Bubble condensation

The subcooled core bubble-layer liquid exchange and bubble condensation analysis was suggested by Tong (1975). 

The spacer grid in a rod bundle is also a turbulence promoter that enhances liquid-vapor exchange and bubble condensation. The local intensity of such turbulence is a function of the grid pressure loss coefficient, K, and the distance from the grid, t D. Thus an empirical spacer factor, Fs, can be defined as... 

These different approaches are complementary to each other in basic concept. However, these analyses have not provided clear insight information of the bubble layer at the CHF about the bubble shape (spherical or flat elliptical), bubble population and its effect on turbulent mixing, and bubble behavior. The bubble behavior in a bubble layer could involve bubble rotation caused by flow shear, normal bubble velocity fluctuation, and bubble condensation in the bubble layer caused by the subcooled water coming from the core. Further visual study and measurements in this area may be desired. 

The bubble layer is assumed to have constant void fraction along the length before DNB, with a balanced rate of bubble detachment and bubble condensation in the layer. Hence, the average properties p, p, and c of the bubble layer are assumed to be independent of position. 

W-3 CHF correlation. The insight into CHF mechanism obtained from visual observations and from macroscopic analyses of the individual effect of p, G, and X revealed that the local p-G-X effects are coupled in affecting the flow pattern and thence the CHF. The system pressure determines the saturation temperature and its associated thermal properties. Coupled with local enthalpy, it provides the local subcooling for bubble condensation or the latent heat (Hfg) for bubble formation. The saturation properties (viscosity and surface tension) affect the bubble size, bubble buoyancy, and the local void fraction distribution in a flow pattern. The local enthalpy couples with mass flux at a certain pressure determines the void slip ratio and coolant mixing. They, in turn, affect the bubble-layer thickness in a low-enthalpy bubbly flow or the liquid droplet entrainment in a high-enthalpy annular flow. 

Rate of bubble condensation Pi Viscosity of Phase i (centipoise... 

However, as experiment shows, supersaturated systems under pure conditions, in the absence of the phase with respect to which the system is unstable (bubbles, condensate drops, small crystals in the examples given), turn out in practice to be quite stable within a rather broad range. 

Meier M, Andreani M, Smith B, Yadigaroglu G (1998) Numerical and Experimental Study of Large Stream-Air Bubbles Condensing in Water. Proc Third Int Conf Multiphase Flow, Lyon, June 8-12... 

Solution When the first drop condenses the system is at the dew point, D. If we draw the tie line at D, the composition of the first drop is read at the intersection of the tie line with the bubble line. We find jc, 0.13. When the last bubble condenses the system is at the bubble point, B. The corresponding composition is y, 0.9. 

Fig, 15,1 Heat flux data from an electrically heated platinum wire in water [2]. (a) Pure convection heat transferred to water/air interface where evaporation occurs (b) Nucleate boiling bubbles condense in super-heated liquid (c) Nucleate boiling bubbles rise to surface (d) Partial nucleate boiling and unstable nucleate film (e) Stable film boiling (0 Radiation coming into play. 

DRASYS performed continuously PHARE 2.13, Bubble condenser qualification LBLOCA... 

The sample stream originates from the process through a sample probe. The probe is inserted through a process valve into the center of the process stream. This provides a representative sample by minimizing the effects of laminar flow, gas bubbles, condensed liquids, and particulates. 

As shown, reasonable temperature stability of the liquid cryogen permitted data collection over the full range of conditions consistent within facility limitations. Greater stability was achieved in LN2 over LH2 due to the warmer saturation temperature. Greater temperature stability of the liquid was achieved using the non-condensable pressurant over the condensable pressurant. Continuous condensable pressurant gas operation tended to warm the liquid more rapidly due to warm GH2 vapor bubbles condensing into the liquid as testing proceeded. 

ABSTRACT The paper presents an application of the probabilistic analysis of structural resistance of the containment of a VVER 440/213. The evaluation is based on an extension of the smeared crack model developed on the basis of Kupfer s bidimensional failure criterion and implemented into ANSYS. The non-linear analysis is considered for the median values of the input data and the probabilistic analysis models the uncertainties of loads, material resistance and other modeling issues. Results show that the effects of thermal load are relevant mainly for the bubble condenser and at the interface between the floor of hermetic zone and the rooms beneath. A comparison of the performance of linear and non-linear analyses is also reported. 

The overpressure in the containment can arise after a loss-of-coolant accident initiating event or a progression of an accident to severe accident conditions (after primary depressurization). In such cases, the primary steam is released in the hermetic zone and expands from the reactor hall to the bubble condenser. 

The NPP buildings with the reactor VVER 440/213 consists the turbine hall, middle building, reactor building and bubble condenser (Fig. 1). 

Figure 4.77 WER 440/213 containment building with the bubble condenser...

Figure 4.78 Diagram of the bubble condenser system used in the containment...

As we approach the triple pressure, the free energy difference between metastable liquid solvent and stable solvent-vapor decreases, and bubble condensation occurs... 

Kato, M. Konishi, H. Sato, T. Hirata, M. Measurement of vapor-liquid equilibriums by the dew-bubble point method and the bubble condensation point method. J. Chem. Eng. Jpn. 1971, 4, 6-10. 

W. Tian, Y. Ishiwatari, et al., Numerical Computation on Thermally Controlled Steam Bubble Condensation Using MPS-MAFL, Proc. 4th Int. Symp. on SCWR, Heidelberg, Germany, March 8-11, 2009, Paper No. 05 (2009)... 

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