FI75462C - ELUPPVAERMNINGSANORDNING. - Google Patents

Description

1 75462

ELECTRIC HEATING DEVICE - ELUPPVÄRMNINGSANORDNING

The invention relates to an electric heating device for heating a flow, comprising a plurality of superimposed plate-like heating elements, in which the two adjacent electric heating elements each form an annular recess having in each case

Heating devices 10 as described above are known, for example, from U.S. Pat. No. 1,514,357 and FR 931,619. These heating devices have a heating wire coil with electrically connected sub-sections between individual plate-shaped heating elements with external elements with internal surfaces. the heating wire coil is in contact with the liquid to be heated. Since the heating wire coil is relatively poorly subjected to liquid rinsing in these heating devices, the heat dissipated must also be relatively low at the maximum temperature at which the heating 1 duck coil is used.

For example, it is known from FR 1 263 738 to tension a heating coil on a star-shaped support so that it will be helically level and the flow will be perpendicular to it at this level, however, such a device does not achieve high temperatures of the liquid to be heated.

It is an object of the present invention to provide a heating device as described above which enables high heat transfer in a relatively compact construction.

This object is achieved by the features of claim 1.

2 75462

In the above-mentioned heating device, the flow to be heated, be it gas, gas mixture, air or liquid, is conducted in a plane through a heating wire coil, with respect to which the axis of the heating wire coil is substantially perpendicular. In this case, very good heating is achieved by rinsing the wire coil and, as a result, excellent heat exchange. The heating coil can then give a high heating result at a predetermined temperature, resulting in relatively small structural shapes. Despite the compact design, a relatively low flow resistance can be achieved in this heating device as a result of the heating from the arrangement of the wire coil to the narrow steps with respect to the cross section of the flow. This makes it possible to use low-power fans with low power, which makes the heating devices according to the invention particularly comfortable in household and home hobby devices.

Since the flow to the heating device flows through the individual subsections 20 of the heating wire coil in the present heating device, the liquid receives multiple heating, whereby very high temperatures for the liquid to be heated are achieved. However, an increase in the temperature of the flow along the heating device results in the downstream sections 25 cooling less than the upstream sections, because the flow arrives here at a relatively high temperature. In order to obtain the optimum benefit of the heating wire coil along its entire length, it is desirable that the cycles have as similar a temperature as possible everywhere. This object is achieved by the features of claim 2. Due to the radially flowing flow channels in the downstream heating device elements between the axial opening and the intermediate bridge between the steps, the sub-sections of the heating-35 wire coil closest to the downstream end of the heating device with flow conduction (ambient temperature1a or slightly elevated ambient temperature1a). This reduction in the thermal load 5 is not only due to the introduction of a lower temperature flow into the heating wire coil, but essentially to the fact that the flow rate increases with the introduction of the increased flow.

The preceding application of claim 2 results in a further temperature equalization in the flow direction. Due to the larger cross-section of the downstream diameter, more cool flow enters here, whereby the downstream section 15 of the heating wire coil cools less strongly due to the already preheated liquid, but cools more strongly than the adjacent downstream section due to the large downstream flow.

Claim 4 relates to a further application which enables the object of claim 3 to be carried out in an extremely simple manner, namely by varying the cross-sectional areas of the radial flow channels so that the heating device elements are superimposed so that the two cross-sectional areas as a back hole with a double flow cross section.

A particularly preferred embodiment is the subject of claim 5. According to this requirement, all heating device elements with radial flow channels are only in the region of the central core and the cylindrical outer surface. In this case, the common cross-sectional surface forms a common radial fracture point between the outer outer wall and the central core, which connects all the axial openings together.

75462

The embodiment according to claim 6 helps to keep the temperature in the individual sub-sections of the heating wire coil as constant as possible. This application may be an additional patent in the application according to claim 5 2, but may also occur without this.

Thanks to the embodiment according to claim 7, a simple possibility of electrically connecting the individual sub-sections of the heating wire coil 10 is achieved, which does not require any other structural costs and also enables a simple installation of the heating wire coil.

The invention will be illustrated in more detail below with reference to the application examples shown in the drawings, in which Figure 1 shows a side view of a pre-installed heating device, Figure 2 shows a top view of the flow inlet of Figure 1, Figure 3 shows a section of the heating device 1 of Figures 1 and 2 without heating device holder and without heating wire coil, Figures 4a and 4b show a top view and section of a primary heating device element 25 without a radial flow path, Figures 5a and 5b show a top view and section of another heating device element 6 show a top view and a section of a third heating device element, and Fig. 7 shows a perspective view 1 of a heating wire coil belonging to a heating device.

Figure 1 shows a heating device comprising seven superimposed heating device-35 elements 1 held together by a clamping member 2 placed centrally therethrough. This heating device 1a is arranged in a mounting unit 3 comprising an annular flange.

Il 5 75462

The heating device elements 1, the individual embodiments of which are shown in Figures 4a, 4b, 5a, 5b and 6a, 6b, consist of a ceramic or other heat-resistant material. They comprise a perforated ring 4 with a perforated cylinder-5, with inwardly radially extending steps 5 terminating in a central core 6. When superimposed, the individual heating device elements form a continuous integral jacket surface. The steps 5 are formed relatively narrow in the radial direction 10 so as to form only a slight resistance to the air flow flowing axially through the heating device. They have almost semicircular recesses 7 at their edges, which form an annular recess running around the superimposed heating element 1 in the stacked heating elements 1, in which the individual sections of the heating wire coil, as shown in Fig. 7, are arranged. Figure 7 shows how the heating wire coil is heated inside the device. The individual sections 8 of the heating wire coil 20 are connected in series perpendicularly by means of connections 9 against the sub-sections 8. Since the sub-sections 8 do not form a complete circle, the connections are arranged at an angle to each other. They pass through the axial channels 10 which are always displaced relative to each other in the heating device and which are delimited by two adjacent stages 5. The planes 11a and 11b of the heating wire coil are guided axially, as can also be seen in Figures 1 and 2. heating-30 to a specific location of the wire coil to dissipate a predetermined portion of the total voltage of the heating wire coil that can be used, e.g., for a fan voltage motor.

Figure 2 shows the heating device with air inlet-35 inlet side. Air enters through the twelve axial ducts 10 between the steps 5, then flushes the individual sections of the heating wire coil 75462 6 8 and exits the downstream side of the respective ducts 10. The diameters of the individual coils of the heating wire coil are only slightly smaller than the radial diameter of one of the channels 10, whereby a large thermal power 5 is possible in a relatively small heating device. The steps 9 of the individual heating device elements are arranged axially on top of each other in order to create the lowest possible air resistance through the ducts 10. To facilitate this arrangement, the individual heating device elements 1 are superimposed with marking grooves 12 (see Fig. 6a). The individual heating device elements can also be provided with interlocking projections and recesses, so that the heating device elements can only be placed one on top of the other in a certain order. In the present case, the central opening 13 for the tightening member 2 is formed square, which also results in a rotational lock in connection with the tightening member of square cross-section. The tightening member 20 is here provided with a thread with associated nuts.

In the central core 6, all the heating device elements 1 except the downstream last heating device element Ig are provided with three axial bores a, b, c 14. The bore 14a opens diagonally into outwardly extending chutes 15a and 15b terminating in adjacent channels 10. This the axial bore 14a acts to return the heating wire coil connection 10a. The gutters 15a and 30 15b function to form connections 9 between the sub-sections 8 of the heating coil.

The bores 14a, b, c further facilitate the conduction of cool air to the downstream sections of the heating wire coil 8 through the radial flow-through ducts 17. Without this "fresh without additional supply", the sub-sections 8 downstream of the heating wire coil would heat up more strongly than the current

II

75462 are located upwards as these are flushed by already heated air. The heating wire coil could then not be used optimally. However, this "fresh air supply" allows the heating wire coil to be operated at almost the same length along its entire length for the sub-sections downstream of the heating wire. Fig. 3 schematically shows the flow of air through the heating device, whereby the individual heating wire elements 1 are provided with the same letters as in Fig. 1. The heating element elements 1a-1d are formed identically and do not have any radial underflow ducts17. These heating device elements 1 are illustrated in Figures 4a and 4b. The heating device elements le and lf are again similar, however, differing from the heating device elements 1a-1d in that they have radial flow channels 17 on each of their front surfaces in the region of the axial bores 14a, b, c and the axial channels between the stages 5 and the stages 5. Through these radial flow paths 20, air flows from the axial bores 14a, b, c into the area of the axial channels 10 and mixes with the already heated air there. The flow through these radial flow channels 17 is ensured in such a way that the axial bores 14a, b, 25c are closed by the last heating device element 1 lg. This heating device element differs from the heating device element 1a in the missing axial bores 14a, b, c.

Figure 3 shows another specialty in the arrangement of the individual heating device elements 1a-Ig.

As already stated above, the heating device elements le and lf have radial flow channels 17 on their front surfaces. When the heating device element le is heated on top of the heating element, where the latter 35 does not have a radial flow channel, a flow cross section is formed between the two heating device elements in a simple manner. In contrast, when the heating device elements 1 and lf having radial flow openings 17 on each side overlap, a double cross-sectional area is formed opposite the cross-sectional surface 5 between the heating device elements Id and le. In this case, it is achieved that the sub-period 8 between the heating device elements le and lf cools more strongly than the further upstream sub-period 8 between the heating device elements ld-le. If necessary, for this purpose, a radial flow opening of the desired height can be placed in the last heating device element Ig to achieve a corresponding cooling of the heating wire coil there.

A corresponding variation in the flow-15 cross-section of the radial flow openings 17 can also be achieved when one heating device element is used instead of heating device elements le and lf with radial flow openings on opposite sides, where said one heating device element 20 has only one radial through virtaustiehyt. In this case, such a heating device element would be placed on top of the last closed heating device element Id so that its radial flow-through background ducts are downstream. Also, the next heating-25 device element would be positioned so, while the next one should have radial flow channels on its upstream side to achieve a double flow cross-section. In this star pattern, however, the latter heating element 30 should then either be closed on the plate in order to close the axial air-conducting bores 14a, b, c, or other similar measures should be taken in this respect.

Figures 5a and 5b show in detail how radial flow channels 17 are formed in a single heating device element. They do not extend into a single narrow channel

II

75462 between the axial bore 14a, b, c and this adjacent axial channel 10, but occupy a common surface between the inner core body 18 and the area of the steps 5, whereby only the inner core body 18 and the outer core wall 19 of the heating device element 1 are provided with maximum height and all other points thinner. The superimposed heating device elements 1 therefore rest only against the hollow cylindrical ring 4 and the inner core body thereof. Due to the relatively large surface area of the radial flow channels 10, it is provided that fresh air is uniformly obtained throughout the entire section 8 of the heating wire coil.

In the illustrated application example, an axial bore 14a, b, c displaced by an angle of transition of about 120 ° is shown. Of course, thanks to the three such bores, more than three bores can also be used. It is also possible to form the core in such a way that it has no filling material 20 with its axial bores at all, but radial steps and air flow channels between them, as well as in the area where the hot wire coil is located.

In order to keep the temperature of the hot wire coil almost constant over its entire length, it is also possible to vary the thread distance of the hot coil, from which it can simply follow by equipping the individual heating device elements with pipes . The longer the individual coils are apart, the lower the thermal load on the sheath wire coil. This operation may be sufficient even without the introduction of fresh air as described above to provide sufficient temperature equalization. A combination of both of these measures makes sense when very precise temperature control along the entire length of the heating wire coil is necessary when using a very compact construction method and a high thermal load on the heating wire coil.

tl

Claims (6)

An electric heating device for heating a flow, comprising a supporting structure for supporting a heating tree coil1 (8,9), of said construction belonging to single heating elements (1) which are annular in the cross-section of the heating device and are positioned axially in the upper direction. and provided with recesses (7) in which the tree coil has been placed, characterized in that when the heating elements (1) are placed on one another their outer walls (4) form the interconnecting cylindrical outer wall of the supporting structure, so that the heating elements exhibit the outer walls radially inwardly projecting ribs (5) forming a depression (7) in which the tree coil (8,9) is placed and axial flow channels (10) for flow between the elements, that there is at least one axial flow channel in the central part of the heating device (14a, 14b, 14c), which are closed at their end on the downstream side of the heater, that at least one element (le, lf) on the node current side there is at least one throughput passage (17) between an axial flow channel (14a, 14b, 14c) and the axial channels (10) between the ribs (5). Heating device according to claim 25, characterized in that the heating device has at least two consecutive radial flow-through passages (17) in the flow direction, the flow-through passage on the downstream side having a larger cross-section than the flow-through passage on the upstream side. 30 3. Heating device according to claim 1 or 2, characterized in that the radial flow passage (17) is located on the axial end side of the heating element (1). Heating device according to any of claims 1-3, characterized in that the heating device element (1) is thinner in the whole area between the substantially cylindrical casing surface (4) and