US2907174A

US2907174A - Vortex tube and method of operating a vortex tube

Info

Publication number: US2907174A
Application number: US643121A
Authority: US
Inventors: Hendal Willem Pieter
Original assignee: Shell Development Co
Current assignee: Shell Development Co
Priority date: 1956-03-01
Filing date: 1957-02-28
Publication date: 1959-10-06
Anticipated expiration: 1976-10-06

Description

Oct. 6, 1959 w. P. HENDAL 2,907,174

VORTEX TUBE AND METHOD OF OPERATING A VORTEX TUBE Filed Feb. 28, 1957 3 Sheets-Sheet 1 FIG. l

II IO \22 2O 2| PC I70 f INVENTOR:

WILLEM PIETER HENDAL HIS ATTORNEY w ll")? W. P. HENDAL Oct. 6, 1959 VORTEX TUBE AND METHOD OF OPERATING A VORTEX TUBE Filed Feb. 28, 1957 3 Sheets-Sheet 2 FIG. 5

INVENTOR:

WILLEM PIETER HENDAL BY: Mf /W HIS ATTORNEY Oct. 6, 1959 w. P. HENDAL 1 2,907,174

VORTEX TUBE AND METHOD OF OPERATING A VORTEX TUBE Filed Feb. 28, 1957 3 Sheets-Sheet 3 INVENTOR:

WILLEM PIETER HENDAL B Wil /M HIS ATTORNEY United States Patent VORTEX TUBE AND METHOD OF OPERATING A VORTEX TUBE Willem Pieter Hendal, Amsterdam, Netherlands, assignor to Shell Development Company, New York, N.Y., a corporation of Delaware Application February 28, 1957, Serial No. 643,121 Claims priority, application Netherlands March 1, 1956 18 Claims. (Cl. 625) This invention relates to a method of operating a vortex tube within which a gas stream is expanded with gyratory motion about the tube axis to separate the gas into hot and cold fractions, and from which tube gas is discharged continuously in a manner dependent upon the particular purpose to which the tube is put, and to an improved vortex tube. Thus, the two gas fractions may be discharged in any desired ratio from zero to infinity; in other words, two gas streams having different temperatures or only one gas stream may be discharged from the tube. The utility of discharging only one stream will become apparent from the sequel.

More particularly, this invention is concerned with the method of admitting the gas into the vortex tube and with an improved arrangement of the tangential inlet duct.

Although not restricted thereto, vortex tubes find particular utility for the production of cold gas streams from gas which occurs initially at superatmospheric pressure, especially when the refrigeration load in a given process wherein the cold gas is to be utilized is so small or intermittent that more elaborate machinery, such as adiabatic expansion engines, are not economically attractive. They are further applicable to effecting chemical reactions by bringing the gas streamwhich may constitute the one or one of the reactants or may be carrier for a reactant suspended therein-for a short time to an elevated temperature. I

The vortex tube, also known as the Ranque tube or Hilsch tube, as applied heretofore, uses no moving parts and is low in cost. Such a tube was described in US. Patent No. 1,952,281 to Ranque, and Hilsch drew further attention to it in articles published in Zeitschrift fiir Naturforschung, vol. 1, pp. 208-214 (Wiesbaden, Germany, 1946) and in Review of Scientific Instruments, vol. 18, pp. 108-113 (New York, 1947). A bibliography on vortex tubes, written by Curley and MacGee, Jr., was published in Refrigerating Engineering, vol 59, 1951, pp. 66 and 191-193.

By a vortex tube is meant an apparatus which includes a vortex chamber having the shape of a body of revolution, such as a cylinder, an inlet for admitting a feed gas under pressure with a gyratory motion, usually situated near one end of the tube, and comprising one or more ducts disposed tangentially and in the same circumferential direction, and suitable outlet means for discharging one or both of the gas fractions which appear within the tube. These fractions are formed respectively as a peripheral stream in contact with the inner surface of the tube wall and as a core rotating coaxially within the peripheral stream, the former being warmer and the latter being colder than the feed gas. Both fractions have pressures lower than that of the feed gas but the pressure of the fraction having the higher temperature exceeds that of the other fraction, in accordance with the Ranque elfect. This phenomenon of the separation of the gas by expansion within the vortex tube into hot and cold fractions is hereinafter referred to as the heat-separation elfect. This heat-separation elfect results in the heating of at least a part of the vortex tube wall, unless it is extraneously cooled. For a well-made vortex tube the centerline temperature can be 50100 F. lower than the inlet temperature while the wallif uncooledis 100200 F. hotter than the inlet.

The dimensions of such tubes may vary within wide limits according to the conditions under which the tube is to operate; suitable dimensions are readily determined experimentally in accordance with the principles and examples given in the art noted above. Thus, the vortex tube may have a length of 6 to 30 diameters, lengths of 18 to 20 diameters being common.

Various outlet arrangements are possible. In one common arrangement, the cold gas fraction is discharged through an orifice situated at the tube axis in a plate or end wall near and to one side of the tangential inlet; the vortex tube extends through almost all of its length to the other side of the inlet, and the latter part, also known as the hot end, has a discharge opening for the hot gas fraction, situated either near the periphery or near the axis. By throttling one or the other of the efiluent streams, e.g., by the use of a throttling valve at the hotgas outlet and/or by selecting a cold-gas orifice of suitable size, their ratio and, hence, their temperatures can be varied; typical temperature elfects are indicated graphically by Hilsch, op.cit., and by Sprenger, on p. 295 of Zeitschrift filr Angewandte Mathematik und Physik, vol. II (Basel, Switz., 1951). Hot gas which travels away from the inlet through the hot end in excess of the amount, if any, which is discharged at the extremity of the hot end flows again with the cold core toward the discharge orifice for the cold gas fraction. By cooling the hot fraction while within the vortex tube, as by applying a coolant to the wall of the hot end of'the tube, (see German Patent No. 468,487) the volume of gas that can be drawn oil as the cold fraction at a given temperature is increased and/or the temperature of the discharged cold fraction can be decreased, and a cooled gas stream is attained even when the hot end of the tube is fully closed, so that all gas is discharged as cold gas; the converse is true when the core of the vortex contains a central heating element, such as a small tube through which a heating fluid is circulated, making it possible to draw olf all or most of the gas as hot gas by greatly restricting or completely closing ofi the central cold-gas orifice. In either case an increased heat-separation within the tubes promotes heat exchange with the extraneous cooling or heating fluid.

Among still other draw-oil arrangements, to which the present invention is also applicable, are those using the so-called uniflow principle, in which the outlets for the cold and hot gas fractions are arranged concentrically at or near the extremity of the hot end, and that using an annular opening surrounding the tube axis at either end of the tube as the cold-gas outlet; these are illustrated in the Ranque patent cited above.

The temperature dilferences attained in the vortex tube depend upon the rotational velocities developed and for this reason it is desirable to admit the gas with as high a tangential velocity as feasible, usually close to the sonic velocity. With the known vortex tubes, which used fixed decreased; thus, in the latter case, no significant increase.

in the heat-separation effect is realized despite the increased expansion ratio.

The known vortex tubes further present difficulties whenconnected "to a gas feed or a 'gas discharge unit, such as a reservoir, which is kept substantially constant. For example, when the source 'of gas under pressure is a plant unit, such as a distillation column, which should operate at substantially constant pressure despite variations in the rate of gas supplied thereby, difficulties arise when a vortex tube having fixed inl'et passages is used inasmuch as a significant increase in the I gas pressure is required to bring about the increased flow of 'gas through the fixed inlet ports of the vortex tube. The alternative of throttling the gas in the feed line during periods of low flow rates to reduce fluctuations in the source pressure expends energy uselessly. A similar problem arises when the gas from the vortex tube is discharged into a constant-pressure reservoir 'or plant unit at avarying rate of flow.

Further, it is often difficult to design theinlet ports of vortex tubes for optimum performance even when the gas flow rate is essentially constant and it is therefore desirable to provide inlet arrangements which can be assembled or adjusted to determine or vary the passages as desired without the capability of effecting changes in the passages during operation of the tube.

Finally, for the attainment of the greatest angular momentum it is desirable to give a special shape to the .part of the enclosing wall of the vortex tube at the inlet ports. It is difficult to machine this section of the wall to attain such shape with the conventional designs.

In accordance with one feature of the present invention the tangential inlet ports of the vortex tube are so designed that the passage thereof can be adjusted, either by assembling the elements in a selected relationship or by means of actuating mechanism which can be operated from the outside of the vortex tube to permit the passage to be varied during operation or as flow rates change from time to time.

According to another feature of the invention the inlet section of the vortex tube is defined by arcuate surfaces at the inner ends of a plurality of plates which are arranged in a circle within a transverse breach in the tube wall, each plate having a pair of edges which extend substantially parallel to the tube axis and form bounding walls of different adjacent tangential inlet ducts. These plates are preferably, although not necessarily, shaped so that they can be assembled in difierentangular relation so that the passage of the inlet ports formed at the inner ends of the ducts can be selected. Moreover, these plates can be mounted to be swung about separate axes of rotation which are parallel and eccentric to the tube axis. \Vhen actuating mechanism is provided, it is preferably arranged to impart equal rotations in the same direction to the several plates. I

The separate axis of rotation of each plate may coincide with the axis of a pivot pin which is mounted in the vortex chamber wall and on which the plate is pivoted. The pivot pin may, however, be omitted and its function performed by the combination of a slot and cam having surfaces in sliding engagement which are concentric cylinders about the axis of rotation. The latter construction makes it possible to attain the preferred arrangement of locating the axis of rotation at the radially inner end of each plate, i.e., substantially at the surface of revolution bounding the vortex chamber at the: inlet ports.

A specific actuating mechanism for said plates includes a crank for each plate having a crankpin movable within a slot in the plate and eccentrically secured to a rotatable member, 'e.g., a separate crank shaft mounted in the vortex tube wall structure parallel to and eccentrically to the vortex tube axis and operable from the outside.

The actuating mechanism may be connected to a servomechanism or other power drive which is controlled by a pressure-measuring device connected to mQ'aSUB? th gas pressure in the feed or discharge unit, e.g., on the pipe leading to the tangential inlet of the vortex tube or the outlet thereof, whereby the passages of the tangential inlet ports are automatically varied as the pressure varies.

The improved method of operation according to the invention resides in varying the inlet passages of the inlet ports in accordance with changes in the pressure of the gas in the feed zone or in the discharge zone.

The invention will be described further in connection with the accompanying drawing forming a part of this specification and illustrating certain preferred embodiments by way of example, wherein:

Figure l is a diagrammatic view showing a vortex tube gas-expansion system according to the invention;

Figure 2 is a view similar to Figure l but showing a modification;

Figure 3 is a fragmentary view of the inlet end of a vortex tube suitable for use in Figures 1 and 2;

Figure 4 is an elevation of the plates defining the tangential inlets, viewed as indicated by the line 4-4 of Figure 3;

Figure 5 is an end elevation of the vortex view, viewed as indicated by the line 5'5 of Figure 3 (the pipe flange 31 being removed);

Figure 6 is an enlarged, fragmentary sectional view taken on a section parallel to one of the plates 32, looking toward the plate;

Figures 7 and 9 are elevation views similar to Figure 4 showing two alternative arrangements of the plates; and

Figure 8 is an enlarged fragmentary sectional view taken on the line 88 of Figure 7.

An understanding of the phenomenon of the heatseparation eifect and the influence thereon of the pressure relation are helpful in understanding the instant invention. A summary thereof is presented in my prior patent application, Serial No. 5 559,422, filed June 5, 6, page 7, line 11, to page 10, line 2. This description is incorporated herein by reference and need not be repeated in extenso.

Referring to Figure l in detail, the vortex tube gasexpansion system includes a feed unit comprising a source 10 and a feed pipe 11; the vortex tube 12 having tangential inlet ports supplied from the pipe '11; and a dis-- charge unit including a cold-gas discharge pipe 13 and reservoir or sink 14. The tube may have also a hot-gas discharge pipe 15. The source 10 may, for example, be a fractionating column which is operated under superatmospheric pressure and from which a gaseous top product is discharged at a rate which varies from time to time and wherein it is desired to maintain a substantially constant pressure. This pressure is measured by .a pressure controller '16 which is connected by a control line 17 to a servo-motor 18. The motor is connected to a vortex tube by a transmission element which includes a shaft 19 to increase the passage of the tangential inlet ports upon a rise in the measured pressure in vice versa. The vortex tube includes a tubular enclosing wall 20 which may diverge from .the inlet end toward the hot end at the right at a small angle, such as a cone angle of 26, preferably 3-4, as shown. The wall 20 may be surrounded by a jacket 21 through which a coolant is circulated by connections22 and 23.

Referring to Figures 3-6, which show the inlet end of the vortex tube in detail, the tubular wall 20, which is shaped as a surface of revolution, is shown to diverge toward the hot end at the left, surrounded by the jacket 21. When this optional jacket is used the wall 20 and the hot gas fraction in contact therewith are cooled, if desired even to a temperature below that of the feed gas; nevertheless they are, for convenience, herein referred to as the hot-end of the vortex tube and the hot gas fraction, respectively, to distinguish themfrom other parts of the vortex tube and from the cold gas fraction, which are at a lower temperature.

The'tubularwall 20is sealed to a flat annular-plate 24,

the central circular hole 25 of which conforms to the inner surface of the wall 20 and which is sealed by a gasket against the flanged end jacket section 26. The latter is bolted to a housing 27 which presses the plate 24 toward section 26 and contains an annular gas feed channel 28 with which the feed pipe 11 communicates. The housing has an orifice 29 which is smaller than the hole 25 and is situated at the central axis of the vortex tube for the discharge of the cold, central part of the gaseous vortex constituting the cold gas fraction. This fraction flows through a short divergence section 30 into the discharge pipe 13, the end flange 31 of which is bolted to the housing. The housing and plate 24 thus provide a breach which extends perpendicularly to the axis of the vortex chamber.

A plurality of identically shaped flat plates 32 is mounted within the said breach in sliding engagement with the plate 24 and the inner face of the end wall of the housing. Each plate has a pair of edges extending parallel to the said axis as follows: The first edge has an inner, arcuate portion 33 which is tangent at 34 to an outer portion 35 extending outwards and shown in this embodiment to be straight; the second edge 36 extends outwards essentially from the inner end 37 of the first edge and is likewise shown to be straight. The edge portion 35 of each plate and the adjacent edge 36 of the adjoining plate are spaced and together define an inwardly converging inlet duct which is in flow communication with the channel 38 and tangential to the portion of the vortex tube defined by the arcuate, inner portions 33 of the several plates. This portion of the vortex tube is the inlet section, wherein the entering gas is first expanded and may have a diameter which slightly exceeds that of the hole 25, as shown in Figure 3. By this arrangement the gas attains a higher angular momentum, resulting in an increased heat-separation effect, for a given entrance velocity through the inlet ports.

The inner, arcuate portion 33 may have any streamlined geometry providing a concavely curved contour. It is preferred to give this inner edge a contour, as shown, such that it recedes gradually from the axis of rotation in the circumferential direction from the inner end 37 to the point of tangency 34. This moves the entering gas along a path which approaches the axis gradually.

Each of the plates is mounted for rotation about a separate axis which is eccentric with respect to and parallel to the central axis of the tube and various arrangements are possible provided they vary the distance between the inner end 37 of one plate and the adjoining edge (near the tangency point 34) of the next plate to vary the passage of the inlet port defined by these parts at the inner ends of the inlet ducts while maintaining the streamlined shapes of the ducts. In the embodiment shown each plate swings about a pivot axis situated at the point 37, which lies substantially at the surface of revolution bounding the vortex chamber. To this end, each plate 32 has a slot 38 both the inner and outer edges of which are shaped as concentric cylindrical surfaces about an axis parallel to the vortex chamber axis and passing through the point 37. Each slot receives a cam 39 which has engaging surfaces conforming to the edges of the slot but is circumferentially shorter. These cams are fixed in recesses in the end wall of the housing 27. It is evident that the plates are thereby constrained to swing in a common plane perpendicular to the central axis of the vortex tube about their respective points 37 to vary the passages of the inlet ports. By locat ing the pivot points at the inner ends 37 of the plates the minimum diameter of the inlet portion of the vortex tube is not altered by changing the passages.

For moving the several plates simultaneously through equal angles thereby to effect simultaneous and equal alteration of the passages of the several inlet ports, any suitable mechanism operable externally of the vortex tube may be provided. In the example illustrated, this mechaa shaft 40 which is pivoted in the end wall of the housing 27 and is sealed thereto, e.g., by the O-ring shown. The shaft 40 carries at its inner end an eccentric crankpin 41 which slides in a slot 42 in the plate and, at its outer end, an eccentric crankpin 43 which slides in a slot 44 formed in an actuating ring 45. The inner face of the end wall of the housing has a niche 46 to accommodate the crank arm. The slot 42 may be aligned toward the pivot axis '37 while the slots 44 are radial. The ring 45 is mounted 'rotatably on the housing 27 by a bolted retaining ring 47 for rotation about the central axis. It is evident that rotation of the ring 45 rotates the several shafts 40, thereby swinging the plates 32 through equal angles. Thus, rotation of the ring 45 in the direction shown by the arrow A in Figure 5 causes the plates 32 to swing in the angular direction of the arrow B, Figure 4, to widen the several passages.

For automatic operation the actuating ring 45 carries a lever 48 which engages the vertically reciprocable drive shaft 19 of the servo-motor at 49.- I

In operation, upon an increase in the rate of gas supply and the gas pressure in the inlet Zone, which are contained in the source 10 and'feed pipe 11, the pressure controller 16 controls the servo-motor 18 to shift the ring 45 in the direction of the arrow A; this rotates the several plates 32 about their individual pivot axes 37 in the direction of the arrow B to widen the passagesof the inlet ports. Conversely, a decrease in the supply rate and gas pressure results in movement in the opposite direction. The ring 45 can, of course, also be set manually from time to time to conform to different flow rates and pressures and clamped each time in adjusted position by the ring 47, which can be modified to fit tightly against the ring 45.

In the operation described in the preceding paragraph, when the pressure in the discharge zone, which is within the pipe 13 and reservoir 14, does not fluctuate significantly, e.g., when it is atmospheric, the tangential velocity of the gas entering the vortex tube and the pres sure drop or expansion ratio of the gas will be substantially constant despite variations in the gas flow rate. It may be noted that it is usually desired to attain the highest cooling effect, which is achieved by the use of high inlet velocities, usually near to the local velocity of sound or somewhat below, e.g., at a Mach number between .6 and 1.0. Because increasing ratios of inlet to discharge pressures above about 20, do not give rise to any appreciable increase in the temperature effect it is usually desirable from the point of view of operating efiiciency to maintain the said ratio constant at 20 or at some lower value.

The system of Figure 1 is not, however, limited to operation with a constant pressure in the reservoir 14. At high expansion ratios the gas flow is but little influenced by the pressure in the reservoir 14 and determined mainly by the passage of the inlet ports.

The invention is also applicable to systems wherein the pressure in the discharge zone is to be maintained more or less constant despite changes in the rate of discharge therefrom. Such a system is represented in Fig. ure 2, wherein the like reference numbers denote parts described for Figure 1 and the reservoir 14 has a flow control valve 50. It is assumed that the source-10 is provided with some regulating means (not shown) to supply gas always at the required rate. To maintain the discharge pressure substantially constant the pressure controller 16a is located to measure the pressure in the discharge zone and its control line 17a, the servo-motor 18a and its connecting linkage 19a are connected to operate in the opposite sense from that of Figure 1; in other words, as the pressure in the pipe 13 rises the passages of the tangential inlet ports to the vortex tube are decreased, or vice versa; This also maintains a substann sm includes a crank for each plate, each crank having 7 tially constant inlet velocity and expansion ratio in the 7 vortex tube, provided the supply pressure is substantially constant.

Figures 7 and 8 show certain variants which may be applied individually or in combination to the vortex tube and vortex tube systems described above.

Referring to Figure 7, the housing wall 27a carries six plates 32a which correspond to the plates 32 but differ therefrom in having their second edges 36a curved, thereby producing a greater convergence in the inlet duct and (b) being pivoted on pins 51 instead of slots and cams. These pivot pins are fixed in the housing 27a. The plates are not provided with mechanism permitting rotation from without the vortex tube; instead, each plate carries an arcuate slot 52 having stepped edges for receiving the head of a clamping bolt 53 which is threaded into the housing wall. Other numbers denote parts previously described for Figure 4.

The operation of the embodiment of Figure 7 is as was previously described save that the plates 32:: are adjusted manually in desired positions, e.g., by placing a gauge block between the points 37 and the adjacent plates, while the vortex tube is disassembled. The bolts 53 are then tightened. When the optimum positions for the plates 3211 have been determined and the vortex tube is installed in a system through which the flow is constant the plates may be fixed against further adjustment by drilling a further hole through each plate and the housing and fixing a pin 56 therein.

When a supersonic nozzle is desired the plates can be shaped as shown for the plates 32b in Figure 9. They are pivoted on pins 51 to the housing 271) and clamped in adjusted position by clamping bolts 53 extending through arcuate slots 52, as described for Figures 7 and 8. The first edge may have the arcuate part 33 which is tangent at 34 to an outwardly extending part 35, as previously described. The second edge, however, cornprises an inner portion 54 which, starting at the point 37, approaches the first edge of the adjacent plate and a second portion 55 which is merged to and diverges from the first edge. The inlet duct thereby first converges the entering gas stream up to the juncture of the

portions

54 and 55 and thereafter provides a diverging section which is necessary for supersonic flow.

It is evident that although the

plates

32, 32a and 32b are especially useful in permitting the widths of the passages to be varied, the construction is useful also when these plates are permanently fixed inasmuch as they facilitate precise shaping of the inlet ducts and the portions 33, which form parts of the confining wall of the vortex tube.

I claim as my invention:

1. In the method of operating a vortex tube gasexpansion system having an inlet zone which includes a source of gas under pressure, a vortex tube having a tangential inlet through which the gas from said inlet zone is admitted to the tube and expanded to form a vortex and separate the gas into coaxially situated hot and cold fractions by the heat-separation effect, and a discharge zone into which gas from said tube is discharged, the improvement of measuring the pressure of the gas in one of said zones and varying the passage of said tangential inlet in accordance with the measured pressure.

2. The method according to claim 1 wherein the said passage is varied adjacently the vortex tube.

3. A vortex tube gas-expansion system comprising: a source of gas under pressure; and a vortex tube having a tangentially directed inlet connected to said source for admitting gas from said source into said tube with a gyratory motion to separate the gas into coaxially situated hot and cold fractions by the heat-separation effect and an outlet for said gas, at least one wall bounding said inlet adjacent to the vortex tube being movable to vary the inlet passage.

4. In combination with the vortex tube system according to claim 3, mechanism operable externally of the vortex tube for moving the said movable wall.

5. A vortex tube gas-expansion system comprising: a feed unit including a source of gas under pressure; a vortex tube having a tangentially directed inlet connected to said source for admitting gas from said source into said tube with a gyratory motion to separate the gas into coaxially situated hot and cold fractions by the heatseparation effect and an outlet for said gas, at least one wall bounding said inlet being movable to vary the inlet passage; a discharge unit connected to receive gas from said outlet; and means responsive to the pressure of the gas in one of said units for actuating the said movable wall to vary the passage in accordance with the said pressure.

6. A vortex tube system according to claim 5 wherein said wall bounding the inlet is adjacent to the vortex tube.

7. Vortex tube gas-expansion device for separating a gas into coaxially situated hot and cold fractions by the heat-separation effect comprising: wall means defining a vortex chamber shaped substantially as a surface of revolution about an axis, said wall means having a transverse breach enclosing a streamlined inlet duct which is bounded on the outside by a first wall the surface of which is tangentially continuous with a portion of said surface of revolution and on the inside by a second wall, one of said walls being movable relatively to the other to vary the passage of the inlet to the vortex chamber while maintaining the said streamlined shape of the duct; and an outlet for discharging said gas from the vortex chamber.

8. Vortex tube gas-expansion device for separating a gas into coaxially situated hot and cold fractions by the heat-separation effect comprising: wall means defining a vortex chamber shaped substantially as a surface of revolution about the chamber axis, said wall means having a transverse breach; a plurality of separate plates se: cured within said breach and arranged consecutively in a circle about said axis, each of said plates having first and second edges forming bounding surfaces of different adjacent inlet ducts which are directed tangentially to said chamber, each said plate being mounted for turning movement in the plane of said transverse breach about a separate axis of rotation so that turning of all plates in a common direction effects a narrowing of the passages of the inlet ports constituted by the inner ends of said ducts and a turning thereof in the opposite direction effects a widening of said passages; and an outlet for discharging gas from said chamber.

9. Vortex tube device according to claim 8 wherein each plate is pivoted on a pin the axis of which is substantially parallel and eccentric to the said chamber axis.

10. Vortex tube device according to claim 8 wherein each plate is mounted for said turning movement by the combination of an arcuate slot and an arcuate cam slidably fitting therein, one element of said combination being on the plate and the other on the said wall means, the engaging surfaces of each slot and cam combination being shaped as concentric cylinders about the axis of rotation of the respective plate, said last-mentioned axis being eccentric to the chamber axis and substantially parallel thereto, and each cam being circumferentially shorter than the enclosing slot.

11. Vortex tube device according to claim 8 wherein said separate axes of rotation of the plates are situated substantially at the surface of revolution bounding the vortex chamber at said inlet ports.

12. In combination with the vortex tube device according to claim 8, mechanism operable externally of said wall means of the vortex tube for effecting turning movement of said plates including a slot in each plate, and for each plate, a crankpin slidable in the slot of the th t corresponding plate and eccentrically secured to a rotatable member.

13. In combination with the vortex tube device according to claim 8, means operable externally of said Wall means of the vortex tube for eflfecting simultaneous turning of said plates in a common direction through equal angles.

14. In combination with the vortex tube device according to claim 8, means for locking said plates in a selected angular position.

15. Vortex tube gas-expansion device for separating a gas into coaxially situated hot and cold fractions by the heat-separation effect comprising: wall means defining a vortex chamber shaped substantially as a surface of revolution about an axis; a plurality of inlets disposed tangentially to said surface at locations in a common plane transverse to said axis and circumferentially distributed, said chamber providing a circumferentially continuous and unobstructed flow path in said plane immediately inside of said inlets; means for varying the passage of at least one of said inlets; and an outlet for discharging said gas from the vortex chamber.

16. Vortex tube gas-expansion device for separating a gas into coaxially situated hot and cold fractions by the heat-separation effect comprising: an enclosing Wall defining a vortex chamber shaped substantially as a surface of revolution about an axis, said wall having a transverse breach; a plurality of separate plates secured within said breach and arranged consecutively in a circle about said axis, each of said plates having first and second edges forming bounding surfaces of different adjacent inlet ducts, the first edge of each plate having an inner, concavely curved portion conforming substantially to a surface of revolution about said axis and an outer portion tangentially continuous to said first portion and extending outwards therefrom, the second edge of each plate extending from the inner end of the first edge in gradually divergent relation to the second portion of the first edge of the adjacent plate; and an outlet for discharging said gas from the vortex chamber.

17. Vortex tube device according to claim 16 wherein the said inner, concavely curved portion recedes gradually away from said axis of rotation in the circumferential direction from the said inner end of the first edge to the point of tangency with the said outer portion.

18. Vortex tube device according to claim 16 wherein said plates are mounted for rotation about separate axes of rotation eccentric and parallel to said chamber axis, whereby rotation of all plates in a common direction effects a narrowing of the passages of the inlet ports constituted by the inner ends of said ducts and rotation in the opposite direction effects a widening of said passages.

References Cited in the file of this patent UNITED STATES PATENTS 2,428,830 Birmann Oct. 14, 1947 2,758,914 King Aug. 14, 1956 2,770,943 Beale Nov. 20, 1956 2,839,901 Green June 24, 1958