Calculation suction side
Widespread use of onboard suction in the industry began in the 30's. Then there were the first theory of the suction and the first formula for calculating them. The pioneers in this business were engineers Vivarelli and Bromley. Their proposed formulas designed to calculate the suction side of plating and pickling baths.
One of the first was proposed formula Ing. Bromley. derived them based on a formula Delavallya and has the form:
- KG, 7x (63)
where vx - speed in the "critical" section at a distance x from the suction gap in% of the needs of the velocity v in the gap;
A - a coefficient of 0.05 with respect to the width
slit to length 1:10; F - cross-sectional area of one suction slot in m2 x - distance from the slot to "critical" section in m for a one-sided suction x = b, for bilateral l = 0,5 b, where b - width of the mirror bath. Is defined by (63) value of i \. in% relative to the velocity v and the gap in wondering required in this case, the speed v / in m / sec in the "critical" section (ie, at the end of exhaust plume), the value of the required speed in the gap v find the words
f -100 v =- [m / sec],
where the silt. - Speed, expressed in%; vx - speed in m / sec. According to the rate found in the suction slit v (in m / sec) and the total area of the suction slots f (m2) calculated the air volume L, removed on-board suction from the bath:
L = 3600 / u [m3 / h]. (64)
Bromley formula gives a good result, if correct wonder velocity vx, ie, the finite speed of the torch. In special cases, for values of vx, less than 5%, the formula gives an exaggerated value of the velocity v in the slot suction.
To calculate the suction side of the plating and pickling baths formula Bromley currently does not apply. Io, it can be used in calculating the suction from the tables, trays, etc., why bring it here.
To facilitate the calculation formula is given in Table Bromley. 21, containing auxiliary quantities.
Calculated using the formula Bromley suction side of the chute for slag under the following conditions: temperature of the slag 900 В° C; off gases harmful to the allowable concentrations to 1 mg/m5 the breadth of the gutter 6 = 500 mm, length is not sheltered parts / = 2,1 m.
Takes the usual one-sided cell exhaustion, the length of one section of 700 mm total length 2100 mm suction; slit height h = 60 mm. In this case
F = 0,7-0,06 = 0,042 m 2, x = b 0,5 m K - 0,05; f - 2,1-0,06 - 0,126 m2.
The result can be declared admissible. However, the height of slit suction should have taken about 100 mm.
Charts Leningrad Promstroyproject to calculate conventional suction side, made by processing the experimental and theoretical material, appeared in the late 40's. The calculation of these graphs is very simple and gives good results.
In Fig. 25 shows graphs 11rometronproekta to calculate the unilateral and bilateral suction depending on the length of baths A and B. The graphs cross the width directly gives the volume of air (Martyrs), remove the onboard suction from the bath. In this case, it is assumed that the finite speed of the suction jet into the "critical" section with. = 0.2 msec. For other values of the finite speed of plume volume of air obtained from the graph, multiplied by a coefficient k. If the volume of exhaust air produced on schedule, denoted L, the estimated amount of L expressed as:
L = kL m
In some cases, relatively harmless baths take the final torch speed (m / sec) less than 0,2 m / sec. In this case, k <\:
A 0.15 ........./e-0, 75
to 0,1 вЂў ........ k - 0,5
The received when calculating the final velocity of the torch, depends on the toxicity of harmful substances on the mirror bath and the temperature of the liquid. The more toxic than isolation and a higher temperature has a solution, the more value is vK.
Table. 22 is a list of electroplating and pickling baths, indicating the composition of the solution, its temperature, the pollutant emitted and the recommended minimum final velocity jet vu in m / sec.
Table. 22 but drawn to different sources.
Define the graphs Promstroyproject volume of air that is needed to suck from the bath chrome: / = 1,5 m /.> = 0,8 m = 60 В° C. Receives IR = 0,5 m / sec. The volume of air on the schedule for bilateral aspiration for / 1 = 1500 mm and B = 800 mm
L = g 2200 m3 / h.