Boiling loop

Bakstad, P., and K. O. Solberg, 1968, RAMONAI A Fortran Code for Transient Analyses of Boiling Water Reactors and Boiling Loops, KR-135, U.K. Atomic Energy Research Establishment, Harwell, England. (3)... 

Figure 9. Sections of condenser leg of boiling loop (see Figure 8) Note mass-transfer crystals in cold trap...

Jain, K.C., 1965. Self-Sustained Hydrodynamic Oscillations in a Natural-circulation Two-Phase-Flow Boiling Loop. Argonne National Laboratory Report ANL-7073. 

Most nuclear reactors use a heat exchanger to transfer heat from a primary coolant loop through the reactor core to a secondary loop that suppHes steam (qv) to a turbine (see HeaT-EXCHANGETECHNOLOGy). The pressurized water reactor is the most common example. The boiling water reactor, however, generates steam in the core. 

Phosphorus(III) Oxide. Phosphoms(III) oxide [12440-00-5] the anhydride of phosphonic acid, is formed along with by-products such as phosphoms pentoxide and red phosphoms when phosphoms is burned with less than stoichiometric amounts of oxygen (62). Phosphoms(III) oxide is a poisonous, white, wax-like, crystalline material, which has a melting point of 23.8°C and a boiling point of 175.3°C. When added to hot water, phosphoms(III) oxide reacts violentiy and forms phosphine, phosphoric acid, and red phosphoms. Even in cold water, disproportionation maybe observed if the oxide is not well agitated, resulting in the formation of phosphoric acid and yellow or orange poorly defined polymeric lower oxides of phosphoms (LOOP). 

PWRs operate differendy from BWRs. In PWRs, no boiling takes place in the primary heat-transfer loop. Instead, only heating of highly pressurized water occurs. In a separate heat-exchanger vessel, heat is transferred from the pressurized water circuit to a secondary water circuit that operates at a lower pressure and therefore enables boiling. Because of thermal transfer limitations, ultimate steam conditions in PWR power plants ate similar to those in BWR plants. For this reason, materials used in nuclear plant steam turbines and piping must be more resistant to erosion and thermal stresses than those used in conventional units. 

Sodium is used as a heat-transfer medium in primary and secondary cooling loops of Hquid-metal fast-breeder power reactors (5,155—157). Low neutron cross section, short half-life of the radioisotopes produced, low corrosiveness, low density, low viscosity, low melting point, high boiling point, high thermal conductivity, and low pressure make sodium systems attractive for this appHcation (40). 

The DTB, crystallizer has a relatively slow-speed propeller agitator located within a draft-tube which draws a fine-crystal suspension up to a boiling zone of wide cross-sectional area, as shown in Figure 3.3(i). The fine-crystal magma then passes through an annular zone in which an additional baffle is located. Liquor flow continues upwards at low velocity while crystals settle out and fall to the base of the vessel. Liquor from the external pumped loop provides an up-... 

The highly interactive nature of the balance and equilibria equations for the distillation period are depicted in Fig. 3.66. An implicit, iterative algebraic loop is involved in the calculation of the boiling point temperature at each time interval. This involves guessing the temperature and calculating the sum of the partial pressures, or mole fractions. The condition required is that Zyi + yw = 1. The iterative loop for the bubble point calculation is represented by the five interconnected blocks in the lower right hand corner of Fig. 3.66. The model of Prenosil (1976) also included an efficiency term E for the steam heating, dependent on liquid depth L and bubble diameter D. 

Use the test-tube clamp to hold the test tube vertically in the boiling water bath. Make sure all of the naphthalene is below the surface of the boiling water. When the naphthalene has melted, insert the rubber stopper assembly into the top of the test tube. CAUTION The test tube may be hot. The thermometer should be immersed in the naphthalene. The stirring wire should loop around the thermometer. Move the stirring wire up and down to stir the contents of the test tube. Stir the naphthalene as it is being heated until all of the naphthalene has melted. 

Top temperatures are usually controlled by varying the reflux ratio, and bottom temperatures by varying the boil-up rate. If reliable on-line analysers are available they can be incorporated in the control loop, but more complex control equipment will be needed. 

Flow boiling is distinguished f rom pool boiling by the presence of fluid flow caused by natural circulation in a loop or forced by an external pump. In both systems, when operating at steady state, the flow appears to be forced no distinction will be made between them, since only the flow pattern and the heat transfer are of interest in this section. 

Pressure drop oscillations (Maulbetsch and Griffith, 1965) is the name given the instability mode in which Ledinegg-type stability and a compressible volume in the boiling system interact to produce a fairly low-frequency (0.1 Hz) oscillation. Although this instability is normally not a problem in modern BWRs, care frequently must be exercised to avoid its occurrence in natural-circulation loops or in downflow channels. 

Gandiosi, G., 1965, Experimental Results on the Dependence of Transition Boiling Heat Transfer on Loop Flow Disturbances, GEAP-4725, General Electric, San Jose, CA. (6)... 

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