Features of metastable superheated water atomization when being discharged through convergent-divergent nozzles at different superheat values

Experiments with the metastable superheated water atomization proved the significant increase of the submicron droplets mass fraction at the outlet of convergent-divergent nozzle from 0.45-0.55 to 0.75-0.9 with an increase of the inlet water temperature from170to255°C. Two different approaches to dimensionless treatment of the atomization processdata and determining the boundary of the zone of flashing predominance are compared. The analysis of two approaches to dimensionless treatment of experimental and calculating results concerning transition to predominating role of nucleation in the process of superheated liquid atomization in convergent-divergent nozzles is done.

Synthesis and characterization of theranostic agents for photoacoustic imaging and therapy.

In this work, phase-change contrast agents were developed for photoacoustic (PA) imaging and therapy. They consist of superheated liquid perfluorocarbon and gold nanoparticles capped by a Poly-(Lactide-co-Glycolic Acid) (PLGA) polymer shell. The phase transition from liquid to gas bubble can be remotely triggered by a laser source. In their liquid state, upon laser irradiation, these agents generated strong PA signals which were proportional to the laser fluence and particle sizes. The vaporization threshold decreased with increasing particle size, and was 850, 670 and 420 mJ/cm2 for 2, 5, 10 μm-sized PLGA particles loaded with 35 nm GNPs, respectively. Cell culture studies, including passive uptake by the cancer cells and mechanical damage to the cancer cells caused by the vaporization inside the cells are also investigated. These agents show potential as photoacoustic imaging contrast and cancer therapy agents for clinical applications.

Synthesis and characterization of theranostic agents for photoacoustic imaging and therapy.

In this work, phase-change contrast agents were developed for photoacoustic (PA) imaging and therapy. They consist of superheated liquid perfluorocarbon and gold nanoparticles capped by a Poly-(Lactide-co-Glycolic Acid) (PLGA) polymer shell. The phase transition from liquid to gas bubble can be remotely triggered by a laser source. In their liquid state, upon laser irradiation, these agents generated strong PA signals which were proportional to the laser fluence and particle sizes. The vaporization threshold decreased with increasing particle size, and was 850, 670 and 420 mJ/cm2 for 2, 5, 10 μm-sized PLGA particles loaded with 35 nm GNPs, respectively. Cell culture studies, including passive uptake by the cancer cells and mechanical damage to the cancer cells caused by the vaporization inside the cells are also investigated. These agents show potential as photoacoustic imaging contrast and cancer therapy agents for clinical applications.

Investigation on Rod Bundle CHF Mechanistic Model for DNB and DO Prediction Under Wide Parameter Range

For a water cooled reactor, the key thermal-hydraulic parameters span a wide range corresponding to different CHF regimes. Under accident conditions, due to the flow regime transition and interchannel mixing effect, the corresponding CHF can transition from the DO to DNB regime. In order to continuously and accurately predict DNB and DO regime CHF under wide parameter range for rod bundle channel, a comprehensive CHF mechanistic model covering the DNB and DO regime CHF prediction is established based on the rod bundle CHF-regime criterion. The DNB regime CHF mechanistic model of superheated liquid layer depletion under turbulence fluctuation bubbles and the mature DO regime CHF mechanistic model are combined to form the comprehensive CHF model. Furthermore, the comprehensive CHF model is assessed by 5 × 5 rod bundle CHF experimental data independently obtained by the Nuclear Power Institute of China (NPIC). The statistical evaluation and parametric trend analysis show that the maximum mean error of P/M is within ±22%, and the local pressure, mass flux, and quality do not have any effects on the average deviations of the predicted flux P from the measured flux M. This indicates that the comprehensive CHF mechanistic model can accurately and continuously predict the DNB and DO regime CHF in the rod bundle channel.

Analytical solution of integro-differential equations describing the process of intense boiling of a superheated liquid

In this article, an approximate analytical solution of an integro-differential system of equations is constructed, which describes the process of intense boiling of a superheated liquid. The kinetic and balance equations for the bubble-size distribution function and liquid temperature are solved analytically using the Laplace transform and saddle-point methods with allowance for an arbitrary dependence of the bubble growth rate on temperature. The rate of bubble appearance therewith is considered in accordance with the Dering-Volmer and Frenkel-Zeldovich-Kagan nucleation theories. It is shown that the initial distribution function decreases with increasing the dimensionless size of bubbles and shifts to their greater values with time.

Effect of Heat Transfer on the Growing Bubble with the Nanoparticles/Water Nanofluids in Turbulent Flow

This paper is devoted to study the effect of heat transfer on the temperature distribution in a superheated liquid during the growth of vapour bubbles immersed in different types of nanoparticles/water nanofluids between two-phase turbulent flow. The mathematical model is formulated and solved analytically depending on Scriven's theory and using the modification of the method of the similarity parameters between two finite boundaries. The characteristics of vapour bubble growth and temperature distribution are obtained by using the thermo-physical properties of nanoparticles nanofluids. The results indicate that the nanoparticle volume concentration reduces the bubble growth process under the effect of heat transfer. The better agreements are achieved, for bubble dynamics in turbulent nanofluid using the appropriate numerical and theoretical data for the values of concentration rate of nanoparticles χ=0,0.2,0.4. The temperature distribution surrounding the regime of bubble growth in pure water is more intensive than in other cases of Al2O3/H2O, Fe3O4/H2O and CuO/H2O nanofluids in turbulent flow. A Comparison of the current solution with previous works is carried out and discussed.