Subcooled water

A boiler bank is also included. The boiler-bank tube bundle provides sufficient heat transfer surface area to provide the rated capacity for saturated steam. Boiler-bank tube spacing and dimensions are arranged so that a steam-water circulation subsystem connects the top and bottom drums with subcooled water passing down the tubes farthest from the furnace and returning as a steam-water mixture. 

Parameters 7c,onb, s.onb, and 74,onb change in the range of 0 < 7 < 1. They account for a specific temperature field in heated micro-channels and are criteria for the relative micro-channel length. Note, if 7 < 1 the value of parameter 7 is significantly less than unity. The paper by Celata et al. (1997) reports the results of experimental research of the onset of subcooled water boiling in the circular... 

Carey van P (1992) Liquid-vapor phase-change phenomena. An introduction to the thermophysics of vaporization and condensation processes in heat transfer equipment. Hemisphere, New York Celata GP, Cumo M, Mariani A (1997) Experimental evaluation of the onset of subcooled flow boiling at high liquid velocity and subcoohng. Int J Heat Mass Transfer 40 2979-2885 Celata GP, Cumo M, Mariani A (1993) Burnout in highly subcooled water flow boiling in small diameter tubes. Int J Heat Mass Transfer 36 1269-1285 Chen JC (1966) Correlation for boiling heat transfer to saturated fluids in convective flow. Ind Eng Chem Process Des Develop 5 322-329... 

Mudawar I, Bowers MB (1999) Ultra-high critical heat flux (CHF) for subcooled water flow boiling. I CHF data and parametric effects for small diameter tubes. Int J Heat Mass Transfer 42 1405-1428... 

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. 

Other data were obtained from subcooled water flowing through small tubes (0.08-0.12 in. or 0.2 to 0.3 cm in diameter) at pressures ranging from 290 to 2,900 psia (2.0 to 20 MPa) (Povarnin and Semenov, 1960). This correlation, coupling the pressure effect with local subcooling, is in the form... 

Effect of surface roughness. CHF for rough surfaces was measured on vertical annular tubes cooled by a downward flow of subcooled water by Durant and Mirshak (1959, 1960). An increase in the apparent critical heat flux of as much as 100% over a smooth surface was obtained at the same coolant velocity, temperature, and pressure. The heated surfaces were 304 SS and Zircaloy-2 tubes about... 

Enhancement of CHF subcooled water flow boiling was sought to improve the thermal hydraulic design of thermonuclear fusion reactor components. Experimental study was carried out by Celata et al. (1994b), who used two SS-304 test sections of inside diameters 0.6 and 0.8 cm (0.24 and 0.31 in.). Compared with smooth channels, an increase of the CHF up to 50% was reported. Weisman et al. (1994) suggested a phenomenological model for CHF in tubes containing twisted tapes. 

Katto, Y., 1992, A Prediction Model of Subcooled Water Flow Boil-CHF for Pressures in the Range of 0.1-20.0 MPa, Int. J. Heat Mass Transfer 35 1115-1123. (5)... 

Povarnin, P. I, and S. T. Semenov, 1960, An Investigation of Burnout during the Flow of Subcooled Water through Small Diameter Tubes at High Pressures, Teploenergetika 7(l) 79-85. (5)... 

Sozzi, G. L., and W. A. Sutherland, 1975, Critical Flow of Saturated and Subcooled Water at High Pressure, in Non-equilibrium Two-Phase Flows, R. T. Lahey and G. B. Wallis, Eds., ASME, New York. (3)... 

Tarasova, N. V., A. I. Leontiev, V. I. Hlopushin, and V. M. Orlov, 1966, Pressure Drop of Boiling Subcooled Water and Steam-Water Mixture Flow in Heated Channels, Proc. 3rd Int. Heat Transfer Conf, vol. 4, pp. 178-183, ASME, New York. (3)... 

Thom, J. R. S., W. M. Walker, T. A. Fallon, and G. F. S. Reising, 1966, Boiling in Subcooled Water during Flow up Heated Tubes or Annuli, Proc. Inst. Mech. Eng. 180(Part 3C). (3)... 

Vliet, G. C., and G. Leppert, 1962, Critical Heat Flux for Subcooled Water Flowing Normal to a Cylinder, ASME Paper 62-WA-174. Winter Annual Meeting, ASME, New York. (5)... 

Zenkevich, B. A., and V. 1. Subbotin, 1959, Critical Heat Fluxes in Subcooled Water Forced Circulation, J. Nuclear Energy, Part B, Reactor Technol. 7.134-140. (5)... 

Meanwhile, the tubes covered with stagnant water would begin to cool. The steam condensate itself around these tubes would cool. This cooled water would be colder than the saturation temperature of the condensing steam. The tubes would then be said to be submerged in subcooled water. 

FIG. 26-63 Discharge mass flux for highly subcooled water (20°C) from orifice and 4-mm pipe of various lengths. Data of Vchida and Narai, 1966 reproduced by permission of ASME.)... 

Figure 22 is typical for the bubble behavior with no forced convection. The sizes of the bubbles decrease rapidly as the liquid temperature is decreased. For water at 60°F., the bubbles are about 12% of the size at 195°F. The lifetime of a bubble in water at 60°F. is only 2 or 3% of that in water at 195°F. There is good visual evidence that the rapid growth and collapse of tiny bubbles in greatly subcooled water causes strong convection near the hot solid. 

V. I. Gomelauri and T. S. Magrakvelidze, Mechanism of Influence of Two Dimensional Artificial Roughness on Critical Heat Flux in Subcooled Water Flow, Therm. Eng. (25/2) 1-3,1978. 

J. Kokado, N. Hatta, H. Takuda, J. Harada, and N. Yasuhira, An Analysis of Film Boiling Phenomena of Subcooled Water Spreading Radially on a Hot Steel Plate, Archivfiir Eisenhiittenwesen, 55, pp. 113-118,1984. 

GIO. Gunther, F. C., and Kreith, F., Photographic Study of Bubble Formation in Heat Transfer to Subcooled Water. Jet Propulsion Lab., Cal. Inst. Tech., Pasadena, California, Progr. Rept. No. 4-120, 1950. 

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