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    Wyświetlanie 1-12 z 12
    Tytuł:
    Increasing of efficiency of the cooling duct by modification of its geometry
    Autorzy:
    Kiedrzyński, Krzysztof
    Powiązania:
    https://bibliotekanauki.pl/articles/240839.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    duct electrochemical limiting current technique
    ELDCT
    heat mass transfer
    efficiency
    Opis:
    Increasing of the efficiency of convective cooling of the inner surface of a short duct by changing its geometry was studied by the use of electrochemical limiting current technique (ELDCT). The duct consisted of seven identical, cylindrical segments. The changes of the duct geometry were obtained by mutual displacement of neighbouring segments, towards the radial direction. Mean values of the mass transfer coefficient for each segment and friction losses for the whole channel were measured for Reynolds numbers spanning the range 7700–35300 at the five values of displacement parameter. The results were used for estimation of cooling efficiency. Recommended values of displacement were determined to point the favourable conditions of heat/mass transfer in the duct. The results may be used, e.g. in the design of heat exchangers and channels for cooling of turbine blades and electronic equipment.
    Źródło:
    Archives of Thermodynamics; 2020, 41, 3; 103-123
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Heat and mass transfer mechanism on three-dimensional flow of inclined magneto Carreau nanofluid with chemical reaction
    Autorzy:
    Rao, B. Madhusudhana
    Gopal, Degavath
    Kishan, Naikoti
    Ahmed, Saad
    Prasad, Putta Durga
    Powiązania:
    https://bibliotekanauki.pl/articles/240005.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    carreau nanofluid
    chemical reaction
    MHD
    heat and mass transfer
    Opis:
    The characteristic of nano sized particles mass flux conditions are engaged in this investigation. Here we assume that the nano sized particle flux is zero and the nano sized particle fraction arranged itself on the boundary layer. With this convincing and revised relation, the features of Buongiorno relation on three-dimensional flow of Carreau fluid can be applied in a more efficient way. The governing partial differential equations of continuity, momentum, energy and concentration equations which are transmitted into set of pair of nonlinear ordinary differential equations utilizing similar transformations. The numeric solutions are acquired by engaging the bvp4c scheme, which is a finite-difference code for solving boundary value problems. A parametric study is accomplished to demonstrate the impact of Prandtl number, Weissenberg numbers, radiation parameter, chemical reaction parameter, thermophoresis parameter, Brownian motion parameter and Lewis number on the fluid velocity, temperature and concentration profiles as well skin friction coefficient, Nusselt number and Sherwood number within the boundary layer. From this we find the way in which magnetic parameter contributes to the increase in local skin fraction, and the decrease in the Nusselt and Sherwood numbers in these cases. The effects of the velocity temperature and concentration profile are obtained and presented graphically.
    Źródło:
    Archives of Thermodynamics; 2020, 41, 2; 223-238
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Bidirectionally stretched flow of Jeffrey liquid with nanoparticles, Rosseland radiation and variable thermal conductivity
    Autorzy:
    Archana, M.
    Gireesha, B. J.
    Rashidi, M. M.
    Prasannakumara, B. C.
    Gorla, R. S. R.
    Powiązania:
    https://bibliotekanauki.pl/articles/240409.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    heat mass transfer
    jeffrey nanofluid
    variable thermal conductivity
    rosseland approximation
    suction
    ciepło
    masa
    zmienna przewodność cieplna
    aproksymacja
    ssanie
    Opis:
    Heat and mass transfer stretched flow of an incompressible, electrically conducting Jeffrey fluid has been studied numerically. Nanoparticles are suspended in the base fluid and it has many applications such as cooling of engines, thermal absorption systems, lubricants fuel cell, nanodrug delivery system and so on. Temperature dependent variable thermal conductivity with Rosseland approximation is taken into account and suction effect is employed in the boundary conditions. The governing partial differential equations are first transformed into set of ordinary differential equations using selected similarity transformations, which are then solved numerically using Runge-Kutta-Felhberg fourth-fifth order method along with shooting technique. The flow, heat and mass transfer characteristics with local Nusselt number for various physical parameters are presented graphically and a detailed discussion regarding the effect of flow parameters on velocity and temperature profiles are provided. It is found that, increase of variable thermal conductivity, radiation, Brownian motion and thermophoresis parameter increases the rate of heat transfer. Local Nusselt number has been computed for various parameters and it is observed that, in the presence of variable thermal conductivity and Rosseland approximation, heat transfer characteristics are higher as compared to the constant thermal conductivity and linear thermal radiation.
    Źródło:
    Archives of Thermodynamics; 2018, 39, 4; 33--57
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The effect of temperature of rocks on microclimatic conditions in long gate roads and galleries in coal mines
    Wpływ temperatury pierwotnej skał na parametry mikroklimatu w długich wyrobiskach korytarzowych
    Autorzy:
    Cygankiewicz, J.
    Knechtel, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/219812.pdf
    Data publikacji:
    2014
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    bezpieczeństwo
    aerologia
    klimatyzacja
    przepływ ciepła i masy
    safety
    ventilation
    air-conditioning
    heat and mass transfer
    Opis:
    The aim of this study was to examine the effect of the temperature of surrounding rocks on enthalpy and temperature of air flowing along several model mine workings. Long workings surrounded by non- -coal rocks as well longwall gates surrounded by coal were taken into consideration. Computer-aided simulation methods were used during the study. At greater depths the amount of moisture transferred into a mine working from the rock mass is two orders of magnitude smaller than the moisture that comes from external (technological) sources, mainly from coal extraction-related processes, therefore in the equation describing temperature changes only the terms representing the flux of heat from rocks were included. The model workings, for calculation purposes, were divided into sections, 50 m in length each. For each of the sections temperature of its ribs and temperature and stream of enthalpy of air flowing along it were calculated with the use of the finite differences method. For workings surrounded by non-coal rocks two variant calculations were carried out, namely with or without technological sources of heat. For coal surrounded workings (longwall gates) a new method for determination of heat from coal oxidation was developed, based on the findings by Cygankiewicz J. (2012a, 2012b). Using the results of a study by J.J. Drzewiecki and Smolka (1994), the effects of rock mass fracturing on transfer of heat into the air stream flowing along a working were taken into account.
    Badano wpływ temperatury pierwotnej skał na strumień entalpii oraz temperaturę powietrza w wyrobisku korytarzowym o długości 2000 m. Rozpatrywano wyrobiska kamienne oraz chodniki podścianowe. W badaniach zastosowano metodę symulacji komputerowych. Na dużych głębokościach wilgoć przenoszona z górotworu do wyrobiska jest dwa rzędy wielkości mniejsza od wilgoci pochodzącej od procesów technologicznych. W związku z powyższym w równaniu opisującym zmiany temperatury w masywie skalnym uwzględniono tylko człon reprezentujący ruch ciepła w skałach. Badane wyrobisko podzielono na odcinki o długości 50 m. Korzystając z metody różnic skończonych dla każdego z odcinków wyznaczono temperaturę ociosu, a następnie temperaturę i strumień entalpii powietrza. W odniesieniu do wyrobisk kamiennych rozważania przeprowadzono dla wariantu z technologicznymi źródłami ciepła oraz bez takich źródeł. Dla chodników węglowych przedstawiono nowy sposób określenia ciepła utleniania węgla, na podstawie wyników badań J. Cygankiewicza (2012a, 2012b). Korzystając z wyników badań J. Drzewieckiego i J. Smołki (1994), uwzględniono wpływ spękań górotworu na przenoszenie ciepła do powietrza w wyrobisku.
    Źródło:
    Archives of Mining Sciences; 2014, 59, 1; 189-216
    0860-7001
    Pojawia się w:
    Archives of Mining Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Two-dimensional CFD modeling of the heat and mass transfer process during sewage sludge drying in a solar dryer
    Autorzy:
    Krawczyk, P.
    Badyda, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/240601.pdf
    Data publikacji:
    2011
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    suszenie osadów ściekowych
    wymiana ciepła i masy
    CFD
    heat and mass transfer
    sewage sludge drying
    Opis:
    The paper presents key assumptions of the mathematical model which describes heat and mass transfer phenomena in a solar sewage drying process, as well as techniques used for solving this model with the Fluent computational fluid dynamics (CFD) software. Special attention was paid to implementation of boundary conditions on the sludge surface, which is a physical boundary between the gaseous phase - air, and solid phase - dried matter. Those conditions allow to model heat and mass transfer between the media during first and second drying stages. Selection of the computational geometry is also discussed - it is a fragment of the entire drying facility. Selected modelling results are presented in the final part of the paper.
    Źródło:
    Archives of Thermodynamics; 2011, 32, 4; 3-16
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modeling of heat and mass transfer during thermal decomposition of a single solid fuel particle
    Autorzy:
    Wardach-Święcicka, I.
    Kardaś, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/240457.pdf
    Data publikacji:
    2013
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    fuel particles
    devolatilization
    pyrolysis
    heat and mass transfer
    ziarna paliwa
    odgazowanie
    piroliza
    wymiana ciepła i masy
    Opis:
    The aim of this work was to investigate the heat and mass transfer during thermal decomposition of a single solid fuel particle. The problem regards the pyrolysis process which occurs in the absence of oxygen in the first stage of fuel oxidation. Moreover, the mass transfer during heating of the solid fuels is the basic phenomenon in the pyrolysis-derived alternative fuels (gas, liquid and solid phase) and in the gasification process which is focused on the generation of syngas (gas phase) and char (solid phase). Numerical simulations concern pyrolysis process of a single solid particle which occurs as a consequence of the particle temperature increase. The research was aimed at an analysis of the influence of particle physical properties on the devolatilization process. In the mathematical modeling the fuel grain is treated as an ideal sphere which consists of porous material (solid and gaseous phase), so as to simplify the final form of the partial differential equations. Assumption that the physical properties change only in the radial direction, reduces the partial derivatives of the angular coordinates. This leads to obtaining the equations which are only the functions of the radial coordinate. The model consists of the mass, momentum and energy equations for porous spherical solid particle heated by the stream of hot gas. The mass source term was determined in the wide range of the temperature according to the experimental data. The devolatilization rate was defined by the Arrhenius formula. The results of numerical simulation show that the heating and devolatilization time strongly depend on the physical properties of fuel. Moreover, proposed model allows to determine the pyrolysis process direction, which is limited by the equilibrium state.
    Źródło:
    Archives of Thermodynamics; 2013, 34, 2; 53-71
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Methods of Thermal Calculations for a Condensing Waste-Heat Exchanger
    Autorzy:
    Rączka, P.
    Wójs, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/185363.pdf
    Data publikacji:
    2014
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    odzysk ciepła kondensacji
    obliczanie transferu ciepła i masy
    wymiennik ciepła
    ciepło odpadowe
    condensation heat recovery
    calculation of heat and mass transfer
    heat exchanger
    waste heat
    Opis:
    The paper presents the algorithms for a flue gas/water waste-heat exchanger with and without condensation of water vapour contained in flue gas with experimental validation of theoretical results. The algorithms were used for calculations of the area of a heat exchanger using waste heat from a pulverised brown coal fired steam boiler operating in a power unit with a capacity of 900 MWe. In calculation of the condensing part, the calculation results obtained with two algorithms were compared (Colburn-Hobler and VDI algorithms). The VDI algorithm allowed to take into account the condensation of water vapour for flue gas temperatures above the temperature of the water dew point. Thanks to this, it was possible to calculate more accurately the required heat transfer area, which resulted in its reduction by 19 %. In addition, the influence of the mass transfer on the heat transfer area was taken into account, which contributed to a further reduction in the calculated size of the heat exchanger - in total by 28% as compared with the Colburn-Hobler algorithm. The presented VDI algorithm was used to design a 312 kW pilot-scale condensing heat exchanger installed in PGE Belchatow power plant. Obtained experimental results are in a good agreement with calculated values.
    Źródło:
    Chemical and Process Engineering; 2014, 35, 4; 447-461
    0208-6425
    2300-1925
    Pojawia się w:
    Chemical and Process Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Agitation efficiency of different physical systems
    Autorzy:
    Karcz, Joanna
    Szoplik, Jolanta
    Major-Godlewska, Marta
    Cudak, Magdalena
    Kiełbus-Rąpała, Anna
    Powiązania:
    https://bibliotekanauki.pl/articles/2086781.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    agitated vessel
    power consumption
    mixing time
    heat and mass transfer
    gas hold-up
    wzburzony statek
    pobór energii
    czas mieszania
    wymiana ciepła i masy
    zatrzymywanie gazu
    Opis:
    Efficiency of agitation was considered for different physical systems on the basis of our own experimental studies on homogenisation, heat and mass transfer as well as gas hold-up. Measurements were performed for different physical systems: Newtonian liquids of low and higher viscosity, pseudoplastic liquid, gas–liquid and gas–solid–liquid systems agitated in vessels of the working volume from 0.02 m3 to 0.2 m3. Agitated vessels of different design were equipped with a high-speed impeller (10 impellers were tested). Comparative analysis of the experimental results proved that energy inputs (power consumption) should be taken into account as a very important factor when agitation efficiency is evaluated in order to select a proper type of equipment. When this factor is neglected in the analysis, intensification of the process can be estimated only.
    Źródło:
    Chemical and Process Engineering; 2021, 42, 2; 139--156
    0208-6425
    2300-1925
    Pojawia się w:
    Chemical and Process Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Entropy increase as a measure of energy degradation in heat transfer
    Autorzy:
    Drożyński, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/240672.pdf
    Data publikacji:
    2013
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    second law of thermodynamics in heat
    heat and mass transfer
    entropy increment
    surface heat exchangers
    Clausius-Rankine cycle
    druga zasada termodynamiki w ogniu
    wymiana ciepła i masy
    przyrost entropii
    obieg Clausiusa-Rankine'a
    Opis:
    Heat transfer is an irreversible process. This article defines the entropy increment as a measure of energy degradation in heat transfer realized in typical surface heat exchangers. As an example of the proposed entropy increase method, presented below are the calculations for heat exchangers working in a typical Clausius-Rankine cycle. The entropy increase in such exchangers inevitably leads to increased fuel consumption and, as a further consequence, to increased carbon dioxide emission.
    Źródło:
    Archives of Thermodynamics; 2013, 34, 3; 147-161
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Experimental and theoretical studies on heat and mass transfer in anti-condensation coatings
    Autorzy:
    Grzebielec, A.
    Rusowicz, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/240246.pdf
    Data publikacji:
    2011
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    powłoka antykondensacyjna
    wymiana ciepła
    wymiana masy
    anti-condensation coating
    heat transfer
    mass transfer
    Opis:
    Anti-condensation coatings are widely used in refrigeration, air conditioning and ships technology. They can store a certain amount of water in its own volume, and then return it back in favorable conditions. Anti-condensation coatings are used also to protect structures from the moisture. This paper presents the results of experimental research on heat and mass transfer in an anti-condensation coating under natural and forced convection. Experimental results are obtained for horizontal and inclined plates. Experimental data are compared with different models of computation.
    Źródło:
    Archives of Thermodynamics; 2011, 32, 3; 45-56
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Experimental and numerical investigation of thermal flow meter
    Autorzy:
    Cebula, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/240345.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    mass flowmeter
    heat transfer
    uniform heat flux
    thermal model
    miernik przepływu
    wymiana ciepła
    model termiczny
    Opis:
    The paper presents analytical and numerical model calculation results of the temperature distribution along the thermal flow meter. Results show a very good conformity between numerical and analytical model. Apart from the calculation results the experimental investigations are presented. The author performed the test where a temperature of duct wall surface was measured. Therelation between mass flow rate in terms of the duct surface temperature difference was developed.
    Źródło:
    Archives of Thermodynamics; 2015, 36, 3; 149-160
    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
      Wyświetlanie 1-12 z 12

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