Wet-steam region

We shall now integrate this expression from the saturated ft-versus-s line into the superheated region, and then consider separately the case of the wet-steam region. 

The integration of equation (16.70) along a line of constant pressure in the wet-steam region is extremely easy, because constant pressure implies constant temperature. Hence we have ... 

III TVvo phase (wet steam) region B Bubble point line... 

It can be seen that the end point of the expansion (point 2 ) is in the area of wet steam. Thus small droplets of condensate will form in the motive jet. In the motive nozzle, combined with the decrease of pressure, the temperature will also decrease. In the wet steam region the steam is cooled to the boiling point temperature corresponding to the pressure. When the motive steam expands to a pressure lower than 6mbar, the corresponding temperature is below 0°C, thus ice will form. Steam jet vacuum pumps for such applications are often heated at the mixing nozzle and sometimes also at the motive nozzle, to prevent the ice crystals from adhering to the internal wall. This would cause a constriction of the cross-sectional area and adversely effect the flow. 

The region to the right of the vapor-pressure curve in Fig. 3.9 is called the superheated region and the one to the left of the vapor-pressure curve is called the sub-cooled region. The temperatures in the superheated region, if measured as the difference (0-N) between the actual temperature of the superheated vapor and the saturation temperature for the same pressure, are called degrees of superheat. For example, steam at 500 F and 100 psia (the saturation temperature for 100 psia is 327.8°F) has (500 — 327.8) = 172.2 F of superheat. Another new term you will find used frequently is the word quality. A wet vapor consists of saturated vapor and saturated liquid in equilibrium. The mass fraction of vapor is known as the quality. 

In Figure 1.69 an example of a conventional DT top-view is shown (oval shape) after collar oxide formation (black region) and DT fill with a highly doped poly-Si. The thermal oxide formed shows a strong dependence on the crystal orientation of the Si surface. This holds true for all oxidation modes, for example, dry and wet oxidation (in the wet -oxidation mode there is a carefully adjusted addition of FI2O as steam to the oxidation chamber resulting in an increased oxidation rate). This also holds true for... 

The value of specific enthalpy in the wet region will be less than the specific enthalpy of saturated steam, being equal to the weighted average of the specific enthalpies of saturated steam and saturated water ... 

In the BWR plants, the out-of-RPV surfaces which are subject to contamination during steady-state operation are mainly those wetted by high-temperature reactor water. These are, in the main, the pipes leading to the reactor water cleanup system and the recirculation lines (as far as the plant is equipped with an external recirculation system). In addition to these surfaces, the main steam lines and the turbine, as well as part of the feedwater system, may be contaminated by radionuclides carried with the steam. In the course of a shutdown of the plant, certain regions of the main steam lines and of the feedwater lines are also in contact with low-temperature reactor water containing radionuclides. 

The turbine is supplied with steam from the reactor at saturation temperature so that the expansion of the steam lies wholly in the wet region. Furthermore, since the steam is generated in the high neutron flux of the reactor core, it is radioactive and special account had to be taken of these two features in the design... 

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