1246
INDUSTRIAL AND ENGINEERING CHEMISTRY
which i t was allowed to crystallize. After recrystallization from acetic acid, it was boiled with water, filtered, and washed free from acid. The material thus obtained was recrystallized from a mixture of benzene and ethyl alcohol and dried for 16 hours at 105" C. (221' F.). The dried material consisted of plates melting a t 285' C. (545' F.) and possessed an intensely bitter taste. Further recrystallization failed to change the melting point. Tests for phenol, higher ketones, nitrogen, halogens, and sulfur were negative. The material reduced Fehling solution at boiling temperature. The evidence seems to indicate that it is limonin which Bernay in 1841 found in the seeds of several varieties of citrus fruit
(0. Analysis: Calculated for C26H3008: C, 66.35; H , 6.43; C, 65.46; H, 6.87; 02,27.67.
27.22; found:
02,
VOL. 32, NO. 9
AcknowIedgment We are indebted to the Citrus Seed Oil Corporation of Winter Haven, Fla., for the crude grapefruit seed oil used in these experiments, and to E. K. Nelson, U. S. Department of Agriculture, Washington, D. C., for the analysis of the bitter principle.
Literature Cited (1) B e r n a y , Ann., 40, 317 (1841). (2) J a m i e s o n , B a u g h m a n , and Gertler, Oil & Fat Industries, 7, No. 5 , 181 (1930). PRESENTED as part of the Symposium on the Utilization of -4gricultursl Wastes before the Division of Agricultural a n d Food Chemistry at t h e 99th hleeting of the American Chemical Society, Cincinnati, Ohio. Contribution 479 from the Food Research Division, Bureau of Agricultural Chemist r y and Engineering, U. S. Department of Agriculture.
Flow Pattern and Pressure Drop in Cvclone Dust Collectors I
N THE earlier paper on
Cyclone without Inlet Vane
termined at a level 3 inches this subject ( 2 ) data on a b e n e a t h the gas exit duct (designated as position 2 in 12-inch glass model the previous tests, 2 ) . All cyclone were reported showC. B. SHEPHERD' AND C. E. LAPPLE readings were taken with the ing the effect of cyclone proportions on the fluid friction loss E I. du Pont de Nemours & Company, Inc., Wilmington, Del. Pitot tube tip in a horizontal position normal to a cyclone and on the flow pattern within radius. Except where otherthe cyclone. I n these tests the wise noted, the Pitot tube concyclone inlet contained a variThe friction loss in a cyclone was observed sisted of two adjacent copper able inlet vane which projected to increase twofold when the cyclone inlet tubes, 1/'16 inch in diameter. halfway into and across the vane employed in the previous tests was The tip of the impact tube and cyclone cylinder along a chord shortened so that no part of it extended the static tube were both 3/4 (Figure 1). The present tests inch long, the latter having a were conducted to determine into the cyclone chamber. Spiral velocities sealed streamlined face pointthe validity of a claim made within the cyclone reflected a corresponding ing into the air stream. Eight by Alden (I) that the use of a increase. Velocity traverses made with an holes of approximately 0.02 deflector vane a t the cyclone improved Pitot tube indicated that for inch diameter were arranged inlet reduced the cyclone preslarger radii the spiral velocity increased in pairs spaced at 90" around sure drop by more than 50 the tube. The static holes in per cent. The same general approximately as the inverse square root each pair were 0.2 inch apart equipment and experimental of the radius; but at a radius of approxiand were spaced to l/z inch .arrangement shown in Figures mately one third that of the cyclone cylinfrom the impact opening. 1, 2, and 3 of the earlier article der, the spiral velocity began to decrease The results of the pressure (2) were employed, with the as the radius decreased. drop measurements are given exception that the variable inin Table I, and the results of let vane was cut off so that no the velocity distribution measDart of it extended into the urements, in Table 11. I n all cases the nomenclature and cylindrical chamber of the cyclone. The methods of measterminology are identical with those in the previous paper urement and computation of velocities, pressure drop, and friction loss were the same as those used previously, except (9). I n the first article the following equation was obtained that an improved form of Pitot tube was employed for the for the friction loss, F,,, in a cyclone with an extended inlet velocity traverses. vane : All runs were made with a n inlet height, h, of 6 inches, an #exitduct length, m, of 18 inches, and an exit duct diameter, F,, = 7.5 .e, of 5.9 inches i. d. The exit duct was made of a sheet of Pyralin approximately inch thick with an over-all length Thus the friction loss was found to vary directly with the ,of 40 inches. The gas was allowed to discharge directly to width, b, and height, h, of the inlet, and inversely as the t h e atmosphere. square of the exit duct diameter, e . The velocity distributions in the cyclone chamber were deMeasurements of friction loss us. inlet width in the present 1 Present address, E. I. d u Pont de S e m o u r s & Company, Inc , Xiagara tests also showed the friction loss to vary directly as the Falls, N. Y .
(g)
INDUSTRIAL AND ENGINEERING CHEMISTRY
SEPTEblBER, 1940 T.4BLE
I.
CYCLONE
FRICTION LOSS
Measured Pressure Calcd Entrance Drop Drop, Inlet Air Entrance Velocity hlanom- hlanom- Manom- C y c l o ~ r ~ ~ e s s u r e eter 4 eter 3 eter 3 FC9 Width Flow Velocity Head CU. f t . / Velocity In. mwa. Ft./sec. --Inches o f water I n . H20 head8
.
2S/a
361 325 217
55.0 49.5 33.1
0,662 0,537 0,240
4.65 3.74 1.61
0.76 0.62 0.26
0.16 0.13 0.06
4.49 3.61 1.55
6.78 6.74 6.46 Av.
7.31 7.27 6.99 7.19
1J/r
324 206
74.0 47.1
1.20 0.486
5.67 2.12
1.37 0.53
0.79 0.32
4.88 1.80
4.07 3.70
4.86 4.49
280
90.0
1.82
6.55
1.90
1.50
5.05
2.78
11,'.
first power of the inlet width (Figure 2). No tests were made to determine the effect of inlet height and exit duct diameter, but it is reasonable to assume that the same type of correlation found in the earlier work will apply. The equation for the friction loss then becomes:
Fo
=
16.0
(g)
Av. 4.68
1247
follows the inverse square root relation. The Pitot tube used in the present tests is not considered accurate a t a radius of less than '/g inch, but when i t is placed a t the center of the cyclone, i t registers a zero reading in both a vertical and horizontal position. Values of ra obtained from the velocity distribution plots of Figure 3 are given in Table 111. From these values the corresponding values of (rs/rd) can be computed as shown by the theoretical equation (Equation 4 of the earlier paper), for the idealized square-root velocity distribution,
3.68
VARIABLE
IN
FIXED INLET
VANE*'
The extended inlet is essentially the equivalent of the inlet deflector described by Alden ( 1 ) . Comparison of Equations 1 and 2 indicates that the presence of such a deflector does reduce the friction loss by over 50 per cent. The velocity distribution data are shown in Table 11. They are plotted on log-log paper in Figure 3, and except for wall effects, the spiral velocity varies approximately as the inverse square root of the radius for the larger radii down to a radius of 2 inches. This corresponds to the results reported in Figure 4 of the previous article ( 2 ) . Although the Pitot tube used in the earlier tests was not considered accurate a t radii of less than 2 inches because of its long tip, the present Pitot tube permitted reliable readings down to a radius of inch. Figure 3 shows that the spiral velocity reaches a maximum at a radius of about 2 inches. For smaller radii the velocity decreases as the radius decreases and no longer
TABLE 11. CYCLONE VELOCITY DISTRIBUTION Inlet Width In. l'/C
la/,
Inlet Velocity Ft./sec. 90.7
73,5
(This r u n was made with t h e
Pitot tube described in t h e previous paper, 2 )
2 5/a 54.3 (In this r u n t h e horizontal velocity directly a t t h e entrance t o t h e exit duct was a t a maximum a t 126 ft./sec. at a radius of 1.8 in.)
Distance in from Wall0 In. 0. 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
Horizontal Velocity Ft./sec. 57.7 71.3 74.5 78.8 85.5 94.3
0.0 0.5 1 .o 1.5 2.0 2.5 3.0 3.5 4.0 4.5
59.6 68.3 74.5 80.3 88.1 100.0 111.5 123 114 84.3
0.0 0. 5 1.0 1.5 2.0 2.5 3 .0 3.5
47.1 59.6 65 0 73.0 80 3 89.5 99 0 112.2 111 2 89.5 47.1
4.0
4.5 5.0 5
106.8
117.2 116.2 85.5 36.5
T h e glass cyclone had a n internal diameter of 11.2 inches.
RUBBER
Static Pressure I n . H20
..
.. ..
SEAL--
GLASS COLLECTING CHAMBER---5 GAL.
..
.. .. .... .. .. ..
FIGURE1. DETAILSO F EXPERIMENTAL CYCLONE EMPLOYED IN EARLIER TESTS( 2 )
4.50 4.35 4.10 3.70 3.25 2.50 1.50
assuming r. = 4 2 . I n these tests the ratio ro/rd is constant and equal to 10 within limits of experimental error. The value of ra is defined by
..
..
ro = 2.56
(?)
(4)
as the last column of Table I11 indicates. The various equations defining the cyclone friction loss and velocity distribution are compared in Table IV for cyclones with and without the inlet deflecting vane. The increase in friction loss in the absence of the inlet deflector vane was attributed by Alden to entrance turbulence resulting from the conflict between the incoming stream and the stream that had already completed one
INDUSTRIAL AND ENGINEERING CHEMISTRY
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VOL. 32, NO. 9
TOTAL FRICLoss. This is o b t a i n e d by adding the values Exit D u c t Inlet Inlet r z of steps 1 to 5 = Diameter Width Velocity Fev re rd/re rd bh 5 . 4 7 i n c h e s of In. In. Ft./sec. In. In. water. 5.9 25,’s 54.3 7.31 6.75 0.096 0.28 2.51 7. TOTAL PRESla/, 73.5 4.86 4.6 0,103 0.30 2.58 SURE DROP FROM l’/r 90.7 3.68 3.3 0,093 0.27 2.60 A TO E. The presAv. 0.097 2.56 sure drop is equal a Obtained from Figure 3 A b y extrapolating the straight line of slope 0.5 t o the friction loss on log-log paper to a radius corresponding t o a velocity of 54.3 feet per plus t h e downsecond. stream velocity head minus the upstream velocity OF EQUATIONS FOR CYCLONE FRICTION TABLE IV. COXPARISON head. Here the Loss AND VELOCITYDISTRIBUTIOS downstream presWithout Inlet Deflector With Inlet Deflector (8) sure is atmospheric and the velocity head (at point E ) L is z e r o . Hence pressure drop ( A t o E) = 5.47 0 0.725 = 4.75 inches revolution. Since an impact loss would hardly be expected of water. to be more than one inlet velocity head, it is unlikely that impact losses alone could account for the large differences It is thus obobserved. The mechanism by which the pressure drop is served that the increased is undoubtedly one of velocity distribution and not total friction loss entrance impact. This is best illustrated by comparing the in this system velocity distributions or values of as given in Figure 3 without the deand Table I11 with those obtained in the earlier investigation. flector vane is The three series of measurements recorded in Table I1 5 . 4 7 i n c h e s of R A D I A L D I S T A N C E . IN. were all made a t approximately the same pressure drop (4.5water, whereas i t FIGURE 3. VELOCITY DISTRIBUTION IX 5.0 inches of water), as runs a t the same velocity in Table I was previously CYCLONE (HORIZONTAL VELOCITY indicate; and despite the differences in inlet widths, the veloccomputed to be COMPONENT IN ABSENCE OF EXTENDED ity distributions shown in Figure 3 are almost identical. 3.08 i n c h e s of INLET VANE) The mechanism by which the spiral velocities are increased water with the Curve Inlet Width Inlet Velocity when the inlet vane is removed is probably due to impact Inches Ft./sec. deflector vane, an a t the entrance. After making its first revolution, part of A 26/8 54.3 appreciable differB l3/4 73.5 the gas stream comes back to comDress the gas which is ence when the fan C 11/4 90.7 just entering the &lone. With performance must the 2b/g-inch inlet, for example, be s~eci6ed. I the spiral velocity a t a radius Thus, as Alden pointed out, an inlet vane of proper design corresponding to any radius will substantially reduce the pressure drop through a cyclone covered by the inlet duct is collector. No quantitative results are available as to t h e actually higher than the average effect of such a deflector vane on dust collection efficiency, inlet velocity. The high readbut where pressure drop is an important factor, a cyclone of ings of manometer 3 probably the type suggested in the earlier paper, combining an inlet also reflect the increased velocideflector vane with exit vanes of suitable design, should give ties resulting from the entrance efficient collection a t a low pressure drop. impact. The present data also show Nomenclature why the cyclones with a helical 3 ,NLET (b), roof, investigated in the earlier Any consistent system of units may be employed; t h e tests, showed no decrease in English system is given by way of example. FIGURE 2. EFFECT OF friction loss. A helical roof is INLET WIDTH O N FRICessentially an alternative for b = width of cyclone entrance, ft. e = cyclone exit duct diameter, ft. T I O N LOSS accomplishing what the inlet F,, = cyclone friction loss, expressed as number of inlet velocity deflector vane does; i. e., it heads prevents compression of the stream entering the cyclone by h = height of cyclone entrance, ft. m = distance t o which exit duct extends into cyclone chamber, the gas completing its first revolution. ft. Conclusions T. = radius at which spiral velocity is equal t o average entrance velocity, ft. The typical problem which was worked out on page 982 ?‘d = inner radius of inner spiral, ft. r0 = distance from cyclone center line to inner edge of outer of the earlier paper tacitly assumes the presence of the spiral, f t . inlet deflector. If this deflector vane had been omitted, the steps in the calculation which would be changed are as follows (numbers correspond to the steps in the original calculaLiterature Cited tion) : (1) A l d e n , J. L., Heating & Ventilating,35, 48-53 (1938); “Design of I n d u s t r i a l E x h a u s t S y s t e m s ” , N e w York, I n d u s t r i a l Press, 3. FRICTION Loss FROM C TO C’ (CYCLONE).Since b = 1939. 1 foot, h = 2 feet, and e = 2 feet, F,, = (16.0)(1)(2)[(2)2 = 8.0 cyclone entrance velocity heads, and cyclone friction loss = (2) S h e p h e r d , C. B., and L a p p l e , C. E., IND. EXQ.CHEM.,31, 97284 (1939). (8.0)(0.562) = 4.50 inches of water. 6.
AND PRESSURE DROP TABLE 111. VELOCITYDISTRIBUTION CORRELATION
TION
+
-
