Stainless-Steel Copper Pipe Fitting for AC Fatigue Life Control
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Solution Overview
Problem
The fatigue life of copper pipe fittings in air conditioning systems is shortened due to increased grain size after furnace brazing, and the selection of pipe wall thickness and outer diameter is fuzzy, leading to high development costs and inefficiencies in model selection.
Innovation Solution
A combined pipe fitting design comprising stainless steel and copper components, where the length of the effective section inversely proportional to the square root of the fatigue life, with a power function relationship between fatigue life coefficient and outer diameter, allowing accurate prediction and optimization of fatigue life and cost control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If furnace brazing is used to weld copper distribution branch pipes, then the pipes are connected in one piece, but the grain size of copper material becomes larger which seriously affects the endurance limit under alternating stress
Solution Approach 1:
The patent changes the material parameter from copper to stainless steel for the distribution branch pipes. This material substitution prevents the grain size enlargement issue that occurs with copper during furnace brazing, thereby maintaining the endurance limit under alternating stress while still achieving integrated welding connectivity.
2Adaptability or versatility
If pipe wall thickness and outer diameter are selected through experience and comparative testing, then various combinations can be provided, but this results in high product development cost, long development cycle and low efficiency
Solution Approach 1:
The patent performs preliminary fatigue strength verification through theoretical calculation using the formula N≥1.5×10^4×(d/t)^2×(P/ΔP)^2×(L/e)^3, where all parameters are clearly defined. This preliminary verification is conducted before actual product development, allowing designers to directly select appropriate wall thickness and outer diameter combinations without extensive comparative testing, thus significantly improving development efficiency while maintaining model selection flexibility.
3Measurement precision
If Goodman diagram is used to predict fatigue life, then fatigue life can be predicted with adjusted wall thickness and outer diameter, but the application has high requirements for professionals and the diagram needs to be drawn after pre-testing a large amount of data
Solution Approach 1:
The patent replaces the complex Goodman diagram method with a simplified theoretical calculation formula that directly provides fatigue life prediction. The formula N≥1.5×10^4×(d/t)^2×(P/ΔP)^2×(L/e)^3 with clearly defined parameters eliminates the need for professional expertise and extensive pre-testing data, making fatigue life prediction accessible and practical for industrial application while maintaining sufficient accuracy.
Data Source
AI summary
A combined pipe fitting and an air conditioning system pipeline. The combined pipe fitting includes a first, a second, and a third pipe fitting. Both the first and the second pipe fittings are stainless steel pipes, and a first end of the second pipe fitting is connected to the first pipe fitting. The third pipe fitting is a copper pipe and includes a first connecting section, an effective section, and a second connecting section. The first connecting section is sleeved with a second end of the second pipe fitting. A length of the effective section L is an axial extension distance on the third pipe fitting from an end face of the second end of the second pipe fitting to a direction away from the first pipe fitting. A fatigue life N of the combined pipe fitting is inversely proportional to √{square root over (L)}, and 1 mm≤L≤35 mm.