Expansion Valve Control for Indoor Heat Exchanger Refrigerant Stagnation
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Solution Overview
Problem
Air-conditioning apparatuses face challenges in ensuring heating capacity when refrigerant stagnation occurs in indoor heat exchangers, leading to reduced heating performance due to stagnated refrigerant, which can be exacerbated by high compressor rotation speeds and varying refrigeration cycle conditions.
Innovation Solution
An air-conditioning system with a control unit that determines refrigerant stagnation in indoor heat exchangers by measuring subcooling and implementing refrigerant stagnation elimination control by adjusting the degree of opening of expansion valves, ensuring the refrigerant flows out and maintaining or increasing heating capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the compressor rotation speed is increased to improve heating capacity, then the heating performance improves, but refrigerant stagnation in indoor heat exchangers is exacerbated
Solution Approach 1:
The control unit continuously monitors the degree of subcooling of the refrigerant and dynamically adjusts the expansion valve opening degree based on this feedback. When refrigerant stagnation is detected (indicated by excessive subcooling), the system automatically increases the expansion valve opening to enhance refrigerant flow, thereby resolving the contradiction between maintaining high compressor speed for heating capacity and preventing refrigerant stagnation.
Solution Approach 2:
The system changes the operating parameters of the expansion valve (opening degree) in response to varying refrigeration cycle conditions. By adjusting the expansion valve opening degree based on the degree of subcooling, the system optimizes refrigerant flow rate dynamically, allowing the compressor to operate at high speeds for maximum heating capacity while preventing refrigerant stagnation through real-time parameter adjustment.
2Reliability
If the expansion valve opening degree is increased to eliminate refrigerant stagnation, then refrigerant flow improves, but heating capacity may be reduced
Solution Approach 1:
The control unit uses the degree of subcooling as a feedback parameter to determine the appropriate expansion valve opening degree. The system continuously monitors refrigerant conditions and adjusts the expansion valve to maintain optimal flow without excessive opening that would reduce heating capacity. This feedback mechanism ensures the expansion valve is opened only enough to eliminate stagnation while preserving maximum heating performance.
Solution Approach 2:
The expansion valve opening degree is made dynamic rather than fixed, allowing real-time adjustment based on refrigeration cycle conditions. The system dynamically balances refrigerant flow requirements with heating capacity maintenance by continuously adapting the valve opening degree to current operational needs, ensuring optimal performance under varying conditions.
3Use of energy by moving object
If the degree of subcooling is increased to improve refrigerant efficiency, then energy utilization improves, but refrigerant stagnation occurs in indoor heat exchangers
Solution Approach 1:
The control unit monitors the degree of subcooling as a key parameter and uses this information to adjust the expansion valve opening degree. When subcooling exceeds optimal levels (indicating potential stagnation), the system responds by increasing the expansion valve opening to improve refrigerant flow. This feedback loop maintains refrigerant efficiency while preventing stagnation by dynamically balancing subcooling levels with flow requirements.
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 mitigates or eliminates refrigerant stagnation, thereby ensuring consistent heating capacity in indoor units performing heating operations, even under conditions of high compressor speeds and varying refrigeration cycles.
Implementation Method 1
a flow rate adjustment unit (40, 41) that adjusts the flow rate of the refrigerant... the control unit increases the degree of opening of the first outdoor expansion valve (40a) and/or the second outdoor expansion valve (41a)
Implementation Method 2
the indoor heat exchangers (81a-81e)... serve as condensers... the refrigerant... exchanges heat with the indoor air... and is thereby condensed
Implementation Method 3
the refrigerant... exchanges heat with the indoor air... and is thereby condensed
Implementation Method 4
the indoor heat exchangers (81a-81e)... exchange heat with the indoor air... thereby heating the indoor air
Implementation Method 5
a compressor (21a, 21b)... that compresses the refrigerant
Data Source
Figure 1
Figure 2
AI summary
An outdoor unit for an air-conditioning apparatus includes an outdoor heat exchanger; a compressor; a refrigerant pipe configured to couple the outdoor heat exchanger and the compressor with an indoor unit including an indoor heat exchanger; and a control unit that determines whether the heating capacity of the indoor unit performing a heating operation is decreased by the refrigerant stagnated in the indoor heat exchanger.