FI75463C - Electric heating device for heating a flow. - Google Patents

Abstract

1. Electrical heater for heating a gaseous or liquid medium, with a holding device for receiving a resistance-wire coil (8, 9), the holding device consisting of individual heater elements (1) of circular cross-section, which are placed on top of one another in the axial direction and in which there are, in regions located opposite one another, recesses (7) in which the resistance-wire coil (8, 9) is located, and the outer walls (4) of the heater elements (1), when these are placed on top of one another, complementing each other to form a closed cylindrical outer wall of the holding device, characterized in that in the heater elements (1) there are webs (5) which extend radially inwards from the outer walls to a central region and have the recesses (7) for receiving the resistance-wire coil (8, 9), and which between themselves determine axial flow channels (10) for the medium to be heated, in that in the central region of the heater there is at least one further axial flow channel (14a, 14b, 14c) which is closed at the downstream end of the heater, and in that on at least one of the downstream heater elements (1e, 1f) at least one radially extending passage (17) is formed between the further axial flow channel (14a, 14b, 14c) and the axial channels (10) located between the webs (5).

Description

1 75463

ELECTRIC HEATING DEVICE FOR FLOW HEATING - ELUPP-VÄRMNINGSANORDNING FÖR UPPVÄRMNING AV EN STRÖMNING

The invention relates to an electric heating device for heating a flow as defined in the preamble of claim 1.

A heated air flow hair dryer, hairbrush or hot air devices for higher heating powers, used for surface drying, soldering, etc. of paint layers, are already known electric heating devices, usually comprising a cylindrical ceramic body with a plurality of shafts provided with several through separate sub-sections of the formed heating-15 wire coil. Holes with sub-sections of the electric heater act as ducts for the heated air that enters cold at one end portion of the ceramic body of the fan and exits hot from the other end portion. It is relatively difficult to equip such electric heating devices with a heating wire coil consisting of a twisted wire of resistance wire, since such a heating wire coil usually has to be pulled through separate relatively narrow holes and care must be taken not to stretch it, as this changes its heating capacity uncontrollably. A disadvantage of these known heating devices is also the fact that the holes formed in the ceramic bodies have a relatively high air resistance, so that the fan must operate at high power in order to achieve the necessary air flow. But high-power fans are not only expensive, but also mostly uncomfortably loud, which is annoying, especially in household and household appliances. Increasing the diameter of the holes in the air flow ducts would partially eliminate this drawback, but would lead to an undesirably large heating device, since on the one hand less resistance wire is placed per unit volume and on the other hand the amount of flow in contact with the heating wire coil is reduced. In said known heating devices, the turns of the heating wire coil are arranged in the walls of the holes formed in the ceramic body and air is blown axially therethrough, whereby a diameter of 10 turns is formed, a relatively large amount of air is formed which does not come into contact with the heating wire coil.

In another known application of the heating device, the ceramic body is formed of separate disc-shaped parts, which include separate parts of the fan-like rising part for the heating wire coil. Although the inner part is open with respect to the cylindrical outer circumference, the contact of the heating wire coil 20 with the air to be heated and thus the heat exchange is then poorly expected. Since the temperature at which the heating wire coil can be used is limited for material reasons, a relatively small heating power is obtained with such a heating device of the size shown.

It is an object of the present invention to provide a heating device as mentioned at the outset, which provides an improvement in at least some of the above-mentioned drawbacks.

This object is achieved by electric heating devices according to claims 30 1 and 2.

What the heating devices according to claims 1 and 2 have in common is that the substance to be heated, be it gas, gas mixture, air or liquid, is passed in planes through the heating wire coil with respect to which the axis of the heating wire coil 35 is substantially perpendicular. In contrast to the flow through the heating wire coil in its axial direction, as initially described, to the prior art

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3 75463, a substantially better flow-through and a substantially increased heat exchange are then obtained. The heating wire coil can then give off a higher amount of heat in the same maximum temperature-5 shown, thus providing a relatively small structure to achieve the shown amount of heat. By means of the flow through the heating coil common to the heating device according to the invention, a larger diameter of the flow channels can also be utilized, which results in a reduction of the flow resistance. The lower flow resistance makes it possible to use low-noise fans that require low power, which makes the heating device according to the invention particularly suitable for use as household and domestic appliances. In both embodiments according to claims 1 and 2, the winding of the heating wire coil becomes very simple. The coil no longer needs to be pulled through relatively narrow and long flow channels, but can be simply inserted into arranged, cut-open interiors or holes. When using a known design of a heating device in which the heating wire coil is in axial flow channels, there is a risk that the parts of the heating wire coil come out of the ceramic part during use and cause tension in the body part, but this is not possible in the heating device according to the invention. at both ends. The assembly of the heating device 30 according to the invention also takes place very simply. In the embodiment according to claim 1, the heating wire coil is periodically placed in the inner parts formed between the partitions of the adjacent heating device elements or the like and threaded into the next cross-sectional plane between the two partition walls 35 and again placed between the two adjacent heating device elements. When the space between the two heating device elements is 4 75463 open and easily accessible, this assembly takes place very simply. In the case of the embodiment according to claim 2, the heating wire coil is wound freely in a helical shape around the cylindrical fastener 5 and then the part thus wound is inserted inside the hollow cylindrical outer shell.

Since in known heating devices the cold flow flows from one end of the heater and is heated along the length of the heater by successive parts of the heating wire coil 10, the parts below the flow of the heating wire coil normally cool less than those above its flow. The parts below the flow of the heating wire coil then become hotter than the areas above the flow 15. Because the maximum temperature of the heating wire coil is limited, the areas above the flow of the heating wire coil are used less favorably than the areas below the flow. In addition, the parts of the heater below the flow become substantially hotter than the other areas. But it would be desirable to achieve as constant a temperature as possible over its entire length, without exerting a thermal stress on the parts of the body surrounding the heater, especially when these are made of plastic. Requirement 3i presents an improvement on this problem. Due to the special inclination of the heating wire coil, more flow is directed to the areas with a larger inclination towards the conductor length and they are thus cooled more strongly.

30 In this case, the temperature rise of the parts below the flow of the heating wire coil is prevented. Such sizing provides even a constant temperature along the entire length of the heating wire coil. In principle, although this operation could also have been carried out in already known heating devices, it was not implemented in practice, whereas in both embodiments of the heating device according to the invention a special

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5 The inclination of the 75463 by corresponding adjustment of the heating wire coil in those below the flow can be realized without difficulty.

However, a preferred embodiment of the application example 5 according to claim 1 is set out in claim 4. However, in the separate cross-sectional planes between the two heating device elements, the heating wire coil can also be formed in an S- or helical shape in order to achieve the advantages described above. However, the embodiment presented in this claim 10 is very simple and easy to manufacture and at the same time offers a simple possibility to keep the separate sub-sections of the heating wire coil and their axially spaced connections securely separated from each other.

The application according to claim 5 to the embodiment according to claim 1 provides a simple possibility for guiding one end of the heating wire coil to the other end through a hole without insulation problems. In the application example-20 according to claim 2, this advantage is obtained according to the content of claim 6. In this embodiment, the connecting cable is routed between the two partitions.

Claim 6 further shows a specific embodiment of the embodiment according to claim 1. This provides a simple possibility for simply and securely connecting all the interconnected heating device elements according to the embodiment of claim 1 and for fastening the outer shell 30 and the fastener according to the embodiment of claim 2 to each other. Next, the invention will be explained in more detail with reference to two application examples shown in the drawing. In the drawing: Fig. 1 shows an embodiment of a first embodiment 35 of the invention in perspective view, Fig. 2 shows a heating wire coil belonging to the embodiment of Fig. 1 in perspective view, Fig. 3 shows 6 heating device elements of embodiment 75463 according to Fig. 1, Fig. 4 shows heating element according to Fig. 3 with associated heating wire coils, Fig. 5 shows end views and a hollow cylindrical outer shell of an embodiment of a second embodiment 5 of the invention in perspective view, and Fig. 6 shows a perspective view of the fastener to be attached to the outer shell of the embodiment of Fig. 5 with the heating wire coils moved thereon.

The drawings show two applications of the heating device according to the invention. The first embodiment can be seen in Figures 1-4 and the second embodiment can be seen in Figures 5 and 6.

The heating device 15 shown in the assembled form in Fig. 1 consists of seven identically formed and interconnected heating device elements 1, one of which is shown enlarged in Fig. 3. This heating device element 1 is made of ceramic or other heat-resistant material and in this embodiment consists of a hollow cylindrical ring 2, a cylindrical inner part 3 and twelve radial partitions 4 between them, which are arranged by dividing the circumference into equal parts. The partition walls 4 are formed as thin walls in which the moon-25 is joined by upper surfaces parallel to each other and extending in the radial and axial directions.

The inner part 3 is provided with a central opening 6, which; is rectangular in shape, and through which a rectangular fastening member 7 can be passed, which member is intended to secure the separate heating device elements 1 against rotation and to fasten them axially to one another. For axial fastening, the end of the fastening member 7 is provided with a thread into which a nut is inserted, as can be seen from Fig. 35 1. In addition, three axial holes 5a, 5b and 5c arranged approximately 120 ° with respect to each other are formed through the inner part 3, the hole 5a being connected by 75463 two laterally guided channels 5d and 5f connecting this hole 5a to adjacent openings or air flow channels.

The partitions 4 have a recess 8 formed on each side on each side 5, the operation of which will be explained below.

A heating wire coil 9 is connected between the separate plate-shaped heating device elements 1, as shown separately in Figure 2. After the assembly 10, the heating wire coil 9 in this application example according to Fig. 1 comprises six sub-sections 9a, each in the cross-sectional plane between two adjacent heating device elements and six axially extending straight-line conductor parts 9b. The twisted subdivisions 15a are in the recesses 8 of the partitions 4, forming a sub-circle of 330 °. The heating wire coil 9 has two conductors 10a and 10b connectable to an electric power source, of which the conductor 10a associated with the sub-section 9a shown on the far left in Fig. 2 is passed through adjacent openings 5a of individual heating device elements 1. This conductor 10a is led through the channel 5e or 5f outwards to the flow channels. The first sub-section 9a is in the recess 8 of the partitions 4 and thus immediately in the flow channel. If this conductor 10 of the heating wire coil 25 9 is followed through the first sub-section 9a, then the first axial part 9b of the heating wire coil 9 is passed through the first opening to the second left-hand heating device element in Fig. 1.

The straight conductor 9b connecting the second sub-section 9a to the third sub-section 9a is then passed to the third heater element 1 through the next opening, and so on until the conductor 10b can be passed through the last heater element 1 from the opening 6b. The auxiliary conductor 10c shown in Fig. 2 acts for a voltage tap which can be used for the current of the fan and which is led out of the hole 5c of the last heating device element. 8 75463 marking grooves 20 are formed on the outer shell of the heating device element 1.

Valmiiksikoottuun supplied to the heating device shown in Figure 1 by the arrow P direction of a flow, preferably air flow, and the air proceeds through the intermediate walls of the openings 5 between 4 kuumennuslankakierukan nine separate compartments and is heated there. In the intermediate space consisting of the ring 2 and the inner part 3, there are only thin partitions 4 and a heating wire coil 9, which can resist without movement. In connection with the assembly, the individual partitions 4 are generally arranged relative to each other so as to form a through wall. The accuracy of the assembly work can be ensured by means of markers 20. The air resistance formed is relatively low and the air flows optimally around the heating coil 9 of the heating-15.

In the embodiment shown in Figures 5 and 6, the heating wire coil 9 is helically wound on the outer surface of the hollow cylindrical body 11.

Twelve radially projecting and axially extending partitions 12 are formed on the outer surface of this body 11 at evenly spaced circumferences, forming separate clearances 13 in which the heating wire coil 9 is located. The interior of the hollow cylindrical body 11 has six partitions 14 which connect to each other in an inner part 15 provided with an axial opening through which a fastening member can be inserted, as in the embodiment according to Fig. 1. The conductor shown on the left in Figure 6 is routed back to the right between the two partitions 14. In this way, the body 11 wound by the heating wire-30 coil 9 is inserted axially into the hollow cylinder 16 shown in Fig. 5 and fastened to the hollow cylinder 16 by a fastening member already shown by means of two end elements 17 each provided with central openings.

35 In Figures 5 and 6 of the sovellutusmuo form the heated air is blown in any case the heating device in the direction of the arrow p. The air is flowing

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75463 in this case through air ducts formed by the hollow cylinder 16, the body 11 and the partitions 14 through separate parts of the heating wire coil 9, whereby also in this case the heating wire coil 9 flows in planes with respect to which the axis of the heating wire coil 9 is oblique. In this case, the area surrounded by the hollow cylindrical member 11 can still be covered with a plate to prevent air flow through this area. Then, when in the Figures 1 and 5-esitetyis 10. An embodiments, the cold air flows in every case, the right side of the heating apparatus are cooled to above 9 kuumennuslankakierukan flow in regions in the normal case more strongly than the already hot air flow beneath the flow of rinsing the parts 15 are located. The parts below the flow of the heating wire coil 9 then become hotter than the parts above the flow. In order to avoid this, a special embodiment of the heating wire coil 9 has been formed, which includes a special coil formation of the helical regions. In the upstream sections, the resistance wire coils are therefore more densely arranged and flow less air per unit length than in the downstream areas, so that an almost constant temperature prevails over the entire length of the heating wire coil 259.

In the embodiment according to Figure 1, e.g. a separate sub-section 9a of the heating wire coil 9 has the following speeds, whereby the speeds decrease as they go below the flow.

30 first sub-period 53 laps, second sub-period 40 laps, third sub-period 32 laps, fourth sub-period 26 laps, 35 fifth sub-cycle 21 laps, sixth sub-cycle 17 laps.

10 75463

In the embodiment according to Figures 5 and 6, the heating wire coil is arranged to extend endlessly from the air inlet side to the deaeration side, so that the speed of the coil per unit length decreases continuously.

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Claims (5)

11 75463 An electric heating device for heating a flow, comprising heating a support structure 1 for supporting a spindle (9), the support structure comprising 5 individual heating elements (1) which are annular in cross section and arranged axially on top of each other and are provided with recesses (8), that, when the heating elements (1) 10 are superimposed, their outer walls (2) form a unitary, cylindrical outer wall of the support structure, and that the heating elements have ribs (* ♦) projecting radially inwards from the outer walls, forming a recess (8) with a wire-15 (?) are located, as well as axial flow channels for flow between the elements. Heating device according to Claim 1, characterized in that the sections (9a) of the heating wire coil (9) are arranged in a substantially closed annular shape in the planes in each case between two adjacent heating elements (1), and that the two sections of the heating wire coil are connected by axial sections. (9b) is led to the adjacent heating elements via ducts which are displaced by a displacement of the rib (* ♦) in the radial direction relative to the respective heating element. Heating device according to Claim 1 or 2, characterized in that the device 30 comprises a central inner part (3) with axial bores (5a, 5b, 5c). 1. In the case of life-saving arrangements for up to 35 days of operation and in the construction of up-to-date structures (9), vilken stöd-