Boiling fully developed

Zhao YH, Masuoka T, Tsuruta T (2002) Unified theoretical prediction of fully developed nucleate boiling and critical heat flux based on a dynamic microlayer model. Int J Heat Mass Transfer 45 3189-3197... 

The relationship between the wall temperature and the coolant temperature can be seen in Figure 4.5. The wall temperature starts to bend at the incipience of subcooled boiling, where the coolant temperature is defined as Tm. The wall temperature follows a curve of partial boiling and then reaches an approximately constant value at a fully developed nucleate boiling where the coolant temperature... 

Fully developed nucleate flow boiling. In fully developed nucleate flow boiling, the heat flux is affected by pressure and wall temperature but not by flow velocity. The difference between the wall temperature and the coolant temperature has been found to be constant for a given p and q" by several investigators. For a relatively clean surface, this difference is (Thom et al., 1966)... 

Liquid core temperature and velocity distribution analysis. BankofT (1961) analyzed the convective heat transfer capability of a subcooled liquid core in local boiling by using the turbulent liquid flow equations. He found that boiling crisis occurs when the core is unable to remove the heat as fast as it can be transmitted by the wall. The temperature and velocity distributions were analyzed in the singlephase turbulent core of a boiling annular flow in a circular pipe of radius r. For fully developed steady flow, the momentum equation is given as... 

The stripping of fully developed azoic dyeings can often be carried out using a hot solution of sodium hydroxide (1.5-3 g/1), sodium dithionite (3-5 g/1) and a surfactant addition of anthraquinone (0.5-1 g/1) generally increases the effectiveness of the process. Yellow azoic dyeings are resistant, however, and can only be partially stripped [30]. On the other hand, stripping of naphtholated material before it has been coupled with the diazo component can be done quite effectively in boiling alkali. 

Table A-2 Boiling and freezing point properties 843 Table A-3 Properties of solid metals 844 846 Table A-4 Properties of solid nonmetals 847 Table A-5 Properties of building materials 848-849 Table A-6 Properties of insulating materials 850 Table A-] Properties of common foods 851-852 Table A-8 Properties of miscellaneous materials 853 TableA-9 Properties of saturated water 854 Table A 10 Properties of saturated refrigerant-134a 855 Table A-11 Properties of saturated ammonia 856 Table A-12 "Properties of saturated propane 857 Table A-13 Properties of liquids 858 Table A-14 Properties of liquid metals 859 Table A- 5 Properties of air at 1 atm pressure 860 TableA-16 Properties of gases at 1 atm pressure 861-862 Table A-17 Properties of the atmosphere at high altitude 863 Table A-18 Emissivities of surfaces 864-865 Table A-19 Solar radiative properties of materials 866 Figure A-20 The Moody chart for friction factor for fully developed flow in circular pipes 867...

Fig. 5 Boiling in a narrow vertical tube. (A) Boiling suppressed by head, natural convection is shown (B) bubble formation (C) slug formation due to bubble coagulation (D) fully developed slug flow (E) breakdown of slugs at high vapor rates (F) annular-flow-climbing film.

Measurements for water in the region of fully developed nucleate boiling with heat fluxes between... 

Another example of chemical decladding is afforded by the Zirflex process, which was proposed for zircaloy-clad UOj fuel before mechanical decladding was fully developed. In the Zirflex process [S17], zirconium or zircaloy cladding is dissolved as ammonium fluozirconate in a boiling solution of ammonium fluoride containing ammonium nitrate, the latter added to reduce hydrogen evolution. Overall reaction is approximately... 

An important technique in studying the mechanism of fully developed boiling is to use electrical conductance probes that can be traversed from the bulk fluid to the surface. A tiny needle tip (typically less than 50 pm in diameter) will record the local presence of liquid or vapor, and the fraction of time spent in contact with the vapor gives the void fraction, typical of the measurements of this type are those of Shoji [100], illustrated in Figs. 15.49 and 15.50. 

Liquid is drawn into this meniscus mainly as a result of the decrease in the radius n in the direction of the axis of the vapor stem. The effect of disjoining pressure were also considered in the analysis but was of less importance. The principal evaporation then occurs in the meniscus region. The analysis was reasonably successful in predicting the fully developed boiling region. 

Macrolayer consumption model. Here it is postulated that the macrolayer formed under the vapor mushrooms in fully developed boiling (see Fig. 15.48) is totally evaporated in the time between the release of the mushroom-shaped bubbles. 

Here q" is the heat flux and BR is the boiling range (difference between dew point and bubble point temperatures, K). The factor Fb has values typically in the range of 1.0-3.0. At heat fluxes typically above 50 kW/m2, Fb is close to unity since the heat transfer is often in the fully developed boiling mode where convection has little effect. However, commercial kettle reboilers and flooded evaporators work typically in the range of 5-30 kW/m2 and a typical Fb value for this range would be 1.5. Alternatively, Fb can be calculated from the following approximate formula from Taborek [217] ... 

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