DE102011114053B4 - Method for producing a heat conducting device and heat conducting device for an absorber - Google Patents

Abstract

Process for producing a heat-conducting device (10) by blow molding, an essentially tubular preform (20) made of a thermoplastic plastic being placed between a multi-part mold and spread there before or during the closing of the multi-part mold (30) and then in the closed mold ( 30) is expanded by an air flow L, characterized in that the preform (20) is spread by two header pipes (11, 12) arranged in it and that the header pipes (11, 12) provided as spreaders remain in the mold and thus in the component ,

Description

The invention relates to a method for producing a heat conducting device according to the preamble of claim 1 and to a heat conducting device for an absorber according to claim 8.

Solar thermal collectors are well known. They usually have a relatively flat and large-area absorber plate, which absorbs energy in the form of light, converts it into heat, and delivers it to a heat transfer medium, the heat transfer medium flowing through the absorber plate.

Various embodiments of such solar thermal collectors are described in the prior art. Usually, the generally flat heat conducting device has a first manifold for supplying the heat transfer medium and a second manifold connected thereto through one or more cavities or conduits for discharging the heat transfer medium, wherein in particular the cavities or conduits are in heat conducting contact with the absorber plate therefore form the actual absorber area of the heat-conducting device. The two headers usually have a larger diameter or a larger cross section than the remaining cavities or lines in the absorber area. Particularly common are, for example, embodiments with a 4- to 5-fold larger diameter of the headers.

In order to be able to inexpensively produce such plastic heat-conducting devices, the use of a blow molding process is desirable. In blow molding for the production of hollow bodies, a thermoplastic material is melted in an extruder and extruded as a tubular, formable preform. The preform is then pressed on one side and inflated via a nozzle which is introduced into the preform in a multi-part blow molding tool enclosing the preform until it bears against the inside of the shaping blow molding tool and has reached its final shape. After the plastic in the blow mold has cooled down until it has a sufficient dimensional stability, the blow mold can be opened and the finished molded hollow body can be removed. Due to the process, the hollow body at the point at which the air was introduced for inflation, a hole that may need to be closed subsequently.

The DE-PS 11 78 580 discloses a method for manufacturing flat hollow bodies, such as in particular hot water bottles, in which an extruded tubular preform is spread between two halves of a blow mold brought by expanding mandrels in a plane so that it forms practically two parallel bands. Subsequently, the mold is closed and the preform is inflated. By spreading the preform before inflation into the final shape, even in the production of a flat hollow body, a relatively uniform wall thickness can be achieved.

The problem with regard to the production of a heat conduction device with the aid of the blow molding process is the fact that the collecting tubes and the cavities or lines in the absorber area have different cross sections or thicknesses. Since the headers usually have a larger diameter, the preform must be particularly strong in these areas. Consequently, the wall thickness achieved in the blow molding process in these areas is less than the wall thickness in the absorber area. This is extremely unfavorable because the headers are exposed to a particularly large mechanical load, especially during assembly of the collector, while in the absorber area a particularly small wall thickness is desirable so that the heat can be absorbed as quickly as possible and passed on optimally.

The invention has for its object to provide a robust heat conducting device for a flat absorber available, which allows rapid and efficient heat transfer and which can be provided at the same time inexpensively by simple means. Furthermore, it is an object of the invention to provide a cost-effective and simple method for producing such a heat-conducting device.

This is achieved with the features of claims 1 and 8 according to the invention. Advantageous developments are shown in the respective subclaims.

In a method according to the invention for producing a heat conduction device according to the invention by blow molding, wherein a substantially tubular preform made of a thermoplastic material is brought between a multi-part mold and there spread before or during the closing of the multi-part mold and then expanded in the closed mold by an air flow L. is, the invention provides that the preform is spread by two arranged in this manifolds and that provided as spreaders headers remain in the mold and thus in the component.

For this purpose, provided as spreaders collecting pipes are fixed in the mold at the ends, preferably in the lower region pliers and / or associated receiving sleeves are provided on a spreading slide and in the upper region pliers on a projection of the molding tool. This reduces the sum of the bending moments in the struts.

Advantageously, the ends of the headers fixed in the molding process to the mold are released after completion of the molding process by lowering the pliers and / or receiving sleeves in the lower region and the pliers are opened in the upper region. For a safe manufacturing process, this release of the manifolds before opening the mold is very important, because at the moment of pressure relief, so the venting of the component, and even more after the mold opening, the majority of the shrinkage in the component. Without releasing the lock, there would otherwise be tensions between the struts which could possibly deform them. Therefore, the tubes must be separated from both the spreader and the pliers.

In such a method, the preform is thus not spread by expanding mandrels, but by two arranged in this manifold. For this reason, the use of expanding mandrels can be dispensed with in the method according to the invention, so that the mechanical construction of the blow-molding device to be used is particularly simple. In addition, the material supernatant usually occurring at the Spreizdornen, which is why in the method according to the invention pleasingly little material waste is obtained.

Of particular advantage, however, is that the formation of the one-piece plastic body is independent of the provision of the manifolds. This allows the headers to have a greater wall thickness than the wall surrounding the cavity. It is also advantageous that the heat conducting device is finished after completion of the blow molding, because neither subsequently removed expanding mandrels, nor the resulting holes must be closed. This allows a particularly simple and inexpensive production.

A preferred embodiment of the method according to the invention further provides that the air flow L is passed through at least one collecting tube in the preform. In this way, not only can be dispensed with the injection nozzle, but also eliminates the subsequent closing of a hole. Instead, the air flow L is introduced directly via the anyway open at least one side manifolds. The air is supplied in an advantageous embodiment of the spreading slide and the lower fixation.

Based on this, an important further development provides that the airflow exits the collecting pipe via the lateral opening. In this way, the cavity through which the two manifolds are connected to each other, particularly easy to be provided.

Another important embodiment of the invention includes that the collecting tube is sealed on one side during the introduction of the air flow L and opened again after cooling of the heat conducting device. By sealing the manifold, an effective blowing of the air flow is achieved in the preform. After cooling of the heat-conducting device, the collecting pipe is opened again and is thus available again for normal use, for example for introducing or discharging the heat-conducting medium.

In a heat conducting device for receiving a heat transfer medium for a flat absorber of a solar thermal collector comprising a first manifold for supplying the heat transfer medium and a second manifold for discharging the heat transfer medium, wherein the manifolds each have at least one lateral opening, via which they are connected to a cavity are, the invention provides that the cavity is formed in a one-piece plastic body, and that the two manifolds are enclosed in the plastic body.

The inventively provided one-piece plastic profile can be inexpensively made by a blow molding of a suitable thermoplastic material. By enclosing the two manifolds in the one-piece plastic body, the headers of the heat-conducting device are additionally reinforced while creating a robust connection between the individual components.

Due to the separate design of the headers and the plastic body is also achieved that each component can be optimally adapted to the particular requirements. For example, the headers can be made comparatively thick-walled to meet the high mechanical stress of the headers during assembly of the solar thermal collector. Independently of this, the inventive design of the heat-conducting device makes it possible for the wall surrounding the cavity at the same time to be so thin-walled that optimum heat transfer to the heat transfer medium is possible. A heat conducting device designed in this way is therefore efficient and at the same time robust.

An important embodiment of the invention provides that a manifold has an anti-rotation. In this way it is ensured that the manifold in the plastic body can not be twisted. The anti-twist device is preferably a nose formed on the collecting tube, a bead or a projection which engages with a corresponding shape on the plastic body.

Another preferred embodiment of the invention includes that the headers have a sealant. The sealant prevents heat transfer medium from escaping between the tubes and the plastic body. Preferably, the sealing means is a ring surrounding the manifold made of an elastic material such as rubber. Such a sealant is easily and inexpensively available in different configurations and can be easily placed on the manifold in the manufacture of the heat conducting device. However, other expedient embodiments, such as a sealing band or a sealing collar formed on or molded onto the manifold or a sealing ring are conceivable.

In a heat conducting device according to the invention, each collecting tube preferably has at least one opening. Thus, it can be ensured that the cavity is flushed as evenly as possible by the heat transfer medium. In addition, the at least one opening provides a means for rapid supply and discharge of the heat transfer medium. The cross-sections of the openings can vary in order to achieve a position and pressure-dependent adapted flow cross-section, which ensures a uniform distribution of the heat transfer medium over the absorber surface.

Further features, details and advantages of the invention will become apparent from the wording of the claims and from the following description of exemplary embodiments with reference to the drawings. Show it:

1 a heat conducting device according to the invention,

2 a detailed view of a manifold of in 1 shown heat conducting device,

3 a preform having two headers disposed therein;

4 a preform which is spread by two collecting tubes arranged in this

5 a parison spread by two headers, which is inflated by an air flow L, which is passed through the two headers in the preform, and

6 a splayed preform between two converging halves of a blow mold.

1 shows a heat conducting device according to the invention 10 for the flow through a heat transfer medium for a flat absorber of a solar thermal collector, the first manifold 11 for supplying the heat transfer medium and a second manifold 12 for the derivation of the heat transfer medium, wherein the manifolds 11 . 12 each have at least one lateral opening, not shown in this illustration, via which they are connected to a cavity, also not shown. This cavity is in a one-piece plastic body 14 formed in which the two manifolds 11 . 12 are enclosed.

2 shows a side view of a manifold 11 . 12 a heat conducting device according to the invention. The manifold 11 . 12 has two side openings 16 on. The side openings 16 are present in each case designed as a slot. It is also conceivable, however, any other design that allows a uniform and rapid inflow or outflow of a heat transfer medium from or into the manifold.

Above and below each side opening 16 is each a sealant 17 arranged. The sealant 17 is in the illustrated embodiment as a collection tube 11 . 12 enclosing O-ring formed. The ring is preferably made of an elastic material such as rubber and can in the manufacture of a heat conducting device according to the invention prior to introduction of the manifold into the preform via the manifold 11 . 12 pushed and then brought into the desired position. By the sealant 17 is prevented later in use of the heat conducting device according to the invention heat transfer medium between the headers 11 . 12 and the plastic body 14 exit. Accordingly, in particular, an arrangement of the sealant 17 makes sense at the two ends of the headers.

The 3 to 6 show schematically with reference to various representations the sequence of a method according to the invention for producing a heat conducting device according to the invention by blow molding.

3 shows one with 20 designated preform with two arranged in this manifolds 11 . 12 which are inserted from below into the preform to laterally spread the preform.

The preform 20 is formed hose-like. It consists of a thermoplastic material which has been melted in an extruder and which is deformable in the state shown. From the preform 20 can with the aid of a blow molding according to the invention a one-piece plastic body 14 a heat conducting device according to the invention are formed.

4 shows a preform 20 before passing this through two arranged in this manifolds 11 . 12 is spread. It can be seen that at the two headers 11 . 12 in each case at the upper end and in the lower area two clamps 15 are attached.

The preform 20 can be splayed by the two headers 11 . 12 be pulled apart or driven sideways in a plane. For this purpose, the two manifolds 11 . 12 at their respective terminals 15 be grasped and moved. Conceivable, however, are other expedient embodiments which are suitable for a uniform moving apart of the two manifolds 11 . 12 to effect.

5 shows the preform 20 from 4 passing through the two headers arranged in this 11 . 12 was spread, with the manifolds 11 . 12 in the preform 20 stay.

The preform 20 is between the halves of a blow molding tool 30 . 31 arranged. The two halves 30 . 31 of the mold are moved together to a defined distance. On the preform 20 facing side of the two mold halves 30 . 31 in each case an indentation is formed, which corresponds to the shape of the hollow body to be produced. After the collapse of the two mold halves 30 . 31 air is blown into the preform. In a method according to the invention, this is done by blowing the air over the laterally in the spread preform 20 arranged and closed on one side manifolds 11 . 12 ,

6 shows a detail view of in 5 shown, between two headers 11 . 12 spread preform 20 when inflating. For the sake of clarity, in contrast to 5 the parts of the blow molding tool not shown here. It can be seen that the preform is inflated by an airflow L into the headers 11 . 12 which is initiated at the two headers 11 . 12 each exiting via at least one lateral opening, not shown. By blowing in the air flow L, the preform can be blown into the two halves of the merging shaping blow molding tool and the plastic body 14 be formed to the hollow profile.

LIST OF REFERENCE NUMBERS

10

heat conducting

11

manifold

12

manifold

13

cavity

14

Plastic body

15

clamp

16

opening

17

sealant

20

preform

30

first half of the mold

31

second half of the mold

Claims (11)

Method for producing a heat conducting device ( 10 ) by blow molding, wherein a substantially tubular preform ( 20 ) made of a thermoplastic material between a multi-part mold and there before or during the closing of the multi-part mold ( 30 ) and then in the closed mold ( 30 ) is expanded by an air flow L, characterized in that the preform ( 20 ) by two arranged in this manifold ( 11 . 12 ) is spread and that provided as spreaders headers ( 11 . 12 ) remain in the mold and thus in the component. Method according to claim 1, characterized in that the collecting pipes ( 11 . 12 ) are fixed in the mold at the ends, being provided for this purpose in the lower region pliers and / or associated receiving sleeves on a Spreizschlitten and in the upper region pliers on a projection of the mold. A method according to claim 1 or 2, characterized in that the fixed in the molding process on the mold ends of the headers ( 11 . 12 ) are released after completion of the molding process by lowering the pliers and / or receptacles in the lower area and open the pliers in the upper area. Method according to one of claims 1 to 3, characterized in that the air flow L via at least one collecting pipe ( 11 . 12 ) in the preform ( 30 ). Method according to one of claims 1 to 4, characterized in that the air is supplied via the spreading slide and the lower fixing. Method according to one of claims 1 to 5, characterized in that the air flow L over the lateral opening ( 16 ) from the manifold ( 11 . 12 ) exit. Method according to one of claims 1 to 6, characterized in that the collecting pipe ( 11 . 12 ) is sealed on one side during the introduction of the air flow L and is opened again after the heat-conducting device has cooled down. Heat conducting device ( 10 ) for receiving a heat transfer medium for a flat absorber of a solar thermal collector, produced by a method according to one of claims 1 to 7, a first manifold ( 11 ) to the supply of the heat transfer medium and a second manifold ( 12 ) for discharging the heat transfer medium, wherein the collecting pipes ( 11 . 12 ) each have at least one lateral opening ( 16 ) through which they are provided with a cavity ( 13 ), characterized in that the cavity ( 13 ) in a one-piece plastic body ( 14 ) is formed, and that the two manifolds ( 11 . 12 ) in the plastic body ( 14 ) are enclosed. Heat conducting device ( 10 ) according to claim 8, characterized in that a collecting pipe ( 11 . 12 ) has an anti-rotation. Heat conducting device ( 10 ) according to one of claims 8 or 9, characterized in that the collecting pipes ( 11 . 12 ) a sealant ( 17 ) for preventing escape of heat transfer medium between the headers ( 11 . 12 ) and the plastic body ( 14 ) in use of the heat conducting device according to the invention. Heat conducting device ( 10 ) according to claim 10, characterized in that the sealing means ( 17 ) a collecting pipe ( 11 . 12 ) enclosing ring.

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