Ductile Stainless Refrigerant Pipe for High-Pressure Air Conditioners
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Solution Overview
Problem
Air conditioners using copper refrigerant pipes face issues with scale accumulation, insufficient pressure resistance, vulnerability to vibration, high installation complexity, and high costs, while stainless steel pipes offer improved strength and corrosion resistance but are difficult to bend and install due to excessive hardness.
Innovation Solution
A ductile stainless steel pipe with a delta ferrite matrix structure of 1% or less is used, providing strength and hardness comparable to copper pipes while maintaining ductility, allowing for easier installation and reduced pressure loss through optimized outer and inner diameters, and improved vibration absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If stainless steel pipe is used to replace copper pipe, then pressure resistance and corrosion resistance are improved, but ductility deteriorates making pipe bending difficult
Solution Approach 1:
The patent applies parameter changes by controlling the microstructure of stainless steel to achieve an austenite matrix with 95% or more grain area and limiting delta ferrite to 5% or less. This microstructural parameter control enables the stainless steel pipe to simultaneously achieve high strength (superior pressure resistance) and high ductility (comparable to copper pipe), resolving the contradiction between strength improvement and manufacturability deterioration
Solution Approach 2:
The patent utilizes composite material principles by creating a controlled microstructure consisting of austenite matrix with controlled delta ferrite content. This composite microstructure combines the advantages of both phases: austenite provides ductility and formability, while the controlled ferrite content contributes to strength, achieving both high pressure resistance and excellent ductility
2Ease of manufacture
If copper pipe is used, then ductility and ease of installation are maintained, but pressure resistance and corrosion resistance are insufficient
Solution Approach 1:
The patent changes the material parameters by selecting specific stainless steel grades (304, 316, or 321) and controlling their microstructure to achieve 95% or more austenite matrix. This parameter change transforms the material properties to simultaneously provide excellent ductility for easy installation and superior pressure resistance for high-reliability operation
3Force
If pipe length is increased to absorb vibration, then vibration absorption capacity is improved, but installation space requirement increases
Solution Approach 1:
The patent changes the material parameter by utilizing the superior strength and hardness of austenitic stainless steel with controlled microstructure. This parameter change enables the pipe to absorb vibration effectively through its material properties rather than requiring increased length, thus improving vibration absorption capacity while maintaining compact installation space
Data Source
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AI summary
The present invention relates to an air conditioner. The air conditioner according to the present embodiment has a refrigeration capacity of 11kW to 16kW, inclusive, and uses R32 as a refrigerant circulating therein, and since a refrigerant pipe therein is made of a ductile stainless steel material having 1% or less of a delta-ferrite matrix structure with respect to the grain size area thereof, the refrigerant pipe can maintain strength and hardness as good as or better than those of a copper pipe, while also maintaining good processability.