scholarly journals DEMONSTRATION TASKS OF LIQUID AND GAS PROPERTIES AND THEIR RATIONALE SENSE

2010 ◽  
Vol 7 (1) ◽  
pp. 29-37
Author(s):  
Violeta Šlekienė ◽  
Loreta Ragulienė
Keyword(s):  
Gas Flow ◽  
Liquid Surface ◽  
Flow Speed ◽  
Pressure Reduction ◽  
Physics Teaching ◽  
Liquid Surface Tension ◽  
Air Stream ◽  
Logical Sense ◽  
Physical Phenomena ◽  
Gas Properties

The article reveals the importance of demonstration tasks in physics teaching in secondary schools. Four demonstration of the liquid and gas properties are presented and analyzed. They are: Pressure dependence of gas flow speed; Pressure reduction in air-stream; Wing lift; Liquid surface tension. Reasoning schemes for giving a logical sense to these physics demo tasks are developed. The proposed reasoning schemes reach to activate students' thinking, understanding the demonstrations during the observed physical phenomena, i.e. help students to: understand the nature of the demo task, determine cause - effect relationships and dependencies, compare conditions and findings, summarize the results, do conclusions. Such using of demonstration tasks is useful to both of teacher and pupil: teacher controls the content of teaching and a learning of pupils, pupils - are focused to self-activities, encouraged to think, analyze, summarize and do conclusions. Key words: physics teaching, demonstration task, liquid and gas properties, reasoning schemes.

DEMONSTRATION TASKS OF ELECTRICAL CURENT PROPERTIES AND THEIR RATIONAL SENSE

2011 ◽  
Vol 8 (2) ◽  
pp. 40-48
Author(s):  
Loreta Ragulienė ◽  
Violeta Šlekienė
Keyword(s):  
Key Words ◽  
Electrical Current ◽  
Physics Teaching ◽  
Anal Ysis ◽  
Logical Sense ◽  
Physical Phenomena

This article reveals the importance of demonstration tasks in physics teaching in sec-ondary schools. The demonstration tasks of electrical current in the gas and their logical anal-ysis is presented and analyzed. Reasoning schemes for giving a logical sense to these physics demo tasks are developed. The proposed reasoning schemes reach to activate students' think-ing, understanding the demonstrations during the observed physical phenomena, i.e. help stu-dents to: understand the nature of the demo task, determine cause - effect relationships and dependencies, compare conditions and findings, summarize the results, do conclusions. Such using of demonstration tasks is useful to both of teacher and pupil: teacher controls the con-tent of teaching and a learning of pupils, pupils - are focused to self-activities, encouraged to think, analyze, summarize and do conclusions. Key words: physics teaching, demonstration task, reasoning schemes.

scholarly journals Trickle/pulse flow regime transition in downflow packed tower involving foaming liquids

2012 ◽  
Vol 18 (3) ◽  
pp. 349-359
Author(s):  
Vijay Sodhi
Keyword(s):  
Surface Tension ◽  
Liquid Flow ◽  
Liquid Surface ◽  
Regime Transition ◽  
Pulse Flow ◽  
Packed Tower ◽  
Flow Rates ◽  
Transition Boundary ◽  
Liquid Surface Tension ◽  
Pulsing Flow

The most of past studies in foaming trickle bed reactors aimed at the improvement of efficiency and operational parameters leads to high economic advantages. Conventionally most of the industries rely on frequently used gas continuous flow (GCF) where operational output is satisfactory but not yields efficiently as in pulsing flow (PF) and foaming pulsing flow (FPF). Hydrodynamic characteristics like regime transitions are significantly influenced by foaming nature of liquid as well as gas and liquid flow rates. This study?s aim was to demonstrate experimentally the effects of liquid flow rate, gas flow rates and liquid surface tension on regime transition. These parameters were analyzed for the air-aqueous Sodium Lauryl Sulphate and air-water systems. More than 240 experiments were done to obtain the transition boundary for trickle flow (GCF) to foaming pulsing flow (PF/FPF) by use excessive foaming 15-60 ppm surfactant compositions. The trickle to pulse flow transition appeared at lower gas and liquid flow rates with decrease in liquid surface tension. All experimental data had been collected and drawn in the form of four different transitional plots which are compared and drawn by using flow coordinates proposed by different researchers. A prominent decrease in dynamic liquid saturation was observed especially during regime transitional change. The reactor two phase pressure evident a sharp rise to verify the regime transition shift from GCF to PF/FPF. Present study reveals, the regime transition boundary significantly influenced by any change in hydrodynamic as well as physiochemical properties including surface tension.

scholarly journals Temperature-compensated fiber-optic gas flow speed sensor based on the ‘Hot-wire’ principle

Optik ◽  
2020 ◽  
pp. 166118
Author(s):  
Zhen Li ◽  
Jiqiang Wang ◽  
Xiaoxing Zhong ◽  
Tongyu Liu ◽  
Yanong Ning ◽  
...  
Keyword(s):  
Gas Flow ◽  
Fiber Optic ◽  
Flow Speed ◽  
Hot Wire ◽  
Speed Sensor

scholarly journals Principle and Characteristics of Microparts Self-alignment using Liquid Surface Tension.

2000 ◽  
Vol 66 (2) ◽  
pp. 282-286 ◽  
Author(s):  
Kaiji SATO ◽  
Tomonori SEKI ◽  
Seiichi HATA ◽  
Akira SHIMOKOHBE
Keyword(s):  
Surface Tension ◽  
Liquid Surface ◽  
Liquid Surface Tension

scholarly journals Liquid-surface entrainment induced by shocked air stream

Shock Waves ◽  
2018 ◽  
Vol 29 (2) ◽  
pp. 361-364
Author(s):  
V. Rodriguez ◽  
G. Jourdan ◽  
A. Marty ◽  
A. Allou ◽  
J.-D. Parisse
Keyword(s):  
Liquid Surface ◽  
Air Stream

scholarly journals Measurements and correlations for gas liquid surface tension at high pressure and high temperature

AIChE Journal ◽  
2018 ◽  
Vol 64 (11) ◽  
pp. 4110-4117 ◽  
Author(s):  
C. Leonard ◽  
J-H. Ferrasse ◽  
O. Boutin ◽  
S. Lefevre ◽  
A. Viand
Keyword(s):  
Surface Tension ◽  
High Pressure ◽  
High Temperature ◽  
Liquid Surface ◽  
Liquid Surface Tension

Effects of Shield Gas Flow on Meltpool Variability and Signature in Scanned Laser Melting

2020 ◽  
Author(s):  
David C. Deisenroth ◽  
Jorge Neira ◽  
Jordan Weaver ◽  
Ho Yeung
Keyword(s):  
Additive Manufacturing ◽  
Aspect Ratio ◽  
Flow Velocity ◽  
Process Monitoring ◽  
Gas Flow ◽  
Laser Energy ◽  
Flow Speed ◽  
Powder Bed ◽  
Flow Speeds ◽  
Gas Flow Velocity

Abstract In laser powder bed fusion metal additive manufacturing, insufficient shield gas flow allows accumulation of condensate and ejecta above the build plane and in the beam path. These process byproducts are associated with beam obstruction, attenuation, and thermal lensing, which then lead to lack of fusion and other defects. Furthermore, lack of gas flow can allow excessive amounts of ejecta to redeposit onto the build surface or powder bed, causing further part defects. The current investigation was a preliminary study on how gas flow velocity and direction affect laser delivery to a bare substrate of Nickel Alloy 625 (IN625) in the National Institute of Standards and Technology (NIST) Additive Manufacturing Metrology Testbed (AMMT). Melt tracks were formed under several gas flow speeds, gas flow directions, and energy densities. The tracks were then cross-sectioned and measured. The melt track aspect ratio and aspect ratio coefficient of variation (CV) were reported as a function of gas flow speed and direction. It was found that a mean gas flow velocity of 6.7 m/s from a nozzle 6.35 mm in diameter was sufficient to reduce meltpool aspect ratio CV to less than 15 %. Real-time inline hotspot area and its CV were evaluated as a process monitoring signature for identifying poor laser delivery due to inadequate gas flow. It was found that inline hotspot size could be used to distinguish between conduction mode and transition mode processes, but became diminishingly sensitive as applied laser energy density increased toward keyhole mode. Increased hotspot size CV (associated with inadequate gas flow) was associated with an increased meltpool aspect ratio CV. Finally, it was found that use of the inline hotspot CV showed a bias toward higher CV values when the laser was scanned nominally toward the gas flow, which indicates that this bias must be considered in order to use hotspot area CV as a process monitoring signature. This study concludes that gas flow speed and direction have important ramifications for both laser delivery and process monitoring.

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