces and fluids could be the best alternative for use in the cooling of electronic devices and which surfaces could be used as thermosyphon or heat pipe evaporator.
    Źródło:
    Transactions of the Institute of Fluid-Flow Machinery; 2015, 128; 59-72
    0079-3205
    Pojawia się w:
    Transactions of the Institute of Fluid-Flow Machinery
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Subcooled flow boiling of a citric acid aqueous mixture
    Autorzy:
    Abdolhossein Zadeh, Mohammad Amin
    Nakhjavani, Shima
    Powiązania:
    https://bibliotekanauki.pl/articles/240356.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    flow boiling
    heat transfer
    citric acid
    bubble formation
    chen type model
    Opis:
    In the present research, an experimental investigation was conducted to assess the heat transfer coefficient of aqueous citric acid mixtures. The experimental facility provides conditions to assess the influence of various operating conditions such as the heat flux (0–190 kW/m2), mass flux (353–1059 kg/m2s) and the concentration of citric acid in water (10%–50% by volume) with a view to measure the subcooled flow boiling heat transfer coefficient of the mixture. The results showed that two main heat transfer mechanisms can be identified including the forced convective and nucleate boiling heat transfer. The onset point of nucleate boiling was also identified, which separates the forced convective heat transfer domain from the nucleate boiling region. The heat transfer coefficient was found to be higher in the nucleate boiling regime due to the presence of bubbles and their interaction. Also, the influence of heat flux on the heat transfer coefficient was more pronounced in the nucleate boiling heat transfer domain, which was also attributed to the increase in bubble size and rate of bubble formation. The obtained results were also compared with those theoretically obtained using the Chen type model and with some experimental data reported in the literature. Results were within a fair agreement of 22% against the Chen model and within 15% against the experimental data.
    Źródło:
    Archives of Thermodynamics; 2020, 41, 1; 193-217
    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:
    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:
    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 1-10 z 10

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