Development of a Simple Correlation between the Mal Distribution Factor and Geometrical Parameters of the Two-Direction Vapor Horn Gas Distributor

2021 ◽  
Vol 54 (1) ◽  
pp. 18-27
Author(s):  
Haojie Li ◽  
Bin Jiang ◽  
Ci Zhao ◽  
Luhong Zhang ◽  
Yongli Sun ◽  
...  
Keyword(s):  
Geometrical Parameters ◽  
Distribution Factor ◽  
Simple Correlation ◽  
Gas Distributor

Performance Evaluation of Heat Transfer Enhancement for Offset Strip Fins Used in Plate-Fin Heat Exchangers

2015 ◽  
Vol 137 (10) ◽  
Author(s):  
Yujie Yang ◽  
Yanzhong Li ◽  
Biao Si ◽  
Jieyu Zheng
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Entropy Generation ◽  
Heat Exchangers ◽  
Operating Conditions ◽  
Geometrical Parameters ◽  
Distribution Factor ◽  
Transfer Enhancement ◽  
Entropy Generation Number ◽  
Fin Thickness

In general, offset strip fin (OSF) used in plate-fin heat exchangers is able to provide a greater heat transfer coefficient than the plain fin with the same cross section, but it will also cause the increase of flow friction and pressure drop owing to the fin offset. A new parameter denoted by Ψ*, called relative entropy generation distribution factor, is proposed in this paper to comprehensively reflect the thermodynamic performance of different passage structures in plate-fin heat exchanger. This parameter physically represents relative changes of entropy generation and irreversibility, which are induced by both heat transfer and friction loss due to the utilization of OSF fins. The high magnitude of Ψ* represents a beneficial contribution of OSF with higher degree of the heat transfer enhancement. The proposed method is more reasonable and comprehensive than either the conventional augmentation entropy generation number, Ns,a, or the entropy generation distribution factor, ψ, to evaluate the heat transfer enhancement for OSF cores subject to various operating conditions. With the proposed method, the relative effects of the geometrical parameters of OSF fins, such as the fin thickness-to-height ratio α, fin density γ, and fin thickness-to-length ratio δ, on the heat transfer enhancement are discussed in detail. The results show that relatively small δ results in a better performance, while the parameter α or γ, which contribute to a higher degree of heat transfer enhancement of OSF fin, should be determined after the selection of the other two geometric parameters.

scholarly journals Experimental Study of the Effect of the Expansion Segment Geometry on the Atomization of a Plain-Jet Airblast Atomizer

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Yi Jin ◽  
Kanghong Yao ◽  
Xiaomin He ◽  
Kai Zhang ◽  
Yunbiao Wang
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Droplet Size Distribution ◽  
Droplet Velocity ◽  
Geometrical Parameters ◽  
Distribution Factor ◽  
Sauter Mean Diameter ◽  
Mean Velocity ◽  
Expansion Segment ◽  
Mean Diameter

In this paper, the idea of adding an expansion segment over traditional airblast atomizer is proposed to improve the spray performance. According to the systematic experiments, the Sauter mean diameter, the droplet size distribution, and the droplet axial mean velocity were obtained to evaluate the spray performance. The correlations between spray performance and four geometrical parameters of the expansion segment which include the length, the angle, the throat area, and position of liquid jet are considered. The atomizer operates at atmospheric pressure and temperature, and the air liquid ratio range is from 0.48 to 2.85. The data of the results were measured by Phase Doppler Particle Analyzer. The results show that more uniform droplet size distribution can be achieved with the addition of expansion segment, and the droplet size distribution factor q of the case adding the expansion segment is 52.8% bigger than that of the case with no expansion segment. q increases as the length and angle of expansion segment increase. The Sauter mean diameter can be reduced by either reducing the length or angle of expansion segment. As for droplet velocity, it is determined that the droplet velocity increases along the radial direction, which is noteworthy because opposite trend is reported for traditional plain-jet atomizers. With an increase of the length, angle, and throat area of the expansion segment, the droplet axial velocity decays.

Bulk drag coefficient of a subaquatic vegetation subjected to irregular waves: Influence of Reynolds and Keulegan-Carpenter numbers

2020 ◽  
pp. 34-42
Author(s):  
Thibault Chastel ◽  
Kevin Botten ◽  
Nathalie Durand ◽  
Nicole Goutal
Keyword(s):  
Drag Coefficient ◽  
Wave Height ◽  
Wave Attenuation ◽  
Empirical Relationship ◽  
Breaking Waves ◽  
Irregular Waves ◽  
Geometrical Parameters ◽  
Flume Experiments ◽  
Seagrass Meadows ◽  
Artificial Vegetation

Seagrass meadows are essential for protection of coastal erosion by damping wave and stabilizing the seabed. Seagrass are considered as a source of water resistance which modifies strongly the wave dynamics. As a part of EDF R & D seagrass restoration project in the Berre lagoon, we quantify the wave attenuation due to artificial vegetation distributed in a flume. Experiments have been conducted at Saint-Venant Hydraulics Laboratory wave flume (Chatou, France). We measure the wave damping with 13 resistive waves gauges along a distance L = 22.5 m for the “low” density and L = 12.15 m for the “high” density of vegetation mimics. A JONSWAP spectrum is used for the generation of irregular waves with significant wave height Hs ranging from 0.10 to 0.23 m and peak period Tp ranging from 1 to 3 s. Artificial vegetation is a model of Posidonia oceanica seagrass species represented by slightly flexible polypropylene shoots with 8 artificial leaves of 0.28 and 0.16 m height. Different hydrodynamics conditions (Hs, Tp, water depth hw) and geometrical parameters (submergence ratio α, shoot density N) have been tested to see their influence on wave attenuation. For a high submergence ratio (typically 0.7), the wave attenuation can reach 67% of the incident wave height whereas for a low submergence ratio (< 0.2) the wave attenuation is negligible. From each experiment, a bulk drag coefficient has been extracted following the energy dissipation model for irregular non-breaking waves developed by Mendez and Losada (2004). This model, based on the assumption that the energy loss over the species meadow is essentially due to the drag force, takes into account both wave and vegetation parameter. Finally, we found an empirical relationship for Cd depending on 2 dimensionless parameters: the Reynolds and Keulegan-Carpenter numbers. These relationships are compared with other similar studies.

Study of the process of forming a hole for a thread at manufacturing a high nut

2020 ◽  
Vol 76 (8) ◽  
pp. 841-846
Author(s):  
I. G. Shubin ◽  
A. A. Kurkin
Keyword(s):  
Metal Flow ◽  
Nonlinear Dependence ◽  
Geometrical Parameters ◽  
Relative Height ◽  
Forming Process ◽  
Normal Height ◽  
Accuracy Class ◽  
Limit Values ◽  
Program Complex ◽  
Class B

During manufacturing nuts of increased height, a problem of obtaining correct cylindrical form of the hole for thread and overall geometrical parameters arises. To solve the problem it is necessary to know regularity of the blank forming process. Results of the study of a technological process of high hexahedral nuts forming presented. The nuts were M18 of 22 mm height, M16 of 19 mm height and M12 of normal height 10 mm according to GOST 5915–70, accuracy class B, steel grade 10 according to GOST 10702–78. The volumetric stamping was accomplished at the five-position automatic presses of АА1822 type. It was determined, that unevenness of the metal flow in the process of plastic deformation of blanks of increased height nuts was caused by different stress conditions by their sections. To simulate the mode of deformation, the program complex QForm-3D was chosen. The complex ensured to forecast with necessary accuracy the metal flow in a blank, as well as to define the deformation force and arising stress in the working instrument. The simulation showed the presence of regularity between preliminary formed buffle and deviation of dimensions and form of a blank wall after its finishing piercing, which can be expressed by a nonlinear dependence. The limit values of the relative height of the buffle С/D = 0.56–0.588 defined, exceeding which will result in rejection of the finished product. Accounting the limit values of the relative height of the buffle will enable to correct a mode of technological operations and technological instruments at stamping of high hexahedral nuts.

Development of Hardware and Software for the System of Remote Control of Geometrical Parameters of Railcar Wheelsets

2017 ◽  
Vol 13 (2) ◽  
pp. 33-42
Author(s):  
Ye.V. Shapovalov ◽  
◽  
V.O. Koliada ◽  
D.D. Topchev ◽  
N.F. Lutsenko ◽  
...  
Keyword(s):  
Remote Control ◽  
Geometrical Parameters

EXPERIMENTAL AND ANALYTICAL STUDIES OF VERTICAL AXIS WIND TURBINES

2018 ◽  
pp. 51-58
Author(s):  
B. P. Khozyainov
Keyword(s):  
Wind Turbine ◽  
Flow Velocity ◽  
Wind Power ◽  
Wind Turbines ◽  
Power Efficiency ◽  
Air Flow ◽  
Geometrical Parameters ◽  
Wind Speeds ◽  
Analytical Studies ◽  
Air Flow Velocity

The article carries out the experimental and analytical studies of three-blade wind power installation and gives the technique for measurements of angular rate of wind turbine rotation depending on the wind speeds, the rotating moment and its power. We have made the comparison of the calculation results according to the formulas offered with the indicators of the wind turbine tests executed in natural conditions. The tests were carried out at wind speeds from 0.709 m/s to 6.427 m/s. The wind power efficiency (WPE) for ideal traditional installation is known to be 0.45. According to the analytical calculations, wind power efficiency of the wind turbine with 3-bladed and 6 wind guide screens at wind speedsfrom 0.709 to 6.427 is equal to 0.317, and in the range of speed from 0.709 to 4.5 m/s – 0.351, but the experimental coefficient is much higher. The analysis of WPE variations shows that the work with the wind guide screens at insignificant average air flow velocity during the set period of time appears to be more effective, than the work without them. If the air flow velocity increases, the wind power efficiency gradually decreases. Such a good fit between experimental data and analytical calculations is confirmed by comparison of F-test design criterion with its tabular values. In the design of wind turbines, it allows determining the wind turbine power, setting the geometrical parameters and mass of all details for their efficient performance.

Pengaruh Bimbingan Kelompok Terhadap Perilaku Asertif pada Siswa

2018 ◽  
Vol 6 (4) ◽  
pp. 427-446
Author(s):  
Rina Nurviani ◽  
Lilis Satriah
Keyword(s):  
Research Method ◽  
Simple Correlation ◽  
Large Influence ◽  
Assertive Behavior ◽  
The Mind ◽  
Group Guidance

Assertive behavior holds important guidelines for the formation of a person's personality can be improved in group guidance, because in group guidance can be utilized the influence of a person or some individual against other members. This study aims to determine (1) the large influence of group guidance on assertive behavior in the expression of the mind, (2) large influence group guidance on assertive behavior in the expression of feeling, and (3) large influence group guidance on assertive behavior in the expression of mind to students. The research method used in this research is a simple correlation research method. The result of calculation obtained by value of porsentase influence group guidance to assertive behavior in expression of mind equal to 2,5%, in expression of feeling of porsentasenya equal to 4,4%, whereas in expression action only equal to 0,1%. So it can be concluded that group guidance has little effect on assertive behavior in the expression of thoughts, feelings, and actions. The overall influence of group guidance on assertive behavior is only 2.5%.   Perilaku asertif memegang pedoman penting bagi pembentukan kepribadian seseorang dapat ditingkatkan dalam bimbingan kelompok, karena dalam bimbingan kelompok dapat dimanfaatkan pengaruh-pengaruh seseorang atau beberapa individu terhadap anggota lainnya. Penelitian ini bertujuan untuk mengetahui (1) besar pengaruh bimbingan kelompok terhadap perilaku asertif dalam ekspresi pikiran, (2) besar pengaruh bimbingan kelompok terhadap perilaku asertif dalam ekspresi perasaan, dan (3) besar pengaruh bimbingan kelompok terhadap perilaku asertif dalam ekspresi pikiran pada siswa. Metode penelitian yang digunakan dalam penelitian ini yaitu metode penelitian korelasi sederhana. Hasil perhitungan diperoleh nilai porsentase pengaruh bimbingan kelompok terhadap perilaku asertif dalam ekspresi pikiran sebesar 2,5%, dalam ekspresi perasaan porsentasenya sebesar 4,4%, sedangkan dalam ekspresi tindakan hanya sebesar 0,1%. Sehingga dapat disimpulkan bahwa bimbingan kelompok berpengaruh kecil sekali terhadap perilaku asertif dalam ekspresi pikiran, perasaan, dan tindakan. Yang secara keseluruhannya pengaruh bimbingan kelompok terhadap perilaku asertif hanya sebesar 2,5%.

Parametric Optimization of Dental Implants

2020 ◽  
Vol 22 (4) ◽  
pp. 1061-1076
Author(s):  
Wafa Bensmain ◽  
Mohammed Benlebna ◽  
Boualem Serier ◽  
Bel Abbes ◽  
Bachir Bouiadjra
Keyword(s):  
Dental Implants ◽  
Clinical Success ◽  
Equivalent Stress ◽  
Radius Of Curvature ◽  
Geometrical Parameters ◽  
Neck Size ◽  
Biomechanical Behavior ◽  
Dynamic Charging ◽  
The Stability ◽  
Masticatory Process

AbstractOsseointegration is a fundamental phenomenon of dental implantology. It ensures the stability, the safety and the durability of dental implants and predictable clinical success in long-term. The geometric form of the implant is a defining parameter of osseointegration and implant-bone charge transfer. This is the essential constitutes of this study. In fact, we demonstrate using the finite elements method with tridimensional numerical computations, that the geometrical parameters of the implant conditionate the level and the repartition of the stresses, induced in the cortical bone and the spongy bone during the masticatory process, simulated here by dynamic charging. The effect of several parameters [size and conicity of the implant neck, size and radius of curvature of the implant apex] and the shape of the implant corps on the biomechanical behavior of the bone. The latest was analyzed in terms of variation of the equivalent stress induced in the bone. The purpose of this analysis was the developing of an implant form allowing stress relaxation, during the mastication process, in the living tissue.

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