Session K.pdf - Clarkson University

The position of the section of maximum intensity of frazil formationanalogously withxmaxx m. f, but using β m. f instead of β f . max in formula (2)is calculated23β m.f = Y − Px.max, (5)Y = U 1 + U 2 , (6)3 2 21 2 w1± w1w 2U , = + , (7)2⎛⎞⎜cvQw 1 = P⎟x . max0,296 Px.max − 0,67 −2, (8)⎝α1b⎠2( 3 )w = + , (9)2 −0,22 P x .max 2 Px.maxc v – volumetric thermal capacity; Q – river water discharge.The water temperature in the stretch between the section of maximum supercooling andmaximum frazil formation intensity can be found with help of the relation (Tregub, 1997):( 1− β )⎛xx⎞max⎜ α b1 f ⎟⎧1t = exp −∫ dx ⎨ ∫ [ α b ( 1−β) ϑ +1⎜ ⋅ ⎟f ec⎝ 0v Q⎠⎩cvQ0( 1−β)⎛xmax⎞ ⎫2⎪]⎜ α1b f+ L ⋅ β⎟v.f v hbf exp⎜ ∫dx⎟dx⎬. (10)cvQ⎝ 0⎠ ⎪⎭The frazil discharge which can get into the withdrawal Q f.w is calculated on the basis ofthe assumption that after getting into the strainer the water supercooling disappearscompletely:cvQw⋅ ∆ tQ f .w = − . (11)LWhere Q w – water discharge coming into the strainer; ∆t – water supercooling comparedwith 0 C. The given formulas were used for calculation of water supercooling andºfrazil discharge on the section of the strainers.There have been tried a lot of ways to prevent frazil getting into withdrawals (e.g. withusing compressed air, electrical heating of the strainer windows). But as a rule thoseways are too expensive and consume great quantity of energy for heating. Even in caseof avoiding ice formation on the strainer windows, supercooled water gets inside andafter crystallizing into frazil it blocks the water-supply system. As a result of a scientificanalysis of different protections a hydraulic way of preventing frazil and other impuritiesgetting into withdrawals was chosen, which allowed creating an umbrella-like typeof strainers with a hydraulic vortex motion under the withdrawal cap.Using hydraulic vortex motion for controlling oil impuraties and frazil. Using hydraulicway of controlling impurities and frazil at the strainers is based on the creation avortex motion at the withdrawal entry. This motion keeps different type of floating im-337v. f