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Wyświetlanie 1-5 z 5
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:
Microstructural Changes of the Nanostructured Bainitic Steel Induced by Quasi-Static and Dynamic Deformation
Autorzy:
Marcisz, J.
Burian, W.
Rozmus, R.
Janiszewski, J.
Powiązania:
https://bibliotekanauki.pl/articles/351132.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
nanostructured bainitic steel
dynamic deformation
adiabatic shear bands
transmission electron microscopy
Opis:
Changes in the microstructure of nanostructured bainitic steel induced by quasi-static and dynamic deformation have been shown in the article. The method of deformation and strain rate have important impact on the microstructure changes especially due to strain localization. Microstructure of nanostructured steel Fe-0.6%C-1.9Mn-1.8Si-1.3Cr-0.7Mo consists of nanometer size carbide-free bainite laths and 20-30% volume fraction of retained austenite. Quasi-static and dynamic (strain rate up to 2×102 s-1) compression tests were realized using Gleeble simulator. Dynamic deformation at the strain rate up to 9×103 s-1 was realized by the Split Hopkinson Pressure Bar method (SHPB). Moreover high energy firing tests of plates made of the nanostructured bainitic steel were carried out to produce dynamically deformed material for investigation. Adiabatic shear bands were found as a result of localization of deformation in dynamic compression tests and in firing tests. Microstructure of the bands was examined and hardness changes in the vicinity of the bands were determined. The TEM examination of the ASBs showed the change from the internal shear band structure to the matrix structure to be gradual. This study clearly resolved that the interior (core) of the band has an extremely fine grained structure with grain diameter ranging from 100 nm to 200 nm. Martensitic twins were found within the grains. No austenite and carbide reflections were detected in the diffraction patterns taken from the core of the band. Hardness of the core of the ASBs for examined variants of isothermal heat treatment was higher about 300 HV referring to steel matrix hardness.
Źródło:
Archives of Metallurgy and Materials; 2017, 62, 4; 2317-2329
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental investigation of gravity-assisted wickless heat pipes (thermosyphons) at low heat inputs for solar application
Autorzy:
Al-Joboory, Hassan Naji Salman
Powiązania:
https://bibliotekanauki.pl/articles/240582.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
wickless heat pipe
adiabatic section
solar heat pipe
fill charge ratio
working fluid inventory
inclination angle
Opis:
The performance of ten wickless heat pipes without adiabatic sections is investigated experimentally at low heat inputs 120 to 2000 W/m2 for use in solar water heaters. Three heat pipe diameter groups were tested, namely 16, 22, and 28.5 mm. Each group had evaporator lengths of 1150, 1300, and 1550 mm, respectively, with an extra evaporator length of 1800 mm added to the second group. The condenser section length of all heat pipes was 200 mm. Ethanol, methanol, and acetone were utilized as working fluids, at inventory of 25%, 50%, 70%, and 90% by evaporator volume respectively. The 22 mm diameter pipes were tested at inclination angles 30°, 45°, and 60°. Other diameter groups were tested at 45° only. Experiments revealed increased surface temperatures and heat transfer coefficients with increased pipe diameter and evaporator length, and that increased working fluid inventory caused pronounced reduction in evaporator surface temperature accompanied by improved heat transfer coefficient to reach maximum values at 50% inventory for the selected fluids. Violent noisy shocks were observed with 70% and 90% inventories with the tested heat pipes and the selected working fluids with heat flux inputs from 320–1900 W/m2. These shocks significantly affected the heat pipes heat transfer capability and operation stability. Experiments revealed a 45° and 50% optimum inclination angle of fill charge ratio respectively, and that wickless heat pipes can be satisfactorily used in solar applications. The effect of evaporator length and heat pipe diameter on the performance was included in data correlations.
Źródło:
Archives of Thermodynamics; 2020, 41, 2; 257-276
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Review on Performances of Reversible Ripple-Carry Adders
Autorzy:
Burignat, S.
De Vos, A.
Powiązania:
https://bibliotekanauki.pl/articles/227089.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
reversible computation
design
implementation
pass-transistor logic
ripple-carry adder
sum-difference block
Spectre simulation
quantum computation
adiabatic signal
test and measurement
error propagation
Opis:
Quantum computing and circuits are of growing interest and so is reversible logic as it plays an important role in the synthesis of quantum circuits. Moreover, reversible logic provides an alternative to classical computing machines, that may overcome many of the power dissipation problems in the near future. Some ripple-carry adders based on a do-spy-undo structure have been designed and tested reversibly. This paper presents a brief overview of the performances obtained with such chips processed in standard 0.35 um CMOS technology and used in true reversible calculation (computations are performed forwards and backwards such that addition and subtraction are made reversibly with the same chip). Adiabatic signals used are known to allow the signal energy stored on the various capacitances of the circuit to be redistributed rather than being dissipated as heat while allowing to avoid calculation errors introduced by the use of conventional rectangular pulses. Through the example of both simulations and experimental results, this paper aims at providing a base of knowledge and knowhow in physical implementation of reversible circuits.
Źródło:
International Journal of Electronics and Telecommunications; 2012, 58, 3; 205-212
2300-1933
Pojawia się w:
International Journal of Electronics and Telecommunications
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Simulation studies on the influence of other combustible gases on the characteristics of methane explosions at constant volume and high temperature
Autorzy:
Luo, Zhenmin
Liu, Litao
Gao, Shuaishuai
Wang, Tao
Su, Bin
Wang, Lei
Yang, Yong
Li, Xiufang
Powiązania:
https://bibliotekanauki.pl/articles/1853863.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
gaz palny
ciśnienie wybuchu
temperatura płomienia
constant volume
volume fraction of combustible gas
initial temperature
adiabatic flame temperature
maximum explosion pressure
Opis:
Gas explosions are major disasters in coal mining, and they typically cause a large number of deaths, injuries and property losses. An appropriate understanding of the effects of combustible gases on the characteristics of methane explosions is essential to prevent and control methane explosions. FLACS software was used to simulate an explosion of a mixture of CH4 and combustible gases (C2H4, C2H6, H2, and CO) at various mixing concentrations and different temperatures (25, 60, 100, 140 and 180℃). After adding combustible gases to methane at a constant volume and atmospheric pressure, the adiabatic flame temperature linearly increases as the initial temperature increases. Under stoichiometric conditions (9.5% CH4-air mixture), the addition of C2H4 and C2H6 has a greater effect on the adiabatic flame temperature of methane than H2 and CO at different initial temperatures. Under the fuel-lean CH4-air mixture (7% CH4-air mixture) and fuel-rich mixture (11% CH4-air mixture), the addition of H2 and CO has a greater effect on the adiabatic flame temperature of methane. In contrast, the addition of combustible gases negatively affected the maximum explosion pressure of the CH4-air mixture, exhibiting a linearly decreasing trend with increasing initial temperature. As the volume fraction of the mixed gas increases, the adiabatic flame temperature and maximum explosion pressure of the stoichiometric conditions increase. In contrast, under the fuel-rich mixture, the combustible gas slightly lowered the adiabatic flame temperature and the maximum explosion pressure. When the initial temperature was 140℃, the fuel consumption time was approximately 8-10 ms earlier than that at the initial temperature of 25℃. When the volume fraction of the combustible gas was 2.0%, the consumption time of fuel reduced by approximately 10 ms compared with that observed when the volume fraction of flammable gas was 0.4%.
Źródło:
Archives of Mining Sciences; 2021, 66, 2; 279-295
0860-7001
Pojawia się w:
Archives of Mining Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-5 z 5

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