DE2850111B1 - Arrangement of an electrical heating element in a channel for heating in particular an air stream flowing through it - Google Patents

Description

2. Arrangement according to claim 1, characterized by winding sections of equal length (5).

3. Arrangement according to claim 1 or 2, characterized in that the lengths of the winding sections (5) correspond approximately to the largest clear width of the channel (2).

4. Arrangement according to one of the preceding claims, characterized in that the turn sections (5) have different lengths per turn.

5. Arrangement according to one of the preceding claims, characterized in that per turn the angles (6) formed by the winding sections (5) are different sizes from one another to have.

6. Arrangement according to one of the preceding claims, characterized in that the angle corners (4) are more or less rounded.

7. Arrangement according to one of the preceding claims, characterized in that more than a conductor (3) is provided and that the conductors (3) in the channel (2) are mutually multi-threaded.

8. Arrangement according to one of the preceding claims, characterized by meander-shaped or similarly shaped conductors (3).

9. A method for producing the heating element characterized in the preceding claims, characterized in that a conductor (3) made of elastic material on a polygonal in profile Rod wound up helically and then stripped from it.

The invention relates to an arrangement of an electrical heating element in the preamble of the claim 1 marked genus.

In a heating element of this type known from DE-OS 26 08 510, the conductor is around one in the Channel to be used, in the profile polygonal carrier made of electrically non-conductive and high-temperature resistant Material wound essentially following a helical line and according to the profile of the beam angled in sections.

Here, however, the carrier forms a considerable one

Flow resistance for the gas flow.

In addition, with such an arrangement of the electrical heater, the efficiency that can be achieved with it relatively low, because here the heating of the air flowing through is essentially only close to Duct walling takes place, so that a relatively long duct and a relatively long heating is required, in order to heat the air flow at least approximately evenly.

ίο According to DE-AS 11 18 904 is also an electrical Water heater known, in which one arranged in the channel through which the utility water flows, uninsulated Heating coil has a polygonal shape that deviates from the circular shape of the channel cross-section and only touches the duct wall at points.

In addition, the corners of the helix are covered by a relatively thin glaze that covers the duct wall attached to the channel wall or the corners of the helix are held in threads of the channel wall to the Position of the helix to be clearly fixed without the heat dissipation of the helix to the heating channel water flowing through is to be disturbed.

But here too, the heating of a medium passing through the channel takes place essentially only close to it the duct wall, which results in a relatively low level of efficiency.

Furthermore, from DE-AS 24 06 768 an electric heater for heating dormant or moving liquids or gases with three or a multiple of three, optionally in parallel, in series, im Triangle or star switchable tubular heaters known.

Here, the tubular heating elements form a heating bundle in a manner known per se multi-thread screw, over which one or more additional heating bundles formed from helical lines Tubular heating elements can be pushed, which have a correspondingly larger diameter and a pitch which is the same as the pitch of the helical-shaped tubular heater of the first Heating bundle in order to achieve the greatest possible heating power with the smallest possible dimensions.

This intended goal is achieved, but the manufacture of such radiators is relatively difficult and expensive. In addition, there is a considerable cost of materials, namely for the electrical heating coil surrounding pipes required.

Furthermore, these voluminous radiators lead in a channel through which a medium flows relatively high flow velocities, which significantly reduce the efficiency.

With the invention, for the purpose of improving the efficiency with the simplest means with the smallest possible reduction in the channel cross-section due to the electrical heating in the channel, a hitherto unattainable uniform distribution of the heating heat transfer surfaces than hitherto is sought.
The solution to this problem is characterized by the features disclosed in claim 1.

These measures mean that a previously additionally required carrier for the heating conductor can be dispensed with, which on the one hand significantly reduces the manufacturing costs. On the other hand, they have also been omitted so far flow resistances caused by the heatsealing band, from which with the same cross-section dimensioning of a duct, as before, lower air flow velocities and the resulting

ORIGINAL INSPECTED

de longer exposure time of the heater to the air flow than before.

In addition, a hitherto unattained uniform flow around all heating zones is achieved and thus Zone-wise overheating of the heating is avoided.

Especially with a heating conductor that is angled twice per turn, it is advantageous if the Turn sections have the same lengths and preferably also the lengths of the turn sections correspond roughly to the largest clear width of the canal.

In particular with a heating conductor that is angled more than twice, preferably three times, per turn it is used to achieve even more even heating over the entire air flow cross-section advantageous to design the turn sections per turn to be of different lengths to one another.

For this purpose, an advantageous development is characterized in that exclusively or in connection with the above-described feature per turn, the angles formed by the turn sections have different sizes to each other.

In all of this, the corner corners can be more or less rounded.

An embodiment of the above-described object that additionally improves the efficiency, claim 7 characterizes an even more compact design of it than before.

Another feature that increases the heat transfer surface in a small space is this characterized in that the heating conductor has been reshaped in a meandering shape or the like before winding.

A method for producing the heating element characterized above is characterized in claim 9.

Embodiments of the invention are shown in the drawing and will be described in more detail below described. It shows

F i g. 1 a part of an electrical heater for heating an air flow in the front view,

F i g. 2 also in cross section,

3 a further embodiment also in cross section,

F i g. 4 another design of a detail.

Here, the electrical heater 1 is circular in a channel 2 through which an air stream can flow Cross-section used.

The heater consists of a ribbon-shaped electrical conductor 3 with high electrical resistance, which essentially follows a helical line angled in sections and so in channel 2 it is arranged that the conductor 3 is located exclusively with its angular corners 4 on the inner wall of the channel 2 supports.

Channel 2 consists of electrical, highly heat-resistant insulation material.

The channel 2 can also only be lined with the aforementioned material.

It is also possible to hold heat-resistant insulating pieces at the angle corners 4 of the conductor, in order to ensure that in any case To reliably prevent turns and shorts to ground. The corner corners 4 are from conductor turn to conductor turn Staggered to one another and an angle leg of each conductor turn is almost diametrical directed. To produce one shown in FIGS. 1 and 2 Heater 1 shown is a ribbon-shaped conductor 3 initially around a substantially rectangular profile Rod with small and rounded short cross-sectional sides, helical and close to the rod wound up tightly.

If then the wound conductor 3 is stripped from the rod, the heating conductor relaxes with enlargement the angle 6 formed by the winding sections 5 and with a simultaneous increase in the Winding pitch, so that now the corner corners 4, as shown in FIG. 2 can be seen, from turn to turn offset to one another and the essentially straight winding sections to one another are approximately star-shaped are arranged crossing.

To produce the in F i g. 3 shown heating element is a conductor 3 around a in cross section triangular rod with cross-sectional sides of unequal length to each other, which is another greater degree of space filling than with that in the F i g. 1 and 2 shown heating conductor can be achieved. It is also possible to use a head 3 z. B. to wrap a cross-sectionally rhombus or trapezoidal rod.

In Figure 4 is a ribbon-shaped conductor 3 for Enlargement of the heat transfer surface has been reshaped in a meander shape before winding.

In terms of production engineering, the production of the heater is easiest when a conductor 3 is around a rod rectangular cross-section of small thickness is wound, after which one in the F i g. 1 and 2 shown Heating received.

It is also advantageous to use a ribbon-shaped conductor instead of a conductor with a round cross-section use, as this is much easier to bring into the shape described above than round wire without twisting.

1 sheet of drawings

Claims (1)

Patent claims: 1. Arrangement of an electrical heating element in a channel for heating one of the channel flowing gas stream, in particular air, consisting of an electrical wire or band-shaped, insulated mounted heating conductor with high electrical resistance, which is essentially Angled in sections following a helical line and exclusively with the Angular corners on the duct inner wall is arranged in a supporting manner, characterized by the following features: a.) the corner corners (4) follow the helical line from turn to turn to each other staggered, and b.) at least one of the angle legs per turn is the central axis of the channel (2) arranged at least approximately crossing.