Heat Exchanger Switching Layout for Stable Refrigerant Circulation
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Solution Overview
Problem
In air-conditioning apparatuses, when heat exchangers are connected in series as condensers, slow refrigerant flow leads to refrigerant accumulation on the downstream side of the evaporator, causing circulation issues.
Innovation Solution
An air-conditioning apparatus with a heat-exchanger flow-passage switching device that switches the refrigerant passage between series and parallel configurations, where the first heat-source-side heat exchanger and the second heat-source-side heat exchanger are connected in parallel on the upstream side and the third heat-source-side heat exchanger is connected in series on the downstream side when used as condensers, and all three are connected in parallel when used as evaporators, reducing refrigerant accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If heat exchangers are connected in series as condensers to increase refrigerant flow velocity, then condenser performance is improved, but refrigerant accumulation occurs on the downstream side of the evaporator
Solution Approach 1:
The heat exchanger is divided into multiple independent heat exchange sections (first, second, and third heat exchange sections) that can be selectively connected in different configurations. This segmentation allows the system to switch between series connection (for high flow velocity in cooling mode) and parallel connection (for reliable refrigerant circulation in heating mode), resolving the contradiction between flow velocity and circulation reliability.
Solution Approach 2:
The system employs dynamic reconfiguration of the heat exchanger connections through switching valves, changing from a fixed series arrangement to a flexible dynamic system. The connection topology can be adjusted in real-time based on operational mode (cooling or heating), allowing the system to optimize refrigerant flow velocity during cooling while ensuring reliable circulation during heating by preventing downstream accumulation.
2Stress or pressure
If heat exchangers are connected in parallel as evaporators to reduce pressure loss, then evaporator performance is improved, but all heat exchangers must be used in parallel which increases device complexity
Solution Approach 1:
The system uses partial parallel connection of heat exchangers rather than requiring all heat exchangers to operate in parallel. The switching mechanism selectively activates only the necessary number of heat exchange sections based on operational requirements, reducing the complexity of flow passage switching while still achieving the pressure loss reduction benefit of parallel connection when needed.
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 ensures effective refrigerant circulation by minimizing the capacity on the downstream side of the evaporator, even at low refrigerant flow velocities, and optimizes the performance of both condensers and evaporators.
Implementation Method 1
refrigerant is circulated to heat or cool indoor air with heat transferred from or received by the refrigerant
Implementation Method 2
heat transferred from or received by the refrigerant
Implementation Method 3
a compressor, a refrigerant-flow switching device, a load-side heat exchanger, a load-side expansion device and at least three heat-source-side heat exchangers are connected by pipes to circulate refrigerant
Data Source
AI summary
An air-conditioning apparatus reduces occurrence of refrigerant accumulation on a downstream side of an evaporator to favorably circulate refrigerant. The air-conditioning apparatus includes: a main circuit in which a compressor, a refrigerant-flow switching device, a load-side heat exchanger, a load-side expansion device and three heat-source-side heat exchangers are connected by pipes to circulate refrigerant; and a heat-exchanger flow-passage switching device which performs switching to apply a first series refrigerant passage in the case where the three heat-source-side heat exchangers are used as condensers, and switching to apply a parallel refrigerant passage in the case where the three heat-source-side heat exchangers are used as evaporators. In the first series refrigerant passage, on an upstream side, the first and second heat-source-side heat exchangers are connected parallel to each other, and on a downstream side, the third heat-source-side heat exchanger is located. In the parallel refrigerant passage, first to third heat-source-side heat exchanger are connected parallel to each other.