EP2084465A1

EP2084465A1 - Pipe arrangement

Info

Publication number: EP2084465A1
Application number: EP08734670A
Authority: EP
Inventors: Volker Liebel
Original assignee: Rehau AG and Co
Current assignee: Rehau Automotive SE and Co KG
Priority date: 2007-03-21
Filing date: 2008-03-19
Publication date: 2009-08-05
Also published as: US8167027B2; EA022199B1; EA200970876A1; WO2008113569A1; DE202007004346U1; DE202007004346U9; DE202008016917U1; US20080236784A1

Abstract

The pipe arrangement for geothermal probes according to this invention comprises at least two pipes (1, 2), having at least one layer surrounding a lumen (3), wherein one of the pipes (1, 2) serves as the feed, and the other serves as the return, and at least one of the pipes (1, 2) is made at least partially of an non-crosslinked polymer material, and is characterized in that the polymer material of the at least one layer of the pipes (1, 2) has an FNCT (fill notched creep test) value according to ISO 16770 of at least 3000h.

Description

pipe arrangement

The invention relates to a pipe arrangement for geothermal probes according to the preamble of claim 1.

Such pipe arrangements for geothermal probes are well known from the prior art. These pipe arrangements have the task to absorb heat from the earth or to give heat into the earth.

For example, DE 202004007567 U1 describes a geothermal probe for introduction into a borehole in the ground. This geothermal probe comprises an outer wall of the geothermal probe forming outer tube which is closed at its lower end and extending inside the outer tube inner tube, wherein the annular space between the outer tube and the inner tube and the interior of the inner tube form lines for a heat transfer medium. The outer tube is formed at least over a major part of its longitudinal extent as a corrugated pipe.

There are further known pipe arrangements for geothermal probes in which pipe pairs are used, which have at their lower end a connecting bow or a connecting piece. One pipe forms the supply line and the other pipe the return line. However, it is also possible to use a plurality of pipe pairs of this kind in a borehole, which have one or more fittings as connecting elements at their lower end.

Furthermore, from EP 05821 18 A1 a pipe arrangement of long, parallel plastic pipes is known, which are connected at the lower end. In this case, at least one head part is connected in a liquid-tight manner to at least two straight, parallel long pipes by welding or bonding and is described by at least one bottom part, which is connected in a liquid-tight manner to at least one of the straight pipes by welding or gluing. Finally, from DE 20202578 U1 a pipe arrangement is known, for the production of tubes made of cross-linked polyethylene are required.

Furthermore, pipe arrangements for geothermal probes are known in which a pipe section helical formed. In this case, the helix can have constant or variable diameters.

It is also known to introduce such pipe arrangements for borehole heat exchangers into boreholes and then to fill these boreholes with material having good heat-conducting properties.

However, such tube assemblies for borehole heat exchangers in particular from uncrosslinked polymethyl ren materials are used for many years only to certain operating temperatures up to about 40 ⁰ C. In addition, the uncrosslinked materials hitherto used for pipe arrangements for geothermal probes have significant slow crack growth, which can lead to a rupture of the pipe arrangements for geothermal probes during operation, in particular during transport, handling on the construction site and introduction into the borehole. In addition, uncrosslinked pipe arrangements for geothermal probes according to the prior art have the serious disadvantage that they are not point load resistant. Contrary to the previous assessment, however, pipe arrangements for borehole heat exchangers also assume that point loads act when installed. Contrary to the representations of the prior art, the pipe arrangements for borehole heat exchangers are in fact not centrally centered in the borehole and surrounded all around by a concrete-bentonite mixture, but are always partially against the wall of the borehole.

Furthermore, again contrary to the previous assessments and representations, the condition of the borehole wall does not have to be smooth, but is estimated to be jarring. Therefore, it must be expected that point loads act on the walls of the pipe arrangements for geothermal probes. In addition, not enough has been taken into account so far that after the introduction of the pipe arrangements for geothermal probes in the hole falling stones can also exert point loads. And finally, it has not been considered that pipe arrangements for geothermal probes are exposed to considerable alternating loads; already in pure heating mode when switching on the heat pump very rapid temperature changes occur by about 10 K with the associated thermal expansions, in heating and cooling, these temperature changes can be up to 40 K. These loads can lead to the formation of cracks on the opposite side of the point load inside the pipe arrangements for geothermal probes, especially in continuous operation, which can continue to grow until it breaks.

Pipe arrangements for geothermal probes of cross-linked polymeric materials are resistant to point loads and do not have slow crack growth, but there is the problem that when attaching the connecting elements of pipe pairs they can not be butt welded, so that the production of such a pipe arrangement for geothermal probes material- and costly.

This is where the invention, which has set itself the task of overcoming the disadvantages of the known prior art and to show a pipe arrangement for geothermal probes, which is inexpensive and economical to produce, which is easy, efficient and damage-free installable and a further improved mechanical Behavior, in particular a balance of the resistance of the tube assembly against outer point loads and external notches and cracks has.

This is achieved by a pipe arrangement with the features of claim 1 according to the invention. Further advantageous embodiments are listed in the subclaims.

It is a tube assembly for geothermal probes from at least two tubes having at least one, a lumen-surrounding layer, wherein one of the tubes the flow and the other forms the return, and at least one of the tubes is made at least partially from a non-crosslinked polymeric material proposed , wherein the polymeric material of the at least one layer of the tubes has a FNCT (Füll Notched Creep Test) according to ISO 16770 of at least 3000 hours. In a further development, a pipe arrangement for geothermal probes is proposed from at least two tubes having at least one, a lumen-surrounding layer having at one end at least one, at least one layer exhibiting, connecting element, wherein at least one of the tubes at least partially from an unver- polymer material, wherein the polymeric material of the at least one layer of the tubes and / or the connecting element has a FNCT (Fill Emergency Creep Test) according to ISO 16770 of at least 3000 hours.

In a further embodiment of the pipe arrangements according to the invention, geothermal probes are proposed in which a pipe is designed to be helical. In this case, the helix can have constant or variable diameters. In a further development of this embodiment, the invention provides to perform the non-helical tube with thermal insulation.

Thus, with the tube assembly according to the invention for geothermal probes far reaching Punktlastbeständigkeit achievable and in the temperature range up to 20 ⁰ C, no slow crack growth can occur, which could lead to a failure of the pipe arrangements for geothermal probes within a defined life of about 50 years. Another advantage of the pipe arrangement according to the invention for geothermal probes is seen in the fact that they are cost-effective and economically producible, as well as butt-weldable with the corresponding connecting elements. Thus, a pipe arrangement according to the invention for geothermal probes can be shown, which can be produced economically and inexpensively, but which is also efficiently transportable or mountable, without the material of the pipe assembly for geothermal probes is exposed to damage.

A further advantage of the pipe arrangement according to the invention for geothermal probes is seen in that the polymeric material of the at least one layer of the pipes and / or of the connecting element has an FNCT value (Füll Notched Creep Test) according to ISO 16770 of at least 5000 hours. This advantageous embodiment of the pipe arrangement according to the invention for geothermal probes a further increased point load resistance and in continuous operation a significantly reduced growth of grooves and notches is achieved. In addition, in this embodiment, a point load resistance is achieved up to a temperature of 40 ^C C, whereby a permanent safety of the pipe arrangements for geothermal probes can be ensured with correspondingly high flow temperatures.

In a further likewise advantageous embodiment of the pipe arrangement for borehole heat exchangers, the polymeric material of the at least one layer of the pipes and / or the connecting element has an MRS value (minimum required strength) of at least 10 MPa at 20 ^° C. over 50 years. Thus, pipe arrangements for borehole heat exchangers with a diameter-wall thickness ratio of 11: 1 can withstand permanently a pressure of 20 bar.

In a further embodiment of the pipe arrangement according to the invention for geothermal probes, the polymeric material of at least one layer of the tubes and / or the connecting element has an MRS value (minimum required strength) of at least 12.5 MPa at 20 ⁰ C over 50 years. Thus, pipe arrangements according to the invention for geothermal probes can be advantageously provided that ensure trouble-free continuous operation within a life of about 50 years, without the transport or assembly in particular in the wells previous damage has been introduced.

In a further likewise advantageous embodiment of the pipe arrangement according to the invention, the polymeric material of the at least one layer of the tubes and / or the connecting element at least one UV resistance-increasing aggregate, with which the allowable periods for outdoor storage of the invention Rohran- orders are increased for geothermal probes can.

Further advantageous in the pipe arrangements according to the invention for geothermal probes is seen that the polymeric material of the at least one layer of the tubes and / or the connecting element have at least one the mechanical resistance increasing additive or reinforcing material.

Thus, by adding known additives or reinforcing materials such as glass fibers, a pipe arrangement according to the invention for geothermal probes can be made available, which can be dimensioned according to the legal requirements or standards easily and inexpensively. The pipe arrangement according to the invention for borehole heat exchangers is advantageously designed such that the polymeric material of the at least one layer of the pipes and / or of the connecting element has at least one additive which increases the diffusion resistance. These additives can be added in additions of about 1% to 30% and thus allow optimal dimensionable mechanical properties of the pipe assembly according to the invention for geothermal probes.

Also advantageous in the pipe assembly according to the invention for geothermal probes is seen that the polymeric material of the at least one layer of the tube and / or the connecting element have at least one coloring additive, so that, for example, in piping arrangements for geothermal probes, which are interleaved, by different coloring additives of the Flow and the return are kennzeichenbar.

Another advantage of the pipe arrangement according to the invention for geothermal probes, we seen that the polymeric material of the at least one layer of the tubes and / or the connecting element has an admixture of at least one antistatic additive, wherein the surface resistance of the tube and / or the connecting element at most 10 ^"10 The invention further teaches a pipe arrangement for borehole heat exchangers in which the polymeric material of the at least one layer of the pipes and / or the connecting element has an admixture of at least one electrically conductive aggregate, wherein the surface resistance of the pipes and / or the connecting element is at most 10 ⁶ ohms / cm. These additives can be added to the poly- mers material is generally between about 1% to about 20%, depending on the legal requirements as well as the dimensioning standards.

Based on the test conditions in accordance with ISO 16770 is in a first exemplary embodiment at 80 ⁰ C, 4.0 MPa and in the presence of 2% wetting agent of the Arkopal

FNCT value of the material for the outer layer of the pipe according to the invention made of polyethylene PE 100 according to EN 12201 with an outer diameter of 1 10 + 0.6 mm and a wall thickness of 10.0 + 0.3 mm about 200 to 750 h and the FNCT value of the material of the inner layer of the pipe according to the invention made of a polyethylene with a wall thickness of about 1.5 mm for about 3000 h. In a further advantageous embodiment, this multilayer pipe has an inner layer made of a polyethylene with a wall thickness of about 0.7 mm, with a FNCT of about 6,000 h, at 80 ⁰ C, 4.0 MPa and in the presence of 2% wetting agent Arkopal®.

The pipe arrangement according to the invention for geothermal probes will now be described in more detail on these non-limiting embodiments.

Figure 1 shows a schematic sectional view of a pipe arrangement according to the invention for geothermal probes

Figure 2 shows a schematic sectional view of another pipe arrangement according to the invention for geothermal probes

Figure 3 shows a schematic side view with a partial section of another pipe arrangement according to the invention for geothermal probes

Figure 4 shows a schematic side view with a partial section of another pipe arrangement according to the invention for geothermal probes.

FIG. 1 shows a tube arrangement according to the invention which has two tubes 1, 2 which have at least one layer surrounding a lumen 3. At the free ends 10, 20 of the tubes 1, 2, a connecting element 4 is arranged, which is liquid-tightly connected to the tubes 1, 2. The tubes 1, 2 and the connecting element 4 are made of an uncrosslinked polymeric material, for example polyethylene. The polymeric material of at least one layer of the tubes 1, 2 and the connecting element 4 in this embodiment has a FNCT value of 3550 hours. Furthermore, the polymeric material of the at least one layer of the tubes 1, 2 and the connecting element 4 is formed so that it has an MRS value of 11, 1 MPa at 20 ⁰ C over 50 years. 2 shows a further schematic representation of a pipe arrangement according to the invention for geothermal probes from two tubes 1, 2 shown. In this embodiment, the tube 2 is inserted concentrically into the lumen 3 of the tube 1. However, it is also within the scope of the invention that a plurality of tubes 2 can be introduced into the lumen 3 of the tube 1, which can be arranged both concentrically and eccentrically.

At the free end 10 of the tube 1, a connecting element 4 is arranged, which is connected via a cohesive connection such as welding liquid-tight manner with the free end 10 of the tube 1. The tube 1 and the tube 2 have approximately the same length, so that between the free end 20 of the tube 2 and the opposite connecting element 4 creates a free space in which the liquid transported through the lumen 3 of the tube 2 via the lumen 3 of the Tube 1 is traceable again.

The polymeric material of the at least one layer of the tube 1 in this embodiment has a FNCT of 5550 hours and an MRS of 13.1 MPa. The polymeric material of the at least one layer of the tube 2 in this embodiment has a FNCT value of 3100 hours and an MRS value of 10.5 MPa at 20 ⁰ C over 50 years.

FIG. 3 shows, in a further schematic representation, that the tube 1, which forms the supply line of the pipe arrangement for borehole heat exchangers, is arranged in a helical shape. The helix has a constant diameter. The tube 2 shown is the return of the tube assembly.

Finally, FIG. 4 shows, in a further schematic representation, that the tube 1, which is arranged helically, is connected to the tube 2 by means of the connecting element 4. Tube 2 is used in this arrangement as a return. The tube 2 is provided with a thermal insulation 21, which reduces heat loss of the guided or stored in the tube 2 fluid. For this purpose, a foam layer or a layer which has a reduced heat transfer due to structure, choice of materials, additives, etc. can be provided as thermal insulation 21. The connecting element 4 of the pipe arrangement according to the invention for geothermal probes can be designed in many ways, in particular, the teaching of the invention also known per se means to liquid-tight connection of the connecting means 4 with the tube 1, 2 in the form of one or more parts plug or welding fittings made of any materials , which can also be designed as a locking sleeve, sliding sleeve, locking element, electric welding sleeve and the like.

The teachings of the invention also include pipe arrangements for geothermal probes in which the connection means 4 is replaced by additional components, such as e.g. comprehensive half-shells, a foam or encapsulation is mechanically protected.

The teachings of the invention also include a geothermal heat recovery or storage device having a tube assembly according to the present invention.

- Protection claims -

Claims

protection claims

1. Pipe assembly for geothermal probes from at least two tubes (1, 2) having at least one, a lumen (3) surrounding layer, wherein one of the tubes (1, 2) serves as a flow and the other as a return, and at least one of Tubes (1, 2) at least partially made of a non-crosslinked polymeric material, characterized in that the polymeric material of the at least one layer of the tubes (1, 2) a FNCT (Füll Notched Creep Test) according to ISO 16770 of at least 3000 h.

2. Pipe assembly according to claim 1, characterized in that, the tube assembly at one end at least one, at least one layer exhibiting connecting element (4), characterized in that the polymeric material of the at least one layer of the connecting element (4) has an FNCT value (Füll Notched Creep Test) according to ISO 16770 of at least 3000h.

3. Pipe assembly according to claim 1 or 2, characterized in that the polymeric material of the at least one layer of the tubes (1, 2) and / or the connecting element (4) an FNCT value (Füll Notched Creep Test) according to ISO 16770 of at least 5000 h.

4. Pipe arrangement according to one of claims 1 to 3, characterized in that the polymeric material of the at least one layer of the tubes (1, 2) and / or the connecting element (4) has an MRS value (minimum required strength) of at least 10, 0 MPa at 20 ⁰ C over 50 years.

5. Pipe assembly according to claim 4, characterized in that the polymeric material of the at least one layer of the tubes (1, 2) and / or the connecting element (4) has an MRS value (minimum required strength) of at least 12.5 MPa at 20 ⁰ C over 50 years.

6. Pipe assembly according to one of the preceding claims, characterized in that the material of at least one layer of the connecting element (4) with the material of at least one, a lumen (3) surrounding layer of a tube (1, 2) is cohesively connectable.

7. Pipe assembly according to one of the preceding claims, characterized in that the material of at least one layer of the connecting element (4) with the material of at least one, a lumen (3) surrounding layer of a tube (1, 2) is non-positively connected.

8. Pipe assemblies according to one of the preceding claims, characterized in that one of the tubes (1, 2) is helical.

9. Pipe assembly according to claim 8, characterized in that the helix has a constant diameter.

10. Pipe assembly according to claim 8, characterized in that the helix has a variable diameter.

11. Pipe arrangement according to one of claims 8 to 10, characterized in that the non-helical pipe has a thermal insulation (21).

12. Erdwärmegewinnungs- or storage device with a tube assembly according to one of claims 1 to 1 1.