Pipework system for a downhole heat exchanger for obtaining geothermal energy, in particular deep geothermal energy
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Solution Overview
Problem
The production of deep geothermal probes faces challenges in creating conveying pipework that balances mechanical and thermal stability while isolating heat transfer media effectively, particularly due to mechanical stresses from weight, buoyancy, and thermal expansion, and existing solutions require complex and costly connections between inner and outer pipe sections.
Innovation Solution
A conveying pipework system that uses a non-positive, form-fitting connection between inner and outer pipe sections, allowing for different plastic materials and layer configurations, with load transfer devices that provide axial support and simplify assembly, eliminating the need for integral connections and reducing production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional steel riser pipes with integral insulation connections are used, then thermal insulation stability is improved, but device complexity and manufacturing cost increase due to complex connections between inner and outer pipe sections
Solution Approach 1:
The conveying pipework is divided into modular sections with standardized connections. The inner pipe sections can be connected to outer pipe sections independently using simple coupling elements, allowing the system to be assembled in segments rather than requiring complex integral connections throughout the entire structure.
Solution Approach 2:
Simple coupling elements act as intermediaries between inner and outer pipe sections. These couplings provide the necessary mechanical connection and thermal insulation without requiring complex integral bonding, simplifying the overall connection system while maintaining insulation stability.
2Ease of manufacture
If plastic tubing with low density is used for delivery piping, then ease of manufacture and cost are improved, but mechanical stability deteriorates due to buoyancy forces causing compressive stresses and buckling
Solution Approach 1:
The delivery piping uses a composite structure combining plastic inner pipe sections with metal outer pipe sections. The plastic provides thermal insulation and corrosion resistance, while the metal outer sections provide the necessary mechanical strength to resist buoyancy forces and prevent buckling at great depths.
Solution Approach 2:
The metal outer pipe sections serve as counterweights to balance the buoyancy forces acting on the lightweight plastic inner pipe. This combination allows the lightweight plastic material to be used without suffering from buoyancy-induced compressive stresses, as the metal sections provide the necessary mechanical support.
3Ease of manufacture
If polypropylene delivery tubing is used, then ease of manufacture is improved, but thermal resistance deteriorates at temperatures above 400°C
Solution Approach 1:
The piping system uses a composite structure where the plastic inner pipe provides thermal insulation for moderate temperature applications, while the metal outer pipe provides the necessary high-temperature resistance for extreme conditions up to 400°C and above, allowing the system to maintain both ease of manufacture and temperature resistance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances mechanical stability and thermal insulation, simplifies installation, and allows for adaptable material properties along the depth of the geothermal probe, reducing assembly effort and production costs while maintaining effective heat transfer.
Implementation Method 1
forces which act on the inner pipe (15) are transferred in sections to the outer pipe (13)
Implementation Method 2
isolates the heat transfer medium to be conveyed to the surface inside it well from the cooler heat transfer medium in the annular space
Implementation Method 3
The mechanical stresses are generated in particular by the dead weight of the production tubing and the buoyancy force counteracting the weight force
Implementation Method 4
a conveying pipework that has sufficient mechanical and thermal stability and at the same time isolates the heat transfer medium to be conveyed to the surface inside it well from the cooler heat transfer medium in the annular space
Data Source
Figure 1
Figure 2a~2b
Figure 3
AI summary
The invention relates to a pipework system for a downhole heat exchanger for obtaining geothermal energy, in particular deep geothermal energy, wherein thermal energy is transported by means of a preferably liquid heat transfer medium from a deep region into an upper region of the downhole heat exchanger, having an outer conveyor pipe (13) made from a metal and having an inner conveyor pipe (15) which is provided within the outer conveyor pipe (13), is made from a thermally insulating plastic, and consists of a plurality of inner pipe sections (15a), wherein the inner conveyor pipe (15) is connected to the outer conveyor pipe (13) at two or more axial positions of the pipework system (5) by means of in each case one load transmission device (23) for introducing axial forces which act on the inner conveyor pipe (15) onto the outer conveyor pipe (13). According to the invention, the inner pipe sections (15a) are coupled in axial sections between two load transmission devices (23) at coupling points between in each case two immediately adjacent ends of the inner pipe sections (15a). In addition, there is a coupling in every section at least at a coupling point between one of the two load transmission devices (23) and the directly adjacent end of the relevant inner pipe section (15a), wherein the coupling is generated or at least assisted by way of axial pressure forces at the coupling points without an integrally joined connection.