Outer pipe for forming a coaxial heat transfer piping, and a heat transfer piping installation method
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Solution Overview
Problem
The installation of coaxial heat transfer piping in deep geothermal wells faces challenges due to pressure losses, thermal expansion, and diameter variations caused by drill bit wear, leading to inefficiencies and potential damage from rubbing against the well wall.
Innovation Solution
An outer pipe made of crystallized plastic with elongated recesses is used, allowing it to be expanded from a first operating form to an expanded form, ensuring tight fit and thermal contact with the well wall, while minimizing gaps and preventing rubbing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the outer jacket is flattened to a U shape for installation, then the installation ease is improved, but an annular gap is left between the outer jacket and the borehole wall requiring heat conductive filler
Solution Approach 1:
The outer pipe is pre-formed with an elongated recess during manufacturing, creating a compression zone that enables subsequent expansion against the borehole wall. This preliminary structural preparation allows the pipe to be inserted in a compact form and then expanded to eliminate gaps, ensuring direct thermal contact with the borehole wall without requiring additional heat conductive filler materials.
2Strength
If the outer jacket is made rigid to maintain structural integrity, then the strength is improved, but thermal expansion causes length variations of several meters leading to rubbing against the borehole wall
Solution Approach 1:
The outer pipe structure incorporates a localized elongated recess that creates a specific compression zone, while the rest of the pipe maintains its structural integrity. This localized structural modification allows the pipe to expand radially against the borehole wall to eliminate gaps, while the overall pipe structure remains strong enough to withstand thermal expansion forces without causing damage to the borehole wall.
3Reliability
If the outer jacket diameter is matched to the borehole diameter, then the thermal contact is improved, but the borehole conicity caused by drill bit wear makes matching difficult
Solution Approach 1:
The outer pipe is designed with an expandable structure featuring an elongated recess that allows the pipe diameter to change dynamically. The pipe is inserted in a compact form, then expanded in-situ against the borehole wall to match the local borehole diameter at any given depth. This dynamic expansion capability allows the pipe to adapt to the conical shape of the borehole caused by drill bit wear, ensuring optimal thermal contact throughout the entire borehole length without requiring precise pre-matching of diameters.
4Reliability
If the outer pipe is expanded to eliminate gaps, then the heat transfer efficiency is improved, but the installation complexity increases
Solution Approach 1:
The elongated recess is pre-formed in the outer pipe during manufacturing, creating a built-in expansion mechanism. During installation, the pipe is simply inserted into the borehole in its compact form, then expanded using the pre-prepared recess structure to eliminate gaps and ensure thermal contact. This preliminary preparation eliminates the need for complex expansion equipment or multi-step installation procedures, maintaining installation simplicity while achieving high heat transfer efficiency.
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 enables efficient heat transfer by maximizing well utilization, reducing pressure losses, and preventing damage from thermal expansion, thus enhancing the efficiency and durability of geothermal heating systems.
Implementation Method 1
The outer pipe is forceable into an expanded operating form in which said main part of the wall of the outer pipe in the cross-section of the outer pipe substantially follows, as a result of straightening of the recess, a second circle which is larger than the first circle
Implementation Method 2
Thermal expansion coefficients of the plastics used as material in the collector are relatively high, whereby in the case of a well which is hundreds of meters deep the back-and-forth length variations caused by the thermal expansion of the heat collector may be several meters
Data Source
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AI summary
An outer pipe (100) formed from a crystallized plastic material for forming an outer jacket of a coaxial heat transfer piping has a first operating form in which, in a cross-section of the outer pipe, a main part of a wall of the outer pipe substantially follows a first circle (101). The wall (105) of the outer pipe comprises an elongated recess (103) extending in a longitudinal direction of the outer pipe, at which recess in the cross-section of the outer pipe in the first operating form of the outer pipe the wall of the outer pipe deviates inwardly from said perimeter of the first circle (101), such that the perimeter of the wall of the outer pipe is longer than the perimeter of said first circle and the outer pipe is forceable into an expanded operating form in which said main part of the wall of the outer pipe in the cross-section of the outer pipe substantially follows, as a result of straightening of the recess (103), a second circle (104) which is larger than the first circle.