GB2039357A

GB2039357A - An apparatus for transferring heat by means of tubes and tubes suitable for this purpose.

Info

Publication number: GB2039357A
Application number: GB7944541A
Authority: GB
Original assignee: Akzo NV
Current assignee: Akzo NV
Priority date: 1978-12-29
Filing date: 1979-12-28
Publication date: 1980-08-06
Also published as: FR2445213A2; DE2856642A1; CA1128928A; IT7951146A0; LU82047A1; BE880753A; FR2445213B2; AU528764B2; ES267914Y; ES267914U; CH645973A5; IT1164801B; DE2856642C2; GB2039357B; NL7909338A; IT7951238A0; JPS55128009A; ES487355A1; AU5398479A; BR7908566A

Abstract

An apparatus for transferring heat by means of thin-walled tubes composed of a melt-spinnable synthetic polymer. Each tube has a cross-section of flow from 30 to 95% of the total cross-section of the tube and a breaking elongation of less than 100%.

Description

SPECIFICATION An apparatus for transferring heat by means of tubes and tubes suitable for this purpose The present invention relates to an apparatus for transferring heat by means of tubes and to tubes suitable for this purpose.

A "thin-walled tube" in the context of the invention of the main patent is 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 is less than about 15% of the largest external dimension of the tube crosssection. With a circular cross-section, the largest external dimension corresponds to the external diameter and with an elliptical cross-section it corresponds to the largest external axis.

The thin-walled tubes are stronger than conventional tubes but nevertheless, have a large crosssection of flow and a closed, i.e. undamaged sheath.

They are characterised by an internal cross-section forflow ranging from 30 to 95% of the total cross-section and by a breaking elongation of less than 100%. Tubes having a cross-section of flow of from 60 to 95% of the total cross-section are preferred.

The thin-walled tubes can be produced from any conventional melt-spinnable polymers. Examples of particularly suitable polymers, due to their special properties in use, include the polyamides, in particular polycaprolactam and polyhexamethylene adipic acid amide; polyesters, in particular polyethyleneterephthalate; polyolefins, in particular polyethylene and polypropylene; 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. Tubes composed of polyolefins, in particular polypropylene are preferred if chemical stability is desired as well as good thermal stability.

The tubes are produced from polyamides, in particular from polyhexamethylene adipic acid amide if greater strengths 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 tubes to have a microporous sheath.

Thin-walled tubes of this 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 strength which could otherwise only be achieved by additional (but difficult) re-drawing.

In order to avoid large spinning heghts (distance from spinneret to take-off device) it is proposed that the phenomenon ofthe "natural bending of the thread" be utilised. This generally occurs 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 measured uniform 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) is gradually removed in a horizontal direction and optionally lifted simultaneously in a vertical direction.

Inspite of the changed position of the take-off device the thread continues to move vertically downwards 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 length of a few centimetres and does not change its position substantially even if the position 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 distance needed for cooling the freshly spun threads.

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 possible 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 possible 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 orderto produce stable tube configurations having larger external dimensions and very small wall thicknesses, as already proposed, a cavityforming 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 the production of heat exchangers in which case they generally have a circular cross-section and an external diameter of from about 40 to 1000 um or more with wallthicknesses of about 5 to 50 um or more.

An object of the present invention is to improve the known heat exchangers composed of hollow filaments with respect to their heat transfer capacity as well as their serviceability and to provide an apparatusfortransferring heat which can be produced in a simple and rapid manner and does not have the disadvantages of the known heat exchangers composed of hollow filaments.

According to the invention there is provided an apparatus for transferring heat, comprising a plurality of thin-walled tubes composed of a meltspinnable synthetic polymer, each tube having a cross-section of flow of from 30 to 95% of the total cross-section of the tube and a breaking elongation of less than 100%. Thus embodiments of the present invention provide on the one hand, by utilising by means of the structural design of the apparatus the flexibility of the thin-walled tubes and on the other hand by the particular configuration of the thinwalled tubes already proposed by means of which their normal conductivity andlor their heat transmission is increased, and, finally, by suitable selection of particularly suitable configurations of the already proposed thin-walled tubes.

In a particularly preferred embodiment of the apparatus according to the invention, each individual thin-walled tube is arranged over the majority of its length, preferably over its entire length and/or the majority of all thin-walled tubes, preferably the entirety of all thin-walled tubes in the form of regular and/or irregular loops.

A heat transfer apparatus of this type, produced from thin-walled tubes has a greater resistance to external mechanical stresses so that it ensures that the heat transfer capacity is not reduced even after prolonged operation. This embodiment of the apparatus according to the invention does not therefore 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 a distance from each other. This known arrangement, which is also conventional in metal tubular heat exchangers, does in fact make the production of such heat exchangers from hollow threads difficult and expensive. Moreover, the bundle of hollow threads can be damaged even by minimal external mechanical influences, for example kinked, in this known arrangement of the hollow threads.

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 particular 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 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 coil, the thin-walled tubes advantageously being arranged in several layers for achieving an easily penetrable winding packet which is stable 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 transfer surface in a small space since, although the thin-walled tubes touch each other at the points of intersection, only an insignificant proportion of the heat transfer surface is lost by the reciprocal contact between the thin-walled tubes.

The reel 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 member can also have a cross-section which increases or decreases along its longitudinal axis.

Thus, its surface area can be designed, for example, conical, diabolo shaped, truncated pyramid shaped with rounded 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 produce 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 polyurethane, 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 projection of this type can however also be provided on one only of the two faces of the wound member.The arc-shaped 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) projections 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 crossing each other several times, whose 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) projections 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, as 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 each 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 the other half of this plane.

It is also possible 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 together.

A heat exchanger according to the invention produced 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 a 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 of desired size, in which case the thin tubes are preferably 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.

Itis also possible 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 fluid 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 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 is 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 whereeverthere are only relatively small temperature differences for 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 suitable 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 exchangers.

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 engine 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 sun, 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 solving 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 materials to gaseous and/or liquid fluids and vice versa, in which case, care has to be taken to limit the temperature of the materials participating in the heat exchange accordingly to the physical and chemical properties of the thin tubes used.

When dimensioning the heat exchanger according to the invention, it should 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 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 nick-resistance 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 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 transmission resistance through the wall of the thin tubes is substantially negligible relative to the heat transfer resistances occurring inside and outside the thin tubes. This means that thin tubes made of a material having relatively good properties of thermal conductivity should have thicker walls than those with very low thermal conductivity values.

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 crosssection 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 crosssection 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-dimensional curvature in which the radius of curvature is sufficiently large to prevent nicking of the thin tubes. The radius of curvature is generally smaller than 1 m but it can also be larger.

To achieve the object forming a basis of the present invention, it is not necessary 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 andor for rectilinear and loop-form thin tubes to be present providing the total length of all the thin tubes and/or tube pieces present in loop form is greater than the total length of all rectilinear thin tubes and or tube pieces.

This loop form of the thin tubes allows the thin tubes to cross over optionally several times at substantially short intervals and to support each other in this way so that each thin tube is generally unsupported only over relatively short portions of their length so that the risk of the thin tubes being nicked is reduced considerably.

In the search for further means of improving the known heat exchangers as well as the apparatus according to the invention, it has now surprisingly been found that a further increase in the heat transfer capacity as well as an additional improvement in the serviceability of heat exchangers composed of hollow threads can be achieved by a particular design of the thin-walled tubes already proposed and by the use of a few of the already proposed embodiments thereof in the apparatus according to this invention.

Particularly significant results are achieved if in the apparatus for transferring heat according to the invention, thin-walled tubes are such that: the heat transmission coefficient, as hereinafter defined, of the wall of the thin-walled tubes is from at least 1,500 to as least 4,500 W m2K and'our the external diameter of the thin-walled tubes ranges from 0.04 to 4 mm and or the wall thickness of the thin-walled tubes ranges from 5 to 100 ttm, in particular from 5 to 20 Ltm and/or the thin-walled tubes are internally andior externally profiled and,or the thin-walled tubes have a cross-section which changes continuously or intermittently in shape and/or size in its longitudinal direction, optionally also periodically and/or the thin-walled tubes are produced from two or more components, wherein one or more components can optionally also be porous.

Since thin-walled tubes having the abovementioned properties have not only proven most suitable in an apparatus for transferring heat with the features according to the invention, but can also lead to improvements in conventional heat exchangers composed of hollow threads, according to a further aspect of the invention there is also provided a thin-walled tube composed of a melt-spinnable synthetic polymer having a cross-section of flow of from 30 to 95% of the total cross-section and a breaking elongation of less than 100%, wherein the coefficient of heat transmission as herein defined of the wall of the thin-walled tube is at least 1,500 to at least 4,500 W/m2K and/or the external diameter of the thin-walled tube is in the range from 0.04 to 4mm andior the wall thickness of the thin-walled tube ranges from 5 to 100 um and/or that the thin-walled tube is internally and/or externally profiled and/or the cross-section of the thin-walled tube varies continuously or intermittently in shape and/or size, in the longitudinal direction thereof and/or the thin-walled tube consists of two or more components and/or only a proportion of the components of the thin-walled tube is porous. The thin-walled tubes can have the properties according to the invention individually or in any combination.

Moreover, it has been found that an increase in the heat transfer capacity as well as an improvement in the serviceability of the apparatus according to the invention for transferring heat can also be achieved by a suitable selection of quite specific embodiments of the already proposed thin-walled tubes. Particularly good results are achieved if: the thin-walled tubes contain fillers, stabilisers, additives, carbon black, dye pigments of the like andior the thin-walled tubes have a substantially circular cross-section and/or the external diameter of the tubes ranges from 0.04 to 1 mm and/or the wall thickness of the thin-walled tubes ranges from 5 to 50 m and/or the thin-walled tubes are porous.

Thus according to the invention, thin-walled tubes having the already proposed properties individually or in combination can also be used.

In order to increase the heat transfer capacity of the apparatus according to the invention, it is particularly advantageous to use those thin-walled tubes which contain good heat conducting materials such as metals, graphite and the like in dust or powder form. The thin-walled tubes can however contain also and in addition for example, fillers, stabilisers, carbon black, dye pigments or the like.

In addition to the heat transfer occurring through the wall of the thin-walled tubes, the use of microporous thin-walled tubes also allows a liquid to be cooled additionally by evaporating or vaporizing a proportion of the liquid to be cooled on the surface of the porous thin-walled tubes when correspond ingly high pressure are applied.

The slight wall thickness of the thin-walled tubes leads to a heat exchanger having a large heat exchange capacity, which can be further increased since the permissible operating pressure inside the tubes and thus the fluid rate of flow obtainable are relatively high due to the high strength of these tubes.

Thin-walled tubes, having for example, an elliptical or triangular, rectangular, pentagonal, hexagonal and polygonal cross-section are suitable for the production of the heat exchanger according to the invention, but particularly those having a round cross-section since, in a heat exchanger with crossing thin-walled tubes according to the invention, produced from thin-walled tubes having a round cross-section, tubes contact each other essentially only at point and thus, only a minute proportion of the entire heat exchange area is lost through these points of contact.

The thin-walled tubes can also be profiled internally and/or externally. It is also possible to join two, three or more thin-walled tubes lying in a parallel position relative to each other together firmly at their respective contacting surfaces, for example, by fusion, welding or adhesion. Thin-walled tubes having a cross-section which optionally changes periodically in shape and/or size continuously or intermittently in their longitudinal direction are also suitable. Thin-walled tubes of this type can advantageously influence the mode of operation of the heat exchanger according to the invention in various ways.Thus, by means of thin-walled tubes which are suitably profiled internally and/or externally it is possible, for example, to increase the internal and/or external heat exchange surface, to improve the nick-resistance of the thin-walled tubes and/or to reduce the contact area of the cross over of the thin-walled tubes. Moreover, the heat transfer capacity is further increased since the heat transition on the profiled surfaces of the thin-walled tubes is improved by the formation of whirls in the respective fluid. Apparatus which are more compact and/or more stable in shape can also be produced in part from thin-walled tubes of a non-circular cylindrical shape.

To ensure good conduction of heat through the thin-walled tubes, the wall thereof should be as thin as possible but should still be sufficiently thick to meet the mechanical requirements. Thin-walled tubes whose wall thickness ranges from 5 to 100 ttm have proven advantageous for most purposes, good heat transmission coefficients being achieved with thin-walled tubes whose wall thicknesses ranges from 5 to 50 tim, and particularly good coefficients with those whose wall thicknesses ranges from 5 to 2Oum.

The cross-sections of the thin-walled tubes used should be suitably dimensioned for achieving good heat transmission (k-coefficient). Thus, from among the thin-walled tubes with round cross-sections, those having an external diameter ranging from 0.04 to 4 mm, in particular from 0.04 to 1 mm have proven particularly advantageous.

With the thin-walled tubes which can be used for the production of the heat exchanger according to the invention, the heat transmission coefficient of the wall of the thin-walled tubes should be at least 1500 W/m2K, but particularly at least 4500 W/m2K.

The term heat transmission coefficient of the wall of the thin-walled tubes is interpreted in this context as the quotient of the thermal conductivity of the material used for the thin-walled tubes measured in W/m K and the thickness of the thin-walled tubes measured in metres m.

The invention will now be described in more detail with reference to the drawings.

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 10 and 11 show a simplified schematic view of the production of a multi-layer wound member from a thin-walled tube, Figure 12 shows a simplified schematic view of a longitudinal section through a spooled member of thin-walled tubes having a flange-like projection at its end 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 16shows 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, Figure 22 to 24 show a simplified schematic view of the production of a spooled member made of two thin-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 crosssectional shapes, Figures 32 to 37 show a simplified schematic view of the production of an embodiment of the heat exchanger according to the invention from a substantially disc-shaped wound member from thinwalled tubes.

Figures 1to 5 show, by way of example, crosssections 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 its 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 longitudinal direction, optionally made of a differing material.

The thin-walled tube illustrated in Figure 3 has a substantially three-tabbed cross-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 thinwalled tube and enterring into its cavity 27, these projections being optionally made of a differing 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 configuration which can be produced, for example, by fusing three thin-walled tubes of round crosssection together on their common lines of contact.

Figure 7 shows a cross-section through a thinwalled tube with a cross member 29 arranged centrally inside the thin-walled 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 cross 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 its 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 for a heat exchanger according to the invention. The continuous thinwalled 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 cross over at a predetermined angle.

Figure 12 shows 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 Figure 13 is formed by the uniform winding of a continuous thin-walled tube on a conically designed reel holder 3 and thus has a conical shape itself. With this spooled member 4, the ends of the individual tube portions are freed by severing a proportion of the flange-like projections 7 (as already described with reference to Figure 12).

The spooled member 4 illustrated in the longitudinal section in Figure 14 is produced by the uniform winding of a continuous thin-walled tube onto a diabolo shape itself. In this spooled member 4, the ends of the individual tune portions are already freed by severing a proportion of the flange-like projections 7 (as already described with reference to Figure 12).

The spooled member 4 illustrated in the longitudinal section in Figure 13 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 this spooled member 4, the ends of the individual tube portions are freed by separating a part of the flange-like projections 7 (as already described with reference to Figure 12).

The spooled member 4 illustrated in Figure 16 is 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 part of the flange-like projection 7 already described.

The path of flow of a fluid through the thin-walled tube of a spooled member 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 produced 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 produced 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 flangelike 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 distribution 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, passes 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.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 leaves 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 cross-section of flow of the individual thin-walled tubes is not interrupted 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 space 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 outlet nozzle 14.

Figure 20 shows a heat exchanger according to the invention in which the thin-walled tubes of the spooled member4accordingto Figure 16 which are provided with flangle-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 offset by 1800 relative to each other, thus opposite to each other, i.e. are arranged in a similar manner to that known from conventional heat exchangers with U-shaped pipes.With this heat exchanger, a first fluid 8 flows through the inlet nozzle 11 into the distribution chamber 16, passes thence into the interior of the thin-walled tubes of the spooled member 4, traverses it firstly in one direction and then in the substantially opposite direction and subsequently enters the collection chamber 17 whence it leaves the heat exchanger again through the outlet nozzle 12. A second fluid flows through the inlet nozzle 13 into the annular cylindrical distribution chamber 20, whence it flows through the spooled member 4 from the exterior inwards in a radial direction and enters the core space 18 of the spooled member 4 which is sealed at the end 15 and thence leaves the 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 flows through the thinwalled 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 spooled member 4 from two thin-walled tubes 1 which are supplied separately from two spools 6 but are wound simultaneously onto a common reel holder 3. By arranging the thread guides 2 offset in the longitudinal direction of the spooled member 4 in the manner shown in Figures 23 and 24, it is possible to produce a spooled member4 in which the respective layers of the two-walled tubes 1 are wound offset relative to each other in the longitudinal direction of the spooled member 4 so as 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 openings 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 according to the invention is illustrated in Figure 25. In addition, the spooled member4 is located in a solid or liquid substance 23 which is a good conductor of heat in this embodiment illustrated in Figure 25. A heat exchanger of this 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 flowing through the corresponding layers of the spooled member 4 formed by a thin-walled tube, for example, in the manner illustrated in Figure 20. In Figure 25, this path of flow is indicated schematically as a broken line, 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 25.

Figure 26 shows a spooled member 4 with flangelike projections 7 arranged at its two ends, the flange-like projections 7 (like those of the spooled member 4 illustrated in Figures 12to 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.

Figure 27 shows that a spooled member 4 can be cast not only at its ends and cut up accordingly in the manner described above but can also be cast 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 resins, which, as explained with reference to the Figures already described, act as distribution and collectng 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 shows 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, along 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 heat transfer 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.

Figure 32 shows a cross-section through an annular coil holder 31 of the type which is suitable, for the production of a disc-shaped coiled memberfrom thin-walled tubes.

Figure 33 shows a possible arrangement for the individual thread portions, for example, of a continuously wound thin-walled tube, on the annular coil holder 31. In this case, the tube portions can be arranged in several superimposed layers which each cross each other several times. By casting the external portion of the annular coil holder 31, for example, into a curable casting composition and then removing a part of the annular casting composition projection into the region of the turned back fragment 32 of the tube portions, the thin-walled tube 1 which is initially continuous is divided into a plurality of equally long tube portions arranged in several layers and crossing each other several ttimes and the openings in the individual tube 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 a 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 inlet at anytime is divided so that only half of each partial stream 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 fourtube portions drawn as thick lines.

Figure 35 shows a cross-section along the line XXVI-XXVI through Figure 34. The annular coil holder 31, the annular projection 7 made of a curable casting composition, the wound member 4 as 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 embodiments 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 member 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 traverses the heat exchanger illustrated in Figure 28 in substantially the axial direction thereof.

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 Figures 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 of 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.

Claims

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

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

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

4. An apparatus according to any preceding claim wherein the thin-walled tubes are arranged in the form of regular and/or irregular loops over the entirety of their respective lengths.

5. An apparatus according to any preceding claim wherein the thin-walled tubes are arranged in the form of a spatially extending coil and/or a spiral lying in one plane.

6. An apparatus according to any preceding claim, wherein the thin-walled tubes are arranged in several layers.

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

8. An apparatus according to any preceding claim comprising a multi-layer spooled or wound member.

9. An apparatus according to any preceding claim comprising a spooled or wound member having a round, elliptical or polygonal annular cross-section with rounded corners.

10. An apparatus according to any preceding claim comprising a spooled or wound member having a rectangular annular cross-section with rounded corners.

11. An apparatus according to any preceding claim comprising a spooled or wound member with an annular cross-section which increases and/or decreases along its longitudinal axis.

12. An apparatus according to any preceding claim, comprising a woven, worked or knitted sheet or from a sheet produced by a depositing method.

13. An apparatus according to any preceding claim, further comprising at least one inlet each and at least one outlet each for at least three fluids participating in the hear transfer.

14. An apparatus according to claim 1 substantially as herein described with reference to the accompanying drawings.

15. A thin-walled tube composed of a meltspinnable synthetic polymer having a cross-section of flow of from 30 to 95% of the total cross-section and a breaking elongation of less than 100%, wherein the coefficient of heat transmission as hereinafter defined of the wall of the thin-walled tube is at least 1,500 to as least 4,500 W/m2K and/or the external diameter of the thin-walled tube is in the range from 0.04 to 4 mm and/or the wall thickness of the thin-walled tube ranges from 5 to 100 um and/or that the thin-walled tube is internally and/or externally profiled and/or the cross-section of the thinwalled tube varies continuously or intermittently in shape and/or size, in the longitudinal direction thereof and/or the thin-walled tube consists of two or more components and/or only a proportion of the components of the thin-walled tube is porous.

16. Atube according to claim 15, wherein the wall thickness of the tube is in the range of from 5 to 20 ttm.

17. A tube according to claim 15 or 16, wherein the cross-section of the tube varies periodically in the longitudinal direction.

18. An apparatus according to any of claims 1 to 14, wherein the thin-walled tubes have the features, individually or in any combination, claimed in any of claims 15to 17.

19. An apparatus according to any of claims 1 to 14 and 18 wherein the thin-walled tubes contain fillers, stabilisers, additives, carbon black or dye pigments andiorthe thin-walled tubes have a sub stantially circular cross-section and/orthe external diameter of the tubes is in the range of from 0.04 to 1 mm and/or the wall thickness of the thin-walled tubes is in the range of from 5 to 50 vim and/or that the thin-walled tubes are porous, the thin-walled tubes having the above-mentioned features individually or in any combination.