US1961907A - Apparatus for heat exchanging - Google Patents

Description

5 Sheets-Sheet l G T. MOTT APPARATUS FOR HEAT EXCHANGING Original Filed Nov. 25. 1931 Ulllllllll l 1 June 5, 1934.

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June 5, 1934. G MQTT APPARATUS FOR HEAT EXCHANGING 3 Sheets-Sheet 2 Original Filed Nov. 25. 1931 A TTORNE Y1.

June 5, 1934. G MOTT 1,961,907

APPARATUS FOR HEAT EXCHANGING Original Filed Nov. 25. 1951 3 Sheets-Sheet 3 A TTORNEYI Patented June '5, 1934 UNITED STATES- PATENT OFFICE" Application November 25, 1931, Serial No. 577,171 Renewed March 16, 1933 30 Claims. (01. 257-238) The invention relates generally to heat exchangers; and, while the device may be employed in constructions adapted for various purposes, it is more particularly directed to the tubes used in heat exchangers as heat transfer surfaces between the heat-containing and the heat-absorbing agents and thru which tubes one of the agents flows.

A prime object of the invention is to provide, in a heat exchanger, a double tube circuitous return flow element furnishing heat transfer surface; in which element, while the flow of the heat agent in the inner tube and the flow in the annular space between the inner and outer tubes are each diagonally at counter cross current with the other, there is no change in the direction of rotation of the flow of the heat agent thru the tubes. This arrangement brings about a double rotary scouring eifect with a consequent, material increase in thermal transfer, and more particularly avoids the flow resistant eddies incident to the direct abrupt flow reversal in the double tube flow elements of the art. The same rotative principle adopted to lessen flow resistance thru the tubes is in part included for a similar purpose at the point of initial flow entry of the heat agent to the tube element. While not essential, it is desirable that the inner tube shall always be the' tube of initial entry of the heat agent.

A further object of the invention is to permit the tubes to be so freely arranged mechanically in relation to each other and the shell of the heat exchanger that they may freely expand and that they may be manufactured of cast materials thruout, if desired, thus materially reducing the construction cost and also the maintenance cost thereof by permitting the use of a cast corrosiveresistant allow in their construction-altho, of course, they may also be made of metals of any character.

These and other objects of the invention will be more fully set forth in the following description.

In the accompanying drawings, which are referred to herein and form part hereof,

Fig. 1 is a view of a heat exchanger or condenser for an. oil refining apparatus, partly in perspective .andpartly in section, made in accordance wth the principles of the invention, parts being broken away and certain parts being omitted;

Fig. 2 is a view'in cross-section taken on the line 2-2 of Fig. 1;

Fig. 3 is a similar view taken on the line 3-3 of Fig. 1;

Fig. 4 is a sectional elevation taken on the line 4-4 of Fig. 2;

. Fig. 5 is a transverse section taken on the line 5-5 of Fig. 1;

Fig. 6 is an enlarged view, parts being broken away, in longitudinal cross-section of an inner and an outer tube shown in Fig. 1;

Fig. 7 is a fragmentary perspective view of the tubes shown in Fig. 6;

Fig. 8 is a longitudinal cross-section of the entry end of an inner tube shown in Fig. 1;

Fig. 9 is an elevation of the entry or inlet port shown in Fig. 8;

Fig. 10 is a cross-section taken on the line 10-10 of Fig. 6, looking in the direction of the arrows;

Fig. 11 is a cross-section taken on the line 11-11 of Fig. '1;

Fig. 12 is a fragmentary perspective of an end of an outer tube shown in Fig. 1.

Referring to the drawings in detail, there is illustrated therein a preferred embodiment of the invention as used in a heat exchanger of the type shown in my Patent No. 1,738,914, dated Dec. 10, 1929, and which need not be described in detail herein. Said heat exchanger consists generally of a main vapor receptacle 15 formed with a cylindrical shell 16, having heads 19 and 20 and provided with the usual flow ports 41 and 42. At one end of said vapor receptacle 15 and spaced apart therefrom is arranged a container 26, see Fig. 1, divided by a partition wall 29 into receptacles 39 and 40, from which additional chambers 39 and 40 are divided oil by division plates 43 and 44, said receptacle 40 being provided with the outlet port 42. One of the heat agents, as, for example, oil, enters the receptacle 39 and passes into the inner tubes 61. These inner tubes lead from the receptacle 39, and fluid passing thru-these tubes enters a transition chamber 100, to which further reference will be made, and thence passes thru outer tubes 53 into the receptacle 40.

It is preferred that the inner tubes function always as the initial entry tubes for the heat agent into the double tube flow elements, as the oil, and for this purpose conduits 40 are provided, see Figs. 2 and 3, thru which the oil flows from the chamber 40 to the chamber 39, as clearly shown in Fig. 4. Thence the oil enters again the inner tubes 61, where the flow process is repeated, the oil thus passing thru the flowpipes of the flow sections, here shown as four in number, and into which the heat exchanger is divided, as shown in Figs. 2 and 3.

The outer tubes 53 lead from the receptacle 40 and, traversing the space between the container 26 and the described vapor chamber 15,

project into the chamber 15 thru the head 19. The closed ends of the tubes 53 are freely supported on curved supporting members 54*, see Fig. 1, preferably cast integrally with the head plate 20. These supporting members 54 are are shaped and are employed, four to each tube end, with space between each two are members and are of sufficient length to provide for tube expansion. The supported ends of the tubes 53 are sealed with plugs 55, see Fig. 6, preferably screwed into the ends of the tubes. Further reference will be mad to these plugs.

Here it may be noted that the direction of flow of the heat-absorbing agent, as oil, thru the tubes may be reversed and flow, first, thru the outer tube and thence into and thru the inner tube. Preferably, however, the inner tube, as heretofore stated, will be the tube of initial entry flow since thereis in said tube a centrally disposed rotative flow of the relatively colder entering fluid rotating at cross-wiseangl'es against the return flow, and equivalent in location to that of a central core, but contrary in flow to the fixed parallel core-center flow cf the art. The admission of this colder rotating fluid to the centrally disposed inner tube, adds materially to the thermal flow thru-the outer walls of the double tube element by reason of its central disposition, cross-wise flow, and temperature.

Also, theheat exchanger may be used so that the heat-containing agent flows thru the tubes, while the heat-absorbing agent is in the chamber 15. It may further be noted that both said heat-containing and heat-absorbing agents may be gases or liquids of any character, or one of said agents may be a gas and the other of said agents may be a liquid.

The prime feature of the invention, as heretofore stated, resides in the peculiar construction of the inner and outer tubes and the transition chamber therebetween by which the fluid passing thru the flow element is given thruout 'its entire flow travel a circuitous,.spiral, rotating cross-current flow action, exactly the equivalent of lengthening the tubes or flow travel, and permits this without actually increasing the length of the tubes. To obtain this effective flow, therefore, the inner tubes 61 are preferably of cylindrical formation, the outer surface in this,

embodiment being shown as smooth and round. The inner tubes 61 are provided on their inner surfaces with deflecting members arranged in spiral formation, such members in the embodiment of the invention herein shown taking the form of inwardly extending integral lugs 61 spirally winding thruout the length of the tube. It preferred, the same effect may be obtained in another manner, as by the groove method or by inserting a free member of similar spiral. Further reference will be made to this. The spiral path thus provided for the oil may, as shown in Fig. 6, for viscous products he graduated and variable in its turns or pitch. The lugs will in some measure interrupt the contacting. surface flow even though rotating, as the flow center of this fluid being'less impeded will have a tendency to travel faster longitudinally (especially as the liquid is rotating) than the contacting sides of the fluid and will thus thru rotative action upset the bane of liquid tube flow, namely, the fixed flow core of even velocity.

It is obvious that with an inner tube constructed asshown, arranged for continuous rotative flow therethru, and with entry ports arranged for a glidingly, rotating fluid entry, and including means to prevent the customary fluid body contraction, evidenced in an entry port set at right angles to the line of flow, the rotating flow thru such an inner tube would be materially greater in velocity and volume than that thru a tube with parallel flow and flow ent'ry contraction, and in addition the friction head would also be materially reduced, and in consequence a much smaller inner tube would be required for a given service than would otherwise be the case.

The influence of the continuous rotative action in the inner tube 61 will .extend somewhat beyond the actual fluid entry point, much in the manner of a slight whirlpool. To take advantage of this rotary or whirlpool action of the entering fluid in reducing. the entry resistance, the entry port of the tube 61 has been tongued much the same as in my Patent No. 1,758,582, dated May 13, 1930, but improved, as now will be described. As shown in Figs. 8 and 9, the tongue 63 presents directly against the rotary or whirlpool flow of fluid a thin upper deflecting edge made by chamfering under-this edge 63, thus presenting 'said edge 63 against the flow as a straight line substantially parallel with the length of the tube and set directly against the rotary flow, much as the cutting edge of a bit is applied, excepting in this instance the fluid is rotated instead of the cutting edge. The edge 64 of the opposite extending tongue at the inlet is curved back continuously from the depth of the tongue recess, as shown in Fig. 8, and curves across a line drawn on the perimeter of the tube, which line is parallel with the pipe longitudinally, thus gradually widening the inlet space between the tongues. This tongue is chamfered or rounded on the upper edge, thus permitting the fluid glidingly to rotate into the inner tube 61 thru the two chamfered or rounded-out edges of the tongue recess. Outwardly, the inner tube presents, preferably, a

smooth cylindrical surface to the rotating flow of the outer tube presently to be described.

It is desirable in a double tube return flow element that the annular space between the tubes should permit freely the transmission of the volume of fluid delivered by the inner tube. It is well known in the art, however, that where a circular inner tube of given cross-sectional area is contained within a second circular tube and wherein the cross-sectional annular space between the tubes equals the net cross-sectional area of the inner tube, such a narrow annular flow space is thus provided between the tubes as to create such a frictional and adhesive resistance' as to preclude the passage of a viscous body.

Otherwise, the outer tube must be of excessive dimensions for continuous flow of equal volume, and at a cost of a much lessened velocity and consequent lowthermal transfer, and at a further excess cost of metal and space. ,1

According to the present invention, therefore, the return flow element is so designed, by reason of the area contained in the rotative flume presently to be described, as to give ample flow space (or the equivalent of the customary annular space between the tubes) without excess flow area in said annular space between the tubes and without constricting the flow, and, at the same time,

preserve adequate velocities and the incident increased transfer surface over that included in a straight enveloping tube of the art, where the internal areas of the inner tube and the annular space between the two tubes are equal. This outer tube 53 is also so fashioned as to provide a rotative transitional chamber to effect the service of return flow, to which feature further reference will be made.

The outer tube, therefore, in the embodiment shown in Figs. 1 to 12, inclusive, is fashioned to present with the inner tube a spirally formed multi-flumed passage between the two tubes, said passage being divided into three flumes 53 of equal area. It is to be noted that these flumes may be of any number, size, relationship, pitch,

variation, or progression of pitch, and are grouped around the central inner tube and are of such shape as to provide a ready flow with a minimum of flow resistance compared with the small annular space of the flow elements of the art. This outer tube, as stated, is shown in spiral or twisted formation with inturned ribs or partitions 53 between the flumes. These ribs are in this form entwined sufficiently close to and around the inner tube 61 as to afford a support for said inner tube 61 and so that a viscous fluid will practically seal the contact between the inner tube and said ribs and thisconstruction will also preclude a tendency on the part of the inner tube to chatter. If desired, instead of the ribs 53*, there may be provided between the tubes a free member having the same spiral formation as the ribs 53, and the same rotating flow effect will be produced or the ribs 53 may be extended from the outer surface of the inner tube.

As the outer tube spirals about the inner tube, its line of spiral is plainly indicated, see Fig. 7, in a somewhat similar contouron the outer surface of the outer tube. I

This construction, it will be observed, provides also for a spiral flow of the contacting, condensing vapors flowing longitudinally in the chamber 15. And here it may be noted that a vapor flow longitudinal with the tubes and confined within the narrow limitations of a section of tubes all spirally wound and in the same spiral direction must of necessity create a spiral flow of the contacting vapor or liquor. Obviously, the spiral flow may be in either right or left direction of rotation. This construction further permits following the inner flume-like formation of the tube, thereby providing a relatively thin wall for heat transfer purposes and for economy in metal. The spiral, again, in this instance, provides for a material increase in equivalent length of contact travel without actual increase in tube length and may, as stated, be graduated for a heavy flow body. It will be seen that the inner and outer tubes are so arranged and related as to preserve the sequence of direction of rotative flow of the fluid from the inner to the outer tube and that the spiral contour of the external surface of the outer tube and within the chamber 15 provides for a series of rotated channels 53 at the depth of the spiral, which, in multiple grouping of the spiral construction of the tubes may be uniform in direction of turn or twist or obviously may be in right or left twists for insertion from opposite ends of the vapor chamber or for differing passes to provide for continuous uniform, rotative vapor flow direction, for any given pass. This provides for an additional highly efficient measure also in the constantly rotating action of the flow body in contact with the outer surface of the outer tube and as exposed within the chamber 15.

It is to be observed that at the point, where the flow from the inner tube enters the flumes of the outer tube, these entry ports are constructed in propeller-like formation. At this point the rotating fluid from the inner tube is rotatingly insinuated into these propeller-shaped orifices, the fluid continuing in its 'rotative screwing effect into and thru the flume spaces between the tubes. It will be further observed that while thefpropeller-like structure does not rotate but on the contrary the fluid rotates into the propeller-like structure, nevertheless the function of propulsion is performed.

According to another and important feature of the invention, a rotative transition chamber 100 100 is arranged between the rotative discharged end of the inner tube 61 and the propeller-like entries to the flumes of the outer tube 53. This chamber is formed by the end of the outer tube 53, see Fig. 6, and is cylindrical in shape and has a portion 101 which extends a measurable dislance withinthe limits of the projecting inner tube 61, and it is at this inner end of the portion 101 of the chamber 100 that the flume structure of the outer tube 53 begins. As shown, see Fig. 6. the chamber 100 immediately adjacent the plug 55 has its walls taperingly thickened to reduce the area in order to assist the diverging element, presently to be described, in creating a slight fluid pressure at this point on the projecting, rotating fluid entering the chamber from the inner tube and assist said diverging element in deflecting the rotating fluid body into the ex tension 101 of the chamber 100 leading to the multi-flumed passage. If desired, the walls of the transition chamber may be made in spiral formation in the direction of rotation of the rotating fluid entering the chamber, or a spiral free member may be provided.

It is also important to note that that part of the outer tube 53 which provides entry to the multi-flume structure, that part 101 surrounding the projecting inner tube 61, has a materially increased area over that of the inner tube 61 or of that of the combined times 53 thus permitting at this point a continued easy rotating flow cont'nuously rotating in one direction and being de-- livered centrifugally from the inner tube against the outer circular wall of the rotation chamber and thus being automatically twisted or screwed into the spiral fiumes by reason of the propellerlike entrance to the flumes and the continued rotating action of the fluid. Due to the constant rotating centrifugal action of the fluid in the transition chamber there is created a vortex condition, which has a tendency to create the vortex void customary with centrifugal action of fluids.

By reason of this constant rotating, scouring flow of the fluid without change of direction a great reduction in friction head is afforded and a further freedom from precipitation in the transition chamber.

According to another feature of the invention, the seal plug 55 is provided with a cone-shaped diverging element 69 see Fig. 6, which extends into the rotative transition chamber 100 and the surface of which is coarsely threaded in a peculiar manner so as to present facets 102 set to deflect the fluid pressure, created by the projecting fluid rotating on this thread, directly against that part or part 101 of the transition chamber leading to the propeller-like flume entrances. At the juncture of the threaded part of the plug 55 with the walls of the rotative transition chamber 100 the two elements are well rounded out together thereby forming a receptacle 103 back of the direct influence of the threaded diverging element 69 extending from the plug .55, and in which receptacle 103 a fluid cushion will be retained which assists in minimizing the friction head.

In the conventional straight tube of the art efficiency of heat exchange is due not only to velocity but to a phase of velocity that assures a turbulence; or, in other words, this efficiency is directly dependent on the rapidity and variance or turbulence with which a heat-absorbing body can be made in its flow thru the tube to cut across the straight lines of incoming heat flow thru the wall of the tube. However, while the velocity may be established as a constant, the degree of turbulence in a straight tube may not be. It will be seen that in the double tube of the invention, as herein shown and described, there is provided not only means for intercepting in a marked degree the straight lines of incoming heat flow, thru the inclusion of the rotary flow of the heat-absorbing agent in the annular space between the tubes, but this interception is further accentuated to a maximum degree by the rotary, cross-wise, counter-flow of the agent set up in the inner tube against the crosswise-flow in the annular space between the tubes. In this fixed relation of rotative action is established the constant for the scouring effects and degrees of interception of the incoming straight line heat flow. Because of the induced thermal capacity of this inner, cross-wise, rotative counter-flow as a constant, in its substitution for the casual turbulent effect of the art, and the consequent exceptional thermal demand in the counter-flow, quite apart from the comparative thermal demand of the straight tube of the art, or that of the incident mean temperature, the inner tube may properly be described as a thermal induction core.

It will be observed that the construction herein described and illustrated is an improvement upon the return fiow element set forth in my Patent No. 1,818,082, dated August 11, 1931, in that the circuitive flow thru the inner tube of the flow element of said patent is by means of the improved construction of the present invention continued into and thru the multi-fiume passage between the inner and outer tubes Without change of direction of the rotation of the flow of the liquid.

The operation of the device will be apparent from the foregoing description but may be briefly summarized, as follows:

The oil or other agent enters the exchanger thru the entry port 41, passing into the receptacle 39, thence passing rotatingly into and thru the inner tube 61, and into the rotative transition chamber 100. From this chamber 100 the fluid rotatingly enters the extension 101 of the chamber 100 and thence passes rotatingly and under the influence of centrifugal force into and thru the multi-flume passage between the inner and outer tubes; the oil then enters the receptacle 40 and thence flows thru-the conduits 4.0 into the chamber 39 from whence the process is repeated,

the 011 after passing thru the several passes of the exchanger eventually leaving the exchanger thru the discharge port 42.

The invention in its broader aspects is not limited to the particular construction shown and described, as many changes may be made in the details thereof without departing from the principles of the invention or sacrificing its chief advantages.

I claim:

1. A double tube, circuitous return flow, heat exchange element, including in combination, an inner tube, deflecting members associated with the inner surface of said tube and arranged in spiral formation, .a communicating outer tube having a closed end, and deflecting members associated with the inner surface of said outer tube and arranged in spiral formation.

2. A double tube, circuitous return flow, heat exchange element, including in combination, an inner tube, deflecting members associated with the inner'surface of said tube and arranged in spiral formation to afford a rotative flow passage thru said tube, a communicating outer tube having a closed end, and deflecting members associated with the inner surface of said outer tube and arranged in spiral formation to afford a flow passage between said tubes, permitting a continuous rotary flow thruout the double tube element, without change of rotative direction.

3. A double tube, circuitous return flow, heat exchange element, including in combination, an inner tube, having its inner surface formed to afford a rotative flow passage thru said tube, and

a communicating outer tube having a closed end and having its inner surface formed to afford a flow passage between said tubes permitting a continuous rotary flow thruout the double tube element, without change of rotative direction.

4. A double tube, circuitous return flow, heat exchange element, including in combination, an inner tube, having its inner surface formed to afford rotative flow passage thru said tube, and a communicating outer tube having a closed end and having an inner surface formed to afford a rotative flow passage between said tubes, said outer tube at its closed end forming a transition chamber for continuing said rotative flow thruout the double tube element without change of rotative direction.

5. A double tube, circuitous return flow, heat exchange element, including in combination, an inner tube having an inner surface, near a.discharge end of said tube, formed to afford a rotative flow delivery from said tube, and a communicating outer tube, having a closed end and having its inner surface formed to afford a flow passage between said tubes, permitting a rotary flow from the inner tube thru the outer tube without change of rotative direction, said outer tube at its closed and forming a transition chamber for continuing said rotative flow into the outer tube.

6. A double tube, circuitous return flow, heat exchange element, including in combination, an inner tube, having its inner surface formed to afford a rotative flow passage thru said tube, and a communicating outer tubehaving a closed end and having an inner surface formed to afford a' rotative flow passage between said tubes. said outer tube at its closed end forming a transition chamber for continuing said rotative flow thruout the double tube element without change of rotative direction, said transition chamber tapering within toward its outer end.

7. A double tube, circuitous return flow, heat exchange element, including in combination, an inner tube, having its inner surface formed to aiford a rotativeflow passage thru said tube, and a communicating outer tube having a closed end and having an inner surface formed to afford a rotative flow between said tubes, said outer tube at its closed end forming a transition chamber of cylindrical shape for continuing said rotative flow thruout the double tube element, said transition chamber extending inwardly a distance between the tubes.

8. A double tube, circuitous return flow, heat exchange element, including in combination, an inner tube, having its inner surface formed to afford a rotative flow passage thru said tube, and a communicating outer tube having a closed end and having an inner surface formed to afford a rotary flow passage between said tubes, said outer tube, at its end, forming a transition chamber of cylindrical shape and smooth surface for continuing said rotary flow thruout the double tube distance be having its surface arranged in spiral formation.

10. A double tube, circuitous return flow, heat exchange element, including in combination, an inner tube, having an inner surface formed to afford a rotative flow passage in said tube, and a communicating outer tube having a closed end and having its inner surface formed to afford a flow passage between said tubes, permitting a rotary flow from the inner tube thru the outer tube without change of rotative direction, said outer tube at its closed end forming a transition chamber of cylindrical shape for continuing said rotary flow, a diverging element arranged in said chamber, and rotary deflecting members associated with the surface of said element and ar ranged in spiral formation thereabout, said spiral being arranged for continuation of the direction of rotary flow. I

11. A double tube, circuitous return flow, heat exchange element, including in combination a pair of tubes, oneproiecting into the other, an open end of the entry tube of saidpair being formed for the rotative entry of a fluid, having arc-shaped tongues, and arc-shaped valleys between said tongues, an edge of one of said tongues being set substantially in parallel relationship.

with the tube, and the edge on the tongue opposite in the entry valley being curved back from the depth of the tongue recess.

12. A double tube, circuitous return flow,.heat exchange element, including in combination a pair of tubes, one projecting into the other, an open end of the entry tube of said pair being formed for the rotative entry of a fluid, having arc-shapedtongues, and arc-shaped valleys between said tongues, an edge of one of said tongues being set substantially in parallel relationship with the tube and chamfered at its under parallel edge, and the edge on the tongue opposite in the entry valley being curved back from the depth of the tongue recess and chamfered on its upper edge. f

13. A return flow element, including in combination, an outer tube, deflecting members associated with the inner surface of said tube and arranged in spiral formation, and an inner tube supported on said members. 1

14. A return flow element, including in combination, an outer tube, deflecting members associated with the inner surface of said tube and arranged in spiral formation, and an inner tube supported on said members, said inner tube arranged with its inner surface formed to afford a spiral flow in angular cross-wise flow to the flow between the tubes.

15. A double tube, circuitous return flow, heat exchange element, including in combination, an inner tube, deflecting members associated with the inner surface of said tube and arranged in spiral formation, a communicating outer tube having a closed end, and deflecting members associated with the inner surface of said outer tube and arranged in spiral formation, said spiral formations being of progressively variable pitch adapted to the viscosity of the flow of the fluid at its given temperature, at any given point of contact.

16. A return flow element, including in combination, anv inner tube, a communicating outer tube having a closed end, and a diverging element arranged in an end of said outer tube, and deflecting members associated with the surface of said deflecting element and arranged in spiral formation thereabout.

17. A return flow element, including in combination, an inner tube, deflecting members associated with the inner surface of said tube and arranged in spiral formation, a communicating outer tube having a closed end, and deflecting members associated with inner surface of said outer tube and arranged to presenta spirally formed 'multi-flumed passage the entrances of said passages being of propeller-like formation.

18. A return flow element, including in combination, an inner tube having its inner surface formed to afford a rotative flow passage thru said tube, and a communicating outer tube having a closed end and having an inner surface formed to afford a spirally formed multi-fiumed passage between said tubes permitting a continuous rotative flow thruout the return flow element without change of direction of rotation, the entrances of said multi-flumed passage being of propellerlike formation, and said outer tube at its closed end forming a transition chamber of cylindrical shape for continuing the said rotative flow from the inner into the outer tube without change of direction of rotation.

19. A return flow element, including in combination, an outer tube having a closed end, an inner tube, deflecting members associated with the inner surface of said inner tube and arranged in spiral formation, .and deflecting members associated with outer surface of said inner tube and arranged in spiral formation.

20. A double tube, circuitous return flow, heat exchange element, including in combination, an inner tube, deflecting members associated with the inner surface of said tube and arranged in spiral formation, a communicating outer tube having a closed end, and deflecting members associated with the inner surface of said outer tube and arranged in spiral formation, said outer tube being of spiral formation on its outer side, presenting an additional rotating scouring contact in the heat transferm'e'dium outside of the double tube element.

21. A double tube circuitous return flow heat exchange element including in combination, a circular inner tube formed for the rotative entry flow of a fluid, means associated therewithjo eliminate entry contraction of the fluid, said inner tube being further arranged to provide for a continued rotative flow of the fluid therethru, an outer tube formedwith flumes and enclosing, supporting and communicating with said inner tube; and a flow receiving, transition member forming a chamber associated with said outer tube, whereby the flow from the inner tube passing rotatingly into said transition chamber is discharged and delivered in rotation against the peripheral wall of the transition chamber and is thereby insinuated into the surrounding flumes of the outer tube under the influence of centrifugal force.

22. A double tube, circuitous return flow, heat exchange element including in combination, an inner tube, deflecting members associated with the inner surface of said tube and arranged to induce a rotating flow of a fluid therethru, an

with the inner surface of said outer tube to in. .duce a rotative flow between the tubes, and said tubes being so associated as to provide a continuous rotative flow throughout the tube element without changeof rotative direction and whereby a diagonal cross counter flow is created which causes the irmer entry tube to become a thermal induction core.

23. A double. tube circuitous return flow heat exchange element including in combination, an inner tube having an inner surface formed to afford a rotative flow passage in said tube, an enclosing outer return flow tube associated therewith, a transition member forming a chamber associated with the inner and outer tubes and formed so as rotatingly to receive fluid discharging from the inner tube and permit it to be rotatingly insinuated into spaces in the outer tube and a diverging member located in the transition chamber at the point where the vortex void due to centrifugal action of the fluid therein would be created.

24. A double tube, circuitous return flow heat exchange element including in combination, an inner tube having an inner surface formed to afford a rotative flow passage 'in said tube, a return flow tube formed withflumed passages and associated with said inner tube, a transition member forming a chamber and associated with the inner and outer tubes and arranged to receive a rotating fluid discharging from the inner tube, and a diverging member located in the transition chamber at the point where the vortex void due to centrifugalaction of the fluid therein would be created, said member being of such shape as to divert the rotating fluid directly toward the entrance to the flumed passages of the outer tube.

25. A double tube, circuitous return flow heat exchange element including in combination, an inner tube having an inner surface formed to afford a rotative flow passage in said tube, a return flow tube formed with flumed passages and associated with said inner tube, a transition member forming a chamber and associated with the inner and outer tubes and arranged to receive a rotating fluid discharging from the inner tube, and a diverging member located in the transition chamber at the point where the vortex void due to centrifugal action of the fluid therein would be created, said member being of such shape as to divert the rotating fluid directly toward the entrance to the flum'ed passages of the outer tube, said transition member being rounded out at the base of said diverging member to form a receptacle for a fluid body in continued rotation and outside the influence of the diverging member, and said fluid body forming a fluid friction cushion for the rotating fluid.

26. A double tube, circuitous return flow element including in combination, an inner tube, deflecting members associated with the inner surface of said tube, said tube being arranged for rotative flow of a fluid thereto, a communicating enclosing outer tube terminating in a transition chamber, said outer tube being formed with entwining multi-flumed passages around said inner tube, said passages terminating at one end ofthe tube in said transition chamber and presenting to the rotating fluid in the transition chamber, inlet ports arranged obliquely to the diameter of said transition member and forming propeller-like entrances set against the fluid in rotation in the transition chamber, whereby said fluid rotatingly enters the fiumes of the outer tube under propulsion efiect.

27. A double tube, circuitous, return flow heat exchange element, including in combination, an entry tube, a return tube, and a transition mem ber forming a chamber of cylindrical shape associated with said tubes, and means for establishing a rotative flow of fluid discharged from the entry tube to the transition chamber whereby said fluid assumes a centrifugal action for entry into the return tube.

28. A double tube, circuitous return flow, heat exchange element including in combination, an innertube, deflecting means arranged within said tube for upsetting the continuity of straight line flow of fluid thru said tube, a communicating outer tube having a closed end, and deflecting means arranged between said tubes for upsetting the continuity of straight line flow of fluid thru the annular space between the tubes.

29. A double tube, circuitous return flow, heat exchange element including in combination, an inner tube, spiral deflecting means arranged within said tube for upsetting the continuity of straight line flow of fluid thru said tube, a communicating outer tube having a closed end, and spiral deflecting means arranged between said tubes for upsetting the continuity of straight line flow of fluid thru the annular space between the tubes.

30. A double tube, circuitous return flow, heat exchange element, including in combination, an inner tube having an inner surface, near an entry end of said tube, formed to afford a rotative flow delivery thru said tube, and a communicating outer tube, having a closed end and hav-' ing its inner surface formed to afford a flow passage between said tubes, permitting a rotary flow from the inner tube thru the outer tube without change of' rotative direction, said outer tube at its closed end forming a transition chamber for continuing said rotative flow into the outer tube.

GEORGE T. MOT'I.

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