GB2190687A - A heater - Google Patents

Abstract

A heater (2), e.g. for a yarn texturing device, comprises a hollow elongate body (4), a liquid (6), and a heat source (18, 20) for heating the liquid, the heater being such that the liquid has a liquid head of from 3-100mm. The liquid may be contained in the hollow body or in a separate reservoir. The use of a lower than conventional head of liquid is said to prevent oscillating bubbling off of vapour when the device is being used at low temperatures eg 100 DEG C. <IMAGE>

Description

SPECIFICATION A heater This invention relates to a heater.

Thermosyphon heaters have been in common use onyarntexturing machines for many years. The thermosyphon heaters have an evacuated elongate hollow body which is known as a track assembly and which is partiallyfilled with a heat transfer liquid.

The heattransfer liquid isvapourised by heat from electrical heating elements. The temperature is controlled with an appropriate electrical control system.

Various heat transfer liquids are available and these heat transfer liquids or fluids have various boiling points. The various heat transfer liquids have different advantages and disadvantages. Those heat transfer liquids with high boiling points have the advantage of having a relatively low vapour pressure at high temperatures of the order of 250 C and hence they are saferto use in a thin wall elongate hollow body. However, they have the disadvantage that at lowertemperatures, the vapour pressures are so low that the bubbles ofvapourformed insidethe elongate hollow body are so large thatthe elongate hollow body is heated by bursts ofvapourwhich cause the heater to oscillate, and the lowerthe temperature, the worse the problem becomes.

Those heat transfer liquids with low boiling points work satisfactorily at low temperatures with regard to oscillation but the pressures are so high atthe maximum temperature required (250"C) that the heater requires a much thickerwall for the elongate hollow body in order to withstand the pressure. Such thickerwall cannot readily be formed into desired track profiles. With a compromise on the liquid selected, a temperature range of 1 500C - 245 C has been produced and has been available for several years in the known heaters.

Recent trends in texturising technology have called for a heater with a lower operating temperature,typically 100"C, but which still retains the uppertemperature limit of 250 C. The standard known heaters would not meet this requirement without giving the above mentioned undesirable low temperature oscillation. The oscillation problem was found to be aggravated by the head of liquid which existed in the standard known heaters, which head of liquid could not be reduced without a radical redesign ofthestandard known heaters.

In addition to the problem oftemperature oscillation ofthe heaters, it was also found that some of the known heaters suffered from cold areas at theirtop,thisbeing duetosmall amounts of inert non-condensible gases at normal temperatures and pressures expanding to large volumes at low temperature. Such cold areas are clearly a disadvantage and may affectthetexturising ofyarns.

It is an aim of the present invention to provide a heaterwhich obviates or reduces the above mentioned problems.

Accordingly, this invention provides a heater comprising an elongate hollow body, a liquid, and a heat source for heating the liquid, the heater being such that the liquid has a liquid head of from 3-100mm.

By redesigning the heater so that it is able to have a liquid head of from 3-100mm (which is considerably lowerthan the existing liquid heads on known heaters which may be of the order of 250mm), bubble formation at low temperatures is reduced.

This is believed to be because the bubbles often start from the bottom of the liquid head and get biggeras they pass upwardlythrough the liquid in the liquid head.

Preferably, the liquid head is in the range of 30-70mm high and a preferred heightforthe liquid head is substantially 50mm.

Preferably, the heater is a contact heater. The contact heater is preferably a yarn texturing contact heaterfortexturing yarn. The contact heater may be used for texturing materials otherthan yarn.

The elongate hollow body may have at least one elongate groove in its surface, the groove being for receiving material to be textured wherebythe material to betextured can be run along the groove during use ofthe heater.

Usually, there will be more than one groove.

Preferably, there are two, six or twelve grooves, the grooves being arranged in pairs.

If desired, as an alternative to employing grooves, the elongate hollow body may have a plain outer surface.

The elongate hollow body may be curved to facilitate the above mentioned contact of the material to betextured orotherwisetreated. If desired, however, the elongate hqllow body may be straight.

Where the heater is such that the elongate hollow body is curved, then the curve may have an eighteen metre radius. The hollow elongate body may be madeto any desired lengths and 1.5 metres long is a presently preferred length.

The heater of the invention can be a non-contact heater. Such an alternative heater may be one employingtwoconcentrictubesandtheannular space between the two concentric tubes may contain the liquid to be heated and the gases arising from heating the liquid. Yarn or other material to be textured may then be passed through the inner tube.

The liquid may be contained in the bottom of the elongate hollow body. Such an arrangement is usually used where the heaters have two or six grooves in the elongate hollow body and where the heaters are contact heaters. Alternatively, if desired, the liquid may be contained in a reservoir which is separate from, but which is connected to, the elongate hollow body. A reservoir may be advantageously employed where the heater is a contact heater having twelve grooves in its elongate hollow body.

The liquid employed in the heater may be any one of the known liquids, these liquids sometimes also being known as fluids. A presently preferred liquid is a mixture ofthethree isomers ofdiethylbenzene.

Alternatively, the liquid may be aeutectic mixture of diphenyl oxide and diphenyl. Alternatively, the liquid may be any ofthe proprietory products known as Dowtherm E, Calotherm, Samtotherm, or one of the Flutec liquids known as Flutec PP1 - 9 liquids.

Usually, the heat source will be an electrical heat source. Other heat sources such for example as a gas heat source can however be employed.

Preferably, the electrical heat source is such that the liquid runs through it. Such an electrical heat source may be formed as at least one electrical catridge heating element. Preferably, there are two electrical cartridge heating elements. It has been found thatwith two such electrical cartridge heating elements, the watts densityofthefluid can be reduced so that hot spots in the liquid (which may lead to degradation of the liquid) which may occur with the use of just one electrical cartridge heating element can be avoided.

Preferably, the or each electrical cartridge heating element will extend transversely ofthe elongate hollow body.

The electrical cartridge heating elements may be vertically or horizontally aligned, orthey may be substantially horizontally aligned but slightly staggered in a vertical direction. With the horizontal alignment or the substantial horizontal alignment, the height of the fluid head may be kept to an absolute minimum.

Each electrical cartridge heating element may be a metal or a ceramic housing containing the actual heating element. A metal housing is preferred since it gives a better heattransferthan a ceramic housing.

Presently preferred metals are stainless steel and brass.

Advantageously,theoreach electrical cartridge heating elementhasa rough outersurface,which gives the electrical cartridge heating element an increased surface area which provides for better heat dissipation and which also provides nucleation sites for bubble formation.

The rough surface may be formed by knurling or threading the outside ofthe housing. Alternatively, the rough surface may be provided by a separate device such for example as gauze on the outside of the housing.

As an alternative to employing an electrical cartridge heating element, the electrical heat source may be a flat heating element which is secured to the rearface ofthe elongate hollow body and through which the liquid does not pass.

The elongate hollow body can be made of any desired materials. If the elongate hollow body is made of mild steel,then it is preferably coated with a proprietory product known as Kanigen which is an electroless nickel coating. Where the hollow elongate body is provided with grooves, then the base ofthe grooves are preferably provided with a ceramic coating over the Kanigen coating to provide good wear properties. Where the elongate hollow body is made of stainless steel,then only the ceramic coating for the bottom of the grooves (where grooves are employed) is normally used. Coatings otherthan a ceramic coating may of course be employed.

Embodiments of the invention will now be described solely byway of example and with reference to the accompanying drawings in which: Figure 1 shows a known heater; Figure 2 shows a first heater in accordance with the invention; Figure 3 shows a section through the elongate hollow body of the heater shown in Figure 2; Figure 4 shows the rear of the bottom of the heater shown in Figure 2; Figure 5shows a section through the electrical cartridge heating element shown in Figure4; Figure 6shows an alternative type of electrical heating element; Figure 7shows a second type of heater in accordance with the invention; Figures 8 and 9 are side and rear views of a third heater in accordancewiththe invention; Figure 10 shows a fourth type of heater in accordance with the invention; and Figures 11 and 12 show a fifth type of heater in accordance with the invention.

Referring to Figure 1, there is shown a known heater2 comprising a curved elongate hollow body4 which contains a liquid 6 giving a liquid head of 250mm as shown. The heater 2 also comprises a flat electrical heating element 8 which is clamped to the bottom ofthe rear face of the body 4 as shown. A temperature sensor is provided in the body 4 and it senses the temperature of the gases coming from the liquid during operation ofthe heater 2. The temperature sensor loins connected to a temperature controller 12 which is effective to control operation of the heating element 8 and the entire heater 2. The temperature sensor 10will normally beafail safe temperature sensor which will go open circuit in the event of a malfunction.The heater 2 also comprises a thermostat 14which is for sensing the temperature ofthe liquid and which operates only in the event of the liquid 6 becoming dangerously hot, the thermostat 14then acting to switch off the heating element 8 via the lead 16. A lead 18 comes from the bottom of the heating element 8 and is appropriately connected in circuit.

Referring now to Figure 2, similar parts as in Figure 1 have been given the same reference numerals and their precise construction and operation will not again be given. In Figure 2, the heater 2 is quite similartotheheater2shown in Figure 1 exceptthat in Figure 2, the liquid 6 has been reduced to one having a liquid head of only approximately 50mm as shown. This has been made possible by replacing the heating element 8 with a pair of electrical cartridge heating elements 18,20 which extend across the body 4 as shown in Figure 4 and which are vertically aligned.

The cross sectional shape of the body 4 is shown in Figure 3. This body 4 can be made of mild steel which is then preferably coated with a Kanigen coating, which is an electroless nickel coating. Itwill be seen thatthebody4isprovidedwith a pair of grooves 22,24 and the base of these grooves are further coated with a ceramic coating 26. The ceramic coating 26 may contain chromium oxide.

Figure 5 shows the cartridge heating element 18 and illustrates how both ofthe cartridge heating elements 18,20 have a housing 28 through which a pair of electrical heating wires 30,32 pass. As shown, the outer surface of the housing 28 is rough and this rough surface is provided by knurling or other appropriate means. The rough surface gives an increased surface area for contact by the liquid 6 passing overthe housing 28 and also the rough surface provides nucleation sites for bubble formation.

Figure 6 shows that the cartridge heating elements 18,20 could be replaced by a heating element 8which would be like the heating element8shown in Figure 1 but which would haveto be considerably smallerto givethe 50mm liquid head shown in Figure2.With such a small heating element8asshown in Figure 6, care must be taken that adequate heat can be produced.

In Figure 4, and also in Figures 7 and 9,the grooves 22,24 in the body 4 have not been shown for ease of illustration.

Referring now to Figure 7, there is shown a heater 2 comprising three of the bodies 4 and each body4 will be provided with the grooves 22,24. In Figure 7, the cartridge heating elements 18,20 extend across all three of the bodies 4. They are housed in a housing 34. The housing 34 is similarto the housing 34 shown in Figures 2 and 4 except that the housing 34shown in Figures2and4issmallerthanthe housing 34 shown in Figure 7. The lead 36 coming from the housing 34as shown in Figure 2will usually be neutral and the lead 38 coming from the thermostat 14 as shown in Figure2will usually be live.

Also shown in Figure 7 is a condenser 40 for assisting in condensing the hot gasses in the body4 during use ofthe heater 2.

In the heaters2 shown in Figures 2 and 7, the liquid 6is in the bodies4and runs overthe heating elements 8. In contrast, in Figures 8 and 9, the heater 2 is such that the liquid 6 is contained in a remote boiler 42 which is connected to the hollow interior of the body 4 buy a connecting tube 44. In Figure 8 itwill be seen that the cartridge heating elements 18,20 are horizontally aligned rather than being vertically aligned as shown in Figures 2 and 7.The heater2 shown in Figures 8 and 9 also has a condenser 40, the condenser40 being connectedtothe body4by means of a connecting tube 46. As shown in Figure 9, the heater 2 comprises six ofthe bodies 4 and the grooves 22,24 are in each body 4 so that the heater 2 comprises a total of twelve grooves.

Referring nowto Figure 10, there is shown an alternative heater 48 which has a boiler 42 and a condenser40. The body4 is formed bya pair of concentric tubes 50,52 and it will be seen that there are two of the bodies 4forming the heater 48. Vapour from liquid6 inthe boiler2 passes uptheannular space 54 between the two tubes 50,52. Yarn threads 56 pass continuously through the centre of the inner tube 52 as shown.

The heater 48 is a non-contacttype of heater since the yarn thread 56 does not touch the tubes 52. The heaters 2 shown in Figures 1 to 9 arse contact heaters since the yarn thread contacts the heaters 2, and more specifically, runs in the grooves 22,24.

Referring nowto Figures 11 and 12, similar parts in the illustrated heater2 as in earlier drawings have been given the same reference numerals and their precise construction and operation will nowt again be given. In Figures 11 and 12, three cartridge heating elements 18,20,21 are employed. These cartridge heating elements 18,20,21 are vertically aligned as shown. The cartridge heating elements 18,20,21 are housed in a housing 34 which has a sloping upper portion 58 as shown. This sloping upper portion can be effective to give a consistent heat output from the heater 2.

The connecting tube 46 is provided with a restrictor60which, during use ofthe heater2 is effective to keep a pressure differential between the pressure in the body 4and the pressure in the connecting tube 46. Under normal conditions of use, the body4 isto be heated uniformly over its full length. However, when the heater 2 is operated for a long time, vapour produced from low boiling liquids which are contained in trace amounts in the heat medium liquid 6, results in an uneven temperature distribution at low temperature running in the upper part of the body 4. The use of the restrictor 60 helps to stop this and to keep the body 4 at a uniform temperature over its full length, even when the heater2 has been in operation for a long time.More specifically, heated vapour can pass through the restrictor 60 and to the condenser 40 via the connecting tube 46. The condenser 40 is at a lower pressure than the pressure inside the body 4 so that the vapour in the upper portion 62 ofthe body 4 is continuously sucked through the restrictor 60 into the condenser 40. The restrictor 60 can be effective to increase the velocity of the vapourflow and also to lower the pressure of the vapour. The low pressure may serve to lead impurities in the form of vapours and gases into the condenser 40. The rising velocity of the saturated vapourwithin the body 4 may be greater than it would otherwise be.Condensed liquid that condenses in the condenser 40 can be drained backthrough a return pipe 64 to the bottom ofthe housing 34 as shown.

For a two metre long heater ofthe type shown in Figures 11 and 12, the restrictor may be 0.8 mm to 2.5 mm in diameter. The size of the restrictor 60will vary with varying sizes of heater 2. The condenser 40 may be of a volume which is from ten to fifteen percent and preferably twelve per cent ofthe volume within the body 4. The apparatus 2 shown in Figures 11 and 12may be particularly useful for preventing cold areas forming at the top ofthe body 4. The heating elements 18,20,21 are preferably knurled or otherwise provided with a rough surface to give a lower watts density requirement as discussed above.

It is to be appreciated that the embodiments ofthe invention described above have been given byway of example only and that modifications may be effected. Thus, for example, the bodies 4 need not be curved as shown in Figure 2 and Figure 11 and they could be straight. Also, if desired, the grooves 22,24 could be omitted. The grooves forthe yarn have not been shown in Figure 11 for simplicity of illustration but any desired and appropriate number of grooves may be employed. Further, the cartridge heating elements 18,20 as shown in Figure 2 and 18,20,21 as shown in Figure 11 could be horizontalyaligned ratherthan being substantially vertically aligned.

Claims (14)

1. A heater comprising an elongate hollow body, a liquid, and a heat source for heating the liquid,the heater being such that the liquid has a liquid head of from 3-100mm.

2. Aheateraccordingto claim 1 inwhichthe liquid head is in the range of 30-70mm high.

3. A heater according to claim 2 in which the liquid head is 50mm high.

4. A heater according to any one of the preceding claims and which is a contact heater.

5. A heater according to claim 4 in which the contact heater is a yarn texturing contact heaterfor texturing yarn.

6. A heater according to any one of the preceding claims in which the elongate hollow body has at least one elongate groove in its surface, the groove being for receiving material to be textured wherebythe material to be textured can be run along the groove during use ofthe heater.

7. A heater according to claim 6 in which there are two, six or twelve grooves.

8. A heater according to any one ofthe preceding claims in which the elongate hollow body is curved.

9. A heater according to any one ofthe preceding claims in which the liquid is contained in the bottom ofthe elongate hollow body.

10. A heater according to any one ofthe preceding claims in which the heat source is an electrical heat source.

11. A heater according to claim lOin which the electrical heat source is at least one electrical cartridge heating element.

12. A heater according to claim 11 in which the or each electrical cartridge heating element has a rough outer surface.

13. Aheateraccording to claim 12inwhichthe rough outer surface is a knurled outer surface.

14. A heater substantially as herein described with referenceto Figures 2 to 12ofthe accompanying drawings.