Air-conditioning apparatus
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Solution Overview
Problem
In air-conditioning apparatuses with heat exchangers of different inner volumes, refrigerant shortage or overfilling can occur, leading to operational issues such as compressor damage and abnormal stops due to deviations in suction and discharge pressures.
Innovation Solution
An air-conditioning apparatus with a refrigerant circuit including a compressor, flow passage switching device, outdoor and indoor heat exchangers, expansion devices, and a controller that adjusts the flow passage and expansion device openings to balance refrigerant distribution, ensuring the indoor heat exchanger receives sufficient refrigerant during startup by switching to a heating flow passage and setting the second expansion device to a larger opening degree than the first during cooling operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If the inner volume of the evaporator is small, then the apparatus is more compact, but refrigerant shortage occurs causing suction pressure to drop below compressor operating range
Solution Approach 1:
The patent applies preliminary action by pre-charging the evaporator with refrigerant before compressor startup. The control unit opens the expansion valve before starting the compressor to allow refrigerant to fill the evaporator in advance, ensuring sufficient refrigerant is available when the compressor begins operation, thus preventing suction pressure from dropping below the operating range.
2Volume of stationary object
If the inner volume of the condenser is small, then the apparatus is more compact, but refrigerant overfilling occurs causing discharge pressure to exceed compressor operating range
Solution Approach 1:
The patent applies feedback by implementing pressure monitoring and control. The control unit continuously monitors the discharge pressure of the compressor and adjusts the expansion valve opening or refrigerant flow based on feedback from pressure sensors. When discharge pressure approaches the upper limit of the operating range, the system reduces refrigerant flow to prevent overfilling and pressure exceedance.
3Adaptability or versatility
If heat exchangers have different inner volumes, then the system can be optimized for specific applications, but pressure fluctuations become more remarkable during compressor startup
Solution Approach 1:
The control unit performs preliminary actions by pre-charging the heat exchanger with smaller inner volume before compressor startup. This ensures that the heat exchanger is adequately filled with refrigerant in advance, reducing the magnitude of pressure fluctuations when the compressor begins operation and maintaining more stable refrigerant circulation throughout the system.
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 prevents refrigerant shortages and overfilling, stabilizing suction and discharge pressures, thereby enhancing the reliability and preventing operational failures in air-conditioning systems.
Implementation Method 1
the outdoor heat exchanger being located outside of a room and causing heat exchange to be performed with refrigerant, the indoor heat exchanger being located inside of a room and causing heat exchange to be performed between air in an air-conditioned space and the refrigerant
Implementation Method 2
causing heat exchange to be performed with refrigerant
Implementation Method 3
causing heat exchange to be performed between air in an air-conditioned space and the refrigerant
Implementation Method 4
the first expansion device depressurizing the refrigerant between the outdoor heat exchanger and the refrigerant container, and the second expansion device depressurizing the refrigerant between the indoor heat exchanger and the refrigerant container
Data Source
AI summary
An air-conditioning apparatus includes a refrigerant circuit in which a compressor, a flow passage switching device, an outdoor heat exchanger, an indoor heat exchanger, a refrigerant container, a first expansion device and a second expansion device connected by pipes, wherein the indoor heat exchanger and the outdoor heat exchanger have inner volumes satisfying a relationship of an inner volume of the indoor heat exchanger<an inner volume of the outdoor heat exchanger, and a controller which, performs control so as to allow the flow passage switching device to switch the flow passage to the heating flow passage and allow an opening degree of the second expansion device to be larger than that of the first expansion device, starts the compressor, performs control so as to allow the opening degrees of the first expansion device and the second expansion device to be initial opening degrees for the cooling operation.