Refrigerant Flow Switching for Three-Way Valve Failure in Air Conditioning
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Solution Overview
Problem
Air-conditioning systems face issues with closed circuit operations due to failed three-way valves, leading to reduced heating capacity and potential refrigerant leakage, especially during heating and cooling operations.
Innovation Solution
The air-conditioning apparatus incorporates a refrigerant circuit with constant-energized-type three-way valves and a controller that manages the flow switching between cooling and heating circuits, ensuring refrigerant flow even if one of the three-way valves fails, by using bypass pipes and expansion devices to alternate defrosting between upper and lower outdoor heat exchangers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a three-way valve is used for flow switching in the refrigerant circuit, then the circuit can be simplified and operation is easier, but the valve may fail and cause closed circuit operation
Solution Approach 1:
The outdoor heat exchanger is divided into an upper-side outdoor heat exchanger and a lower-side outdoor heat exchanger with independent flow passages. This segmentation allows the refrigerant circuit to be divided into multiple paths, so that if one three-way valve fails, the other can still maintain proper refrigerant flow and prevent closed circuit operation.
2Productivity
If a three-way valve fails in heating operation mode, then heating capacity is reduced, but the system continues to operate
Solution Approach 1:
The system is designed with redundant flow paths through the upper-side and lower-side outdoor heat exchangers before a failure occurs. When a three-way valve fails, the pre-designed alternative path allows the system to maintain heating capacity by routing refrigerant through the functional heat exchanger, cushioning against the impact of valve failure.
3Productivity
If a three-way valve fails in cooling operation mode, then discharge pressure may abnormally increase causing refrigerant pipe to burst, but the system continues to operate
Solution Approach 1:
The cooling circuit is segmented into upper-side and lower-side paths with independent three-way valves. If one valve fails and causes abnormal discharge pressure, the segmentation allows the system to isolate the faulty path while maintaining cooling operation through the other path, preventing refrigerant pipe burst.
Solution Approach 2:
The independent three-way valves for upper-side and lower-side outdoor heat exchangers act as intermediaries that can independently control refrigerant flow. When one valve fails, the other valve serves as a mediator to redirect refrigerant flow and prevent dangerous pressure buildup that could cause pipe burst.
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 configuration prevents closed circuit operations, maintains heating capacity, and reduces the risk of refrigerant leakage, ensuring continuous and efficient operation even when one of the three-way valves is in a de-energized state.
Implementation Method 1
a compressor configured to compress and discharge refrigerant
Implementation Method 2
an indoor heat exchanger connected by a pipe via the flow switching device and configured to exchange heat between refrigerant discharged from the compressor and indoor air
Implementation Method 3
an expansion device configured to decompress refrigerant condensed in the indoor heat exchanger
Implementation Method 4
an outdoor heat exchanger including an upper-side outdoor heat exchanger and a lower-side outdoor heat exchanger each having an independent flow passage, the outdoor heat exchanger being configured to exchange heat between refrigerant having passed through the expansion device and outdoor air
Data Source
AI summary
In an air-conditioning apparatus, a first flow passage selection device and a second flow passage selection device each are a constant-energized-type three-way valve in which a position of a main valve can be fixed in a de-energized state. When the refrigerant circuit is switched to the cooling circuit by a flow switching device, when at least one of the first flow passage selection device and the second flow passage selection device is in a de-energized state, the first flow passage selection device or the second flow passage selection device in the de-energized state is configured to output refrigerant discharged from the compressor and input therein via the flow switching device and the bypass pipe to a corresponding one of an upper-side outdoor heat exchanger and a lower-side outdoor heat exchanger.