Method, apparatus, header, and composition for ground heat exchange
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Solution Overview
Problem
Existing ground heat exchanger systems face inefficiencies due to high thermal resistance between the working fluid and the earth, leading to reduced heat transfer and thermal storage capacity, as well as issues with corrosion, mechanical strength, and installation complexity, particularly in concentric pipe designs and supply/return headers.
Innovation Solution
The system employs a low thermal resistance casing with a ribbed drop tube, standoffs for centralization, and a thermally conductive grout composition, along with a novel supply and return header design that eliminates flange connections and reduces installation depth, using a thermosetting plastic composite with reinforcing fibers and a graphite-enhanced backfill for improved thermal conductivity and mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ground heat exchanger systems are used, then the system structure is simple, but thermal resistance between working fluid and earth is high
Solution Approach 1:
The patent employs a multi-layer composite structure consisting of an inner corrosion-resistant pipe (plastic or metal), an intermediate annular space for working fluid flow, and an outer protective casing. This composite design simultaneously achieves corrosion resistance, low thermal resistance, and mechanical strength, resolving the contradiction between heat transfer efficiency and system reliability.
Solution Approach 2:
The concentric pipe configuration nests the inner pipe within the outer casing, creating multiple flow channels and thermal pathways. The inner pipe carries working fluid while the annular space between pipes provides additional heat exchange surface area, effectively increasing heat transfer efficiency without proportionally increasing overall system complexity.
2Ease of manufacture
If metal pipe loops are used, then capital cost is reduced, but anodic corrosion from electrical currents causes eventual failure
Solution Approach 1:
The patent introduces an intermediate protective layer (corrosion-resistant pipe material such as plastic or coated metal) between the working fluid and the earth/soil environment. This intermediary barrier prevents direct contact between metal components and corrosive elements, eliminating anodic corrosion while maintaining the structural integrity and low cost benefits of metal pipe loops.
Solution Approach 2:
The system uses composite piping structures where corrosion-resistant materials (plastic, coated metal) are combined with structurally sound materials. This composite approach provides both corrosion resistance and mechanical strength, resolving the contradiction between manufacturing ease and long-term reliability.
3Reliability
If plastic ground loop installations are used, then corrosion resistance is improved, but local ground temperature increases or decreases when seasonal load is unbalanced
Solution Approach 1:
The concentric pipe design with multiple flow channels increases the effective heat exchange surface area between working fluid and earth. This enhanced surface area improves thermal coupling, allowing the system to more effectively balance seasonal thermal loads and reduce ground temperature fluctuations while maintaining the durability benefits of plastic piping.
4Ease of manufacture
If flange connections are used in headers, then assembly is simplified, but installation depth increases and reliability decreases
Solution Approach 1:
The patent integrates the header connections directly into the pipe structure itself, eliminating separate flange components. The header is formed as a continuous integral part of the piping system, which reduces the number of connection points, minimizes installation depth requirements, and eliminates potential failure points associated with flange connections while maintaining assembly simplicity.
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 configuration significantly enhances heat transfer efficiency, reduces thermal resistance, and increases the system's reliability and ease of installation, while maintaining mechanical strength and resistance to corrosion, thereby improving heating, cooling, and thermal energy storage capabilities.
Implementation Method 1
a low thermal resistance casing (12)... a thermosetting plastic composite with reinforcing fibers... for improved thermal conductivity
Implementation Method 2
graphite-enhanced backfill for improved thermal conductivity
Implementation Method 3
an internal delivery conduit (222) having a series of discrete, spaced-apart, radial ribs (44) wherein the series of ribs (44) extends along an exterior of the internal delivery conduit (222) such that the radial ribs (44) project into a flow annulus (26)
Data Source
AI summary
A subterranean ground heat exchange system, a method of installation, and a grout composition therefor. The grout composition is a pumpable slurry formed of from about 70 to about 85 parts by weight natural flake graphite and from about 30 to about 15 parts by weight bentonite. The solids content of the pumpable grout slurry is preferably at least 35% by weight and is more preferably at least 40% by weight. The ground exchange apparatus preferably utilizes an improved supply and return header comprised of supply and return ports which are provided through the vertically extending outer wall of a header housing. The header also includes an interior supply conduit which extends from the supply port into the interior of the header housing and includes a bend positioned in the interior of the housing for directing the heat transfer fluid downwardly.