Multi-air conditioner for heating and cooling operations
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Solution Overview
Problem
In multi-air conditioners, especially in cold regions, the lack of oil in the compressor during heating operations poses a risk of compressor damage due to insufficient oil levels, as the oil temperature and superheat may not rise quickly enough, leading to oil being swept away with the refrigerant, and existing technologies do not effectively address this issue during initial operations.
Innovation Solution
A multi-air conditioner system that includes a receiver capable of storing oil, an oil recovery valve, and an accumulator, which periodically checks outdoor temperatures and compressor oil levels to perform an oil recovery operation when the temperature is below a certain threshold, ensuring sufficient oil is stored in the compressor for heating operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If heating operation is performed in cold regions with limited low pressure, then heating function is provided, but oil level in compressor drops below minimum required level causing oil burnout risk
Solution Approach 1:
The system performs preliminary oil recovery to the receiver before heating operation begins in cold regions. By recovering oil in advance when the air conditioner is off or in cooling mode, the system ensures sufficient oil level in the compressor before heating starts, preventing oil burnout during heating operation in cold conditions.
Solution Approach 2:
The system changes operational parameters by switching between oil recovery mode and heating mode based on detected conditions (temperature, operation mode). The control unit adjusts the oil recovery valve opening degree and duration dynamically, and modifies heating operation parameters such as compressor frequency to maintain adequate oil levels while providing heating function.
2Reliability
If oil recovery operation is performed continuously, then oil level in compressor is maintained, but refrigerant circulation and system efficiency are reduced
Solution Approach 1:
The system performs oil recovery periodically rather than continuously. The control unit determines optimal timing based on operation mode transitions, temperature conditions, and accumulated operation time. Oil recovery is performed at specific intervals or transition points, allowing refrigerant circulation to proceed efficiently during normal operation while maintaining oil levels through periodic recovery actions.
Solution Approach 2:
The system applies partial oil recovery action by controlling the oil recovery valve opening degree rather than fully opening it. The control unit adjusts the valve opening to recover only the necessary amount of oil, avoiding excessive recovery that would unnecessarily reduce refrigerant circulation efficiency while still maintaining adequate oil levels in the compressor.
3Reliability
If multiple components (receiver, oil recovery valve, accumulator) are added to manage oil levels, then compressor protection is improved, but system complexity increases
Solution Approach 1:
The receiver component is designed to serve multiple functions: it acts as both a refrigerant storage device during normal operation and an oil storage device during oil recovery operation. This multi-functionality allows the system to protect the compressor from oil burnout without adding a separate dedicated oil storage component, thereby reducing overall system complexity while maintaining reliable compressor protection.
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 prevents oil burnout by recovering and storing oil in the receiver, ensuring the compressor operates safely and efficiently even in cold regions by maintaining adequate oil levels, thereby enhancing the reliability and guaranteeing operation temperatures.
Implementation Method 1
Korean Patent Publication No. KR20010059700A discloses a technology for circulating oil back to the compressor and sending only the refrigerant to a condenser through an oil separator that separates the oil and the refrigerant discharged from the compressor
Implementation Method 2
an outdoor heat exchanger for heat-exchanging the circulated refrigerant with outdoor air
Implementation Method 3
an indoor heat exchanger that heat-exchanges the circulated refrigerant with indoor air
Implementation Method 4
a compressor that compresses a gaseous refrigerant of low temperature and low pressure to be a high temperature and high pressure refrigerant
Implementation Method 5
Each of the plurality of indoor units includes an expansion device
Data Source
AI summary
A multi-air conditioner for heating/cooling operations, including at least one indoor unit for heating/cooling operations including an indoor heat exchanger; and an outdoor unit for heating/cooling operations including a compressor, an outdoor heat exchanger, and a switching unit configured to be disposed in a discharge side of the compressor to switch a flow of refrigerant. The outdoor unit includes a receiver that selectively stores refrigerant or oil according to a cooling or heating operation mode and provides the stored refrigerant or oil to the compressor. Accordingly, in the accumulator of the multi-air conditioner using the receiver, the receiver which is not used in the heating mode may be converted and used for oil storage, thereby preventing oil burnout without adding structure.