DE20120821U1 - Electric heater for absorption cooling systems - Google Patents

Description

Neymeyer & Partner GbR, patent attorneys

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Applicant: Türk + Hillinger GmbH, 78532 Tuttlingen Applicant No.: 1522213

Designation: Electric heating device for absorption cooling systems

The invention relates to an electrical heating device for attachment to the riser pipe or cooker pipe located in the coolant circuit of an absorption cooling system, through which the coolant flows and in which the coolant is heated, wherein in an externally open cavity of a carrier block with good heat conduction, which has on the outside a recess adapted to the cross-sectional profile of the riser pipe or cooker pipe, at least one PTC heating element is arranged in contact between two flat electrodes connected to a power source and electrically insulated from the carrier block and is pressed against a contact surface of the carrier block under the effect of a clamping force.

In absorption refrigerators, it is important that the energy required to start the cooling circuit is transferred over the shortest possible distance in the form of

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Heat is transferred to the so-called riser pipe, which is also called the cooker pipe. Of course, as little heat energy as possible should be released into the environment and should be released as completely as possible directly, i.e. without delay and via the shortest route, to the cooker pipe or riser pipe.

A so-called PTC thermistor heater is already known from EP 0 333 906 B1, which consists of an elongated carrier profile body made of thermally conductive material with at least one support surface and at least one PTC heating element resting flat on one side in a thermally conductive connection. The heater has an upper and a lower electrode plate, between which at least one PTC resistance element is arranged. On the outside of the carrier profile body opposite a trough-like recess adapted to the cross-sectional shape of a riser pipe, holding rails are formed on both sides of a flat support surface, each of which tightly accommodates the edge strips of a cover body designed as a cover plate. At least one longitudinal bead is formed along the edge strips of this cover plate, so that the edge strips of this cover plate can be clamped in the holding rails and the middle surface section of the cover plate presses on the PTC heating element in order to ensure good heat conduction from the PTC heating element via the cover plate.

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or the carrier profile body into the outer areas of the carrier profile body.

However, in this known PTC thermistor heater, a large part of the heat generated by the PTC heating element or elements is released into the environment via the cover plate, so that the achieved efficiency needs to be improved.

The invention is based on the object of creating an electric heating device of the type mentioned at the outset, which can be manufactured simply and at low cost and can be easily attached to the riser pipe of an absorber cooling system using simple fastening means and with rapid, delay-free and low-loss heat transfer.

This object is achieved according to the invention in that the carrier block has a groove with parallel inner surfaces in which the PTC heating element is arranged in such a way that the electrodes lying on its flat sides and electrically insulated from the outside of the carrier block

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under compressive stress lie completely against the inner surfaces of the groove.

The heating device according to the invention has the considerable advantage over the known PTC thermistor heater that the heat emitted via the two flat sides of the PTC heating elements cannot be emitted to the environment via a cover that is free on the outside, but is conducted completely to the support block via the two electrodes made of a good heat-conducting material and the thin insulating film, which is also made of a good heat-conducting material, and via this directly to the riser pipe. This heat transfer is greatly promoted by the pressure with which the two inner surfaces of the groove are pressed against the flat sides of the PTC element.

The design according to claim 2 allows the introduction of the PTC elements with the two electrodes covering their flat sides and an electrically insulating but highly heat-conducting polyimide film to be made simple and thus inexpensive, to which the designs according to claims 3 and 4 also contribute. In principle, the carrier block can be made of metal as well as

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made of a ceramic material, it is important that it has a high thermal conductivity and, in order to keep the manufacturing costs as low as possible, can be manufactured using the extrusion process.

The embodiment according to claim 5 is also advantageous in terms of manufacturing technology.

The design of the heating device according to claim 6 offers the possibility of achieving a very high heating output with a compact design and/or of providing PTC heating elements for different operating voltages according to the design according to claim 7.

The clamping force provided according to claim 8, which contributes to an improvement in the heat transfer between the PTC heating element(s) and the carrier block, can be generated either according to claim 9 by screws and/or according to claim 10 by suitable tension springs.

The embodiments of claims Ii and 12 result in simple, but advantageous with regard to heat transfer, mounting and fastening options for the carrier block on the riser pipe or cooker pipe to be heated.

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The embodiment according to claim 13 also relates to an advantageous possibility of fastening the heating device to the riser or cooker pipe.

The embodiments according to claims 14 and 15 show the possibility of a different arrangement of the recess and thus also a different arrangement of the support block on the riser pipe or cooker pipe.

The embodiment according to claim 16 relates to an embodiment in which two heating devices can be attached to the riser pipe in a particularly effective arrangement using simple means and in a simple manner.

By anodizing the carrier block, which preferably consists of aluminum or an aluminum alloy, as provided in claim 17, if the anodic oxide layer produced thereby has the required minimum thickness or the required electrical insulation resistance, the use of the insulating film provided in claim 2 can be dispensed with; this means the insulation resistance which is required to insulate the two electrodes from the carrier body.

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The invention is explained in more detail below with reference to the drawing. It shows:

Fig. 1 shows a heating device attached to a vertical riser pipe or cooker pipe in side view;

Fig. 2 shows a section II-II of Fig. 1;

Fig. 2a the support block of Fig. 1 and 2 in isometric view,-

Fig. 3 shows a section III-iii of Fig. 2;

Fig. 4 in the same sectional view as Fig. 2 another embodiment of the carrier block;

Fig. 5 shows a section through a support block with two grooves, each of which accommodates at least one PTC heating element;

Fig. 6 shows in the same sectional view another embodiment of the heating device shown in Fig. 5;

Fig. 7 shows a side view of another embodiment of the heating device on a vertical riser pipe,

Fig. 8 shows a section VIII-VIII from Fig. 7;

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Fig. 9 shows a side view of a simplified embodiment of the heating device shown in Figs. 7 and 8;

Fig. 10 is a section X-X of Fig. 9;

Fig. 11 shows in section the heating device shown in Fig. 10, but with a different type of fastening of the bow spring;

Fig. 12 shows a side view of two heating devices mounted in diametrical arrangement on a vertical riser pipe;

Fig. 13 shows a section XIII from Fig. 12;

Fig. 14 a two-legged spring clip in isometric view;

Fig. 15 is an isometric view of a spring clip with two of which the two heating devices shown in Figs. 12 and 13 are attached to the riser pipe.

The heating devices shown in the drawing figures 1 to 13 are each designed to be easily attached to a vertical riser pipe 1, also called a cooker pipe, which

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This is an integrated component of a self-contained coolant circuit of an absorption cooling system, in particular of a refrigerator.

The different designs of the heating device are described in more detail below.

In the embodiment of Figs. 1 to 4, the heating device 2 consists of a substantially cuboid-shaped carrier block 3, which preferably consists of aluminum or an aluminum alloy, but which could also consist of copper, brass or another metal with good heat conduction. For cost reasons, it is expedient to choose a metal that can be processed using the extrusion process, so that the cross-sectional profile of the carrier block shown in Figs. 2 and 4 can be produced in the simplest and most cost-effective way.

The carrier block 3 has a rectangular profiled groove 4 running in the longitudinal direction with two inner surfaces 5 and 6 running parallel to one another. A PTC heating element 7 is arranged in this groove 4 between two flat electrodes 8 and 9 made of electrically conductive material, preferably aluminum or an aluminum alloy. The two flat electrodes 8 and 9 lie without a gap on the flat sides of an elongated PTC heating element with a rectangular cross-section, so that they

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on the one hand, make electrical contact with the heating element 7 and, on the other hand, are in contact with it in such a way that heat is transferred from the heating element 7 to the two electrodes 8 and 9 with at least almost no loss. The two electrodes 8 and 9, which protrude beyond the heating element 7 on its two narrow long sides, are electrically insulated from the carrier block 3 by an insulating film 10. This insulating film 10 can be very thin. It consists of polyimide, which has a high electrical resistance on the one hand, but also a high thermal conductivity on the other, so that it is able to conduct the heat generated by the heating element 7 via the two electrodes 8 and 9 with almost no delay and no loss to the two strip-like block legs II and 12 of the carrier block 3, between which the groove 4 is arranged.

It is sufficient if the insulating film 10 only covers the surfaces of the electrodes 8 and 9 which are directly opposite an inner surface 5 and 6 and the bottom surface 6' (Fig. 2a) of the groove 4.

It can be seen from the illustrations in Fig. 2 and 4 that the heating element 7 with the two electrodes 8 and the insulating film 10 surrounding them covers the entire

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Fill width b of groove 4 without gaps to ensure heat transfer with as little loss as possible.

This heat transfer is further improved by the fact that the two block legs II and 12 are subjected to a clamping force by which they are pressed against each other and thus also against the flat sides of the electrodes 8 and 9 or the PTC heating element 7. In the embodiment of Fig. 1, 2 and 3, this clamping force is generated by a clamping spring 13 designed as a two-leg bow spring or by a clamping screw 14.

The tension spring 13 has two spring legs 15 and 16, the inwardly rounded leg ends 17 and 18 of which engage in locking grooves 19 and 20 arranged on the outside of the carrier block 3.

As can be easily seen, the groove 4 is open on the narrow side of the essentially rectangular cross-sectional profile of the carrier block 3. The groove 4 is also open on the two end faces 21 and 22 of the carrier block 3. From Fig. 3 it can be seen that the two electrodes 8 and 9 are each provided with connecting wires 23 and 24, via which the electrical energy is supplied to the PTC heating element 7.

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On the narrow longitudinal side opposite the groove 4, the support block 3 is provided with a U-shaped profiled recess 25, the cross-sectional shape of which is adapted to the diameter d of the cylindrical riser pipe 1. The depth t of the recess 25 is smaller than the diameter d of the riser pipe 1, to which the width bl of the recess 25 corresponds exactly.

To fasten the support block 3 or the entire heating device 2 to the riser pipe 1, a two-legged spring clip 26 is provided, the leg ends 27 and 28 of which engage in locking grooves 29 and 30 of the support block 3. The spring clip 26 is provided with a concavely shaped bracket back 31 which rests resiliently on the riser pipe 1 and presses it into the recess 25.

Instead of the locking grooves 19 and 20 or 29 and 30 for the leg ends 15 and 16 or 27 and 28 of the tension spring 13 on the one hand and the spring clip 26 on the other hand, as shown for example in Fig. 11, fastening grooves 32 can also be provided, into which leg ends 33 of a tension spring or a spring clip bent at a right angle can engage in a form-fitting manner.

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The heating device 2 shown in section in Fig. 4 differs from that of Figs. 1 and 2 only in that a carrier block 3' is provided, the strip-like block legs 11' and 12' of which are provided with a clamping screw 14 instead of a tension spring 13 in order to generate the contact pressure or clamping force already mentioned.

In order to achieve a uniform pressing stress over the entire length L of the PTC heating element 7, several clamping screws 14 can be provided in a distributed arrangement. These clamping screws 14 each freely extend through a transverse bore 34 of the block leg 12' and are each screwed into a threaded bore 35 of the opposite block leg ¹¹¹ .

In the embodiment of the heating device shown in Fig. 5, a support block 3/2 is provided which has two adjacent grooves 4/1 and 4/2 which are separated from one another by a central block leg 12/1. As in the embodiment of Fig. 2, the two outer block legs 11 and 12 are each provided on the outside with locking grooves 19 and 20, into which the leg ends 17 and 18 of a two-leg tension spring 13 engage in a locking manner and thereby use their spring force to press the two block legs II and 12 against the central block leg.

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legs 12/1 or against the heating elements 7 inserted in the grooves 4/1 and 4/2 or their electrodes 8 and 9 in order to ensure good heat transfer.

It is possible to provide the two PTC heating elements accommodated in the grooves 4/1 and 4/2 in different embodiments, in particular for different operating voltages of, for example, 10 to 30 volts or 100 to 150 volts or 200 to 250 volts. On the other hand, it is also possible to operate both heating elements 7 with the same operating voltage at the same time in order to achieve a higher heating output.

The fastening of this support block 3/2 to the riser pipe 1 is again accomplished with a two-leg spring clip 26', which rests with its concave bracket back 31' springily on the riser pipe 1, which is accommodated in the recess 25. The leg ends 27 and 28 of this spring clip 26' engage in a locking manner in the lateral locking grooves 29 and 30 of the support block 3/2, which are also present here.

In the embodiment shown in Fig. 6, the carrier block 3/3 differs from the carrier block 3/2 of the embodiment according to Fig. 5 only in that the middle

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The block leg 12/1 is shorter and the two outer block legs II and 12 are connected to one another by a clamping screw 14'. The block leg 12 is provided with a continuous transverse bore 34 and the block leg 11 with a threaded bore 35 into which the clamping screw 14' is screwed. Here too, several clamping screws 14' can be arranged distributed over the length of the two PTC heating elements in order to obtain a uniform compressive stress.

In the embodiments shown in Fig. 7 to II, the support blocks 3/4, 3/5 and 3/6 each have only one groove 4, as is also the case with the embodiments of Fig. 2 to 4. In these support blocks 3/4, 3/5 and 3/6, however, the recess 25/1 is arranged on the outside of a block leg 12. It has a much smaller depth than the recesses 25 and is essentially designed as a circular segment-shaped groove. To attach these support blocks 3/4, 3/5 and 3/6 to a riser 1, a bow spring 40 with a bow section 41 is provided. This bow spring 40 engages with at least one bow leg 42 in a locking groove 19 on the outside of the support block 3/4 or 3/5. Instead of this grid connection, as shown in Fig. II, the bow

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The bracket leg 42 with a leg end 33 bent at a right angle engages in a fastening groove 32 in a form-fitting manner. On the side opposite the bracket leg 42, the bracket spring 40 is provided with a clamp section 44 which resiliently surrounds the riser pipe l and which creates the resilient connection between the support block 3/4 or 3/5 or 3/6 and the riser pipe l located in the recess 25/1 in a force-fitting manner. As shown in Fig. 7, two or even more such bracket springs 40 can be provided.

In the embodiment of Figs. 7 and 8, these bow springs 40 are arranged on the rear side of the support block 3/4 opposite the groove 4. As in the embodiment of Figs. 1 to 3, the two block legs 11 and 12 are subjected to a tension force by a tension spring 13. In the embodiment of Figs. 1 and 10, however, the bow spring 40 is arranged on the opposite, open side of the groove 4, in such a way that the groove 4 is bridged by the bow section 41 and the clamp section 44 springily surrounds the riser pipe 1. The length L1 of the bow spring 40 can be selected so that it covers most of the length L2 of the support block 3/5. However, it is also possible to use several shorter bow springs over the length L2.

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of the support block 3/5. By arranging the bow spring 40 on the open side of the groove 4, the tension spring 13 of Fig. 7 and 8 can be omitted.

As can be seen from Figs. 8 and 11, the bow spring 40 can also be provided on the side on which the clamp section 44 is located with a locking bead 45 which engages in a locking groove 20 of the carrier block 3/4 or 3/5 or 3/6.

As the embodiments of Fig. 12 and 13 show, it is also possible to attach two heating devices 2 of the type shown in Fig. 1 to 3 to a riser pipe 1 at the same time if the depth t of the recess 25 is kept smaller than half the outside diameter d of the riser pipe 1. As can be seen from Fig. 12 and 13, it is possible to arrange two such heating devices 2 diametrically opposite each other on the riser pipe 1 and to attach them to the riser pipe 1 by means of one or more spring clips 50, as shown as individual parts in Fig. 15. The two heating devices 2 differ from the heating device 2 of Fig. 1 and 2 only in that the recesses 25 which accommodate the riser pipe only have a smaller depth ti.

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Otherwise they are not different. The spring clip 26 is replaced by two spring clips 50, each of which has a claw 51 that positively grips the block legs 11 and 12 of one support block 3 and a locking strip 52 at the opposite end of the spring clip 50 that locks the opposite block legs II and 12 of the second support block 3. The section 53 of the spring clip 50 that lies between the claw 51 and the locking strip 52 is wave-shaped in order to be able to generate a clamping force between the claw 51 and the locking strip 52, by means of which the two support blocks 3 are pressed against the riser pipe 1. In order to generate the clamping force pressing the two block legs 12 against the heating elements 7, tension springs 13/1 are provided which have the same cross-sectional profile as the tension spring 13, but which have a recess 47 in the longitudinal center region in which the spring clamps 50 with their claws 51 or locking strips 52 can grip the block legs 11 and 12 of the two support blocks.

It is particularly advantageous if the carrier block 3 to 3/6, which preferably consists of aluminium (aluminium alloy), is coated at least in the area of the inner surfaces 5, 6 and 6' of its grooves 4 or 4/1 and 4/2 with an anodic oxide layer which provides the required electrical insulation resistance with respect to the two electrodes 8, 9.

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(anodized). In order to ensure the necessary safety and to be able to replace the insulating film 10, such an oxide layer should have a minimum thickness of about 3μ (3 thousandths of a mm). In accordance with the usual anodizing process, the oxide layer can also cover the entire surface of the carrier block 3 to 3/6. But even together with the insulating film 10, such an oxide layer offers the advantage of greater operational safety.

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Claims (18)

1. Electrical heating device for attachment to the riser pipe or cooker pipe in the coolant circuit of an absorption cooling system, through which the coolant flows and in which the coolant is heated, wherein in an externally open cavity of a carrier block with good heat conduction, which has on the outside a recess adapted to the cross-sectional profile of the riser pipe or cooker pipe, at least one PTC heating element is arranged in contact between two flat electrodes connected to a power source and electrically insulated from the carrier block and is pressed against a contact surface of the carrier block under the effect of a clamping force, characterized in that the carrier block ( 3 ) has a groove ( 4 ) with parallel inner surfaces ( 5 , 6 ), in which the PTC heating element ( 7 ) is arranged in such a way that the electrodes ( 8 , 9 ) resting on its flat sides and electrically insulated on the outside from the carrier block ( 3 ) are in contact over the entire surface under compressive stress on the inner surfaces ( 5 , 6 ) of the groove ( 4 ) are present. 2. Electric heating device according to claim 1, characterized in that the two electrodes ( 8 , 9 ) contacting the flat sides of the PTC element ( 7 ) are each covered by an insulating film, in particular a polyimide film ( 10 ) , at least on the outer surfaces opposite an inner surface ( 5 , 6 ) of the groove ( 4 , 4/1 , 4/2 ) of the carrier block ( 3 to 3/6 ). 3. Electric heating device according to claim 1 or 2, characterized in that the carrier block ( 3-3 / 6 ) consists of a metal with good heat conduction, in particular of aluminum. 4. Electric heating device according to one of claims 1 to 3, characterized in that the electrodes ( 8 , 9 ) consist of copper, aluminum or their alloys. 5. Electric heating device according to claim 1, characterized in that the carrier block (3, 3/1, 3/4-3/6) has a rectangular cross-sectional shape and that the groove ( 4 ) is open at both ends and lies between two strip-like block legs ( 11 , 12 ). 6. Electric heating device according to claim 5, characterized in that the carrier block ( 3/2 ) has two grooves ( 4/1 , 4/2 ) which are separated from one another by a central block leg ( 12 ') and run parallel to one another , in each of which at least one PTC heating element ( 7 ) is housed in an insulated manner between two electrodes ( 8 , 9 ). 7. Electric heating device according to claim 6, characterized in that the PTC heating elements ( 7 ) arranged in the two grooves ( 4/1 , 4/2 ) of the carrier block ( 3/2 ) are designed for different operating voltages, in particular for 10 V to 30 V or for 100 V to 150 V or 200 V to 250 V. 8. Electric heating device according to claim 5 or 6, characterized in that the inner surfaces ( 5 , 6 ) of the grooves ( 4/1 , 4/2 ) are pressed against the flat sides of the PTC heating elements ( 7 ) or against the electrodes ( 8 , 9 ) by at least one clamping force acting on the outside of the respective outer block legs ( 11 , 12 ). 9. Electric heating device according to claim 8, characterized in that the respective outer block legs ( 11 , 12 ) are connected to one another by clamping screws ( 14 , 14 '). 10. Electric heating device according to claim 8, characterized in that the respective outer block legs ( 11 , 12 ) are connected by a tension spring ( 13 ) which is designed as a two-leg bow spring, the leg ends ( 17 , 18 ) of which engage in a locking manner in locking grooves ( 19 , 20 ) or in a form-fitting manner in fastening grooves ( 32 ) of the carrier block ( 3 , 3 / 2-3 / 6 ). 11. Electric heating device according to claim 1, characterized in that the recess ( 25 ) has a U-shaped cross-section with a width (b1) which corresponds to the diameter (d) of the riser pipe ( 1 ) and with a depth (t) which is smaller than the diameter (d) of the riser pipe ( 1 ). 12. Electric heating device according to claim 1 or 11 , characterized in that the recess (25) is arranged on the outside of the carrier block (3, 3/1, 3/2 , 3/3 ) opposite the open longitudinal side of the groove ( 4 ). 13. Electric heating device according to one of claims 1, 11 or 12, characterized in that at least one two- legged spring clip ( 26 , 26 ') is provided for fastening the carrier block ( 3 , 3/1 , 3/2 ) to the riser pipe ( 1 ), the leg ends ( 27 , 28 ) of which engage in a form-fitting or locking manner in fastening grooves or locking grooves ( 29 , 30 ) of the carrier block ( 3 , 3/1 , 3/2 ) and the bracket back ( 31 , 31 ') of which is concave and rests resiliently on the riser pipe ( 1 ) . 14. Electric heating device according to claim 1 or one of claims 1 to 10, characterized in that the recess ( 25/1 ) is arranged in the form of a circular segment-shaped groove on the outside of a block leg ( 12 ). 15. Electric heating device according to claim 14, characterized in that a bow spring ( 40 ) with a bow section ( 41 ) and with at least one bow leg ( 42 ) and a clamp section ( 44 ) encompassing the riser pipe ( 1 ) is provided for fastening the support block ( 3/4 , 3/5 , 3/6 ) to the riser pipe ( 1 ), wherein the bow section ( 41 ) bridges either the open longitudinal side of the groove ( 4 ) or the side of the support block ( 3/4 , 3/5 , 3/6 ) opposite thereto and engages with at least one bow leg ( 42 ) in a form-fitting or locking manner in an external fastening groove ( 32 ) or locking groove ( 19 ) of the support block ( 3 / 4-3 / 6 ). 16. Electric heating device according to one of claims 1 to 12, characterized in that two support blocks ( 3 ), each provided with at least one PTC heating element ( 7 ), are arranged diametrically opposite one another on the riser pipe ( 1 ) and are fastened thereto by means of one or more spring clips ( 50 ) or the like. 17. Electric heating device according to one of claims 1 to 16, characterized in that the carrier block ( 3 , 3/1 , 3/2 , 3/4 , 3/5 , 3/6 ) is coated ( anodized ) with an anodic oxide layer at least in the region of the inner surfaces ( 5 , 6 , 6 ') of its groove ( 4 ) or grooves ( 4/1 , 4/2 ) . 18. Electric heating device according to claim 17, characterized in that the anodic oxide layer has a minimum thickness of 3µ (thousandths of a mm).