Session K.pdf - Clarkson University

tive withdrawal the efficiency of the impurities removal is about 10 % higher than withthe active one. If there are a few withdrawals, this fact allows cleaning the area underthe withdrawal cap when one of the withdrawals is inactive. Using this model and thegiven size of the strainer more than 60 % of the impurities can be removed from underthe withdrawal cap in this way.The influence of the umbrella ceiling position in reference to the collector position isseen well in fig.3. The analysis of the given curves shows that the removal of the ‘umbrella’ceiling 0,08 m from the strainer level leads to the extremely low efficiency of the‘round-about’ (the emission of the particles is about 30 %). The reduction of the distanceto 0,05 m increases the efficiency almost twice. The further reduction of this distanceto 0,03 m does not practically influence the efficiency. Three different verticalpositions of the tangential-oriented nozzles of the ‘hydraulic round-about’ were tested,which showed the lower position was impractical, since the jets went from under the‘umbrella’ without creating the effect of water acceleration under the withdrawal cap.As to the upper position, in this case the nozzles were situated too close to the strainerswindows that made extra impurities get inside the system. After that all the further testswere performed with the middle position of the nozzles. In addition two positions of thenozzles along the ‘umbrella’ diameter were tested: in 5cm from the ’umbrella’ edge andclose to the collector pipe. The latter position proved to be ineffective. In the test theparticles moved actively vertically, but the absence of the horizontal movement did notdrive the particles from the strainer. That is why the main and recommended position ofthe nozzles close to the ‘umbrella’ edge was chosen.The impurities fromunder withdrawal cap, %7060504030201000 0,05 0,1 0,15The concentration of the impuritiesdistance 5,15 sm;distance 3,16 sm;distance 8,00 smFig.3. The dependence of emission of impurities from under the withdrawal cap in percentfrom their concentration in the flow with different positions of the cap over the activewithdrawal and the water discharge of the ’hydraulic round-about’ 0,24 l/secThe developed type of the strainer does not allow suspended impurities and frazil to getinside the system. Supercooled water, however, can get there freely. For controlling thefrazil formation inside the water supply system, collector well heating is proposed touse to avoid supercooling. Different kind of wells can be used for this purpose, where ablock of heaters can be installed. Crystallization starts when supercooled water gets intothe pipe leading from the strainer to the collector well. As frazil particles grow they beginto flow up. The size of ice particles, when the process of their flowing up starts isdefined by the expressions given in (Zakharov, Beilison, Shatalina, 1972) at the flowspeed 1,23 m/sec and Shezy coefficients 40,9 m 0,5 /sec. According to those relations the340