GB1581827A

GB1581827A - Heat transfer to and from yarns

Info

Publication number: GB1581827A
Application number: GB1502376A
Authority: GB
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1974-10-18
Filing date: 1977-07-12
Publication date: 1980-12-31

Description

(54) HEAT TRANSFER TO AND FROM YARNS (71) We, IMPERIAL CHEMICAL INDUSTRIES LIMITED, Imperial Chemical House, Millbank, London SW1P 3JF, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to heat transfer to and from yarns and in particular to an improvement in or modification of the apparatus described in patent specification 1 529 674 for transferring heat between a fluid and an advancing filamentary yarn which may be twisting as for example in a false twist crimping (texturing) process.

In the present invention it has been found that apparatus as described in the above mentioned specification is effective when the bores of the yarn entry and exit tubes are partially restricted eg by narrowing or tapering at the end portions thereof remote from the vortex chamber, and when the fluid entry channels are inclined at an acute angle to the yarn entry tube. By using such restricted tubes an increase in the efficiency of heat transfer between fluid and yarn may be obtained. By this is meant that for heating a yarn at a given speed of advance and air temperature, the yarn achieves a higher temperature for a given air pressure and flow; conversely a lower air pressure and flow can be used to achieve the same yarn temperature. A corresponding increase in the efficiency of heat transfer is also obtained when the apparatus is used to cool an advancing yarn.By using such angling of the fluid entry channels a forwarding effect on the yarn is obtained. This is particularly useful in processes where an advancing filamentary yarn is to be heated while in an overfed or relaxed condition eg as in the relaxation or stabilisation stage of a false twist crimping (texturing) process.

Thus according to the present invention there is provided apparatus for transferring heat between an advancing filamentary yarn and a fluid which is at a different temperature from the yarn in which means for inducing two non false twisting and non interlacing fluid vortices substantially along or parallel to the longitudinal yarn axis comprise fluid entry channels tangentially around the periphery of a chamber and yarn entry and exit tubes with partially restricted bores arranged coaxially of each other one on either side of the chamber so that the yarn may advance substantially along or parallel to the longitudinal axis of two vortices generated in the chamber and contained by the tubes.

Preferably, the yarn after passing through apparatus according to the invention is advanced to false twisting means. Advantageously, more than one such apparatus may be employed in a yarn false twist texturing process so that the yarn may be successively but separately heated and cooled before it reaches the false twisting means.

The yarn entry and exit tubes are long in comparison with the size of the chamber so that the vortices may be maintained in contact with an advancing yarn for a relatively long period.

The restriction may take various forms but preferably it should be the extreme ends only of the tubes which are restricted and the nature of the restriction should be such as not to unduly distort the fluid vortex as it passes through the tube, eg by placing suitably tapered or narrowed inserts in the ends of each of the entry and exit tubes.

Apparatus suitable for carrying out the present invention is shown in the figures of the accompanying drawings in which: Figure 1A shows a horizontal section through the centre of a device for generating fluid vortices, and Figure 1B shows a vertical section through the same device when fitted with partially restricted end yarn entry and exit tubes (fluid exit tubes).

Referring to these figures the vortex generator comprises a central chamber 11 located in a continuous metal tube 16 of circular cross section with four tangential fluid entry channels or jets 12 arranged symmetrically around the circumference of the chamber. Yarn entry and exit parts of the tube 16, ie parts 13 and 14 respectively, which may be identical (as shown) or different in diameter and/or length, are located co-axially one on each side of the vortex chamber and serve to contain the two fluid vortices which are generated in the chamber. The cross-sectional area of the bore of the tube 16 is reduced by narrowing or tapering at each end by the presence of suitably profiled metal inserts 13A and 14A.

Fluid, eg air, is supplied to the tangential jets as indicated in the drawings via a passageway 17 in a surrounding concentric metal block 18. High temperature resistant compressible seal rings 19 provide a fluid tight joint between the metal parts 16 and 18.

Any fluid, gaseous or liquid, which is substantially inert to the yarn may be used but preferably the fluid is gaseous at the operating temperature. In addition to air mentioned above, carbon dioxide, nitrogen or steam may also be employed.

One or more chambers may be employed in the vortex generator each with two or more fluid entry channels or jets and the jets also be in staggered relationship so long as effective fluid vortices can be produced and maintained.

The yarn entry and exit tubes may not have the same diameter as that of the vortex chamber.

In operation, a fluid such as air, which may be at ambient temperature or be cooled or heated by external means (not shown) is supplied to the four tangential jets of the vortex generator (as shown) while yarn 15 enters and leaves the chamber through co-axially arranged tubes 13 and 14 respectively. The two air vortices generated in the chamber pass in opposite directions into the tubes 13 and 14 where they are contained so that the yarn advances substantially along or parallel to the longitudinal axes of the vortices. The vortices slowly decay as they move along the tubes and away from the chamber, finally escaping through the partially restricted end portions 13A and 14A into the surrounding atmosphere.

Clearly, the bore of the tubes 13 and 14 must not be so restricted that the apparatus cannot be conveniently "strung-up" prior to use, or that when the yarn is advancing, fluid cannot escape from the bores.

In all of the subsequent examples the polyester yarn used was derived from polyethylene terephthalate.

The various measurements reported in the examples were taken by conventional means well known to those skilled in the art. Yarn exit temperatures were measured using an infra-red scanning pyrometer, available from Cambridge Consultants Ltd., Cambridge, England.

All of the following examples are intended only to illustrate the present invention.

Example I In this example apparatus similar to that shown in Figures 1A and 1B, but having unrestricted yarn entry and exit tubes, i.e. similar to that described in specification 1529674 was used. The vortex "chamber" had an internal diameter of 2.29 mm and the four air entry jets a diameter of 0.51 mm. The continuous yarn entry and exit tube had an overall length of about 380 mm.

The apparatus was employed as a yarn heater in a simultaneous drawing and false twist crimping (texturing) process, in which a partially oriented or drawn 325 decitex 30 filament polyester yarn (birefringence 27 x 10-3) was advanced by feed rolls, first through the apparatus and then to a friction twisting bush (single pass) followed by draw rolls. The draw roll speed was 600 metres/minute and the bush was rotated at 18,500 r.p.m.The draw ratio was 2.1 Results, employing a variety of air pressures and flows, were as follows: Mean Air Air Air Flow Mean Yarn Temp in Pressure (ambient Temp on Chamber (psi) temp.) Exit from ( C) apparatus* cfh ( C) 280 20 35 150 288 50 74 180 289 60 85 187 289 80 110 205 289 100 130 212 289 108 140 212 289 112 145 215 * Mean yarn temperature on entry into apparatus 20"C (ambient) These results are consistant with those described in the above mentioned specification.

Example 2 In this example, which demonstrates the high heat transfer efficiency of the present invention, the previous Example was repeated except that the apparatus shown in Figures 1A and 1B was used, ie. having partially restricted yarn entry and exit tubes.

Results, employing a variety of air pressures and flows, with three different partially restricted bore diameters, were as follows: Bore diameter 2.29 mm (maximum) Bore diameter at narrowed end portions 1.14 mm (minimum) Mean Air Air Air Flow Mean Yam Temp in Pressure (ambient Temp on Chamber (psi) temp.) Exit from (0C) aparatus * cfh ("'cm 287 40 50 170 289 60 72 187 289 80 95 200 289 100 115 210 289 114 125 214 B Bore diameter 2.29 mm (maximum) Bore diameter at narrowed end portions 0.89 mm (minimum) Mean Air Air Air Flow Mean Yarn Temp in Pressure (ambient Temp on Chamber (psi) temp.) Exit from ( C) apparatus* cfh ('9 C) 287 40 50 169 289 60 65 186 289 80 80 199 289 100 95 209 289 115 100 214 C Bore diameter 2.29 mm (maximum) Bore diameter at narrowed end portions 0.76 mm (minimum) Mean Air Air Air Flow Mean Yarn Temp in Pressure (ambient Temp on Chamber (psi) temp.) Exit from (' C) apparatus * cfh ( C) 287 40 50 169 289 60 65 186 289 80 80 199 289 100 95 209 289 115 100 214 * Mean yarn temperature on entry into apparatus 20"C (ambient) The results from Examples 1 and 2 are illustrated graphically in Figure 2 which compares yarn exit temperatures with airflows for the different apparatus investigated. The various plots clearly distinguish the apparatus of the present invention over that described in specification 1529674.It would also appear that increasing the restriction ie reducing the bore diameter, increases yarn exit temperature, but that the effect reaches a maximum, ie there is a maximum improvement in heat transfer efficiency.

In neither of the Examples did the fluid vortices cause significant filament interlacing or false twist in the advancing yarns and in this respect the present apparatus differs markedly from similar apparatus which is known to induce considerable yarn interlacing and false twist.

The invention is applicable to the heating and/or cooling of twisting, twisted or untwisted filamentary yarns though the heating and/or cooling of twisting yarns is preferred.

The invention is also useful in processes where an advancing filamentary yarn is to be heated while in an overfed or relaxed condition, eg as in the relaxation or stabilisation stage of a false twist crimping (texturing) process. In such an instance the fluid entry channels may be inclined at an acute angle to the yarn passageway, or alternatively or in addition, the diameter of the yarn passageway upstream of the fluid entry channels may be less than the diameter of the passageway downstream of the channels, so as to produce a forwarding effect on the yarn due to the escape of the fluid vortex in a preferential direction.

Though the present invention has been exemplified with respect to filamentary polyester yarns, the invention is equally applicable to a large variety of other filamentary yarns, for example, as may be derived from other synthetic materials, such as polyamides, polyacrylics or polyolefins; regenerated material polymers such as cellulose acetate or viscose rayon, or inorganic materials such as glass.

WHAT WE CLAIM IS: 1. Apparatus for transferring heat between an advancing filamentary yarn and a fluid which is at a different temperature from the yarn in which means for inducing two non-false twisting and non-interlacing fluid vortices substantially along or parallel to the longitudinal yarn axis comprise fluid entry channels tangentially around the periphery of a chamber and yarn entry and exit tubes with partially restricted bores arranged coaxially of each other one on either side of the chamber so that the yarn may advance substantially along or parallel to the longitudinal axis of two vortices generated in the chamber and contained by the tubes.

2. Apparatus according to claim 1 in which the yarn tubes are restricted by narrowing or tapering at the end portions thereof remote from the chamber.

3. Apparatus according to either of claims 1 or 2 in which the fluid channels are inclined at an acute angle to the yarn entry tube.

4. Apparatus for transferring heat to and/or from an advancing filamentary yarn substantially as hereinbefore described with reference to figures 1A and 1B of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

C Bore diameter 2.29 mm (maximum) Bore diameter at narrowed end portions 0.76 mm (minimum) Mean Air Air Air Flow Mean Yarn Temp in Pressure (ambient Temp on Chamber (psi) temp.) Exit from (' C) apparatus * cfh ( C)

287 40 50 169

289 60 65 186

289 80 80 199

289 100 95 209

289 115 100 214 * Mean yarn temperature on entry into apparatus 20"C (ambient) The results from Examples 1 and 2 are illustrated graphically in Figure 2 which compares yarn exit temperatures with airflows for the different apparatus investigated. The various plots clearly distinguish the apparatus of the present invention over that described in specification 1529674.It would also appear that increasing the restriction ie reducing the bore diameter, increases yarn exit temperature, but that the effect reaches a maximum, ie there is a maximum improvement in heat transfer efficiency.

In neither of the Examples did the fluid vortices cause significant filament interlacing or false twist in the advancing yarns and in this respect the present apparatus differs markedly from similar apparatus which is known to induce considerable yarn interlacing and false twist.

The invention is applicable to the heating and/or cooling of twisting, twisted or untwisted filamentary yarns though the heating and/or cooling of twisting yarns is preferred.

The invention is also useful in processes where an advancing filamentary yarn is to be heated while in an overfed or relaxed condition, eg as in the relaxation or stabilisation stage of a false twist crimping (texturing) process. In such an instance the fluid entry channels may be inclined at an acute angle to the yarn passageway, or alternatively or in addition, the diameter of the yarn passageway upstream of the fluid entry channels may be less than the diameter of the passageway downstream of the channels, so as to produce a forwarding effect on the yarn due to the escape of the fluid vortex in a preferential direction.

Though the present invention has been exemplified with respect to filamentary polyester yarns, the invention is equally applicable to a large variety of other filamentary yarns, for example, as may be derived from other synthetic materials, such as polyamides, polyacrylics or polyolefins; regenerated material polymers such as cellulose acetate or viscose rayon, or inorganic materials such as glass.

WHAT WE CLAIM IS: 1. Apparatus for transferring heat between an advancing filamentary yarn and a fluid which is at a different temperature from the yarn in which means for inducing two non-false twisting and non-interlacing fluid vortices substantially along or parallel to the longitudinal yarn axis comprise fluid entry channels tangentially around the periphery of a chamber and yarn entry and exit tubes with partially restricted bores arranged coaxially of each other one on either side of the chamber so that the yarn may advance substantially along or parallel to the longitudinal axis of two vortices generated in the chamber and contained by the tubes.
2. Apparatus according to claim 1 in which the yarn tubes are restricted by narrowing or tapering at the end portions thereof remote from the chamber.
3. Apparatus according to either of claims 1 or 2 in which the fluid channels are inclined at an acute angle to the yarn entry tube.
4. Apparatus for transferring heat to and/or from an advancing filamentary yarn substantially as hereinbefore described with reference to figures 1A and 1B of the accompanying drawings.