Evaporator Coating Process for Humidity-Resistant Copper Corrosion
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Solution Overview
Problem
Copper piping in refrigeration apparatuses suffers from rusting and ant nest-shaped corrosion due to dew condensation water and rainwater, leading to potential leaks, as conventional benzotriazole-based rust inhibitors are water-soluble and lose effectiveness in humid environments.
Innovation Solution
A method involving the application of a benzotriazole-based compound in a metal working oil coating agent to the outer surface of copper piping, followed by drying at 130-200°C, which forms a rust preventive film that remains effective even when exposed to dew or rainwater, and the heat transfer pipes are inserted into and expanded within heat transfer fins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a water-soluble benzotriazole rust inhibitor is applied to copper piping, then rust prevention is achieved, but the inhibitor dissolves out in humid environments and loses effectiveness
Solution Approach 1:
The patent changes the solubility parameter of the benzotriazole compound by introducing hydrophobic alkyl groups (C12-C22) at the N1 position, transforming it from water-soluble to water-insoluble. This parameter change allows the rust inhibitor to remain stable and effective in humid environments without dissolving out, while still providing adequate rust protection.
2Object-affected harmful factors
If a rust preventive film is formed on copper piping, then corrosion resistance is improved, but the film may not withstand exposure to dew condensation water or rainwater
Solution Approach 1:
The patent modifies the chemical structure of the benzotriazole molecule by adding hydrophobic alkyl chains, which changes the film's interaction with water from soluble to insoluble. This creates a rust preventive film that is resistant to dew condensation water and rainwater, maintaining corrosion protection in outdoor environments.
3Object-affected harmful factors
If conventional rust inhibitors are used, then initial rust protection is provided, but long-term protection against ant nest-shaped corrosion is insufficient
Solution Approach 1:
By changing the solubility parameter of the benzotriazole compound through structural modification, the patent creates a rust inhibitor that does not dissolve in water. This ensures long-term protection against ant nest-shaped corrosion caused by dew condensation water and rainwater, extending the duration of rust prevention significantly.
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
The method effectively reduces the occurrence of corrosion holes and maintains rust prevention, ensuring the integrity of the refrigeration system by preventing the benzotriazole-based compound from eluting and sustaining its protective effect.
Implementation Method 1
applying a coating agent containing a benzotriazole-based compound... forms a rust preventive film... the benzotriazole-based compound is difficult to elute
Implementation Method 2
drying at 130-200°C
Data Source
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AI summary
A method of manufacturing an evaporator for a refrigeration apparatus capable of reducing corrosion is provided. The method of manufacturing an evaporator (23, 31) of an air conditioner (100) includes a first step of applying a coating agent containing: a benzotriazole-based compound having a structure represented by the following formula (I) (wherein R1 to R4 each independently represent hydrogen or a methyl group, and R5 represents an aliphatic hydrocarbon group having 1 to 18 carbon atoms or (CH2)n-N-R6-R7, n being an integer of 1 to 3, R6 and R7 being each independently an aliphatic hydrocarbon group having 1 to 18 carbon atoms); and a metal working oil to an outer surface of a heat transfer pipe (50) to form a rust preventive film (52), a second step of inserting the heat transfer pipe (50) having the rust preventive film formed thereon into a hole (62) of a heat transfer fin (60), and a third step of expanding the heat transfer pipe (50) inserted the heat transfer fin.