Determination of Void Fraction, Incipient Point of Boiling, and Initial Point of Net Vapor Generation in Sodium-Heated Helically Coiled Steam Generator Tubes

1978 ◽  
Vol 100 (2) ◽  
pp. 268-274 ◽  
Author(s):  
H. C. U¨nal
Keyword(s):  
Heat Flux ◽  
Mass Velocity ◽  
High Speed ◽  
Initial Point ◽  
Operating Conditions ◽  
High Speed Photography ◽  
Centrifugal Forces ◽  
Vapor Generation ◽  
Volumetric Rate ◽  
Rate Ratios

Void fraction was measured with high-speed photography in a 26.7 m and a 40.1 m long, sodium-heated helically coiled steam generator tube of 0.018 m ID. The ratio of coil diameter to tube diameter was 38.9. The operating conditions for the tests were as follows: Pressure: 4–18 MN/m2, mass velocity: 429–1518 kg/m2s, heat flux: 0.013–0.42 MW/m2, outlet subcooling: 0.3–12.5 K, outlet steam quality: 0.000032–0.075. For vapor volumetric rate ratios greater than 0.4, the so-called distribution parameter is not affected by centrifugal forces, and is equal to 0.875. For vapor volumetric rate ratios smaller than 0.4, this parameter is affected by centrifugal forces and the aforesaid ratio. The incipient point of boiling and initial point of net vapor generation were determined with high-speed photography in the aforementioned 26.7 m long helical coil for the following range of operating conditions: Pressure: 4–18 MN/m2, mass velocity 757–1518 kg/m2s, heat flux: 0.082–0.413 MW/m2, outlet subcooling: 4.4–12.5 K. The data were correlated by using both the average and local values of the operating conditions.

Forensic Uncertainty Quantification for Experiments on the Explosively Driven Motion of Particles

2018 ◽  
Vol 3 (4) ◽  
Author(s):  
Kyle Hughes ◽  
S. Balachandar ◽  
Nam H. Kim ◽  
Chanyoung Park ◽  
Raphael Haftka ◽  
...  
Keyword(s):  
Uncertainty Quantification ◽  
High Speed ◽  
Early Time ◽  
Operating Conditions ◽  
Quality Data ◽  
High Speed Photography ◽  
Particle Array ◽  
X Ray Imaging ◽  
Drag Models ◽  
Air Force Research Laboratory

Six explosive experiments were performed in October 2014 and February of 2015 at the Munitions Directorate of the Air Force Research Laboratory with the goal of providing validation-quality data for particle drag models in the extreme regime of detonation. Three repeated single particle experiments and three particle array experiments were conducted. The time-varying position of the particles was captured within the explosive products by X-ray imaging. The contact front and shock locations were captured by high-speed photography to provide information on the early time gas behavior. Since these experiments were performed in the past and could not be repeated, we faced an interesting challenge of quantifying and reducing uncertainty through a detailed investigation of the experimental setup and operating conditions. This paper presents the results from these unique experiments, which can serve as benchmark for future modeling, and also our effort to reduce uncertainty, which we dub forensic uncertainty quantification (FUQ).

Research of bubble flow characteristics in microfluidic chip

2017 ◽  
Vol 31 (10) ◽  
pp. 1750109
Author(s):  
Chao Qiu ◽  
Han Cheng ◽  
Shuxian Chen
Keyword(s):  
Heat Flux ◽  
Microfluidic Chip ◽  
High Speed ◽  
Flow Characteristics ◽  
Hydrophobic Surface ◽  
High Speed Photography ◽  
Bubble Flow ◽  
Hydrophilic Surface ◽  
Biological Detection ◽  
Speed Up

Bubble is the heart of the microfluidic chip, which takes a significant role in drug release, biological detection and so on. In this case, bubble flow characteristics in microfluidic chip are the key to realize its function. In this paper, bubble flow characteristics in the microfluidic chip have been studied with high speed photography system by controlling the wettability and the heat flux of the microelectrode surface. The result shows that bubble flows faster on the electrode with hydrophobic surface. In addition, loading current to the electrode with hydrophilic surface could also speed up the movement of bubble, and the flow rate of bubble increases with the increasing heat flux of the electrode.

scholarly journals Second law analysis of laminar forced convection in a rotating curved duct

2015 ◽  
Vol 19 (1) ◽  
pp. 95-107 ◽  
Author(s):  
Esmail Razavi ◽  
Hosseinali Soltanipour ◽  
Parisa Choupani
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Entropy Generation ◽  
Operating Conditions ◽  
Second Law ◽  
Centrifugal Forces ◽  
Dean Number ◽  
Maximum Heat ◽  
Curved Duct ◽  
Force Ratio

In this paper, flow characteristics, heat transfer and entropy generation in a rotating curved duct are studied numerically. The continuity, Navier-Stokes and energy equations are solved using control volume method. The effects of Dean number, non-dimensional wall heat flux, and force ratio (the ratio of Coriolis to centrifugal forces) on the entropy generation due to friction and heat transfer irreversibility and also overall entropy generation are presented. Optimal thermal operating conditions (based on dimensionless parameters) are determined from the viewpoint of thermodynamics second law. The comparison of numerical results at different force ratios indicates that for any fixed Dean number or non-dimensional heat flux, the minimal frictional entropy generation occurs when the Coriolis and centrifugal forces have the same value but in the opposite direction. For a specific non-dimensional heat flux, there is a force ratio with maximum heat transfer irreversibility which depends on Dean number. Based on optimal analysis, the optimal force ratio with minimal total entropy generation depends on heat flux and Dean number.

scholarly journals Simultaneous Pressure Measurement and High-Speed Photography Study of Cavitation in a Dynamically Loaded Journal Bearing

1993 ◽  
Vol 115 (1) ◽  
pp. 88-95 ◽  
Author(s):  
D. C. Sun ◽  
D. E. Brewe ◽  
P. B. Abel
Keyword(s):  
Pressure Measurement ◽  
Cavitation Bubble ◽  
High Speed ◽  
Journal Bearing ◽  
Operating Conditions ◽  
High Speed Photography ◽  
Pressure Data ◽  
Oil Film ◽  
Dynamically Loaded ◽  
Insight Into

Cavitation of the oil film in a dynamically loaded journal bearing was studied using high-speed photography and pressure measurement simultaneously. Comparison of the visual and pressure data provided considerable insight into the occurrence and non-occurrence of cavitation. It was found that (1), cavitation typically occurred in the form of one bubble with the pressure in the cavitation bubble close to the absolute zero; and (2), for cavitation-producing operating conditions, cavitation did not always occur; with the oil film then supporting a tensile stress.

scholarly journals Influence of Discharge Gap On Material Removal and Melt Pool Movement in EDM Discharge Process

2021 ◽  
Author(s):  
Xiaoming Yue ◽  
Ji Fan ◽  
Qi Li ◽  
Xiaodong Yang ◽  
Zuoke Xu ◽  
...  
Keyword(s):  
Heat Flux ◽  
Material Removal ◽  
High Speed ◽  
Electrical Discharge Machining ◽  
External Pressure ◽  
High Speed Photography ◽  
Discharge Process ◽  
Melt Pool ◽  
Discharge Gap ◽  
Gap Width

Abstract In electrical discharge machining (EDM), gap control is the key to stable processing; the discharge gap plays a significant role in EDM. To determine the influence of the discharge gap on material removal and melt pool movement, which are two fundamental issues in EDM, high-speed photography and molecular dynamics (MD) simulations were used to study the discharge process. Research results demonstrate that the discharge gap has a significant influence on material removal during the discharge process. A smaller gap width produces more and larger removed materials. The influence mechanism of the gap width on material removal is explained as follows. A smaller gap width produces discharge plasma with a smaller diameter and greater heat flux. Discharge with a greater heat flux generates more material removed during the discharge process. In addition, a smaller gap width and greater heat flux produce a stronger interaction of metal vapor jets, generating a stronger shear force acting on the melt pool. The discharge gap also influences the movement of the melt pool and the final topography of the discharge crater through external pressure acting on the melt pool. Smaller gap width produces greater external pressure acting on the melt pool, generating a bowl-shaped melt pool and a discharge crater with a depression in the center and a bulge around the edge. A larger gap width produces less external pressure acting on the melt pool, generating a flat melt pool and a discharge crater with swelling in the center and a depression around the edge.

scholarly journals Kinematic Analysis of a Clamp-Type Picking Device for an Automatic Pepper Transplanter

Agriculture ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 627 ◽  
Author(s):  
Md Nafiul Islam ◽  
Md Zafar Iqbal ◽  
Mohammod Ali ◽  
Milon Chowdhury ◽  
Md Shaha Nur Kabir ◽  
...  
Keyword(s):  
Kinematic Analysis ◽  
High Speed ◽  
Model Simulation ◽  
Mechanical Damage ◽  
Maximum Velocity ◽  
Operating Conditions ◽  
High Speed Photography ◽  
Virtual Model ◽  
Significant Difference ◽  
Simulation And Validation

Pepper is one of the most vital agricultural products with high economic value, and pepper production needs to satisfy the growing worldwide population by introducing automatic seedling transplantation techniques. Optimal design and dimensioning of picking device components for an automatic pepper transplanter are crucial for efficient and effective seedling transplantation. Therefore, kinematic analysis, virtual model simulation, and validation testing of a prototype were conducted to propose a best-suited dimension for a clamp-type picking device. The proposed picking device mainly consisted of a manipulator with five grippers and a picking stand. To analyze the influence of design variables through kinematic analysis, 250- to 500-mm length combinations were considered to meet the trajectory requirements and suit the picking workspace. Virtual model simulation and high-speed photography tests were conducted to obtain the kinematic characteristics of the picking device. According to the kinematic analysis, a 350-mm picking stand and a 380-mm manipulator were selected within the range of the considered combinations. The maximum velocity and acceleration of the grippers were recorded as 1.1, 2.2 m/s and 1.3, 23.7 m/s2, along the x- and y-axes, respectively, for 30 to 90 rpm operating conditions. A suitable picking device dimension was identified and validated based on the suitability of the picking device working trajectory, velocity, and acceleration of the grippers, and no significant difference (p ≤ 0.05) occurred between the simulation and validation tests. This study indicated that the picking device under development would increase the pepper seedling picking accuracy and motion safety by reducing the operational time, gripper velocity, acceleration, and mechanical damage.

Recasting the Fay-Riddell formulae for computing the stagnation point heat flux

2000 ◽  
Vol 214 (2) ◽  
pp. 115-120 ◽  
Author(s):  
G Zuppardi ◽  
A Esposito
Keyword(s):  
Heat Flux ◽  
Stagnation Point ◽  
High Speed ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Total Enthalpy ◽  
High Enthalpy ◽  
Computing Procedure ◽  
The University ◽  
Made In

The Fay-Riddell formulae, used to compute the heat flux at the stagnation point of spherical bodies in very high speed, laminar flow and dissociating air, have been revived and recast. As these formulae were obtained by fitting a number of results of the original Fay-Riddell computing procedure, which suffered from inaccuracies concerning operative parameters, it is to be expected that these inaccuracies also influence the correctness of the formulae. A sensitivity analysis has been made in order to identify the most critical parameter. Recast formulae have been calibrated using the results of the improved version of the Fay-Riddell computing procedure and then validated both by numerical results of a Navier-Stokes code and by experimental data. For this purpose two sets of heat flux measurements have been made in HEBDAF (high enthalpy blown-down arc facility) at the University of Naples, matching the operating conditions of the formula for a frozen boundary layer and non-catalytic wall. Recast formulae are valid in the range of free-stream total enthalpy between 3 and 37 MJ/kg.

Investigations of Arc Behavior and Particle Formation in the Wire Arc Spray Process Using High Speed Photography

2000 ◽  
Author(s):  
N.A. Hussary ◽  
J. Heberlein
Keyword(s):  
Thermal Spray ◽  
High Speed ◽  
Imaging System ◽  
Metal Droplet ◽  
Droplet Formation ◽  
Operating Conditions ◽  
Arc Spraying ◽  
High Speed Photography ◽  
Spray Process ◽  
The Wire

Abstract The wire arc spraying process, one of several thermal spray processes, gained a sizable part of the thermal spray market, however, more control is needed for this process to be used for high precision coatings. This study is aimed at investigating the liquid metal droplet formation process in order to identify methods for droplet trajectory control. A high speed Kodak imaging system has been used to observe the droplet formation for different operating conditions. Decreasing the upstream pressure and the current levels lead to the reduction in the asymmetric melting of both anode and cathode. By decreasing the interactions of the large eddy structures with the formed metal agglomerates one can achieve better control of the particle trajectories and jet divergence. Thus, coatings can be obtained with higher definition and improved reliability.

A Comprehensive Model for Nucleate Pool Boiling Heat Transfer Including Microlayer Evaporation

1976 ◽  
Vol 98 (4) ◽  
pp. 623-629 ◽  
Author(s):  
R. L. Judd ◽  
K. S. Hwang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Speed ◽  
Methylene Chloride ◽  
Significant Proportion ◽  
Laser Interferometry ◽  
Nucleate Boiling ◽  
High Speed Photography ◽  
Evaporation Heat ◽  
Microlayer Evaporation

The results of an experimental investigation are presented in which dichloromethane (methylene chloride) boiling on a glass surface was studied using laser interferometry and high-speed photography. New data for active site density, frequency of bubble emission, and bubble departure radius were obtained in conjunction with measurements of the volume of microlayer evaporated from the film underlying the base of each bubble for various combinations of heat flux and subcooling. These results were used to support a model for predicting boiling heat flux incorporating microlayer evaporation, natural convection, and nucleate boiling mechanisms. Microlayer evaporation heat transfer is shown to represent a significant proportion of the total heat transfer for the range of heat flux and sub-cooling investigated.

Random Behavior of Kerosene Spray Autoignition in Crossflow

2016 ◽  
Author(s):  
Yongsheng Zhao ◽  
Chi Zhang ◽  
Yuzhen Lin
Keyword(s):  
High Speed ◽  
Flow Reactor ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
High Speed Photography ◽  
Primary Analysis ◽  
Photoelectric Detection ◽  
Random Behavior ◽  
Gauss Distribution ◽  
Autoignition Delay

Based on the flow reactor with rectangle cross-section, this paper studies the spray autoignition characteristics of liquid kerosene injected into air crossflow under high temperature and high pressure conditions. Millisecond-level kerosene injection, millisecond-level photoelectric detection, and high speed photography record experiment techniques are adopted in this research. The operating conditions of this research are as follows: 2.3MPa inlet pressure, 917K inlet temperature, fuel/ air momentum ratio of 52, and Weber number of 355. Photoelectric sensor and photomultiplier equipped with CH filter are used to get the autoignition delay time (ADT). A total of 320 experiments are conducted under the same operating conditions in order to obtain the random ADT probability distribution. The high speed photography is utilized to observe and record the developing process of spray autoignition of kerosene. The results show that the ADT varies from 2.5–5.5millisecond (ms) in the above operating conditions, and confirm the existence of the random behavior of kerosene spray autoignition in the crossflow. These random behaviors of ADT can be correlated well with Gauss distribution. The primary analysis shows that the random behavior stems from the random distributions in the diameter and dispersion due to intrinsic turbulence breakup and transportation which dominate the characteristics of spray autoignition.

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