CA1128928A - Thin-walled tube composed of a melt spinnable synthetic polymer and its use in apparatus for transferring heat - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Thin-walled tube made of a melt-spun synthetic polymer and having a flow cross section of 30 to 95% of the total cross section and an elongation at rupture of less than 100% is employed in an apparatus for transferring heat;
the thin-walled tube can be beneficially modified by the addition of graphite, metal particles, filling material, stabilizers, additives, soot or pigments; or by other characteristics.

Description

~1289Z8 The present invention relates to a device for trans-ferring heat through tubes and to tubes suitable for this purpose, more especially the invention is concerned with such tube~ which are thin-walled and composed of a melt-spinnable synthetic polymer.
t Heat-exchangers made of tubes, and also hollow threads or hollow fibres, are known, in which the tube~ are arranged in straight lines, parallel with each other, and spaced from each other.
Thin-walled tubes and their method of production have previously been proposed, such tubes being comp~sed of a melt-spinnable synthetic polymer, and having a cross-section of flow of from 30 to 95% of the total cross-section and a breaking elongation of less than 100%.
A "thin-walled tube" in the context of the invention i8 a hollow, cylindrical configuration of any length having, for example, a circular or elliptical cross-section, whose wall thickness which is constant in the longitudinal and circumferential direction iQ less than about 15% of the largest external dimen~ion of the tube cross-section. With a circular cross-section, the largest external dimension corre~ponds to the external diameter and with an elliptical cro~s-section it corresponds to the largest external axis.
The thin-walled tubes of the invention are stronger than conventional thin-walled tubes but neverthele~s, have a large cross-section of flow and a closed, i.e., undamaged sheath. They are characterised by an internal flow cross-section ranging from 30 to 95% of the total cross-section and by an elongation at rupture of less than 100~/o~ Tubes having a cross-section of flow of from 60 to 95% of the total cross-section are preferred.

Thin-walled tubes can be produced from any conventional melt-spinnable polymers. Examples of particularly suitable polymers, due to their ~pecial properties in use, include the polyamide~, in particular polycaprolactam and polyhexa-methylene adipic acid amide, polyester~, in particular poly-ethyleneterephthalate; polyolefins, in particular polyethylene and polypropylene: and polyvinylchloride.
Polyesters, in particular polyethyleneterephthalate are particularly preferred due to their chemical stability for example, toward food stuffs, liquids containing carbon dioxide or the like. Tubeq compo~ed of polyolefins, in particular polypropylene are preferred if chemical stability i8 desired as well as good thermal stability.
The tubes are produced from polyamides, in parti-cular from polyhexamethylene adipic acid amide if high ~trengths are desired.
Stabilisers, carbon black, pore forming agents or other additives can be added to the polymers.
The tubes usually have a sheath which does not allow any liquids through. When using thin-walled tubes for filter units, however, it is advantageous for the thin-walled tube8 to have a microporous ~heath.
Thin-walled tubes of thi~ type are produced in the manner described above by the melt-spinning of synthetic polymers, the production process being characterised in that the take-off speed is higher than 3500 m~min. Take-off speeds ranging from 5000 to 7000 m/min are preferred. In fact, at these take-off speeds, the thin-walled tubes have a Atrength which could otherwise only be achieved by additional (but difficult) re-drawing.

ilZ89Z8 In order to avoid large spinning height~ (distance from spinneret to take-off device) it is propo~ed that the phenomenon of the `'natural bending of the thread" be utilised, This generally occur~ during the melt-spinning of threads from synthetic polymers in a fairly large distance from the spinneret if the take-off device is moved laterally from its normal position located substantially vertically below the spinneret. It can be seen clearly if, for example, a monofilament polyester thread having a final count of 100 dtex is taken off at 3700 m/min and the take-off device initially arranged vertically below the spinneret (rapid spooling device or thread injector) i9 gradually removed in a horizontal direction and optionally lifted simultaneously in a vertical direction, In spite of the changed position of the take-off device the thread continues to move vertically downward~
below the spinneret over a certain distance and is then deflected toward the take-off device, The region of this "natural" bending of the thread, i.e., bending of the thread which is adjusted without additional mechanical thread-guiding devices, extends only over a Iength of a few centi-metres and does not change its position substantially even if the po~ition of the take-off device is changed significantly.
On the other hand, the position of the region of the "natural"
bending of the thread can be varied by changing the spinning conditions. For example, it becomes more distant when the through-put of-melt from,the spinneret is increased. The phenomenon occurs even during the rapid spinning of thin-walled tubes.
Using this phenomenon, it is possible to keep the spinning height low by the lateral arrangement of the take-off device, while at the same time, maintaining the cooling ~:lZ89Z8 distance needed for cooling the freshly spun thread~, Moreover, if, as already proposed, the distance of the take-off device from the region of the "natural bending of the thread" is selected sufficiently large, the tube is subjected to re-drawing, in which process it is stretched to from two to three times its original length.
Although it is not po~sible to deflect the rapidly spun thin-walled tubes in the region of the "natural bending of the thread" mechanically, i.e., using a deflecting device, deflection is po~sible by arranging a baffle plate vertically below the spinneret, so as to shift the region of the "natural bending of the thread" closer to the spinneret. The region of the "natural bending of the thread"
can also be shifted to a coolant by arranging, for example, a small water tank instead of the above-mentioned baffle plate.
In order to produce stable tube configurations having larger external dimensions and very small wall thick- !
nesses, a cavity-forming fluid, in particular a gas, is blown into the tube whilst the thin-walled tube is being spun from the spinneret, Thin-walled tubes of this type which are spun by rapid spinning, are suitable, for example, for the production of heat exchangers in which case they generally have a circular cross-section and an external diameter of from about 40 to lOOO~m or more with wall-thicknesses of about 5 to 50 ~m or more.
It is the purpose of the present invention to improve known heat-exchangers consisting of hollow fibres as regards their heat-transfer capacity and serviceability, and to make available a device for the transfer of heat which can be produced easily and rapidly and does not have the dis-~289Z8 advantage~ of known hollow-fibre heat-exchanger~.
According to the invention, this purpose is achieved, on the one hand, by utilizing the flexibility of thin-walled tubes by designing the device accordingly and, on the other hand, by special configurations of the thin-walled tubes already proposed which increase their thermal conductivity and heat-transmission and, finally by imparting suitable shapes to the tube~.
According to the invention there is provided an apparatus for transferring heat through tubes comprising a plurality of thin-walled tube~ composed of a melt-spinnable synthetic polymer, each tube having a flow cross-section or internal cross-section of between 30 and 95% of the total cross-section and an elongation at rupture of less than 100~.
In one preferred embodiment of the invention, each individual thin-walled tube is arranged over most of~ts length, preferably over its entire length, and/or most of the thin-walled tubes, preferably all of them, are arranged in the form of regular and/or irregular tubes.
A heat-transfer device of thi~ kind, made out of thin-walled tubes, has greater resistance to external mechanical stre~sing, thus assuring undiminished heat-transfer capacity, evèn after long periods in operation.
This embodiment of the device according to the invention therefore does not have the disadvantages of the known heat exchangers composed of hollow threads in which the hollow threads are arranged in straight lines, parallel to each other and at distances from each other. In fact, this known arrangement, of the type which is also conventional in metal tubùlar heat exchangers, makes the production of such heat exchanger~ from hollow threads difficult and expensive.

~lZ89~8 In addition, with this known arrangement of the hollow threads, the bundles of hollow threads can be damaged, for example, buckled, even by minor external mechanical influences.
The looped or partially looped arrangement of the thin-walled tubes in an apparatus according to the invention which is also called a heat exchanger in the rest of the description for the sake of simplicity, is achieved according to the invention in a simple manner. In parti-cular it is achieved in that one or more continuous thin-walled tubes are wound using a spooling or winding device with one or more thread guides which are moved to and fro parallel to the rotational axis of the spooling device, for example, on a perforated tubular reel holder (also known as a bobbin or spool) and, in this way, form a single or multiple layered spool or wound member.
This arrangement is particularly advantageous since, in the serviceable condition of the apparatus, the thin-walled tubes have the shape of a spatially extending 1 coil, the thin-walled tubes advantageously being arranged in several layers for achieving an easily penetratable winding packet which i A ~table in shape in such a way that the thin-walled tubes in each layer contact the thin-walled tubes of the adjacent layers and cross, optionally several times.
This arrangement of the thin-walled tubes allows a large heat tran~fer surface in a small space since, although the thin-walled tubes touch each other at the points of inter-section, only an insignificant proportion of the heat transfer surface is lost by the reciprocal contact between the thin-walled tubes.

llZ8928 The spool holder accommodating the spooled or wound member need not necessarily have a circular cross-section as its cross~section can also be designed elliptical or as a polygon, in particular as a rectangle with rounded corners.
Similarly, the reel holder used for producing the spooled or wound mem~er can also have a cross-section which increases or decreases along its longitudinal axis. Thusj its sur~ace area can be designed, for example, conical, diabolo shaped, truncated pyramid shaped with rou~ded lateral edges or barrel-shaped, so that the thin-walled tubes wound on a reel holder shaped in this way generally form a spooled or wound member whose shape corresponds to the shape of the respective reel holder.
In another embodiment of the apparatus according to the invention, the thin-walled tubes have the shape of a spiral lying in one plane.
The heat exchanger according to the invention can, however, also be produced from one or more sheets which have been produced by a weaving, knitting or stretching method or a depositing method. Like the spooled or wound member, sheets'of this type can also be produced in a rapid and simple manner, In order to pr~oduce a heat exchanger, according to the invention from a spooled or wound member, two face ends can be cast on a short portion, measured in the longitudinal direction, of the wound member, in for example, a curable casting composition such as, for example, cast resin or poly-urethane, the casting composition penetrating completely into this region of the wound member and optionally forming one flange-like projection outside each wound member having a larger circumference than the wound member. A flange-like ~289Z8 projection of this type can, however, also be provided on one only of the two faces of the wound member. The arc-ahaped turn backed parts of the individual layers of the wound member lying at the ends of the wound member are removed by taking off a proportion of each of these (flange-~-~ shaped) pxojections from the end, into the region of the thin-walled tubes, and a configuration is produced in this way from the original wound member which consists of a plurality of tubular pieces arranged in several layers in the form of a coil and cro~ing each other severaI times, who~e openings emerge from the casting composition at the external face, generally running perpendicularly to the longitudinal axis of the wound member, of the remaining part of each of the (flange-like) projection~ described above.
To produce a heat exchanger according to the invention from sheets, one or more edges of the sheets which are optionally also superimposed, can be cast in a suitable , ~
manner, for example, in cast resin, in each case and the ; openings of the thin tubes can then be freed in a similar manner, aa already described above for spooled and wound members.
, By winding or shifting the thin tubes in a suitable ,~ , . . .
manner or by arranging them in another manner and by cutting the bundle of tubes in a suitable manner it is possible to . .
~; produce a heat exchanger according to the invention in which the inlet openings and the outlet openings of the thin tubes lie in one and the same plane, but are shifted, for example, by 180 and/or at equal or differing distances from each other in each case and thus arranged in such a way that all inlet openings lie in one half of this plane and all outlet openings lie in the other half of this plane.

~lZ89Z8 It is also po~sible to produce a heat exchanger according to the invention which allows as much fluid as desired to participate in the heat transfer, without the individual fluids being mixed to~ether.
A heat exchanger according to the invention pro-duced from a spooled or wound member can, for example, be equipped in such a way that the inlet openings and the outlet openings for a first fluid lie at one end of the heat exchanger and those for the second fluid lie at the other end of the heat exchanger.
To produce a plurality of smaller heat exchangers, it is possible according to the invention to divide the spooled or wound members or sheets intended for the production of the heat exchanger into units! for example, strips or discs or the like of desired size, in which case the thin tubes are preferabl;y fixed in shape and position beforehand in a suitable manner, for example, by casting into cast resin or the like as already described, in those regions in which the division is to take place, and their openings can thus be freed without difficulty by the division.
It is also posslble within the scope of the present invention to cast the thin tubes in a material which is a good conductor of heat in order to transfer heat in this manner from one fluid to the said material which is a good conductor of heat or vice versa. A heat exchanger according to the invention which is designed in this way and which also has, for example, two separate circuits for two fluids which are to be kept apart allows heat to be transferred from, for example, the first 1uid initially into the cast member which is a good conductor of heat and thence to deliver it to the second fluid. It is also possible with a heat exchanger of _ g _ ~lZ89Z8 this type, for example, to deliver the heat taken up, for example, by radiation, from the cast member which is a good conductor of heat, simultaneously to two fluids.
The heat exchanger according to the invention iq suitable for solving even the most demanding problems of heat transfer of the type which can arise, for example, during evaporation or condensation. In particular, the heat exchanger according to the invention is suitable wherever there are only relatively small temperature differences for t the recovery of energy which inevitably demand large heat transfer surfaces which obviously have to be arranged in the minimum of space. Due to the desirable corrosion properties of the thin tubes which can be used for the production of the heat exchanger according to the invention, the heat exchanger according to the invention is particularly ~uitable for corrosive media such as, for example, acids and caustic solutions. By selecting suitably thin tubes to be used, it is possible, by means of the known differing surface properties thereof, also to use the heat exchanger according to the invention for those fluids which tend to form deposits on the tube walls in conventional metal tubular heat exchanger 8 .
The heat exchanger according to the invention is therefore equally suitable for chemical processes, in the production or conversion of energy, in refrigeration, in air-conditioning, in the food industry, in central heating, in land, in water and air vehicles, in particular as an oil cooler, as a water cooler for discharging enginè heat or for heating the fresh air supplied to the interior of the vehicle, as a condenser and as an evaporator, in particular also as a flash evaporator. The heat exchanger according to the invention is quite specifically suitable for heat pump devices in which, for example, heat from the surrounding air or from the ground is used for heating housing space or as collectors for receiving the heat of the ~un, for which purpose those embodiments of the heat exchanger according to the invention in which the thin tubes are arranged in only one layer and, moreover, are black, have proven particularly advantageous.
The heat exchanger according to the invention is thus suitable for ~olving most problems of heat transfer, i,e., for the heat transfer of gaseous fluids to gaseous fluids, from liquid fluids to liquid fluids, from liquid fluids to gaseous fluids and vice versa, from solid mate-rials to gaseous and/or liquid fluidY and vice versa, in which case, care has to be taken to limit the temperature of the materials participating in the heat exchange are limited by the physical and chemical properties of the thin tubes used.
When dimensioning the heat exchanger according to ,." !
the invention, it ~hould be noted that the heat transfer - surface attainable per unit volume available is greater, the smaller the diameter of the tubes to be used. The amount of heat to be transferred generally increases as the ~ diameter of the tubes decreases if the cross-section of t flow of all thin tubes and the quantity of fluid remain constant. It should however be noted that the pressure loss in the thin tubes also increases in this case. It should also be noted that the buckling strength or nick-resistancè
of the thin-walled tubes generally decreases as the diameter increases and the wall thickness stays constant. With a suitable choice and dimensioning of the thin tubes used for - ~\
~lZ89Z8 the heat exchanger according to the invention, it is possible to achieve specific heat transfer capacities which can be better, and in part even considerably better than those which can be achieved with conventional metal tubular heat exchangers. The choice of suitable thin tubes should be made as far as possible in such a way that the heat trans-mission re~istance through the wall of the thin tubes is substantially negligible relative to the heattransfer resistances occurring inside and outside the thin tubes.
This means that thin tubes made of a material having relatively good propertie~ of thermal conductivity should ~' have thicker walls than those with very low thermal con-ductivity value~. ;
The term cross-section of the thin tubes, the spooled or wound member or the reel holder is interpreted in the context of the invention as the cross-sectional area obtained if a thin tube, a spooled or wound body or a reeL
holder is cut at a random point or at a point described in more detail perpendicularly to its longitudinal or rotational axis. In the case of a round thin tube, a circular cross-section is obtained in this way. In the case, for example, of a spooled or wound member which is wound on a reel holder having a rectangular cross-section with' ;' rounded corners, a rectangular annular cross-section with rounded corners is obtained according to this definition.
The term loop form in the context of the present invention is interpreted'as that form which differs from a rectilinear form and, in particular, that type of flat or three-dimension-al curvature in which the' radius of curvatùre is sufficiently large to prevent buckling or nicking of the thin tubes. The radius of curvature is generally smaller than 1~289Z8 1 m but it can also be larger. To achieve the object forming a ba~is of the present invention, it is not nece~sary for all thin tubes to have a loop form over their entire length, but rather it is sufficient for a majority of the thin tubes to have a loop form, i.e., for each individual thin tube in the apparatus according to the invention to have a loop form over the majority of its length and/or for recti-linear and loop-form thin tubes to be present providing the total length of all the thin tubes and/or tube portions ~7 10 present in loop form is greater than the total length of all rectilinear thin tubes and/or tube portions.
This loop form of the thin tubes allows the thin tubes to cro~ over optionally several times at ~ubstantially ~hort intervalq and to support each other in this way!so that each thin tube ~8 generally unsupported only over relatively short portions of their length 90 that the risk of;the thin tube~ being buckled or nicked is reduced considerably.
In the ~earch for possible further improvements to known heat-exchanger~, and to the device according to the invention, it was found, ~urprisingly enough, that an additional increase in héat-transfer capacity, and further improvement to the ~erviceability of hollow-fibre heat-exchangers, might be achieved by special configuration~ of the thin-walled tubes already proposed, and by the use of a few of the already proposed designs thereof in the device according to the invention.
In another a~pect of the invention novel thin-walled tubes are provided.
In this connection, outstanding result~ are obtained when the tubea of the invention are employed in the apparatus for transferring heat.

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~ ~128928 Thu~ in accordance with the invention there i9 provided a thin-walled tube composed of a melt-spinnable synthetic polymer, having an internal cross-section of between 30 ; and 95% of the total cross-section and an elongation at rupture of less than 10~/ol the tube being characterised by at least one characteristic selected from: i) the coefficient of heat-transm~ssion of the wall of the thin-walled tube i9 at least 1500 to at least 4500 W/m2K, ii) the outside diameter - of the thin-walled tube is between 0.04 and 4 mm, iii) the wall-thickness of the thin-walled tube is between 5 and 100 ~m, iv) at least one of an internal and an external surface of the thin-walled tube is profiled, v) the cros~-section of the thin-walled tube varies, in the longitudinal direction, in at least one of shape and size, vi) the thin-walled tube consists of two or more component~, vii) only some of the components of the thin-walled tube are porous.
In the case of iii), the wall-thickness~of the thin-walled tube~ is preferably within the range of 5 to 20 ~m.
- In the case of v), the cross-section of the thin-walled tubes may vary continuously or intermittently and po~sibly periodically.
Since thin-walled tubes having the properties mentioned above have not only proven satisfactory in a device - for transferring heat having the characteristics of the invention, but can also lead to improvements in conventional hollow-fibre heat-exchangers, thin-walled tubes h~ving the above-mentioned properties are included in the invention.
The thin-walled tubes of the invention may possess the indicated properties individually or in any desired combination.
'~ 30 It was alco found that an increase in heat-transfer capacity and improvements in serviceability, of the device - 14 _ ,, ~' 11289~8 according to the invention for transferring heat may also be achieved by a suitable choice of quite specific embodiments of the proposed thin walled tubes. In thi~ connection, particularly good results are obtained if:
a) the thin-walled tubes contain fillers, stabilizers, additives, pigments, or the like, and/or b) the thin-walled tubes are substantially circular in cross-section, and/or c) the outside diameter of the tubes is between 0.04 and 1 mm, - 10 and/or d) the wall-thickness of the thin-walled tubes is between 5 and 50 ~m, and/or e) the thin-walled tubes are porous.
Here again, according to the invention, thin-walled tubes may be used which possess the properties already pro~osed either singly or in combination.
For the purpose of increasing the heat-transfer capacity of the device of the invention, it is particularly advantageous to use thin-walled tubes containing good heat-conducting substances, for example, metals, graphite, or the like, in the form of dust or powder. However, the thin-walled tubes may also contain fillers, stabilizers, additives, carbon black, pigments, or the like.
The use of micro-porous thin-walled tubes, together with high pressures, makes it possible not only to transfer heat through the walls thereof, but also to cool a liquid, in that some of the liquid to be cooled evaporates or vapourizes on the surfaces of the porous thin-walled tubes.
The thinness of the walls of the tubes produces a heat-exchanger having a greater heat-exchange capacity, and this may be stiLl further increased in that, due to the high - 15 _ strength of these tubes, the permissible op~rating pres~ure within them, and the flow of fluid therethrough, are relatively high.
Suitable thin-walled tu~e for the heat-exchanger according to the invention are those of, for example, elliptical, triangular, square, pentagonal, hexagonal or polygonal cross-section, but more particularly those of circular cross-section, since in the case of a heat-exchanger according to - the invention made with intersecting thin-walled tubes of circular cross-section, the said tubes make only point-contact with each other, and only a small part of the total heat-exchange surface is lo~t at these point contacts.
The thin-walled tubes may, moreover, be internally and/or externally profiled. Two, three or more tubes, lying parallel with each other, may also be connected together at their contacting surfaces by fusing, welding, or adhesion, or the like. Also ~uitable are thin-walled tubes of which the cross-sections vary, in the longitudinal direction, in shape and/or size continuously, intermittently and, optionally, periodically. Thin-walled tubes of this kind may advantageously affect the operation of the heat-exchanger according to the invention in different ways. For instance, app~opriate internal and/or external profiling of the tubes may increase the internal and/or external heat-transfer surface, or improve the resistance of the tube to buckling, and/or may reduce the areas of contact between intersecting tubes.
Furthermore, the heat-transfer capacity may be increased by the forming of vortices or noles in the relevant liquid, at the profiled surfaces of the tubes. Moreover, more compact and/or more dimensionally stable devices may be produced with thin-walled tubes of non-circular shape.

l~Z8928 In order to ensure satisfactory heat-conductivity, the walls of the tubes must be as thin as possible, but must still be thick enough to meet mechanical demands. Tubes found most satisfactory for most purposes have wall thic~nesses of between 5 and lO0 ~m, while good heat-transmission values have been obtained with wall-thicknesses of between 5 and 50 ~m, and particularly good values with wall-thicknesses of between 5 and 20 ~m.
In order to obtain satisfactory heat-transmission (K coefficient), the cross-sections of the thin-walled tubes used must be of suitable size. In the case of tubes of circular cross-section, outside diameters of between 0.04 and 4 mm, more particularly of between 0.04 and l mm, have been found advantageous.
In the case of thin-walled tubes for the manu-facture of the heat-exchanger according to the invention, the coefficient of heat-transfer of the walls should be at least 1500 W/m K, particularly at least 4500 W/m2K. In this connection the coefficient of heat-transfer of the walls of -; 20 thin-walled tubes is to be understood to mean the quotient of the heat-conductivity of the material used for the tubes, measured in W/mK, and the wall-thickness of the said tubes measured in metres.
The invention will now be described in more detail w~th reference to the accompanying drawings in which:
FIGURES 1 to 7 show cross-sections through thin-walled tubes of various shapes, FIGURES 8 and 9 show longitudinal sections through thin-walled tubes which are not designed as circular cylinders, FIGURES lO and ll show a simplified schematic view of the production of a multiJlayer wound member from a thin-walled tube.

- 17 _ llZ8928 FIGURE 12 shows a simplified schematic view of a longitudinal section through a spooled member of thin-walled tubes having flange-like projections at its ends cast from a casting composition, FIGURES 13 to 15 show a simplified schematic view of longitudinal sections through spooled members of various shapes composed of thin-walled tubes having flange-like projections cast from a casting composition at their ends, FIGURE 16 shows a simplified view of a spooled member from thin-walled tubes having only one flange-like projection made of a casting composition arranged at its end, FIGURE 17 shows a simplified schematic view of a spooled member having flange-like projections cast from a casting composition at both its ends, FIGURES 18 to 21 show a simplified schematic view of embodiments of the heat exchanger according to the invention using a spooled member made of thin-walled tubes, FIGURES 22 to 24 show a simplified schematic view of the production of a spooled member made of two thi~-walled tubes, FIGURE 25 shows a simplified schematic view of an embodiment of the.heat exchanger according to the invention using a spooled member produced according to Figures 22 to 24, FIGURES 26 to 31 show a simplified schematic view of various embodiments of banks of tubes produced from spooled members each having differing cross-sectional shapes, FIGURES 32 to 37 show a simplified schematic view of the production of an embodiment of the heat exchanger accord-ing to the invention from a substantially disc-shaped wound member from thin-walled tubes.

.- 18 -. , ~128928 With-further reference to the drawing~, Figures 1 to 5 show, by way of example, cross-9ection~ of profiled thin-walled tubes of a type which are suitable for the heat exchanger according to the invention.
In the form illustrated in Figure 1, a thin-walled tube has a substantially circular cylindrical cavity 27 while it has a rib-like projection 26 running in it~
longitudinal direction on its exterior, which can optionally consist of a different material from the tube sheath.
The thin-walled tube illustrated in Figure 2 also has a substantially circular cylindrical cavity 27 and four rib-like projections 26 running in its longitudina~
direction, optionally made of a differing material.
The thin-walled tube illustrated in Figure 3 has a substantially three-tabbed cros~-section, the cavity 27 having a similar shape to the tube sheath 28 so that this thin-walled tube has a wall of substantially constant thickness over its circumference.
The thin-walled tube illustrated in Figure 4 has a sheath 28 which is externally substantially circular and has on its interior four rib-like projections 26 running in the longitudinal direction of the thin-walled tube and pro-jecting into its cavity 27, these projections being optionally made of a different material from the sheath 28.
Figure 5 shows a thin-walled tube in which the sheath 28 has a hexagonal annular cross-section and the cavity 27 has a hexagonal cross-section.
Figure 6 shows a cross-section through~a tube con-figuration which can be produced, for eYample, by fusing three thin-walled tubes of round cross-section together on their common lines of contact.

~289Z8 Figure 7 shows a cross-section through a thin-walled tube with a croqs member 29 arranged centrally inside the thin-waIled tube and running in its longitudinal direction.
This thin-walled tube therefore has two cavities 27 of equal size which are separated from each other by the cro~s member 29, run parallel to each other and have a semi-circular cross-section.
Figure 8 shows a longitudinal section through a thin-walled tube having an external diameter or circumference which increases and then decreases again at optionally regular intervals in itq longitudinal direction and having an internal diameter or cavity circumference which decreases and then increases again at optionally regular intervals in its longitudinal direction. The thin-walled tube thus has a sheath 28 whose wall thickness changes in the longitudinal direction of the thin-walled tube.
Figure 9 shows a longitudinal section through a thin-walled tube with a cross-section which increases at optionally regular intervals in its longitudinal direction, the wall thickness of the thin-walled tube remaining constant in its longitudinal direction.
Figures 10 and 11 show a simplified schematic view of a known device for the production of spooled members which are suitable fora heat exchanger according to the invention. The continuous thin-walled tube 1 supplied is wound by means of a thread guide 2 which moves to and fro onto a rotating perforated reel holder 3 so that a spooled member 4 is produced which is made up in the manner of a coil of several layers or portions of continuously supplied and wound thin-walled tube 1 which crosses over at a predetermined angle.
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., -~28928 Figure 12 3hows a longitudinal section through a spooled member 4 which is produced, for example, using a device described with reference to Figures 10 and 11. The spooled member 4 is provided at its two ends 5 with flange-like projections 7 made of a curable casting composition which has been brought into the desired shape by centrifugal casting. The openings of the thin-walled tubes of the spooled member 4 can be freed by severing a part of the flange-like projections 7 along the lines A and B. The perforated reel holder 3 ensures that the spooled member 4 is traversed radially.
The spooled member 4 illustrated in a longitudinal section in Fig~re 13 is formed by the uniform winding of a - continuous thin-walled tube on a co~ically designed reel holder 3 and thus has a conical shape itsel. With this ~pooled member 4, the ends of the individual tube portions are freed by severing a portion of the flange-like projections 7 (as already described with reference to Figure 12).
The qpooled member 4 illustrated in the longitudinal - 20 section in Figure 14 is produced by the uniform winding of a continuous thin-walled tube onto a diabolo shaped reel holder 3 and therefore has a diabolo shape itself. In this spooled member 4, the ends of the individual tube portions are already freed by severing a portion of t~e flange-like pro-jections 7 (as already described with reference to Figure 12).
The spooled member 4 illustrated in the longitudinal ; section in Figure 15 is produced by the uniform winding of a continuous thin-walled tube onto a barrel-shaped reel holder 3 and is thus barrel-shaped itself. With thi~ spooled - 30 mémber 4, the ends of the individual tube portions are freed by separating a portion of the flange-like projections 7 (as already described with reference to Figure 12).

- 21 _ ~12892~

The spooled member 4 illustrated in Figure 16 i9 produced by the uniform winding of a continuous thin-walled tube on a circular cylindrical reel holder and thus has a circular cylindrical shape itself. This spooled member 4 is provided with a flange-like projection 7 only at one end so that the ends of the individual tube portions of the spooled member 4 are freed only on this one side by the severing of portion of the flange-like projection 7 already described.
The path of flow of a fluid through the thin-walled tube of a spooled me~ber of this type runs in the manner of that of a U-shaped pipe. This means that the inlet and outlet openings for the fluid lie in one and the same plane in this spooled member.
Figure 17 shows a spooled member of the type pro-duced when the flange-like projections 7 are partially severed, for example, in the manner shown in Figure 12 along the lines A-A and B-B.
Figure 18 shows the use of a spooled member 4 pro-duced in the manner described with reference to Figures 10 to 12 in a heat exchanger according to the invention. The spooled member 4 with the flange-like projections 7 is arranged in a correspondingly dimensioned housing 10 in this case. A first fluid 8 flows through the inlet nozzle 11 into a di~tribution chamber 16 of the heat exchanger and passes thence into the inlet openings of the thin-walled tubes arranged in the spooled member 4, flows through them and leaves them at the opposite end of the spooled member 4, passe~ into a collecting chamber 17 of the heat exchanger and leaves it through an outlet nozzle 12. It can also flow through the thin-walled tubes in the opposite direction.

. ~

11289Z~3 A second fluid 9 flows through an inlet nozzle into a core chamber 18 of the spooled member 4 which is sealed at its end 15, and flows through the spooled member 4 in the radial direction from the interior outwards and passes into an annular cylindrical collection chamber 19, whence it leave~
the heat exchanger through an outlet nozzle 14.
Figure 19 shows a heat exchanger according to the invention in which the spooled member 4 is provided with a partition wall 21 which is arranged in such a way, however, that the free flow cross-section of the individual thin-walled tubes is not interrupted thereby. A first fluid 8 traverses the heat exchanger in the same way as described with reference to Figure 18. A second fluid 9 flows through the inlet nozzle 13 of the heat exchanger into an annular cylindrical distribution chamber 20, then traverses the right half of the spooled member 4 in a radial direction from the exterior inwards and enters the core chamber 18 of the spooled member 4 which is sealed at both end faces 15. The second fluid 9 then traverses the left half of the spooled member 4 in a radial direction from the interior outwards and passes into the annular cylindrical collection chamber 19, whence it leaves the heat exchanger through the outiet nozzle 14.
Figure 20 shows a heat exchanger according to the invention in which the thin walled tubes of the spooled member 4 according to Figure 16 which are provided with flange-like projection 7 only on one side and are cut away and the inlet openings and the outlet openings of the individual thin-walled tubes are each off~et by 180 relative to each other, and thus face each other, i.e., are arranged in a similar manner to that known from conventional heat llZ8928 exchangers with U-shaped pipes. With thiR heat exchanger, a first fluid 8 flows through the inlet nozzle 11 into the distribution chamber 16,' passes thence into the intqrior of the thin-walled tubes of the spooled member 4, traverses it firstly in one direction and then in the sub~tantially opposite direction and subsequently enters the collection chamber 17 whence it leaves the heat exchanger again through the outlet nozzle 12. The second fluid 9 flows through the inlet nozzle 13 into the annular cylindrical distribution chamber 20, whence it flows through the spooled mem~er 4 from the exterior inwards in a radial direction and enters the core chamber 18 of'the spooled member 4, which is sealed at' the end 15, and thence leavesthe heat exchanger through the outlet nozzle,14.
Figure 21 shows a heat exchanger according to the invention which combines the essential features of the spooled member shown in Figures 19 and 20. In this case, the first fluid 8 1OWS through the thin-walled tubes of the spooled member 4 in the manner described with reference to Figure 20 and the second fluid 9 flows round the thin-walled tubes of the spooled member 4 in the manner described with reference to Figure 19. ' Figures 22 to 24 'show a simplified schematic view of a device for the production of a ~pooled member 4 from two thin-walled tubes 1 which are supplied separately from two : . .
spoolq 6 but are wound simultaneously onto a common reel holder 3. By arranging the thread guides 2 offset in the longitudinal direction of the ~pooled member 4 in the manner ~hown in Figures 23 and 24, it is possible to produce a 30 spooled member 4 in which the respective layers of the two thin-walled tubes 1 are wound offset relative to each other . - 24 -1~2892~3 in the longitudinal direction of the spooled member 4 90 a~
to form a region 22 at each of the ends of the spooled member 4 which is formed only by one of the two thin-walled tubes, A spooled member which has the inlet and the outlet opening~
for a first fluid on one side and those for a second fluid at the opposite end is produced by removing these two regions 22.
The use of a spooled member produced in this way in accordance with Figures 22 to 24 in a heat exchanger accord-ing to the invention is illustrated in Figure 25. In addition, the spooled member 4 is located in a solid or liquid sub-stance 23 which is a good conductor of heat in this embodi-ment illustrated in Figure 25. A heat exchanger of thiq type allows, for example, the heat to be transferred from a first fluid 8 to a second fluid 9 utilising the good heat conducting properties of the substance 23, the fluid 8 flow-ing through the corresponding layer~ of the spooled member 4 formed by a th.in-walled tube, for example, in the manner illustrated in Figure 20. In Figure 25, this path of fl.ow iB indicated schematically as a broken llne, while the second fluid 9 follows a path of flow which is a mirror image of it, which is indicated by the continuous line in Figure 2S.
. Figure 26 shows a spooled member 4 with flange-like projections 7 arranged at its two ends, the flange-like projections 7 (like those of the spooled member 4 illustrated in Figures 12 to 21) having a larger external circumference than the spooled member 4. The flange-like projections 7 and the spooled member 4, however, have an elliptical annular cross-section in this case.

_ 25 -1121~92~
Figure 27 shows that a spooled member 4 can be cast not only at its ends and cut up accordingly in the manner de~cribed above but can also be ca~t along one or more of its generating lines. In the embodiment illustrated in Figure 27, the thin-walled tubes consequently merge into two circular cylindrical cavities 24 and 25 which are surrounded by a wall consisting, for example, of cast resin~, which, as explained with reference to the Figures already described, act as distribution and collecting chambers for the fluid flowing through the thin-walled tubes.
Figure 28 shows a cross-section through a spooled member 4 which is obtained if thin-walled tubes are wound on a reel holder 3 with a rectangular cross-section having rounded corners.
Figure 29 showæ a cross-section through a spooled member 4 which is obtained if a spooled member 4 according to Figure 28 is cast, for example, in cast resin, aiong two of its generating lines in the manner described with reference to Figure 27 and the openings of the thin-walled tubes are then freed in the manner already described.
Figure 30 shows a cross-section through a spooled member 4 which can also be produced from the spooled member 4 illustrated in Figure 28, and Figure 31 shows one which is obtained in a manner similar to that described in Figure 27 from a spooled member 4 of circular annular cross-section.
The embodiments according to the invention illustrated in Figures 27 to 31 are eminently suitable for heattransfer from a Liquid medium to a gaseous medium (for example, as a car radiator) or vice versa, the liquid medium preferably flowing through the thin-walled tubes and the gaseous medium flowing round the thin-walled tubes.

`` llZ8928 Figure 32 shows a cross-section through an annular coil holder 31 of the type which is suitable, for the pro-duction of a disc-shaped coiled member from thin-walled tubes.
Figure 33 shows a possible arrangement for the - individual thread ~ortions, for example, of a continuously wound thin-walled tube`, on the annular coil holder 31. In this case, the tube protions can be arranged in se~eral superimposed layers which cross each other several time~.
By casting the external portion of the annular coil holder 31, for example, in a curable casting composition and then removing a part of the annular casting-composition-projection to the region of the turned back parts 32 of the tube portions, the thin-walled tube 1, which i9 initially continuous, ïs divided into a plurality of equally long tube portions arranged in several layers and crossing each other several times and the openings in the individual tubè portions are freed at each severing point. The external diameter of the unworked part of the annular casting composition projection is thus generally equal to, or slightly smaller than, the external diameter of the annular coil holder 31.
Figure 34 shows a sectional illustration of the plan view of a disc-shaped embodiment of the heat exchanger according to the invention in which a wound member 4 according to Figure 33 has been used. By suitably arranging the inlet nozzle 11 and the distribution chambers 16 as well as the collection chambers 17 and the outlet nozzle 12 for a first fluid 8 and the inlet nozzle 13 and the distribution chambers 20 as well as the collection chambers 19 and the outlet nozzle 14 for the second fluid 9, a heat exchanger having a total of two inlets and two outlets for each of the two fluids 8 and 9 is obtained. In this case, the liquid stream entering the heat exchanger through the inle~ at any time is divided so that only half of each partial atream of fluids 8 and 9 reaches the two outlets communicating with the corresponding inlet at any time and combines there with one of the halves of the other partial stream of fluids 8 and 9. Figure 34 shows this path of flow by arrows and four tube portions drawn as thick lines.
Figure 35 shows a cross-section along the line XXV - XXV through Figure 34. The annular coil holder 31, the annular projection 7 made of a curable casting com, position, the wound member 4 a~ well as the two opposing distribution chambers 16 for the first fluid 8 can be seen.
Figure 36 shows another possible arrangement of a continuous thin-walled tube 1 on an annular coil holder 31 for the production of a tube winding for disc-shaped em~odi-ments of the heat exchanger according to the invention.
Figure 37 shows a cross-section through a heat exchanger according to the invention in which a wound mem~er according to Figure 36 has been used. The openings in the ~ individual tube layers have been freed here, as already ;~ described with reference to Figures 32 to 35. In this embodiment, the first fluid 8 flows through the inlet nozzle -11 into the distribution chamber 16, then traverses the thin-walled tubes of the wound member 4, enters the collection chamber 17 and leaves the heat exchanger through the outlet nozzle 12. The reference numerals of the remaining parts of this heat exchanger correspond to the parts described by way of example with reference to Figure 34. An exemplary second fluid participating in the heat transfer traverAes the heat exchanger illustrated in Figure 37 in substantially the axial direction thereof.

A 28 _ Whereas the heat exchanger illustrated in Figure 37 is thus suitable for transferring heat from one medium to another, a total of three media can participate in the heat transfer in the heat exchanger illustrated in Figure~
34 and 35. With the heat exchanger illustrated in Figures 34 and 35, the third medium could be, for example, a solid or liquid substance which is a good conductor of heat and which surrounds the thin tubes from the outside or a third fluid which flows through the heat exchanger in its axial direction.
The use of the disc-shaped wound member described by way of example with reference to Figures 33 and 36 is ; not restricted to the production of substantially disc-shaped heat exchangers but rather it is possible according to the invention to superimpose a plurality of these wound members and, in this way, to allow an optional number of fluids to participate in the transfer of heat.
Thus it has now been found that the specific heat transfer capacity of the thin-walled tubes can also be used in heat tran~fer apparatus (heat exchangers), with consider-able improvement. Thin-walled tubes of this type which can be produced by a rapid spinning process are in fact parti-cularly suitable for heat transfer if they have properties and/or a shape which increase their thermal conductivity and/or their heat transmission, and if they are arranged, utilising their flexibility, in such a way that the heat exchange apparatus produced from thin-walied tubes of this type have a greater resistance to external mechanical stresses so that they guarantee an undiminished heat transfer capacity even after prolonged operation.

_ 29 -~28928 The invention thus permits an improvement in the thermal conductivity, heat transmission and heat transfer properties of thin-walled tubes, and the provision of a heat transfer apparatus produced from such tubes which, with regard both to its production and to its serviceability and heat transfer capacity, does not have the disadvantages of the heat exchangers produced from known hollow threads.

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:,

Claims (50)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. An apparatus for transferring heat through tubes, comprising:
a plurality of thin-walled tubes composed of a melt-spinnable synthetic polymer, each tube having an internal cross-section of from 30 to 95% of the total cross-section of the tube and an elongation at rupture of less than 100%.

2. An apparatus according to claim 1, wherein all of the thin-walled tubes are arranged in the form of at least one of regular loops and irregular loops over their respective lengths.

3. An apparatus according to claim 1, wherein the thin-walled tubes are arranged in the form of at least one regular loop and irregular loops over the entirety of their respective lengths.

4. An apparatus according to claim 1, wherein the thin-walled tubes are arranged in the form of at least one of a spatially extending coil and a spiral lying in one plane.

5. An apparatus according to claim 1, wherein the thin-walled tubes are arranged in several layers.

6. An apparatus according to claim 5, wherein the thin-walled tubes in each layer cross over the thin-walled tubes in each of the adjacent layers several times.

7. An apparatus according to claim 1, 4 or 6, in the form of a multi-layer spooled or wound member.

8. An apparatus according to claim 1, 4 or 6, in the form of a spooled or wound member having a round, elliptical or polygonal annular cross-section with rounded corners.

9. An apparatus according to claim 1, 4 or 6, in the form of a spooled or wound member having a rectangular annular cross-section with rounded corners.

10. An apparatus according to claim 1, comprising a spooled or wound member with an annular cross-section which varies along its longitudinal axis.

11. An apparatus according to claim 10, wherein said cross-section increases along said axis.

12. An apparatus according to claim 10, wherein said cross-section decreases along said axis.

13. An apparatus according to claim 1, formed of a woven, worked or knitted sheet or form a sheet produced by a depositing method.

14. An apparatus according to claim 1, further comprising at least one inlet each and at least one outlet each for at least three fluids participating in the heat transfer.

15. An apparatus according to claim 1, wherein a majority of the individual thin-walled tubes are arranged in the form of at least one of regular loops and irregular loops over a majority of their respective lengths.

16. A thin-walled tube composed of a melt-spinnable synthetic polymer, having an internal cross-section of between 30 and 95% of the total cross-section and an elongation at rupture of less than 100%, the tube being characterised by at least one characteristic selected from:
i) the coefficient of heat-transmission of the wall of the thin-walled tube is at least 1500 to at least 4500 W/m2K, ii) the outside diameter of the thin-walled tube is between 0.04 and 4 mm, iii) the wall-thickness of the thin-walled tube is between 5 and 100 µm, iv) at least one of an internal and external surface of the thin-walled tube is profiled, v) the cross-section of the thin-walled tube varies, in the longitudinal direction in at least one of shape and size, vi) the thin-walled tube consists of two or more components, vii) only some of the components of the thin-walled tube are porous.

17. A thin-walled tube composed of a melt-spinnable synthetic polymer, the tube having an internal cross-section of from 30 to 95% of the total cross-section thereof and an elongation at rupture of less than 100% wherein the thin-walled tube contains at least one additive selected from graphie, metal particles, fillers, stabilisers, additives, carbon black and dye pigments.

18. A thin-walled tube according to claim 17, wherein the heat transmission coefficient of the thin-walled tube is from at least 1500 to at least 4500 W/m2K.

19. A thin-walled tube according to claim 17, wherein the tube has a substantially circular cross-section.

20. A thin-walled tube according to claim 17, 18 or 19, wherein the tube has an external diameter in the range of from 0.04 to 4 mm.

21. A thin-walled tube according to claim 17, 18 or 19, wherein the tube has an external diameter ranging from 0.04 to 1 mm.

22. A thin-walled tube according to claim 17, 18 or 19, wherein the tube has a wall thickness in the range of from 5 to 100 µm.

23. A thin-walled tube according to claim 17, 18 or 19, wherein the tube has a wall thickness in the range of from 5 to 50 µm.

24. A thin-walled tube according to claim 17, 18 or 19, wherein the tube has a wall thickness in the range of from 5 to 20 µm.

25. A thin-walled tube according to claim 17, 18 or 19, wherein at least one of an internal surface and an external surface of the thin-walled tube is profiled.

26. A thin-walled tube according to claim 17, wherein the tube has a cross-section which changes continuously or intermittently in at least one of shape and size in the longitudinal direction thereof.

27. A thin-walled tube according to claim 26, wherein the tube has a cross-section which changes periodically in the longitudinal direction thereof.

28. A thin-walled tube according to claim 17, wherein the thin-walled tube consists of two or more components.

29. A thin-walled tube according to claim 28, wherein a proportion of the components is porous.

30. A thin-walled tube according to claim 17, 18 or 19, wherein the thin-walled tube is porous.

31. A thin-walled tube composed of a melt-spinnable synthetic polymer, the tube having an internal cross-section of from 30 to 95% of the total cross-section thereof, and an elongation at rupture of less than 100%, wherein the heat transmission coefficient of the thin-walled tube wall is from at least 1500 to at least 4500 W/m2K.

32. A thin-walled tube, composed of a melt-spinnable synthetic polymer, the tube having an internal cross-section of from 30 to 95% of the total cross-section thereof, and an elongation at rupture of less than 100%, wherein the tube has a substantially circular cross-section.

33. A thin-walled tube, composed of a melt-spinnable synthetic polymer, the tube having an internal cross-section of from 30 to 95% of the total cross-section thereof, and an elongation at rupture of less than 100%, wherein the tube has an external diameter in the range of from 0.04 to 4 mm.

34. A thin-walled tube composed of a melt-spinnable synthetic polymer, a tube having an internal cross-section of from 30 to 95% of the total cross-section thereof and an elongation at rupture of less than 100%, wherein the tube has an external diameter ranging from 0.04 to 1 mm.

35. A thin-walled tube composed of a melt-spinnable synthetic polymer, the tube having an internal cross-section of from 30 to 95% of the total cross-section thereof and an elongation at rupture of less than 100%, wherein the tube has a wall thickness in the range of from 5 to 100 µm.

36. A thin-walled tube according to claim 35, wherein the tube has a wall thickness in the range of from 5 to 50 µm.

37. A thin-walled tube according to claim 35, wherein the tube has a wall thickness in the range of from 5 to 20 µm.

38. A thin-walled tube composed of a melt-spinnable synthetic polymer, the tube having an internal cross-section of from 30 to 95% of the total cross-section thereof and an elongation at rupture of less than 100%, wherein at least one of an internal surface and an external surface of the thin-walled tube is profiled.

39. A thin-walled tube composed of a melt-spinnable synthetic polymer, the tube having an internal cross-section of from 30 to 95% of the total cross-section thereof and an elongation at rupture of less than 100%, wherein the tube has a cross-section which changes continuously or intermittently in at least one of shape and size in the longitudinal direction thereof.

40. A thin-walled tube according to claim 39, wherein the tube has a cross-section which changes periodically in the longitudinal direction thereof.

41. A thin-walled tube composed of a melt-spinnable synthetic polymer, the tube having an internal cross-section of from 30 to 95% of the total cross-section thereof and an elongation at rupture of less than 100% wherein the thin-walled tube consists of two or more components.

42. A thin-walled tube according to claim 41, wherein only a portion of the components is porous.

43. An apparatus according to claim 1, 2 or 6, wherein said tubes have at least one characteristic selected from:
i) the coefficient of heat-transmission of the wall of the thin-walled tube is at least 1500 to at least 4500 W/m2K, ii) the outside diameter of the thin-walled tube is between 0.04 and 4 mm, iii) the wall-thickness of the thin-walled tube is between 5 and 100 µm, iv) at least one of an internal and an external suface of the thin-walled tube is profiled, v) the cross-section of the thin-walled tube varies, in the longitudinal direction in at least one of shape and size, vi) the thin-walled tube consists of two or more components, vii) only some of the components of the thin-walled tube are porous.

44. An apparatus according to claim 1, 2 or 6, wherein said tubes have at least one characteristic selected from:
i) the tubes contain at least one of fillers, stabilizers, additives and pigments, ii) the tubes are of substantially circular cross-section, iii) the outside diameter of the tubes is between 0.04 and 1 mm, iv) the wall-thickness of the thin-walled tubes is between 5 and 60 µm, v) the thin-walled tubes are porous.

45. An apparatus according to claim 1, 4 or 6, wherein the tube walls have a coefficient of heat-transmission of at least 4500 W/m2K.

46. A tube according to claim 16, wherein the tube wall has a coefficeint of heat-transmission of at least 4500 W/m2K.

47. A tube according to claim 17, 19 or 27, wherein the tube wall has a coefficient of heat-transmission of at least 4500 W/m2K.

48. A tube according to claim 31, 32 or 33, wherein the tube wall has a coefficient of heat-transmission of at least 4500 W/m2K.

49. A tube according to claim 34, 35 or 38, wherein the tube wall has a coefficient of heat-transmission of at least 4500 W/m2K.

50. A tube according to claim 39 or 41, wherein the tube wall has a coefficient of heat-transmission of at least 4500 W/m2K.