Air-Conditioning Refrigerant Leak Detection by Resistance Sensing
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Solution Overview
Problem
Current air-conditioning systems for buildings face challenges in detecting refrigerant leaks, particularly for multiple types of refrigerants, and do not adequately consider the adverse effects of leaks on human safety, with existing technologies relying on indirect detection methods and limited to carbon dioxide refrigerants.
Innovation Solution
An air-conditioning apparatus equipped with a concentration detecting device that uses electrical resistance changes to compute refrigerant concentrations, enabling precise detection of leaks and ensuring safety by shutting off refrigerant flow when leaks are detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If indirect detection method based on refrigeration cycle pressure is used, then the system can detect refrigerant leaks, but the detection accuracy is insufficient and cannot distinguish between different refrigerant types
Solution Approach 1:
The patent replaces the indirect mechanical pressure-based detection system with an electrical sensing system. The detecting unit uses electrical resistance changes to directly measure refrigerant concentration, eliminating the need for complex pressure-based indirect detection and enabling direct, accurate measurement of refrigerant leaks.
Solution Approach 2:
The patent introduces an electrical resistance-based detecting unit as an intermediary between the refrigerant and the detection system. This intermediary converts refrigerant concentration into measurable electrical resistance changes, enabling precise detection while maintaining system simplicity through the use of standard electrical measurement techniques.
2Reliability
If the system stops operation when refrigerant leak is detected, then safety is improved, but no consideration is made regarding the threshold of leakage that has adverse effect on human body
Solution Approach 1:
The patent implements a feedback-based control system where the detecting unit continuously monitors refrigerant concentration and provides feedback to the control unit. The control unit compares the detected concentration against predetermined safety thresholds and adjusts system operation accordingly, allowing continuous operation when safe and automatic shutdown when dangerous levels are reached.
Solution Approach 2:
The patent changes the control parameter from a binary stop/start approach to a threshold-based continuous monitoring approach. By establishing predetermined concentration thresholds, the system can operate continuously at safe levels while automatically responding when hazardous concentrations are detected, optimizing both safety and operational continuity.
3Object-affected harmful factors
If carbon dioxide refrigerant is used, then global warming potential is reduced, but the detection technology cannot be applied to other refrigerant types
Solution Approach 1:
The patent creates a universal detection system that can identify multiple refrigerant types through electrical resistance measurement. The detecting unit measures the electrical resistance characteristics of different refrigerants, and the control unit identifies the refrigerant type based on these measurements, enabling the same system to work with various refrigerant types including CO2, HFO, R32, and HC refrigerants.
Solution Approach 2:
The patent uses parameter changes in electrical resistance as the basis for refrigerant identification. Different refrigerant types exhibit distinct electrical resistance characteristics, allowing the system to differentiate between refrigerant types by measuring these parameter variations and comparing them against stored correlation information.
4Quantity of substance
If large quantities of refrigerant are required in multi-air-conditioning system, then cooling/heating performance is improved, but the risk of hazardous leakage increases
Solution Approach 1:
The patent implements preliminary detection and warning capabilities that monitor refrigerant concentration before hazardous levels are reached. The system continuously measures refrigerant concentration and provides early warning when approaching dangerous thresholds, allowing preventive action to be taken before a hazardous leakage situation develops.
Solution Approach 2:
The patent uses continuous feedback monitoring of refrigerant concentration to manage the trade-off between using large quantities of refrigerant for performance and minimizing leakage hazards. The detection system provides real-time feedback on refrigerant levels and concentration, enabling operators to respond to potential leakage issues before they become hazardous.
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 system effectively detects leaks of various refrigerants, improving safety by preventing further leakage and ensuring the air-conditioning apparatus operates safely even in the presence of combustible or toxic refrigerants.
Implementation Method 1
a detecting unit capable of detecting the refrigerant concentration of a plurality of types of heat source side refrigerants from an electrical resistance that changes in accordance with the refrigerant concentration
Implementation Method 2
a heat exchanger related to heat medium that exchanges heat between the heat source side refrigerant and the heat medium
Implementation Method 3
a pump that pumps the heat medium by pressure
Implementation Method 4
an expansion device that depressurizes the heat source side refrigerant
Data Source
AI summary
An air-conditioning apparatus directly detects leakage of a plurality of types of refrigerant by computing refrigerant concentrations, and ensure safety. On the basis of calibration curve information, a computing device computes the concentration of heat source side refrigerant in a heat medium relay unit from detected information received from a concentration detecting device.