The Effect of Temperature on Water Cavitation Phenomena in Converging-Diverging Nozzle Flow

2017 ◽  
Author(s):  
Zayed Ahmed ◽  
B. Terry Beck ◽  
Mohammad H. Hosni
Keyword(s):  
Liquid Phase ◽  
Vapor Pressure ◽  
Saturated Vapor Pressure ◽  
Saturated Vapor ◽  
New Technology ◽  
Phase Region ◽  
Operating Conditions ◽  
Working Fluid ◽  
Absolute Pressure ◽  
Two Phase

A vapor-compression refrigeration cycle typically uses standard refrigerants as the working fluid. Traditional refrigerants, however, have been associated with Ozone level Depletion Potential (ODP) and significant Global Warming Potential (GWP). An innovative cooling technology has been investigated using sonic multi-phase flow in a critical-flow nozzle to create a low-pressure and low-temperature region for heat absorption. The strength of the new technology is its potential to produce cooling using water and/or other working fluids with low ODP and GWP. While the full potential for using water as the working fluid may not be fully-realized, because of property limitations still under investigation, water still provides a very useful media for investigating the underlying cavitation phenomena for the development of the new technology. As part of ongoing research into the potential cooling capacity of the cavitation phenomena, cavitation in a converging-diverging nozzle is being investigated using water as the working fluid. Cavitation in a fluid is the formation of the vapor phase from the liquid phase by reduction in the pressure of the fluid below its saturated vapor pressure. Due to the constricting nature of the throat of a converging-diverging nozzle, the liquid water velocity at the throat is increased and the local absolute pressure can drop to values below the saturated vapor pressure of water at a given temperature; thus, causing the fluid to cavitate. The effect of water temperature on both the onset of the cavitation within the nozzle, and the resulting length of the cavitation region within the nozzle, are the subject of the current paper. Flow Visualization using a high speed digital camera under these different operating conditions was aimed at investigating the region of cavitation onset, which also appears to be associated with the region of boundary layer separation just downstream of the throat of the nozzle. The length of the two phase region at different operating temperatures was measured and it was observed that as the temperature of the fluid was increased, the length of two-phase region before it condensed into single-phase liquid became longer. Experimental results and analysis are presented which also show that near the onset of cavitation, the flowrate can likely go well beyond a choking condition without cavitating, and can remain in this metastable state for an extended amount of time before nucleating (cavitating) into a stable state. In particular, analysis indicates that significantly negative absolute pressures can likely be achieved within the nozzle, suggesting the presence of tension in the liquid phase just prior to cavitation.

Surface Tension and Bubbles

2011 ◽  
Vol 354-355 ◽  
pp. 37-40
Author(s):  
Cai Xia Xu ◽  
Hai Rong Tang
Keyword(s):  
Phase Transition ◽  
Surface Tension ◽  
Liquid Phase ◽  
Vapor Pressure ◽  
Saturated Vapor Pressure ◽  
Saturated Vapor ◽  
Surfactant Solution ◽  
Liquid Phase Transition ◽  
Almost All

From a molecular perspective, we described the origin of surface tension. Surface tension is exceptionally good at rounding things out, such as bubbles can produce in surfactant solution , also in liquid or vapor-liquid phase transition. Through the experiment of determination of saturated vapor pressure of pure liquids, maybe we can conclude that almost all the bubbles were generated as result of the breakup of the gas-liquid interface.

scholarly journals Glycerin-containing Working Fluids for Hydraulic Drives for Special Purposes

2020 ◽  
pp. 1-16
Author(s):  
K. D. Efremova ◽  
V. N. Pilgunov
Keyword(s):  
Vapor Pressure ◽  
Saturated Vapor Pressure ◽  
Saturated Vapor ◽  
Experimental Studies ◽  
Practical Interest ◽  
Hydrodynamic Cavitation ◽  
Absolute Pressure ◽  
Flow Section ◽  
Hydraulic Machines ◽  
The Absolute

The cavitation properties of a liquid must be taken into account in the engineering design of hydraulic machines and devices for hydraulic automation in cases when in their working process the absolute pressure in the liquid may drop below atmospheric, and the liquid is in a rarefied state for a certain time. Cold boiling, which occurs at a relatively low temperature and reduced absolute pressure inside or on the surface of the liquid, is considered as hydrostatic cavitation, if the liquid is stationary, or as hydrodynamic cavitation, if the liquid enters conditions under which the velocity head sharply increases in the flow section and the absolute pressure.In accordance with the theory of cavitation, the first phase of cavitation occurs when the absolute pressure in the degassed liquid drops to the value of the saturated vapor pressure and the air dissolved in the liquid, leaving the intermolecular space, turns into microbubbles of undissolved air and becomes a generator of cavitation "nuclei". Of practical interest is a quantitative assessment of the value of the minimum permissible absolute pressure in a real, partially or completely degassed liquid, at which hydrostatic cavitation occurs.Since the pressure of saturated vapor of a liquid is, to a certain extent, associated with the forces of intermolecular interaction, it is necessary to have information on the cavitation properties of technical solutions, including the solution of air in a liquid, since a solute can weaken intermolecular bonds and affect the value of the pressure of saturated vapors of the solvent. The article describes an experiment carried out by the authors to evacuate liquids. During the experiment, evacuation of various liquids was carried out using a developed hydraulic vacuum pump with a pneumatic drive.The article presents the technologies of hydrostatic and hydrodynamic degassing of liquids used in the experiment.As a result of experimental studies of the cavitation properties of pure glycerin and glycerin in the form of a 49/51% solution in water, mineral oil and aviation kerosene, quantitative estimates of the permissible absolute pressure in the considered technical fluids and solutions were obtained, its dependence on the saturated vapor pressure, the influence of the degree of hydrodynamic degassing the liquid, and the amount of dissolved substance in it on the strength of the liquid to rupture.In the process of studying the cavitation properties of solutions, it was found that the level of permissible absolute pressure in the solution is greater than that of the solvent. It has been suggested that dissolved solid, liquid or gaseous substances weaken the intermolecular bonds of the solvent and increase the pressure of its saturated vapor.On the basis of the experimental studies, a method for determining the highest rarefaction in solvents and in glycerol solutions has been developed. In addition, a comparative assessment of the cavitation properties of the considered technical fluids is given.

scholarly journals An experimental investigation of the saturated vapor pressure of solutions proL pane in compressor oils in the presence of fullerene C60 in oil

2021 ◽  
pp. 89-99
Author(s):  
V. Zhelezny ◽  
S. Korniievych ◽  
O. Khliyeva ◽  
D. Ivchenko
Keyword(s):  
Vapor Pressure ◽  
Saturated Vapor Pressure ◽  
Saturated Vapor ◽  
Fullerene C60 ◽  
Working Fluid ◽  
Vapor Compression ◽  
Refrigeration System ◽  
Concentration Dependences ◽  
Vapor Compression Refrigeration ◽  
Object Of Study

An investigation of the saturated vapor pressure for the solutions of propane in the two type of industrial compressor oils ProEco®RF22S and RENISO SP46, also as in oil ProEco®RF22S containing fullerene C60 6.837·10-4kg·kg-1is presented in this paper. The measurement of the saturated vapor pressure was conducted using a static method in a temperature range (273…333) K and thepropanemass fraction (0.11…0.595) kg·kg-1. An analysis revealed that the expanded uncertainties of the measured saturated vapor pressure do not exceed 0.0419·105Pafor solutionpropane/ProEco®RF22S,0.0716·105Pa for solution propane /RENISO SP46, and 0.0095·105Pa for solution propane/ProEco®RF22 Scontaining C60.The temperature and concentration dependences of the saturated vapor pressure for the object of study have been discussed. The excess of saturated vapor pressure for the solution of propane in oil ProEco®RF22S over the pressure of the solution of propane in oil RENISO SP46 reaches 1.5 105 Pa at a temperature of 330 K and propane fractionof 0.1 kg·kg-1. This effect decreases with temperature decreasing and propane fraction increasing.It was proven that the additive of the fullerene C60 increase the saturated vapor pressure of the solution propane/ProEco® RF22S up to 0.4·105Pa at low temperature and low propane mass fraction insolution. The results obtained proved the expediency of the introduction in the industry the solution of propane/compressor oil ProEco® RF22Scontaining the fullerene C60 as working fluid of vapor compression refrigeration system. The ability of C60additive in oil to increase the saturated vapor pressure of considered working fluid will contribute to increasing the energy efficiency of refrigeration systems.

scholarly journals Modification of the Redlich-Kwong-Aungier Equation of State to Determine the Degree of Dryness in the CO2 Two-phase Region

2021 ◽  
Vol 24 (4) ◽  
pp. 17-27
Author(s):  
Hanna S. Vorobieva ◽  
Keyword(s):  
Experimental Data ◽  
Equation Of State ◽  
Gas Phase ◽  
Saturated Vapor ◽  
Phase Region ◽  
Working Fluid ◽  
Two Phase ◽  
Real Gas ◽  
Liquid Phases ◽  
Good Agreement

The degree of dryness is the most important parameter that determines the state of a real gas and the thermodynamic properties of the working fluid in a two-phase region. This article presents a modified Redlich-Kwong-Aungier equation of state to determine the degree of dryness in the two-phase region of a real gas. Selected as the working fluid under study was CO2. The results were validated using the Span-Wanger equation presented in the mini-REFPROP program, the equation being closest to the experimental data in the CO2 two-phase region. For the proposed method, the initial data are temperature and density, critical properties of the working fluid, its eccentricity coefficient, and molar mass. In the process of its solution, determined are the pressure, which for a two-phase region becomes the pressure of saturated vapor, the volumes of the gas and liquid phases of a two-phase region, the densities of the gas and liquid phases, and the degree of dryness. The saturated vapor pressure was found using the Lee-Kesler and Pitzer method, the results being in good agreement with the experimental data. The volume of the gas phase of a two-phase region is determined by the modified Redlich-Kwong-Aungier equation of state. The paper proposes a correlation equation for the scale correction used in the Redlich-Kwongda-Aungier equation of state for the gas phase of a two-phase region. The volume of the liquid phase was found by the Yamada-Gann method. The volumes of both phases were validated against the basic data, and are in good agreement. The results obtained for the degree of dryness also showed good agreement with the basic values, which ensures the applicability of the proposed method in the entire two-phase region, limited by the temperature range from 220 to 300 K. The results also open up the possibility to develop the method in the triple point region (216.59K-220 K) and in the near-critical region (300 K-304.13 K), as well as to determine, with greater accuracy, the basic CO2 thermodynamic parameters in the two-phase region, such as enthalpy, entropy, viscosity, compressibility coefficient, specific heat capacity and thermal conductivity coefficient for the gas and liquid phases. Due to the simplicity of the form of the equation of state and a small number of empirical coefficients, the obtained technique can be used for practical problems of computational fluid dynamics without spending a lot of computation time.

Measurements of Saturated Vapor Pressure above the Liquid Phase for Isomeric Dichlorobenzenes and 1,2,4-Trichlorobenzene

1998 ◽  
Vol 43 (5) ◽  
pp. 770-775 ◽  
Author(s):  
Vladislav Roháč ◽  
Vlastimil Růžička ◽  
Květoslav Růžička ◽  
Karel Aim
Keyword(s):  
Liquid Phase ◽  
Vapor Pressure ◽  
Saturated Vapor Pressure ◽  
Saturated Vapor

scholarly journals Effects of nanoparticles on hydraulic cavitation

2018 ◽  
Vol 240 ◽  
pp. 03004
Author(s):  
Min-rui Chen ◽  
Jin-yuan Qian ◽  
Zan Wu ◽  
Chen Yang ◽  
Zhi-jiang Jin ◽  
...  
Keyword(s):  
Vapor Pressure ◽  
Saturated Vapor Pressure ◽  
Saturated Vapor ◽  
Geometric Model ◽  
Pressure Ratio ◽  
Perforated Plate ◽  
Significant Parameter ◽  
Operation Conditions ◽  
Small Bubbles ◽  
Crucial Condition

When liquids flowing through a throttling element, such as a perforated plate, the velocity increases and the pressure decreases. If the pressure is below the saturated vapor pressure, the liquid will vaporize into small bubbles, which is called hydraulic cavitation. In fact, vaporization nucleus is another crucial condition for vaporizing. The nanoparticles contained in the nanofluids play a significant role in vaporization of liquids. In this paper, the effects of the nanoparticles on hydraulic cavitation are investigated. Firstly, a geometric model of a pipe channel equipped with a perforated plate is established. Then with different nanoparticle volume fractions and diameters, the nanofluids flowing through the channel is numerically simulated based on a validated numerical method. The operation conditions, such as the temperature and the pressure ratio of inlet to outlet, are the considered variables. As a significant parameter, cavitation numbers under different operation conditions are achieved to investigate the effects of nanoparticles on hydraulic cavitation. Meanwhile, the contours are extracted to research the distribution of bubbles for further investigation. This study is of interests for researchers working on hydraulic cavitation or nanofluids.

scholarly journals Thermodynamics and Machine Learning Based Approaches for Vapor–Liquid–Liquid Phase Equilibria in n-Octane/Water, as a Naphtha–Water Surrogate in Water Blends

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 413
Author(s):  
Sandra Lopez-Zamora ◽  
Jeonghoon Kong ◽  
Salvador Escobedo ◽  
Hugo de Lasa
Keyword(s):  
Machine Learning ◽  
Liquid Phase ◽  
Phase Equilibria ◽  
Aspen Plus ◽  
Phase Region ◽  
Two Phase ◽  
Technical Literature ◽  
Phase Liquid ◽  
Liquid Vapor ◽  
Vapor Liquid

The prediction of phase equilibria for hydrocarbon/water blends in separators, is a subject of considerable importance for chemical processes. Despite its relevance, there are still pending questions. Among them, is the prediction of the correct number of phases. While a stability analysis using the Gibbs Free Energy of mixing and the NRTL model, provide a good understanding with calculation issues, when using HYSYS V9 and Aspen Plus V9 software, this shows that significant phase equilibrium uncertainties still exist. To clarify these matters, n-octane and water blends, are good surrogates of naphtha/water mixtures. Runs were developed in a CREC vapor–liquid (VL_ Cell operated with octane–water mixtures under dynamic conditions and used to establish the two-phase (liquid–vapor) and three phase (liquid–liquid–vapor) domains. Results obtained demonstrate that the two phase region (full solubility in the liquid phase) of n-octane in water at 100 °C is in the 10-4 mol fraction range, and it is larger than the 10-5 mol fraction predicted by Aspen Plus and the 10-7 mol fraction reported in the technical literature. Furthermore, and to provide an effective and accurate method for predicting the number of phases, a machine learning (ML) technique was implemented and successfully demonstrated, in the present study.

Porous Hydroxyapatite with Tailored Crystal Surface Prepared by Hydrothermal Method

2005 ◽  
Vol 284-286 ◽  
pp. 353-356 ◽  
Author(s):  
Koji Ioku ◽  
Giichiro Kawachi ◽  
Nakamichi Yamasaki ◽  
Hirotaka Fujimori ◽  
Seishi Goto
Keyword(s):  
Aspect Ratio ◽  
Vapor Pressure ◽  
Hydrothermal Method ◽  
Saturated Vapor Pressure ◽  
Crystal Surface ◽  
Saturated Vapor ◽  
Pure Water ◽  
Porous Hydroxyapatite ◽  
Exposure Method ◽  
The Mean

Porous plates of hydroxyapatite (Ca10(PO4)6(OH)2; HA) with about 0.5 to 5 mm in thickness and porous HA granules of about 40 µm to 1 mm in size with tailored crystal surface were prepared by the hydrothermal vapor exposure method at the temperatures above 105 °C under saturated vapor pressure of pure water. Porous HA plates with about 75 % porosity prepared at 120 °C were composed of rod-shaped crystals of about 20 µm in length. Porous HA granules prepared at 160 °C were also composed of rod-shaped crystals of about 20 µm in length with the mean aspect ratio of 30. These crystals were elongated along the c-axis. Rod-shaped HA crystals were locked together to make micro-pores of about 0.1 to 0.5 µm in size. Both of materials were nonstoichiometric HA with calcium deficient composition. These materials must have the advantage of adsorptive activity, because they had large specific crystal surface and much micro-pores.

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