Expansion Valve Feedback for Refrigerant Leak Detection
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Solution Overview
Problem
Refrigerant leakage in refrigeration cycles is not reliably detected, leading to inefficiencies and potential damage, as existing systems lack accurate methods to identify leaks between pipes.
Innovation Solution
A refrigeration cycle apparatus with a controller that predicts the degree of opening of an electrically-actuated expansion valve based on changes in operating conditions, comparing this prediction to the actual opening to detect refrigerant leakage, thereby preventing further operation and notifying users.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional refrigeration cycle systems are used without advanced detection methods, then the system structure remains simple, but refrigerant leakage cannot be reliably detected
Solution Approach 1:
The system uses feedback control by continuously monitoring the expansion valve opening degree and comparing it with the commanded opening degree. When a discrepancy is detected, the system generates a leakage determination signal, creating a closed-loop detection mechanism that improves measurement precision without requiring complex external detection equipment.
Solution Approach 2:
The refrigeration cycle system detects its own leakage conditions using its existing operational parameters (expansion valve opening degree, refrigerant flow characteristics). The system serves itself by utilizing its own operational data for detection, eliminating the need for separate complex detection devices and reducing overall system complexity.
2Measurement precision
If the detection threshold is set low to detect small leaks, then detection sensitivity improves, but false positive rate increases
Solution Approach 1:
The system changes the detection parameter from absolute opening degree values to the difference between commanded and actual opening degrees. This parameter transformation allows the system to detect small leaks by measuring deviations in valve behavior, improving sensitivity while maintaining reliability through comparison-based detection rather than fixed threshold detection.
Solution Approach 2:
The system applies partial action by detecting only the deviation portion (difference between commanded and actual opening) rather than requiring complete system failure or large leaks. This allows detection of small leaks through partial measurement of valve behavior, improving detection capability for minor leakage while avoiding false positives from normal operational variations.
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 solution enables reliable and accurate detection of refrigerant leakage, preventing compressor operation during leaks and improving maintenance efficiency by setting a low threshold for detection, ensuring accurate identification even with small leaks.
Implementation Method 1
an electrically-actuated expansion valve (4) whose degree of opening is continuously adjusted in accordance with the number of input drive pulses
Implementation Method 2
a compressor (1) that sucks a refrigerant from a suction port, compresses the refrigerant and discharges the refrigerant from a discharge port
Implementation Method 3
an outdoor heat exchanger (3) connected to a discharge port of a compressor (1)
Data Source
Figure 1
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Figure 3
AI summary
A leakage detect section predicts a degree of opening of the expansion valve in a case where the refrigerant is not leaked from the refrigeration cycle based on a quantity of change in state of the refrigeration cycle. Then, the leakage detect section detects leakage of the refrigerant in the refrigeration cycle by comparing the predicted degree of opening with an actual degree of opening.