Air conditioning machine
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Solution Overview
Problem
Conventional air conditioning machines experience refrigerant counter-flow through the discharge hole of the compressor towards the indoor heat exchanger after a pump down operation, leading to inefficiencies and potential leaks.
Innovation Solution
The air conditioning machine incorporates a pump down operation control unit that positions the compression member to overlap the discharge hole, combined with a liquid side on-off valve that automatically closes after a specified time to confine refrigerant within the outdoor heat exchanger and compressor, reducing counter-flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pump down operation is performed to collect refrigerant into the outdoor heat exchanger, then the refrigerant concentration in the indoor unit is reduced, but the refrigerant counter-flows through the discharge hole toward the indoor heat exchanger after the operation ends
Solution Approach 1:
The compression member is positioned in advance to overlap the discharge hole before the pump down operation ends, creating a barrier that prevents refrigerant counter-flow from occurring in the first place. This preliminary positioning action ensures that when refrigerant tries to flow back through the discharge hole, it encounters the compression member barrier immediately.
Solution Approach 2:
The compression member acts as an intermediary barrier between the outdoor heat exchanger and the indoor heat exchanger. By positioning it to overlap the discharge hole, it mediates and blocks the refrigerant flow path, preventing direct counter-flow from the outdoor unit back to the indoor unit without requiring additional valve mechanisms.
2Reliability
If the compression member is positioned to overlap the discharge hole, then refrigerant counter-flow is suppressed, but the compressor structure and control complexity increases
Solution Approach 1:
The compressor's existing compression member is utilized as a dual-purpose component: it performs its normal compression function and also serves as a flow barrier by positioning it to overlap the discharge hole. This self-service approach eliminates the need for separate barrier mechanisms or complex additional control systems, as the existing components are made to perform multiple functions.
Solution Approach 2:
The compression member is designed with multi-functionality, serving both as the compression element and as a controllable barrier for the discharge hole. By making the compression member overlap the discharge hole, it simultaneously maintains compression functionality while preventing refrigerant counter-flow, reducing the need for separate dedicated components.
3Reliability
If the liquid side on-off valve is closed after pump down operation, then refrigerant is confined in the outdoor heat exchanger and compressor, but the valve operation timing and control complexity increases
Solution Approach 1:
The liquid side on-off valve is operated periodically based on the pump down operation timing. The valve closes after a specified period from the start of pump down operation, creating a time-based control sequence that automatically manages refrigerant confinement without requiring complex real-time monitoring or adjustment mechanisms.
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
An air conditioning machine is provided by which a refrigerant collected into an outdoor heat exchanger can be suppressed from counter-flowing through a discharge hole of a compressor toward a side of an indoor heat exchanger in a refrigerant circuit after an end of a pump down operation. The air conditioning machine includes a refrigerant circuit 100, a refrigerant leakage sensing unit 95 that senses leakage of the flammable refrigerant from the refrigerant circuit 100, and a pump down operation control unit 931 that carries out the pump down operation for accumulating the flammable refrigerant in the outdoor heat exchanger 103 in the refrigerant circuit 100 when the refrigerant leakage sensing unit 95 senses the leakage of the flammable refrigerant. The compressor 101 includes a cylinder chamber, a compression member that is placed in the cylinder chamber and that compresses the flammable refrigerant, and a discharge hole through which the flammable refrigerant compressed in the cylinder chamber is discharged. At the end of the pump down operation, the pump down operation control unit 931 controls the compressor 101 so that the compression member stops at a position where the compression member overlaps at least a portion of the discharge hole when viewed in an axial direction of the cylinder chamber.