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Tytuł:
Power System Transient Stability Case Study: A Power Sub-Station Plant in Sudan
Autorzy:
Abbas, Asma
Kamal, Ramadan Doud
Elmustafa, Sayed Ali Ahmed
Powiązania:
https://bibliotekanauki.pl/articles/1193487.pdf
Data publikacji:
2021
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Dynamic Stability
GARRI power stations
Swing Equation
Transient Stability
power angle
synchronism
Opis:
Power system stability is defined by the tendency of the energy system to develop recovery forces equal or greater than the disturbing forces to maintain a stable equilibrium state. In general, power system stability problems are usually divided into two parts, steady state and transient state. An extension of steady-state stability is dynamic stability. Transient stability deals with the effects of large disturbances such as malfunctions, sudden line interruptions, and sudden application or load removal. This research is presents load angle method to transient stability problem for multi-machine system. The ETAP program is used to simulate the above method to study transient stability. A sub-station plant in Khartoum (GARRI) with four generation sections (1, 2 and 4) has been taken as a case study. The simulation result shows that when a single line-ground fault occurs at main busbar and cleared at time t = 0.4 sec the system is stable, in case 2, when the same fault cleared at t = 3 sec the system become unstable.
Źródło:
World Scientific News; 2021, 158; 267-284
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Power and thrust coefficients of the horizontal axis tidal stream turbine with different twist angles, blade numbers, and section profiles
Autorzy:
Abbasi, Alireza
Ghassemi, Hassan
Molyneux, David
Powiązania:
https://bibliotekanauki.pl/articles/135026.pdf
Data publikacji:
2019
Wydawca:
Akademia Morska w Szczecinie. Wydawnictwo AMSz
Tematy:
HATST
twist angle
blade profile
blade number
power coefficient
thrust coefficients
Opis:
The purpose of this research was to investigate the power and thrust coefficients of a horizontal axis tidal stream turbine (HATST) with different blade geometries, including twist angles, blade numbers, and section profiles. The RANS equations and Star-CCM+ commercial software were used to numerically analyze these variables. Furthermore, the turbulence model used in this study is a Realisable k-ε turbulent model. Nine different models were defined by changing the twist angle, thickness, camber, and blade numbers. The results are presented, and the power and thrust coefficients are compared against TSR for each of the nine different models. The pressure distribution and flow velocity contour are also presented and discussed.
Źródło:
Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2019, 57 (129); 11-20
1733-8670
2392-0378
Pojawia się w:
Zeszyty Naukowe Akademii Morskiej w Szczecinie
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermal analysis of a gravity-assisted heat pipe working with zirconia-acetone nanofluids: An experimental assessment
Autorzy:
Abdolhossein Zadeh, Amin
Nakhjavani, Shima
Powiązania:
https://bibliotekanauki.pl/articles/240484.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
heat pipe
zirconia-acetone nanofluid
tilt angle
filling ratio
Opis:
An experimental investigation was performed on the thermal performance and heat transfer characteristics of acetone/zirconia nanofluid in a straight (rod) gravity-assisted heat pipe. The heat pipe was fabricated from copper with a diameter of 15 mm, evaporator-condenser length of 100 mm and adiabatic length of 50 mm. The zirconia-acetone nanofluid was prepared at 0.05–0.15% wt. Influence of heat flux applied to the evaporator, filling ratio, tilt angle and mass concentration of nanofluid on the heat transfer coefficient of heat pipe was investigated. Results showed that the use of nanofluid increases the heat transfer coefficient while decreasing the thermal resistance of the heat pipe. However, for the filling ratio and tilt angle values, the heat transfer coefficient initially increases with an increase in both. However, from a specific value, which was 0.65 for filling ratio and 60–65 deg for tilt angle, the heat transfer coefficient was suppressed. This was attributed to the limitation in the internal space of the heat pipe and also the accumulation of working fluid inside the bottom of the heat pipe due to the large tilt angle. Overall, zirconia-acetone showed a great potential to increase the thermal performance of the heat pipe.
Źródło:
Archives of Thermodynamics; 2020, 41, 2; 65-83
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Computational analysis for the effect of the taper angle and helical pitch on the heat transfer characteristics of the helical cone coils
Analiza numeryczna różnic między charakterystykami działania stożkowych wężownic spiralnych i zwykłych wężownic spiralnych stosowanych jako osuszacze w zespołach osuszania i nawilżania w instalacjach odsalania wody
Autorzy:
Abo-Elazm, M
Ragheb, A
Elsafty, A
Teamah, M
Powiązania:
https://bibliotekanauki.pl/articles/139629.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
computational analysis
helical cone coil
heat exchanger
heat transfer
analiza numeryczna
wężownica spiralna stożkowa
wymiennik ciepła
wymiana ciepła
Opis:
This numerical research is devoted to introducing the concept of helical cone coils and comparing the performance of helical cone coils as heat exchangers to the ordinary helical coils. Helical and spiral coils are known to have better heat and mass transfer than straight tubes, which is attributed to the generation of a vortex at the helical coil. This vortex, known as the Dean Vortex, is a secondary flow superimposed on the primary flow. The Dean number, which is a dimensionless number used in describing the Dean Vortex, is a function of Reynolds Number and the square root of the curvature ratio, so varying the curvature ratio for the same coil would vary the Dean Number. Numerical investigation based on the commercial CFD software fluent is used to study the effect of changing the structural parameters (taper angle of the helical coil, pitch and the base radius of curvature changes while the height is kept constant) on the Nusselt Number, heat transfer coefficient and coil outlet temperature. Six main coils having pipe diameters of 10 and 12.5 mm and base radius of curvature of 70, 80 and 90 mm were used in the investigation. It was found that, as the taper angle increases, both Nusselt Number and the heat transfer coefficient increase, also the pitch at the various taper angles was found to have an influence on Nusselt Number and the heat transfer coefficient. A MATLAB code was built to calculate the Nusselt Number at each coil turn, then to calculate the average Nusselt number for all of the coil turns. The MATLAB code was based on empirical correlation of Manlapaz and Churchill for ordinary helical coils. The CFD simulation results were found acceptable when compared with the MATLAB results.
W pracy przedstawiono badania numeryczne mające na celu prezentację koncepcji stożkowych wężownic spiralnych i porównanie charakterystyk ich działania jako wymienników ciepła do charakterystyk zwykłych wężownic spiralnych. Jak wiadomo, wężownice spiralne i stożkowe charakteryzują się lepszym przenoszeniem ciepła i masy niż proste rury, co jest związane z powstawaniem wiru w wężownicy spiralnej. Ten tzw. wir Deana (Dean Vortex) jest przepływem wtórnym, nałożonym na przepływ pierwotny. Bezwymiarowy współczynnik Deana, stosowany do opisu wiru Deana, jest funkcją liczby Reynoldsa i pierwiastka kwadratowego ze współczynnika krzywizny, toteż liczba Deana zmienia się dla danej wężownicy wraz z jej krzywizną. Obliczenia numeryczne wykonano przy użyciu komercyjnego oprogramowania CFD w celu zbadania wpływu zmian parametrów strukturalnych wężownicy spiralnej (kąt zbieżności, skok i promień bazowy krzywizny zmieniały się, podczas gdy wysokość pozostawała stała) na liczbę Nusselta, współczynnik wymiany ciepła i temperaturę na wyjściu wężownicy. W badaniach wykorzystano sześć głównych wężownic, o średnicach rury 10 i 12,5 mm i promieniach bazowych krzywizny 70, 80 i 90 mm. W wyniku badań stwierdzono, że zarówno liczba Nusselta jak współczynnik wymiany ciepła rosną wraz ze wzrostem kąta zbieżności. Stwierdzono również, że przy różnych kątach zbieżności skok spirali ma wpływ na liczbę Nusselta i współczynnik wymiany ciepła. Opracowano program w środowisku MATLAB przy pomocy którego obliczono liczby Nusselta dla każdego zwoju wężownicy; na tej podstawie obliczono następnie wartość średnią liczby Nusselta dla całej wężownicy. Program obliczeniowy był oparty na równaniu empirycznym Manlapaza i Churchilla dla zwykłych wężownic spiralnych. Wyniki symulacji uzyskane przy użyciu oprogramowania CFD okazały się możliwe do przyjęcia w zestawieniu z wynikami obliczeń w programie MATLAB.
Źródło:
Archive of Mechanical Engineering; 2012, LIX, 3; 361-375
0004-0738
Pojawia się w:
Archive of Mechanical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental and Theoretical Study on a Wind Energy Unit
Autorzy:
Abusamaha, Hanan M.
Dawoud, Farah
Al-Qalab, B.
Ayadi, O.
Powiązania:
https://bibliotekanauki.pl/articles/123619.pdf
Data publikacji:
2019
Wydawca:
Polskie Towarzystwo Inżynierii Ekologicznej
Tematy:
wind turbine
angle of attack
power curve
Opis:
The conversion process in the wind turbine, from mechanical (kinetic) energy to electrical energy, is affected by many factors that increase or decrease the useful output of the wind energy convertor. In this paper, three factors were studied experimentally on a Horizontal Axis Wind Energy Unit “EEEC” in laboratory-scale. The aim of this experiment was to study the influence of the number of blades, the angle of attack and the incident angle on the wind energy unit parameters to optimize its efficiency. For this purpose, the effect of the number of blades was studied firstly, in order to select the number of blades where the maximum inputs obtained at lab ambient temperature 25 °C and atmospheric pressure. Then, different readings of the incident angle and angle of attacks were taken. The data was analyzed using Microsoft Excel software. The results show that the maximum parameters of wind unite energy that produce the maximum efficiency, namely: voltage (volt), current (ampere) and rotational speed (rpm) are obtained when the number of blades is 4, the incident angle is 0° (when the rotor direction is with wind direction) and the angle of attack is 75°. Finally, these results were implemented in a simulation program (HOMER software) that uses this turbine in a resident along with storage to cover the needs of a selected house.
Źródło:
Journal of Ecological Engineering; 2019, 20, 6; 207-214
2299-8993
Pojawia się w:
Journal of Ecological Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of changes in the angle of orientation of rollers for compacting straw by rolling on parameters of obtained briquettes
Wpływ zmian kąta ustawienia wałków zagęszczających słomę metodą zwijania na parametry uzyskiwanych brykietów
Autorzy:
Adamczyk, F.
Frąckowiak, P.
Spychała, W.
Szaroleta, M.
Powiązania:
https://bibliotekanauki.pl/articles/334194.pdf
Data publikacji:
2016
Wydawca:
Sieć Badawcza Łukasiewicz - Przemysłowy Instytut Maszyn Rolniczych
Tematy:
briquetting
rolling
briquette
briquetting roller
twist angle
axis
specific density
capacity
mechanical strength
brykietowanie
metoda zwijania
brykiet
wałek brykietujący
kąt skręcenia
oś
gęstość właściwa
przepustowość
wytrzymałość mechaniczna
Opis:
Nowadays, many methods for compacting straw for energy purposes are known. Compaction of unchopped straw by rolling it with an operating unit consisting of five conical rollers is a new method not used for this purpose so far. Various compaction of briquettes formed by this method takes place by changing the skew angle of the axes of briquetting rollers β relative to the axis of a briquetting chamber. The work presents the study results of the effect of changes in the twist angle of the axes of briquetting rollers on capacity, specific density and mechanical strength of briquettes. The study was conducted for the following twist angles of roller axes: β = 5 and β = 7. The study results show that there are significant differences between the values of the obtained degree of compaction of briquettes for both studied angles.
Obecnie znanych jest wiele sposobów zagęszczania słomy z przeznaczeniem na cele energetyczne. Nowym, do tej pory do tego celu nie wykorzystywanym sposobem jest zagęszczanie niepociętej słomy metodą zwijania przez zespół roboczy, składający się z pięciu stożkowych wałków. Różne zagęszczenie brykietów tworzonych tą metodą następuje przez zmianę kąta zwichrowania osi wałków brykietujących β względem osi komory brykietowania. W pracy przedstawiono wyniki badań wpływu zmian kąta skręcenia osi wałków brykietujących na przepustowość, gęstość właściwą i wytrzymałość mechaniczną brykietów. Badania przeprowadzono dla kątów skręcenia osi wałków β = 5 i β = 7. Wyniki badań pokazują występowanie istotnych różnic pomiędzy wartościami uzyskanego stopnia zagęszczenia brykietów dla obydwu badanych kątów.
Źródło:
Journal of Research and Applications in Agricultural Engineering; 2016, 61, 1; 5-9
1642-686X
2719-423X
Pojawia się w:
Journal of Research and Applications in Agricultural Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Influence of Static Friction on the Speed and Inclination Angle of a Belt Conveyor
Wpływ tarcia statycznego na prędkość i kąt nachylenia przenośnika taśmowego
Autorzy:
Adamecki, Daniel
Powiązania:
https://bibliotekanauki.pl/articles/1857793.pdf
Data publikacji:
2020
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
friction test
coefficient of wall friction
static friction
inclined conveyors
elastomeric belt
test tarcia
współczynnik tarcia zewnętrznego
tarcie statyczne
przenośnik nachylony
taśma elastomerowa
Opis:
The article describes experimental studies of effective belt tension between the mined hard coal and a rubber conveyor belt. Effective belt tension has a critical impact on the safety and operational reliability of belt conveyors transporting excavated material after ascending or descending. Three samples of flame-retardant conveyor belts from three manufacturers and raw power coal material were used in the tests. In order to determine the significance of the influence of variable parameters on the values of static friction coefficients, the hypothesis on the equality of mean values of the studied variable in three populations was verified by means of the analysis of variance. On the basis of the obtained results, the maximum belt speed was determined as a function of the permissible inclination angle of the belt conveyor.
W artykule opisano badania doświadczalne sprzężenia ciernego między materiałem sypkim i gumową taśmą przenośnikową. Sprzężenie cierne między materiałem sypkim i taśmą przenośnikową jest jednym z podstawowych czynników istotnych dla zapewnienia bezpiecznej i niezawodnej eksploatacji przenośnika taśmowego transportującego materiał sypki pod określonym kątem nachylenia. Badaniom poddano trzy płaskie fragmenty taśm przenośnikowych pochodzących od różnych producentów. Do obliczeń statystycznych zastosowano analizę wariancji. Na podstawie wyników określono zależność maksymalnej prędkości taśmy w funkcji dopuszczalnego kąta nachylenia przenośnika taśmowego.
Źródło:
Tribologia; 2020, 293, 5; 9-16
0208-7774
Pojawia się w:
Tribologia
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Enhanced visibility of graphene: the effect of the Brewster angle
Autorzy:
Adamson, P.
Powiązania:
https://bibliotekanauki.pl/articles/173884.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
optical characterization
two-dimensional material
graphene
Brewster angle
differential reflectance
Opis:
Visibility and simple optical diagnostics possibilities of graphene layers on dielectric and semiconductor substrates at the Brewster angle are analyzed. The analysis is based on a numerical simulation. Several oxide semiconductors (ITO, ZnO, TiO2), weakly absorbing Si, and strongly absorbing GaAs are considered. It is shown that at the Brewster angle the optical contrast of graphene flakes on a bare semiconductor substrate is actually strong enough to see them under an optical microscope and there is really no need to create an additional interference film on the substrate.
Źródło:
Optica Applicata; 2017, 47, 3; 363-372
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Treatment of Collapsible Soils with Granulated Blast Furnace Slag and Calcined Eggshell Waste
Autorzy:
Adjabi, Souhila
Nouaouria, Mohamed Salah
Djebabla, Wafa
Powiązania:
https://bibliotekanauki.pl/articles/2051699.pdf
Data publikacji:
2021
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
recycling of waste
shear strength
cohesion
internal friction angle
blast furnace slag
calcined eggshell
collapsible soil
compaction energy
recykling odpadów
spójność
kąt tarcia wewnętrznego
żużel wielkopiecowy
Opis:
In order to meet environmental and socio-economic challenges, the recycling of waste tobe used in the treatment of geotechnical problems is one of the main ways of preserving the environment with a lower economic value. The objective of this experimental work is to improve the characteristics and to study the mechanical behaviour of collapsible soil treated with a new hydraulic stabilizer composed of Crushed Granulated Blast Furnace Slag (CGBS) active by Eggshell Waste (CES). The specimens were mixed with stabilizer content, varying from 0 to 15% in mass, with an initial water content of 4, 6 and 8% respectively. in mass. Oedometer apparatus was used to study the addition of new hydraulic stabilizer effect on the Collapse Potential. Triaxial tests are also conducted to determine the shear strength parameters (cohesion and internal friction angle) of this treated soil. The results of this research study show that the mechanical properties of the treated collapsible soil were significantly improved. An appreciable reduction in the collapse potential is observed. The addition of 15% of this new stabilizer with initial water content of 4% under a compaction of 60 blows/ layer is capable of increasing internal friction angle and cohesion. It can be concluded from this study that the mixture of granulated slag and calcined eggshell can be used as an effective treatment of collapsibility phenomenon at low cost while protecting the environment from industrial waste.
Źródło:
Civil and Environmental Engineering Reports; 2021, 31, 2; 138-162
2080-5187
2450-8594
Pojawia się w:
Civil and Environmental Engineering Reports
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Effect of Angle of Attack and Flow Conditions on Turbulent Boundary Layer Noise of Small Wind Turbines
Autorzy:
Afanasieva, N.
Powiązania:
https://bibliotekanauki.pl/articles/177922.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
wind turbine
airfoil self-noise
turbulent boundary layer
flow conditions
angle of attack
Opis:
The article aims to solve the problem of noise optimization of small wind turbines. The detailed analysis concentrates on accurate specification and prediction of the turbulent boundary layer noise spectrum of the blade airfoil. The angles of attack prediction for a horizontal axis wind turbine (HAWT) and the estimation based on literature data for a vertical axis one (VAWT), were conducted, and the influence on the noise spectrum was considered. The 1/3-octave sound pressure levels are obtained by semi-empirical model BPM. Resulting contour plots show a fundamental difference in the spectrum of HAWT and VAWT reflecting the two aerodynamic modes of flow that predefine the airfoil self-noise. Comparing the blade elements with a local radius of 0.875 m in the HAWT and VAWT conditions the predicted sound pressure levels are the 78.5 dB and 89.8 dB respectively. In case of the HAWT with predicted local angle of attack ranging from 2.98º to 4.63º, the acoustic spectrum will vary primarily within broadband frequency band 1.74–20 kHz. For the VAWT with the local angle of attack ranging from 4º to 20º the acoustic spectrum varies within low and broadband frequency bands 2 Hz – 20 kHz.
Źródło:
Archives of Acoustics; 2017, 42, 1; 83-91
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Breast hypertrophy, forward head posture, neck and shoulder pain-related disabilities and selected anthropometrics variables of female undergraduate students
Autorzy:
Akodu, Ashiyat Kehinde
Oti, Temiloluwa Grace
Lawal, Abdulrazzaq Oluwagbemiga
Powiązania:
https://bibliotekanauki.pl/articles/2049188.pdf
Data publikacji:
2022-03-30
Wydawca:
Uniwersytet Rzeszowski. Wydawnictwo Uniwersytetu Rzeszowskiego
Tematy:
breast hypertrophy
craniovertebral angle
neck pain
shoulder pain
Opis:
Introduction and aim. Large breast sizes frequently contribute to women presenting with severe pain symptoms. This study determined the association between breast hypertrophy, forward head posture (FHP), neck and shoulder pain related disabilities and selected anthropometric variables of female undergraduate students of College of Medicine, University of Lagos. Material and methods. A cross-sectional analytical study was conducted among 89 female undergraduate students (mean age = 21.45±1.29 years) with breast hypertrophy (cup size D and above). Breast cup sizes, neck and shoulder pain related disabilities, forward head posture were measured using a measuring tape, neck pain disability scale, shoulder pain disability index and craniovertebral angle (CVA) using photography method. Results. The prevalence of forward head posture among the participants was 43(48.3%). Twenty-eight (31.3%) participants had a “DD” cup size, twenty-six (29.2%) participants had a “DDD” cup size. Sixty-five (73%) of the participants had neck pain related disabilities and 10 (11.2%) of the participants had shoulder pain related disabilities. There was association among weight, forward head posture (p=0.027) and breast hypertrophy (p=0.016). Conclusion. Neck, shoulder pain related disabilities, and forward head posture is prevalent among undergraduates with breast hypertrophy and weight has an influence on forward posture and breast hypertrophy.
Źródło:
European Journal of Clinical and Experimental Medicine; 2022, 1; 93-101
2544-2406
2544-1361
Pojawia się w:
European Journal of Clinical and Experimental Medicine
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of the Correlation Between Crimp Parameters and its Effect on Yarn Strength and Hairiness
Autorzy:
Akter, Shilpi
Motalab, Mohammad Abdul
Helali, Maksud
Powiązania:
https://bibliotekanauki.pl/articles/2171963.pdf
Data publikacji:
2022
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Biopolimerów i Włókien Chemicznych
Tematy:
mechanical gear crimp
correlation
crimp length
crimp angle
yarn strength
yarn hairiness
Opis:
The objective of this paper is to analyse the correlation between crimp parameters and the effect of crimps on yarn strength and hairiness. Crimp is an essential property for natural and man-made fibres. Crimps always form with different parameters as they are very much irregular in size and shape. So, if the crimps are regular in size and shape, the end products like yarn and fabric properties will improve. Jute is a natural fibre with no natural crimp. In this research work, the gear crimping method was used as a mechanical crimping system to impart a regular size and shape of crimps into jute sliver. As a result, crimp parameters like the crimp length and crimp angle become uniform, and it is then easy to measure them. Results also showed that the crimp length is directly proportional and the crimp angle is reversely proportional to the number of crimps per unit length, and they are highly correlated. It was also shown that crimp and crimp parameters also affect the yarn strength and hairiness. In conclusion, it is revealed that with an increase in the number of crimps, the yarn strength was increased and hairiness was decreased.
Źródło:
Fibres & Textiles in Eastern Europe; 2022, 2 (151); 55--60
1230-3666
2300-7354
Pojawia się w:
Fibres & Textiles in Eastern Europe
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:
Numerical analysis and optimization of a winglet sweep angle and winglet tip chord for improvement of aircraft flight performance
Autorzy:
Al-Khafaji, Ali J. Dawood
Panatov, Gennady S.
Boldyrev, Anton S.
Powiązania:
https://bibliotekanauki.pl/articles/2096195.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Polskie Towarzystwo Diagnostyki Technicznej PAN
Tematy:
lift
drag
lift coefficient
drag coefficient
aircraft wing
winglet
angle of attack
sweep angle
SOLIDWORKS
CFD
ANSYS FLUENT
współczynnik siły nośnej
współczynnik oporu
skrzydło samolotu
skrzydełko aerodynamiczne
kąt natarcia
SolidWorks
ANSYS Fluent
Opis:
In this paper, a study of the effect of winglet sweep angle and winglet tip chord of the aircraft wing on the aerodynamics performances and how to improve it are carried out, assuming Cant angle 60°, winglet height = 3.5 m, Toe angle = -5°, and Twist angle = +5°. Different sweep angles tested (-25°, -15°, 0°, +15°, +25°, +35°, and +45°) and winglet tip chord (0.25, 0.375, and 0.5 m). Four Angle of attack is presented (0°, 3°, 6°, and 9°). The aerodynamics properties of the wing were measured in terms of calculated lift to drag ratio to decide which wing has a high value of lift and lower drag. All models of a wing (eighty-four models) are drawn for 3D using the SOLIDWORKS program. Boeing 737-800 wing dimensions were used. All models of a wing were analyzed using ANSYS FLUENT. The results showed that sweep angle and winglet tip chord of the winglet by changing their configuration can improve aerodynamic performance for various attack angles. The maximum value of the lift to drag ratio was obtained with a sweep angle -15°, winglet tip chord 0.375m, and angle of attack 3°.
Źródło:
Diagnostyka; 2022, 23, 2; art. no. 2022210
1641-6414
2449-5220
Pojawia się w:
Diagnostyka
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Relative wettability measurement of porous diffuser and its impact on the generated bubble size
Autorzy:
Al-Yaqoobi, Atheer M.G.
Zimmerman, William B.
Powiązania:
https://bibliotekanauki.pl/articles/2173415.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
kąt kontaktu
dyfuzor porowaty
metoda Washburn
zwilżalność
bubble size
contact angle
porous diffuser
Washburn method
wettability
Opis:
Controlling the bubble size is a major concern in enhancing transport performance in gas-liquid systems. The role of wettability of diffuser surface on bubble size is the subject of the current work. The study inspects the contact angle of a set of liquids on HP ceramic diffusers using the Washburn method. The results demonstrate that organic liquids like toluene, methanol–water (1:1 v/v), ethanol– water (1:1 v/v) and decane have small contact angles of 12.9, 37.5, 24.4 and 22.5 respectively. Water has a lower wettability than the organic compounds where the contact angle was about 67.4. The effect of wettability of the bubble size is investigated by measuring the size of air bubble produced using the same diffuser material. The results of bubble size measurement demonstrates that with liquids of small contact angle, i.e. good wetting properties, small bubble sizes are produced in comparison with liquids with a higher contact angle. The study demonstrates the viability of Washburn method in characterization of wettability of porous diffuser, which was verified by measuring the bubble size produced. A high reduction in bubble size can be obtained by a carefully chosen diffuser material that provides better wettability.
Źródło:
Chemical and Process Engineering; 2022, 43, 1; 45--55
0208-6425
2300-1925
Pojawia się w:
Chemical and Process Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 729

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