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    Wyświetlanie 1-14 z 14
    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:
    Experimental investigation of the two-phase flow regimes and pressure drop in horizontal mini-size rectangular test section
    Autorzy:
    Elazhary, A.
    Soliman, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/239912.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    dwufazowy
    minikanał
    przepływ
    spadek ciśnienia
    flow regimes
    mini channel
    pressure drop
    two-phase
    Opis:
    An experimental study was conducted in order to investigate two-phase flow regimes and fully developed pressure drop in a mini-size, horizontal rectangular channel. The test section was machined in the form of an impacting tee junction in an acrylic block (in order to facilitate visualization) with a rectangular cross-section of 1.87-mm height on 20-mm width on the inlet and outlet sides. Pressure drop measurement and flow regime identification were performed on all three sides of the junction. Air-water mixtures at 200 kPa (abs) and room temperature were used as the test fluids. Four flow regimes were identified visually: bubbly, plug, churn, and annular over the ranges of gas and liquid superficial velocities of 0.04 [ less than or equal to] JG [ less than or equal to] 10 m/s and 0.02 [ less than or equal to] JL [ less than or equal to] 0.7 m/s, respectively, and a flow regime map was developed. Accuracy of the pressure-measurement technique was validated with single-phase, laminar and turbulent, fully developed data. Two-phase experiments were conducted for eight different inlet conditions and various mass splits at the junction. Comparisons were conducted between the present data and former correlations for the fully developed two-phase pressure drop in rectangular channels with similar sizes. Wide deviations were found among these correlations, and the correlations that agreed best with the present data were identified.
    Źródło:
    Archives of Thermodynamics; 2012, 33, 2; 47-6
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Pressure drop in two-phase gas-liquid (Taylor) flow in microreactors
    Autorzy:
    Cygański, P.
    Sobieszuk, P.
    Pohorecki, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/185780.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    przepływ Taylora
    przepływ gaz-ciecz
    spadek ciśnienia
    mikroreaktor
    gas-liquid Taylor flow
    microreactor
    pressure drop
    Opis:
    The pressure drop in microreactors for the gas - liquid Taylor flow was measured for 4 different microreactor geometries and 3 different gas - liquid systems. The results have been compared with the existing literature correlations. A selection of the best correlations has been made.
    Źródło:
    Chemical and Process Engineering; 2012, 33, 3; 369-384
    0208-6425
    2300-1925
    Pojawia się w:
    Chemical and Process Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of natural pressure drop in mine main ventilation
    Skutki naturalnego spadku ciśnienia w głównej sieci wentylacyjnej kopalni
    Autorzy:
    Zapletal, P.
    Hudecek, V.
    Trofimov, V.
    Powiązania:
    https://bibliotekanauki.pl/articles/219326.pdf
    Data publikacji:
    2014
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    wentylacja kopalni
    naturalny spadek ciśnienia
    temperatura
    wentylator główny
    mine ventilation
    natural pressure drop
    temperature
    main fan
    Opis:
    Natural ventilation in a mine is ventilation without the use of means of artificial ventilation. The flow of mine air is induced by the difference between the mass column in an intake and that in a return. The difference in mine air density is a result of difference between the temperature of intake air and that of return air. To a certain extent, the influence of differences in mine air humidity and chemical composition can act as well. Gassy mines in the Czech Republic and Ukraine are ventilated merely artificially, i.e. by means of exhaust ventilation. However, even in the case of this type of ventilation, when the total mine air flow is produced by fans, a natural current of air exists and acts in the ventilation network of the mine.
    Naturalna wentylacja w kopalni to wentylacja bez wykorzystania środków sztucznej wentylacji. Przepływ kolumny powietrza wymuszony jest poprzez różnicę ciśnień pomiędzy kolumną powietrza na wlocie a prądem zużytego powietrza. Różnica w gęstości powietrza kopalnianego wynika z różnicy temperatur pomiędzy powietrzem wlotowym i zużytym. W pewnym stopniu uwidacznia się także wpływ wilgotności powietrza kopalnianego i jego składu chemicznego. Kopalnie gazowe w Republice Czeskiej i na Ukrainie są przewietrzane przy użyciu sztucznej wentylacji, z wykorzystaniem instalacji wyciągowej. Jednakże nawet w przypadku zastosowania tego typu systemu wentylacyjnego w którym przepływ powietrza kopalnianego w całości generowany jest przez wentylatory, nadal istnieją naturalne prądy powietrza, których obecność i działanie ujawnia się w sieci wentylacyjnej.
    Źródło:
    Archives of Mining Sciences; 2014, 59, 2; 501-508
    0860-7001
    Pojawia się w:
    Archives of Mining Sciences
    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:
    Numerical analysis of erosion wear and pressure drop for turbulent multiphase slurry flow
    Autorzy:
    Kannojiya, V.
    Darshan, M. B.
    Chandra, Y. P.
    Powiązania:
    https://bibliotekanauki.pl/articles/139624.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    erosion
    computational fluid dynamics
    CFD
    multi-phase flow
    pressure drop
    erozja
    obliczeniowa mechanika płynów
    przepływ wielofazowy
    spadek ciśnienia
    Opis:
    The disposal of ash in a thermal plant through the slurry pipe is subjected to some erosion wear due to the abrasive characteristics of the slurry. A simulation study of particle-liquid erosion of mild steel pipe wall based on CFD-FLUENT that considers the solid-liquid, solid-solid and solid-wall interaction is presented in this work.The multi-phase Euler-Lagrange model with standard k- ϵ turbulence modeling is adopted to predict the particulate erosion wear caused by the flow of bottom ash water suspension. Erosion rate for different particle size and concentration is evaluated at variable flow rate. It is observed that the pressure drop and erosion rate share direct relationships with flow velocity, particle size and concentration. The flow velocity is found to be the most influencing parameter. A model capable of predicting the erosion wear at variable operating conditions is presented.The simulation findings show good agreement with the published findings.
    Źródło:
    Archive of Mechanical Engineering; 2018, LXV, 3; 361-378
    0004-0738
    Pojawia się w:
    Archive of Mechanical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Cooling of High Heat Flux Flat Surface with Nanofluid Assisted Convective Loop. Experimental Assessment
    Autorzy:
    Arya, A.
    Shahmiry, S.
    Nikkhah, V.
    Sarafraz, M.M.
    Powiązania:
    https://bibliotekanauki.pl/articles/139852.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    ZnO nanoparticle
    pressure drop
    heat transfer coefficient
    friction factor
    nanocząstki ZnO
    spadek ciśnienia
    współczynnik przenikania ciepła
    współczynnik tarcia
    Opis:
    Experimental investigation was conducted on the thermal performance and pressure drop of a convective cooling loop working with ZnO aqueous nanofluids. The loop was used to cool a flat heater connected to an AC autotransformer. Influence of different operating parameters, such as fluid flow rate and mass concentration of nanofluid on surface temperature of heater, pressure drop, friction factor and overall heat transfer coefficient was investigated and briefly discussed. Results of this study showed that, despite a penalty for pressure drop, ZnO/water nanofluid was a promising coolant for cooling the micro-electronic devices and chipsets. It was also found that there is an optimum for concentration of nanofluid so that the heat transfer coefficient is maximum, which was wt. % = 0.3 for ZnO/water used in this research. In addition, presence of nanoparticles enhanced the friction factor and pressure drop as well; however, it is not very significant in comparison with those of registered for the base fluid.
    Źródło:
    Archive of Mechanical Engineering; 2017, LXIV, 4; 519-531
    0004-0738
    Pojawia się w:
    Archive of Mechanical Engineering
    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:
    Pressure drop during condensation of refrigerants in pipe minichannels
    Autorzy:
    Bohdal, T.
    Charun, H.
    Sikora, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/240165.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    kompaktowy kondensator
    przepływ
    skraplanie
    skraplaniea w minikanałach
    spadek ciśnienia
    compact condenser
    condensation in minichannels
    pressure drop during flow in condensation
    Opis:
    The present paper describes results of experimental investigations of pressure drop during the condensation of R134a, R404a and R407C refrigerants in pipe minichannels with internal diameter 0.31-3.30 mm. The results concern investigations of the mean and local pressure drop in single minichannels. The results of experimental investigations were compared with the calculations according to the correlations proposed by other authors. A pressure drop during the condensation of refrigerants is described in a satisfactory manner with Friedel and Garimella correlations. On the basis of the experimental investigations, the authors proposed their own correlation for calculation of local pressure drop during condensation in single minichannels.
    Źródło:
    Archives of Thermodynamics; 2012, 33, 1; 87-106
    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
    Tytuł:
    Selected studies of flow maldistribution in a minichannel plate heat exchanger
    Autorzy:
    Dąbrowski, P.
    Klugmann, M.
    Mikielewicz, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/240094.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    pressure drop
    minichannel
    plate
    heat exchanger
    flow maldistribution
    channel blockage
    spadek ciśnienia
    minikanał
    płyta
    wymiennik ciepła
    zły rozkład przepływu
    zablokowanie
    kanał
    Opis:
    Analysis of the state of-the-art in research of minichannel heat exchangers, especially on the topic of flow maldistribution in multiple channels, has been accomplished. Studies on minichannel plate heat exchanger with 51 parallel minichannels with four hydraulic diameters, i.e., 461 μm, 574 μm, 667 μm, and 750 μm have been presented. Flow at the instance of filling the microchannel with water at low flow rates has been visualized. The pressure drop characteristics for single minichannel plate have been presented along with the channels blockage, which occurred in several cases. The impact of the mass flow rate and channels’ cross-section dimensions on the flow maldistribution were illustrated.
    Źródło:
    Archives of Thermodynamics; 2017, 38, 3; 135-148
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Investigations on mixture preparation for two phase adiabatic pressure drop of R134a flowing in 5 mm diameter channel
    Autorzy:
    Muszyński, T.
    Andrzejczyk, R.
    Dorao, C. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/240440.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    adiabatic flow
    frictional pressure drop
    two-phase flow
    flow pattern map
    R134a
    przepływ adiabatyczny
    tarciowy spadek ciśnienia
    przepływ dwufazowy
    mapy przepływu
    Opis:
    The article presents detailed two-phase adiabatic pressure drops data for refrigerant R134a. Study cases have been set for a mass flux varying from 200 to 400 kg/m2s, at the saturation temperature of 19.4°C. Obtained experimental data was compared with the available correlations from the literature for the frictional pressure drop during adiabatic flow. Influence of mixture preparation on pressure drop was investigated, for varying inlet subcooling temperature in the heated section. The flow patterns have also been obtained by means of a high-speed camera placed in the visualization section and compared with literature observations.
    Źródło:
    Archives of Thermodynamics; 2017, 38, 3; 101-118
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Theoretical and experimental analysis on the interaction properties between tracks and sediments considering sand content for unmanned underwater tracked bulldozer
    Autorzy:
    Li, Yong
    He, Dingchang
    Si, Qiaorui
    Powiązania:
    https://bibliotekanauki.pl/articles/2090708.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    unmanned underwater tracked bulldozer
    underwater robot
    river bed sediment
    shear stress
    pressure-sinkage
    spychacz gąsienicowy bezzałogowy podwodny
    robot podwodny
    osad z koryta rzeki
    naprężenie ścinające
    spadek ciśnienia
    Opis:
    The unmanned underwater tracked bulldozer (UUTB) is an indispensable equipment for dredging and cleaning obstacles on the river bed in the flood season. The investigation on the interaction properties between the UUTB tracks and sediments provides foundation for the evaluation of operation performance when it works on the inland river bed. Based on the current worldwide research, the sediments mixed by sand, bentonite and water with sand content 0%, 10% and 20% were configured in this study to replace the real sediments on the inland river bed in China. The current pressure-sinkage model and shear stress-shear displacement model were discussed. Three different tracks were tested for the pressure-sinkage and the shear stress-shear displacement on the platform. The relationship between pressure and sinkage under sand content 0%, 10% and 20% are revealed based on the experimental results. The modulus of cohesive deformation and friction deformation of the sediments under said sand content are presented. The curves of shear stress and shear displacement are also obtained, which demonstrates the properties between the tracks and configured sediments under sand content 0%, 10% and 20%. The relationship between the tractive force and slip ratio with three different tracks under said sand content is also presented based on the quantitative analysis, which provides reference for the dynamics control and performance evaluation of UUTB on the inland river bed.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2021, 69, 1; e136036, 1--13
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Theoretical and experimental analysis on the interaction properties between tracks and sediments considering sand content for unmanned underwater tracked bulldozer
    Autorzy:
    Li, Yong
    He, Dingchang
    Si, Qiaorui
    Powiązania:
    https://bibliotekanauki.pl/articles/2173566.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    unmanned underwater tracked bulldozer
    underwater robot
    river bed sediment
    shear stress
    pressure-sinkage
    spychacz gąsienicowy bezzałogowy podwodny
    robot podwodny
    osad z koryta rzeki
    naprężenie ścinające
    spadek ciśnienia
    Opis:
    The unmanned underwater tracked bulldozer (UUTB) is an indispensable equipment for dredging and cleaning obstacles on the river bed in the flood season. The investigation on the interaction properties between the UUTB tracks and sediments provides foundation for the evaluation of operation performance when it works on the inland river bed. Based on the current worldwide research, the sediments mixed by sand, bentonite and water with sand content 0%, 10% and 20% were configured in this study to replace the real sediments on the inland river bed in China. The current pressure-sinkage model and shear stress-shear displacement model were discussed. Three different tracks were tested for the pressure-sinkage and the shear stress-shear displacement on the platform. The relationship between pressure and sinkage under sand content 0%, 10% and 20% are revealed based on the experimental results. The modulus of cohesive deformation and friction deformation of the sediments under said sand content are presented. The curves of shear stress and shear displacement are also obtained, which demonstrates the properties between the tracks and configured sediments under sand content 0%, 10% and 20%. The relationship between the tractive force and slip ratio with three different tracks under said sand content is also presented based on the quantitative analysis, which provides reference for the dynamics control and performance evaluation of UUTB on the inland river bed.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2021, 69, 1; art. no. e136036
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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