scholarly journals Behavior of Liquid Sodium in a Sinusoidal Pressure Field

1970 ◽  
Vol 92 (4) ◽  
pp. 671-678
Author(s):  
R. E. Nystrom ◽  
F. G. Hammitt
Keyword(s):  
Pressure Field ◽  
Saturation Temperature ◽  
Pressure Oscillation ◽  
Nucleate Boiling ◽  
Liquid Sodium ◽  
Pressure Amplitude ◽  
Pressure Data ◽  
Cavitation Threshold ◽  
Onset Of Cavitation ◽  
Good Agreement

Utilizing an ultrasonic vibratory cavitation facility, the onset of cavitation was observed in liquid sodium for different liquid sodium temperatures and at various sinusoidal pressure field frequencies. It was observed that the pressure oscillation required to initiate cavitation decreases linearly as the temperature of the sodium is increased from 500 to 1500 deg F. For frequencies below 20 kHz the cavitation threshold pressure amplitude is essentially independent of frequency. For frequencies above 20 kHz the cavitation threshold begins to increase sharply. Using the onset of cavitation data and the saturation temperature-pressure data for liquid sodium, the superheat required to produce nucleate boiling in liquid sodium was calculated. As the saturation temperature of liquid sodium is increased the calculated superheat decreases. For frequencies below 20 kHz the calculated sodium superheat requirements, which are independent of frequency, are in good agreement with steady-state sodium superheat data reported in the literature.

Development of a Lifetime Pressure Sensitive Paint Procedure for High-Pressure Vane Testing

2021 ◽  
Author(s):  
Papa Aye N. Aye-Addo ◽  
Guillermo Paniagua ◽  
David G. Cuadrado ◽  
Lakshya Bhatnagar ◽  
Antonio Castillo Sauca ◽  
...  
Keyword(s):  
High Pressure ◽  
Test Section ◽  
Static Pressure ◽  
Pressure Field ◽  
Optical Measurements ◽  
Wall Region ◽  
Pressure Amplitude ◽  
Pressure Sensitive Paint ◽  
Suction Surface ◽  
Pressure Sensitive

Abstract Optical measurements based on fast response Pressure Sensitive Paint (PSP) provide enhanced spatial resolution of the pressure field. This paper presents laser lifetime PSP at 20 kHz, with precise calibrations, and results from a demonstration in an annular vane cascade. The laser lifetime PSP methodology is first evaluated in a linear wind tunnel with a converging-diverging nozzle followed by a wavy surface. This test section is fully optically accessible with maximum modularity. A data reduction procedure is proposed for the PSP calibration, and optimal pixel binning is selected to reduce the uncertainty. In the annular test section, laser lifetime PSP was used to measure the time-averaged static pressure field on a section of the suction surface of a high-pressure turbine vane. Tests were performed at engine representative conditions in the Purdue Big Rig for Annular Stationary Turbine Analysis module at the Purdue Experimental Turbine Aerothermal Lab. The 2-D pressure results showed a gradual increase of pressure in the spanwise and flow directions, corroborated with local static pressure taps and computational results. The variation in PSP thickness was measured as a contribution to the uncertainty. The discrete Fourier transform of the unsteady pressure signal showed increased frequency content in wind-on conditions compared to wind-off conditions at the mid-span and 30% span. Compared to the mid-span region, the hub end wall region had an increase in frequencies and pressure amplitude. This result was anticipated given the expected presence of secondary flow structures in the near hub region.

Evaporation and Nucleate Boiling of an Individual Droplet on Surfaces

2005 ◽  
Author(s):  
X. D. Wang ◽  
G. Lu ◽  
X. F. Peng ◽  
B. X. Wang
Keyword(s):  
Heat Flux ◽  
High Speed ◽  
Bubble Dynamics ◽  
Imaging System ◽  
Dynamical Behavior ◽  
Saturation Temperature ◽  
Nucleate Boiling ◽  
Dynamical Process ◽  
Boiling Regime ◽  
Film Evaporation

A visual study was conducted to investigate the evaporation and nucleate boiling of a water droplet on heated copper, aluminum, or stainless surfaces with temperature ranging from 50°C to 112°C. Using a high-speed video imaging system, the dynamical process of the evaporation of a droplet was recoded to measure the transient variation of its diameter, height, and contact angle. When the contact temperature was lower than the saturation temperature, the evaporation was in film evaporation regime, and the evaporation could be divided into two stages. When the surface temperature was higher than the saturation temperature, the nucleate boiling was observed. The dynamical behavior of nucleation, bubble dynamics droplet were detail observed and discussed. The linear relationships of the average heat flux vs. temperature of the heated surfaces were found to hold for both the film evaporation regime and nucleate boiling regime. The different slopes indicated their heat transfer mechanism was distinct, the heat flux decreased in the nucleate boiling regime more rapidly than in the film evaporation due to the strong interaction between the bubbles.

Physics of the Interaction of Ultrasonic Excitation With Nucleate Boiling

2013 ◽  
Vol 136 (3) ◽  
Author(s):  
Sreenath Krishnan ◽  
Sarit K. Das ◽  
Dhiman Chatterjee
Keyword(s):  
Mechanistic Model ◽  
Interactive Effect ◽  
Nucleate Boiling ◽  
Ultrasonic Frequency ◽  
Pressure Amplitude ◽  
Surface Parameter ◽  
Site Density ◽  
Multiphase Fluid Flow ◽  
Ultrasound Assisted ◽  
Multiphase Fluid

Physics of ultrasound-assisted augmentation of saturated nucleate boiling through the interaction of multiphase fluid flow is revealed in the present work. Different regimes of influence of ultrasound, ranging from augmentation to deterioration and even no effect, as reported in literature in a contradictory fashion, have been observed. However unlike the previous studies, here it has been clearly demonstrated that this apparent anomaly lies in the different natures of interactions between the influencing parameters like heat flux, ultrasonic frequency, and pressure amplitude. The present results clearly bring out an interactive effect of these operating parameters with surface parameter like surface roughness. A mechanistic model unifying all these parameters has been presented to explain quantitatively the physics of the interaction. The model-based predictions match experimental results quite well suggesting the validity of the hypothesis on liquid–vapor-surface interaction through the process of nucleation and its site density, on which the model is built, and thus revealing the underlying physics.

New Relationship Between Resistivity Index and Relative Permeability

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Dong Ma ◽  
Changwei Liu ◽  
Changhui Cheng
Keyword(s):  
Capillary Pressure ◽  
Relative Permeability ◽  
Pressure Data ◽  
Two Phase ◽  
Resistivity Index ◽  
Proposed Model ◽  
Petrophysical Parameter ◽  
Oil Water ◽  
Better Than ◽  
Good Agreement

Relative permeability as an important petrophysical parameter is often measured directly in the laboratory or obtained indirectly from the capillary pressure data. However, the literature on relationship between relative permeability and resistivity is lacking. To this end, a new model of inferring two-phase relative permeability from resistivity index data was derived on the basis of Poiseuille's law and Darcy's law. The wetting phase tortuosity ratio was included in the proposed model. The relative permeabilities computed from the capillary pressure data, as well as the experimental data measured in gas–water and oil–water flow condition, were compared with the proposed model. Both results demonstrated that the two-phase permeability obtained by proposed model were generally in good agreement with the data computed from capillary pressure and measured in the laboratory. The comparison also showed that our model was much better than Li model at matching the relative permeability data.

Development and Testing of Techniques for Oscillating Pressure Measurements Especially Suitable for Experimental Work in Turbomachinery

1971 ◽  
Vol 93 (4) ◽  
pp. 603-609 ◽  
Author(s):  
H. Weyer ◽  
R. Schodl
Keyword(s):  
Evaluation Method ◽  
Pressure Amplitude ◽  
Pressure Oscillations ◽  
Measuring Systems ◽  
High Frequencies ◽  
Pneumatic Measuring ◽  
True Time ◽  
Weighted Values ◽  
Better Than ◽  
Good Agreement

Strong pressure oscillations of high frequencies and high amplitudes occur in the region of turbomachine rotors. The measurement of the average pressures resulting from these oscillations is one of the most important measuring problems in turbomachinery, because the pneumatic measuring systems usually used in such tests yield average pressures which normally do not agree with the true time-integrated values. This paper deals with an investigation aimed at the development of techniques, which permit the measurement of well-defined average values of oscillating pressures. Three different methods developed and tested at DFVLR are described. Two of them—a hydraulic and a mechanical one—are able to measure the true time-averaged pressures with an accuracy better than 0.5 percent of the acting pressure amplitude. The third procedure is based on an evaluation method by means of which the average pressures indicated by special pneumatic measuring systems can be correlated to the true time-weighted values. Experimental and computed results are presented showing a very good agreement.

Mean Wind Pressure Field on the Typical Large-Span Roof Structures

2012 ◽  
Vol 166-169 ◽  
pp. 19-24
Author(s):  
Fang Hui Li ◽  
Ming Gu ◽  
Zhen Hua Ni ◽  
Shi Zhao Shen
Keyword(s):  
Pressure Field ◽  
Pressure Coefficient ◽  
Wind Pressure ◽  
Pressure Data ◽  
Shape Factors ◽  
Local Shape ◽  
Wind Pressure Coefficient ◽  
The Mean ◽  
Urban Terrain ◽  
Wind Pressures

The wind tunnel tests of some typical large roofs, including a saddle roof, pitched roof and domes, are carried out with various terrains which cover suburban and urban exposures. The wind pressure data of roofs are obtained by using the synchronous multi-pressure scanning technique. The wind pressure coefficient and local shape factors of the wind load was investigated. The effects of various terrains on wind pressures of roofs are discussed. From the results, we can see mean pressures of these roofs exposed to the mean pressures exposed to the suburban terrain are 2 or 3 times those exposed to the urban terrain. And the terrains are no directly influence to the wind pressure shape factors.

Predicting Two Phase Flow Pressure Drop With CFD and ANN

2010 ◽  
Author(s):  
I˙smail Teke ◽  
O¨zden Ag˘ra ◽  
Hakan Demir ◽  
S¸. O¨zgu¨r Atayılmaz
Keyword(s):  
Pressure Drop ◽  
Flow Model ◽  
Two Phase Flow ◽  
Saturation Temperature ◽  
Smooth Tube ◽  
Phase Flow ◽  
Two Phase ◽  
Analytical Formulas ◽  
Flow Pressure ◽  
Good Agreement

In this study, the several well known two-phase viscosity models were used for predicting two-phase flow pressure drop in a smooth tube using Computational Fluid Dynamics (CFD) software at homogenous flow conditions. Pressure drop for two different mass flux values (300 and 650 kg/m2s) for R134a with a saturation temperature of 45 °C in a smooth tube has been modeled according to the homogenous flow model and the results have been compared with the analytical formulas and experimental data from the literature. Three different average viscosity correlations were used. It is seen that the numerical results are in a good agreement with the homogenous flow model and fall in ± 30% band. Also, the results derived from the average viscosity expression are in a good agreement with the results calculated using separated two-phase flow correlations. In addition to this, Artificial Neural Networks (ANNs) were employed for predicting the pressure drop in a horizontal smooth pipe. The trained network gives the best values over the correlations with less than 1% mean relative error.

Sign in / Sign up

Export Citation Format

Share Document