Large Vapor Bubble Research Articles

Effects of heat exchanger tube geometries on nucleate pool boiling heat transfer in a scaled in-containment refueling water storage tank

To determine the combined effects of the heat exchanger tube geometries of advanced light water reactors (ALWRs) passive residual heat removal system (PRHRS) on the nucleate pool boiling heat transfer in a scaled in-containment refueling water storage tank (IRWST), a total of 1,966 data (1,076 with horizontal tubes and 890 with vertical tubes) for q″ versus ΔT has been obtained using various combinations of tube diameters, surface roughness, and tube orientation. The experimental results show that (1) for both horizontal and vertical tubes, increased surface roughness enhances heat transfer whereas increased tube diameter decreases heat transfer, (2) both effects of the surface roughness and the tube diameter on the nucleate pool boiling heat transfer are significantly greater for vertical tubes than horizontal tubes, (3) the effectiveness of two heat transfer mechanisms, i.e., enhanced heat transfer dur to liquid agitation by bubbles generated and reduced heat transfer by the formation of large vapor slugs and bubble coalescence, depends on the combined effects of the heat flux, surface roughness, and the tube orientation. In addition, two different forms of empirical heat transfer correlations are obtained that fit present experimental data within +35 and −20%.

Microanalysis of ore-forming fluids using the scanning proton microprobe

Much of the uncertainty in our early method of microanalysis of fluid inclusions using PIXE stemmed from the heterogeneous internal structure of each inclusion, which typically contains a vapor bubble and daughter crystals, and the non-uniform beam dose distribution. This paper reports on recent work to improve the accuracy of quantitative analysis through the use of beam-scanning techniques which provide a controlled beam-dose distribution. Improvements have been made to the PIXE yield modelling to better account for large vapor bubbles, and all fluid inclusion analysis routines have been incorporated as standard features of the GeoPIXE software package. The method has been tested using synthetic fluid inclusions in quartz (solutions of Na, K, Zn, Rb and Cs chlorides). The results demonstrated an accuracy improved to ∼10–15%. Examples show the application of the method for the analysis of ore-forming fluids in magmatic hydrothermal systems.

Sonoluminescence from large plasma-induced vapor bubbles

The light emitted during the collapse of large vapor bubbles has been measured. The emission lasts for tens of microseconds and is so intense it must be filtered, under our experimental conditions, to record the complete time-dependent behavior. The majority of the energy appears to be emitted well below 630 nm. Such a long duration emission appears to be more consistent with adiabatic heating than shock phenomena. The temporal shape of the emission compares well with the temporal shape of the pressure produced prior to and after collapse, as well. Such bubbles promote study of the collapse processes in regions of parameter space which are highly accessible. [Work supported by the U.S. Navy.]

Acoustic modeling of plasma-induced vapor bubbles

Plasma-induced bubbles respond to time-dependent injection of energy which modifies the acoustic output relative to ‘‘classical’’ gas bubbles. Additionally, they consist primarily of hot vapor which complicates the thermodynamics, elevates the importance of some traditionally untreated variables, and requires additional physical process treatments beyond the basic hydrodynamics. A code that is based upon fundamental physical principles was developed to study the importance of many of these variables. The code is capable of treating the actual driving circuit, resultant plasma behavior, transition from cylindrical to spherical geometry early in the discharge, radiation production, plasma chemistry, thermal transport, and hydrodynamics in a modified Flynn formulation. Primary output consists of bubble wall acceleration, radius, etc., energy balance, and far field pressure. The code has been validated with experimental data and will be compared with ongoing hydrocode model development as well. Experimental and theoretical results are presented for large vapor bubbles. [Work supported by the U.S. Navy.]

Mid-infrared pulsed laser ablation of the arterial wall

Pulsed mid-infrared lasers are an alternative to excimer lasers for transluminal angioplasty. The mid-infrared lasers, however, were reported to produce "acoustic" wall damage that might impair the immediate and long-term results. To study the immediate and long-term effects on the arterial wall, 184 craters (1 mm diameter and 1 mm depth) were produced perpendicular to the intimal lining in the thoracic aortas of pigs. Three types of craters were evaluated: Ho-YSGG laser-induced (lambda = 2.09 microns, 2 pulses of 500 microseconds, 0.50 joule/pulse, 50 gm force), mechanically drilled, and "acoustic" craters. "Acoustic" craters were produced by two laser pulses delivered into a saline-filled metal fiber cap, which was placed in a mechanically drilled crater. The metal cap was provided with four outlets for water vapor and isolated "acoustic" from optical and thermal laser effects. The pigs survived 3, 14, and 28 days. Arterial wall damage, medial necrosis, and wall healing were assessed microscopically. At 3 days, laser and "acoustic" craters were accompanied by large tissue ruptures (2.7 +/- 0.9 mm and 2.9 +/- 0.8 mm, respectively, mean +/- standard deviation). These were attributed to large vapor bubbles expanding within the tissue. A zone of medial necrosis was observed adjacent to the laser craters (0.43 +/- 0.15 mm) and to the "acoustic" craters (0.17 +/- 0.14 mm). Neither ruptures nor necrosis was observed with the mechanical craters. At 2 and 4 weeks, the necrotic areas were repopulated with smooth muscle cells and all craters were adequately filled with smooth muscle cells, without any sign of an exaggerated proliferative response. We conclude that within the arterial wall, Ho-YSGG ablation was accompanied by the rapid expansion of a water vapor bubble. The formation of the relatively large vapor bubble is inherent to the use of a mid-infrared laser. The risk of creating dissections clinically, when delivering Ho-YSGG laser pulses, remains to be determined. The present study provided no indication that the arterial wall fissures might affect the restenosis rate unfavorably by promoting myointimal proliferation.

A Theoretical Study of the Growth of Large Sodium Vapor Bubbles in Liquid Sodium, Including the Effect of Noncondensables and of Vapor Convection

The study of the dynamics of the expansion of large bubbles of hot sodium vapor in a pool of liquid sodium plays an important role in understanding the effects of a hypothetical core disruptive accident. A model of the growth of the bubble in the pool is described. The equations of the motion of the liquid and of the nonsteady heat diffusion problem are solved together with the continuity and energy equations for the vapor phase. The first set of calculations has been performed with constant evaporation and condensation coefficients. In the second set, however, due account has been taken of the effect on condensation of noncondensable fission gases and vapor convection. Due to the very high calculated vapor velocities, noncondensable gases have little effect on the condensation rate, and the percentage amount of condensed sodium is considerably higher than previously calculated by other authors.

Resonance properties of vapor bubbles

Vapor bubbles in a fluid experiencing radial pulsations created by an acoustic field are considered. It is shown that the resonance frequency of large vapor bubbles practically coincides with the eigenfrequency of adiabatic gas bubbles as determined by the Minnaert formula, while in the case of small vapor bubbles, the presence of capillary effects and phase transitions leads to a new resonance frequency that differs from the Minnaert frequency. A simple analytic formula is obtained that relates the resonance frequency of a vapor bubble and its radius; the formula is in good agreement with the results of a numerical solution of the problem. Ranges of dimensions of bubbles, and frequencies of the acoustic field are given, within which different approximations of the relation between resonance frequency and bubble radius hold true. Numerical computations of the resonance frequency based on the radius of a vapor bubble and resonance dimension of a bubble based on field frequency are presented. It is shown that there exists two resonance frequencies and two resonance dimensions of a vapor bubble within some range of dimension of bubbles and acoustic field frequencies. It has also been found /1,2/ that the dynamics of vapor bubbles in an acoustic field reveal the existance of two resonance dimensions of the bubbles. The existence of a new resonance frequency for vapor bubble different from the Minnaert frequency /3/ has also been established /1/. The resonance properties of homogeneous, equilibrium vapor bubbles has been previously reviewed /4/, though the resonance frequencies of bubbles were not determined entirely correctly. An attempt has been made /5/ to analytically determine the resonance dimensions of vapor bubbles and to physically explain the nature of the second resonance. However, since surface tension was ignored and other inaccuracies were made, an incorrect formula was derived in the latter article which did not describe the actual values of the resonance dimensions of vapor bubbles, for example, in versions previously considered /1,2/.

Evidence for a Picritic, Volatile-rich Magma beneath Mt. Shasta, California

Large, magnesium-rich olivines are plentiful in several Holocene cinder cones within 20 km of Mt. Shasta Summit. Glasses (formerly silicate melts) included in the olivines are high alumina basalts (tholeiites and olivine tholeiites). In the most magnesian olivines the glass inclusions have large vapor bubbles. Surrounding some of the glass inclusions are broad Fe-rich zones and ghost outlines. These facts indicate crystallization of major proportions of olivine from the initial trapped melts. The initial melts contained an inferred 24 per cent of MgO and were rich in volatiles. The inferred entrapment temperature of the initial melt is 1410 °C. The initial liquid is a possible mantle derived parent of Mt. Shasta basalts and andesites and of some hidden alpine peridotite.

Methods for Calculating Vapor and Fuel Transport to the Secondary Containment in an LMFBR Accident

Calculational models were developed for estimating the transport of sodium vapor and the relatively large (≥10-µm) fuel particles resulting from a fuel-coolant interaction to the secondary containment in an LMFBR core disruptive accident. Following the formation of a large sodium vapor bubble resulting from a fuel-coolant interaction, a potential sequence of events was analyzed. This analysis covers bubble condensation, bubble rise time, aerosol fallout during the bubble rise, gas flow rate through the cover, cover-gas escape during the bubble rise, bubble and cover-gas mixing, and aerosol escape to the secondary containment.Two parametric calculations were made for specified accident conditions for a 1000-MW(e) LMFBR conceptual design. The bubble did not condense in this analysis. Results of the analysis indicated that 2 and 10% of the fuel that took part in the fuel-coolant interaction eventually reached the secondary containment for the two assumed flow areas through the cover, i.e., 0.1 and 1.0 ft2, respectively.

The Effect of Noncondensables on the Rate of Sodium Vapor Condensation from a Single-Rising HCDA Bubble

In considering the process of liquid-metal vapor condensation during the rise of a large vapor bubble in a pool of cool liquid, previous studies have ignored the effect of the noncondensables. By solving the problem of transient mass diffusion in the vapor space in conjunction with the problem of transient heat conduction and convection in the liquid phase, the effect of noncondensables has been shown to seriously retard the condensation process.

One-Dimensional Flow of Liquids Containing Small Gas Bubbles

Early papers on the subject matter of this review, such as Mallock's (1910) Damping of Sound in Frothy Liquids or Minnaert's (1933) Musical Air Bubbles and the Sound of Running Water, were written out of interest in physical phenomena. In papers written during and after World War II this interest was mixed with motives of a more grim nature because it was sought to take advantage of the acoustical properties of bubbly liquids to control the sound produced by propellers, both of surface ships and sub­ merged ships. The literature on the subject deals therefore for a large part with theoretical and experimental studies of the various aspects of propaga­ tion of pressure waves of small amplitude in bubbly liquids. A major part of this review will be devoted to this topic, Sections 2-4. Apart from this, various schemes have been envisaged in which the dynamic properties of bubbly liquids could be profitably used in the design of devices to propel high-speed waterborne craft, such as hydrofoil and aircushion boats. This made it valuable to investigate the flow of bubbly liquids through Laval nozzles and similar configurations. This type of flow will be discussed in Section 5. In recent years research not directed by the need for data on acoustical properties has been carried out on waves in bubbly fluids beyond the acoustical regime, where disturbances to a given quiescent state are no longer of infinitesimal smallness. The effects of nonlinearity, dispersion, and dissipation, discussed in Section 6, lead as in other areas, such as those of plasma waves and water waves, to mathematical description by Burgers' equation and that of Korteweg and de Vries. Nonlinearity, dispersion, and dissipation cooperate in the formation of shock waves in bubbly liquids, the structure of which has been investigated to some extent, as reviewed in Section 6. The present review is restricted to flows described along the above lines. This means that bubbly flow forming the coolant of nuclear reactors is not included. There the bubbles are mostly large vapor bubbles and the interest is primarily in heat transfer.