Composite Refrigeration Line Set With Aluminum Barrier for High Burst Pressure
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Solution Overview
Problem
Current multilayer composite pipes face challenges in achieving high burst pressure and temperature resistance, particularly in refrigeration applications, due to limitations in material thickness and reinforcement, which can lead to reduced strength and increased risk of single-point failures.
Innovation Solution
The development of a composite refrigeration line set featuring an inner polyethylene tube, adhesive layers, an AL 3005-O aluminum layer with specific thickness ranges, and an outer polyethylene tube, optionally including a low-emissivity layer and reinforcement, which is butt-welded and designed to withstand pressures exceeding 1950 pounds per square inch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If material thickness is increased to achieve high burst pressure, then strength is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies composite materials by combining multiple layers with different properties: an inner plastic layer for flexibility and corrosion resistance, an intermediate aluminum layer for high strength and barrier properties, and an outer plastic layer for protection. This multi-material composite structure achieves high burst pressure resistance (exceeding 1950 psi) without requiring excessive thickness of any single material, thereby resolving the contradiction between strength and complexity.
Solution Approach 2:
The pipe is segmented into distinct functional layers: inner plastic tube, adhesive layer, aluminum layer, another adhesive layer, and outer plastic layer. Each layer performs a specific function (flexibility, bonding, strength, bonding, protection), allowing the overall structure to achieve high strength without uniform thickening, thus reducing device complexity while maintaining burst pressure resistance.
2Reliability
If reinforcement is added to prevent single-point failures, then reliability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The composite structure with multiple bonded layers inherently prevents single-point failures because damage to one layer does not propagate catastrophically to the entire pipe. The adhesive layers create a distributed bond structure where stress is shared across multiple interfaces, improving reliability without requiring extreme manufacturing precision if proper adhesive selection and processing are used.
Solution Approach 2:
The adhesive layers serve as cushioning elements between the rigid aluminum layer and flexible plastic layers, absorbing stress concentrations and preventing crack propagation. This beforehand cushioning approach improves reliability by preemptively addressing potential failure points without requiring ultra-precise manufacturing tolerances.
3Strength
If aluminum layer thickness is increased to withstand high pressure, then strength is improved, but weight and material cost increase
Solution Approach 1:
The patent uses a composite structure where the aluminum layer provides high strength-to-weight ratio, while the plastic layers contribute to overall pressure resistance through their own mechanical properties. This allows optimization of aluminum thickness to achieve required strength (burst pressure >1950 psi) without excessive weight, as the plastic layers share the load-bearing function.
Solution Approach 2:
The patent specifies precise aluminum layer thickness ranges (e.g., 0.014-0.020 inches for 1/4 inch pipe, 0.028-0.045 inches for 5/8 inch pipe) rather than using uniform thick aluminum. This parameter optimization allows the aluminum layer to provide sufficient strength while minimizing weight, with the exact thickness adjusted based on pipe size and required pressure resistance.
4Reliability
If multiple adhesive layers are used to bond composite layers, then reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The use of multiple adhesive layers between the plastic and aluminum layers ensures strong bonding across the composite structure, preventing delamination under pressure and temperature cycling. This improves reliability by creating a robust multi-layer bond, while the complexity is managed through standardized manufacturing processes for applying multiple thin adhesive coats.
Solution Approach 2:
The adhesive layers serve as intermediary materials that chemically or mechanically bond the dissimilar materials (plastic and aluminum) together. This intermediary approach ensures reliable bonding between layers with different thermal expansion coefficients and mechanical properties, improving overall structure reliability while the manufacturing complexity is mitigated by using specialized adhesive application equipment.
Data Source
AI summary
One aspect of the invention provides a composite refrigeration line set including at least one selected from the group consisting of: a suction line and a return line, characterized in that one or more of the suction line and the return line are a composite refrigeration line set tube include: an inner plastic tube; a first adhesive layer positioned about the inner plastic tube; an aluminum layer positioned about the first adhesive layer and coupled to the inner plastic tube via the first adhesive layer; a second adhesive layer positioned about the aluminum layer; and an outer plastic layer positioned about the aluminum layer coupled to the aluminum layer via the second adhesive layer. The inner plastic tube is polyethylene of raised temperature. The outer plastic tube is polyethylene of raised temperature. The aluminum layer comprises AL 3005-O.