Variable-SDR Geothermal Probe Tube for Deep Pressure Resistance
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Solution Overview
Problem
Geothermal probe pipes face challenges in withstanding high internal hydrostatic pressure at deep depths due to difficulties in grouting and increased risk of cavity formation, which conventional designs struggle to manage without compromising heat transfer and flow resistance.
Innovation Solution
The geothermal probe pipe design features a constant Standard Dimension Ratio (SDR) in the first longitudinal section and a decreasing SDR towards the second end, allowing the pipe to adapt to increasing hydrostatic pressure with depth, ensuring operational safety and efficiency down to 320 m or more, while maintaining minimal wall thickness for reduced flow resistance and enhanced heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the SDR value is reduced to withstand high internal pressure at great depths, then pressure resistance is improved, but wall thickness increases leading to increased flow resistance and reduced heat transfer
Solution Approach 1:
The pipe is divided into two longitudinal sections with different SDR values. The first section (shallower depth) has a higher SDR value (11-15) with thinner wall, optimizing heat transfer and flow. The second section (greater depth) has a lower SDR value (7-9) with thicker wall to withstand high internal hydrostatic pressure. This local differentiation resolves the contradiction by applying appropriate wall thickness only where pressure resistance is critical.
2Strength
If the SDR value is reduced to withstand high internal pressure at great depths, then pressure resistance is improved, but heat transfer through the pipe wall is reduced
Solution Approach 1:
The pipe structure transitions from uniform wall thickness to variable wall thickness along its length. The first longitudinal section maintains thinner wall (higher SDR) for optimal thermal conductivity and heat exchange. The second longitudinal section increases wall thickness (lower SDR) only in the region where high internal pressure from the heat transfer medium requires enhanced structural strength. This resolves the heat transfer vs. pressure resistance contradiction through spatially differentiated design.
3Ease of manufacture
If conventional pipes with constant SDR are used at great depths, then manufacturing is simplified, but operational safety is compromised due to high internal hydrostatic pressure
Solution Approach 1:
The geothermal probe pipe is segmented into two distinct longitudinal sections along its length. The first section extends from the first end to an intermediate region and the second section extends from the intermediate region to the second end. Each section is assigned an appropriate SDR value based on the pressure conditions at that depth. This segmentation allows the pipe to meet operational safety requirements at great depths while maintaining reasonable manufacturing complexity through a clearly defined two-section structure.
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 design enables safe and efficient operation of geothermal probe systems at greater depths with improved energy balance and operational reliability, maintaining comparable heat transfer properties and flow resistance compared to conventional pipes.
Implementation Method 1
the hydrostatic (internal) pressure of the heat transfer medium on the one hand and from the hydrostatic (external) pressure of the grouting compound
Implementation Method 2
the geothermal probe pipe is dimensioned to withstand the maximum pressure to be expected
Implementation Method 3
the heat carrier is heated by the geothermal heat conducted through the pipe wall
Implementation Method 4
This grout usually has good thermal conductivity, which should ensure good heat transfer from the ground to the borehole heat exchanger tubes
Data Source
Figure 1
AI summary
The present invention relates to a geothermal probe system containing geothermal probe pipes (2) which are connected to one another in pairs via a probe foot in the form of a deflection and which each have a first end (4) and a second end (6 ), wherein the second end (6) is intended to be lowered into the ground as the leading end and is connected to the respective probe foot, and also a first longitudinal section (8) facing the first end (4) and a first longitudinal section (8) facing the second end ( 6) facing the second longitudinal section (10) adjoining the first longitudinal section (8). The geothermal probe system is characterized in that the SDR value is essentially constant according to the equation SDR=pipe outside diameter/pipe wall thickness over the length of the first longitudinal section (8) and in the second longitudinal section (10) in the direction of the second end (6). decreases.