Subcooling region

The graphical correlation shown in Figure 5.30 was originally developed for a steam-water mixture of high quality. Coffield et al. (1967) extended its validity into the subcooled region by comparing their subcooled Freon-113 DNB data with... 

Bowring, R. W., 1962, Physical Model, Based on Bubble Detachment and Calculation of Steam Voi-dage in the Subcooled Region of a Heated Channel, Inst, for Atomenergie Rep. HRP-10, Oslo, Norway. (3)... 

Again, over the subcooled region from q0 to ip, de is zero and e is constant at unity, e0. The solutions for the two cases are as follows ... 

Applicable to subcooled flashing liquid, including saturated, without vapour or gas. Depending on the subcooling region of the liquid at the inlet of the valve,... 

Determine the transition saturation pressure ratio for low or high subcooling region ... 

Ps > rjslP => Low subcooling region (flashing starts upstream of the nozzle)... 

Draw a p-T chart for water. Label the following clearly vapor-pressure curve, dew-point curve, saturated region, superheated region, subcooled region, and triple point. Show where evaporation, condensation, and sublimation take place by arrows. 

You can find the region in which a particular state lies by referring to one of the two tables for saturation properties. If, at the given T or P, the given specific intensive property lies outside the range of properties that can exist for saturated liquid, saturated vapor, or their mixtures, the state must be in either the superheated or the subcooled region. For example, look at a brief extract from the steam tables in SI units ... 

In a recirculation boiler system, see Figure 12.2, the feedwater is normally fed through sparge pipes into the steam drum, where the downward-pointing spargers encourage the formation of a subcooled region. A mixture of subcooled and saturated water is then drawn... 

To a good approximation, we may treat the subcooled region as having a constant volume of the order of 10% of the liquid volume in the drum. It may be treated as separate from the equilibrium thermodynamics of the steam drum. It may be regarded as an extension of the downcomer, with its volume added to that of the downcomer pipework in order to work out a downcomer time delay. 

The subcooM region is modelled separately along with the downcomer pipework. As far as the drum model is concerned, its sole contribution comes in determining liquid level, where it adds a constant term to the liquid volume. As mentioned previously, the subcooled region may make up typically about 10% or less of the water volume of the drum, and so its effect on steam drum dynamics is second-order only. 

Grace, T.M., Krejsa, E.A., 1967. Analytical and Experimental Study of Boiler Instabilities Due to Feed-system — Subcooled Region Coupling. National Aeronautics and Space Administration Report NASA TN D-3961. 

In the hot channel case, the graph includes the saturation temperature that has been partly exceeded by the clad surface temperature with the result of subcooled boilii. The subcooled region is specified by exceeding the heat flux at onset of nucleate boiling (margin to ONB 0.69). In case of die average channel, the clad surface temperature does not reach the saturation temperature that indicates one phase liquid cooling as Fig. 4 shows. 

In the subcooled region, Zauloudeck s correlation is used [23], Mass flux ... 

Low subcooling region This region is defined when the flashing occurs upstream of the throat. 

Critical flow. The critical flow condition depends on the subcooling region. 

Chapter four Overpressure protection Low subcooling region. 

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