Refrigerant Flow Switching in Multi-Heat-Exchanger Air Conditioning
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Solution Overview
Problem
In air-conditioning apparatuses, when heat exchangers are used as condensers in cooling operations, the reduced flow velocity of refrigerant leads to decreased performance and refrigerant accumulation on the downstream side of evaporators, 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 second heat-source-side heat exchanger are connected in parallel upstream and the third heat-source-side heat exchanger is connected in series downstream when used as condensers, and all three are connected in parallel when used as evaporators, optimizing flow velocity and reducing refrigerant accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat exchangers are connected in parallel to reduce pressure loss, then evaporator performance is improved, but refrigerant flow velocity drops and condenser performance deteriorates
Solution Approach 1:
The system dynamically switches between parallel and series connections based on operational requirements. A flow passage switching device changes the refrigerant flow path configuration from parallel (for evaporators) to series (for condensers), allowing the system to optimize performance for each specific component type rather than being fixed in one configuration.
Solution Approach 2:
The refrigerant flow path is segmented into different configurable arrangements. The heat exchangers can be divided into separate groups that are connected differently - some in parallel for evaporator applications and others in series for condenser applications, with switching devices controlling which segmentation is active at any given time.
2Productivity
If heat exchangers are connected in series to increase refrigerant flow velocity, then condenser performance is improved, but pressure loss increases and evaporator performance deteriorates
Solution Approach 1:
The connection configuration is made dynamic through switching devices that can reconfigure the refrigerant flow path. When condensers are in operation, the system switches to series connection to maximize flow velocity and heat transfer efficiency. When evaporators are in operation, the system switches to parallel connection to minimize pressure loss.
Solution Approach 2:
The system segments the heat exchanger network into controllable groups with different connection topologies. The switching device enables selective series or parallel arrangement of heat exchanger segments based on whether condenser or evaporator function is prioritized, allowing optimization for each operational mode.
3Productivity
If multiple flow passage switching valves are used to switch between series and parallel configurations, then heat exchanger performance is optimized, but device complexity increases
Solution Approach 1:
The flow passage switching device is designed to perform multiple functions: it switches between series and parallel configurations, controls refrigerant flow distribution, and adapts the system to different operational modes (heating/cooling). This multi-functionality reduces the need for separate dedicated valves for each function, thereby limiting the increase in device complexity while maintaining performance optimization capabilities.
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 enhances the performance of both condensers and evaporators by maintaining efficient refrigerant circulation and reducing refrigerant accumulation, even at low flow velocities, thereby improving overall air-conditioning efficiency.
Implementation Method 1
heat transferred from or received by the refrigerant
Implementation Method 2
heat transferred from or received by the refrigerant
Implementation Method 3
in the case where the three heat-source-side heat exchangers are used as evaporators
Implementation Method 4
in the case where at least two of three heat-source-side heat exchangers are used as condensers
Data Source
Figure 1
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Figure 3
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.