Heat Exchanger Header Layout for Airflow-Matched Refrigerant Distribution
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Solution Overview
Problem
The flow of air through heat exchangers in air-conditioning apparatuses is unevenly distributed vertically, leading to suboptimal refrigerant distribution and decreased energy efficiency, despite efforts to improve refrigerant distribution using headers and branch tubes.
Innovation Solution
The branch tubes in the header manifold are inserted at varying lengths relative to the vertical direction of the heat exchanger, with some penetrating and others being covered by the liquid layer, to match refrigerant flow with air velocity distribution, enhancing the heat exchanger's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If branch tubes are inserted at equal lengths into the header manifold, then the structure is simple, but refrigerant distribution is insufficient and does not match airflow distribution
Solution Approach 1:
The patent applies local quality by varying the insertion length of branch tubes into the header manifold based on their vertical position. Branch tubes at different heights have different insertion lengths to match the non-uniform airflow distribution, with tubes in high-velocity regions having different insertion depths compared to those in low-velocity regions. This creates locally optimized refrigerant distribution that corresponds to the local airflow characteristics at each vertical position.
Solution Approach 2:
The patent employs asymmetry by intentionally creating asymmetric insertion lengths for branch tubes arranged in a symmetric pattern. Instead of all branch tubes having equal insertion lengths, the design introduces asymmetric variations where tubes at different vertical positions have different insertion depths. This asymmetric configuration compensates for the asymmetric airflow velocity distribution in the heat exchanger, achieving better overall performance.
2Manufacturing precision
If additional structural objects are provided inside the header manifold to improve refrigerant distribution, then distribution performance improves, but cost increases significantly
Solution Approach 1:
The patent applies parameter changes by modifying the insertion length parameter of existing branch tubes into the header manifold. Instead of adding new structural components, the invention optimizes the dimensional parameter (insertion length) of existing branch tubes to achieve improved refrigerant distribution. This approach maintains the simplicity of the overall structure while achieving the desired distribution uniformity through parameter optimization.
3Productivity
If refrigerant is uniformly distributed to the heat exchanger, then distribution simplicity is maintained, but heat exchanger performance deteriorates due to mismatch with airflow distribution
Solution Approach 1:
The patent applies local quality by creating non-uniform refrigerant distribution that matches the local airflow velocity distribution in the heat exchanger. Branch tubes positioned in regions with higher airflow velocity have different insertion lengths compared to those in low-velocity regions, ensuring that refrigerant flow rate corresponds to local air flow characteristics. This local optimization maximizes heat transfer efficiency throughout the heat exchanger.
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 optimizes refrigerant distribution within the heat exchanger, improving its performance and energy efficiency by aligning refrigerant flow with airflow patterns.
Implementation Method 1
the flow of air through the heat exchanger is unevenly distributed relative to the vertical direction... the flow of liquid refrigerant is concentrated in an upper part of the area... the flow of liquid refrigerant is concentrated in a lower part of the area
Data Source
Figure 1~2
Figure 3~4
Figure 5(a)~6
AI summary
The air-conditioning apparatus includes a heat exchanger, an axial fan, and a refrigerant circuit. The heat exchanger includes a plurality of heat transfer tubes in which refrigerant flows, the plurality of heat transfer tubes being arranged so as to be spaced apart from each other in the vertical direction, and a header manifold that has a flow space defined inside the header manifold and extending in the vertical direction, the header manifold allowing refrigerant to flow into the plurality of heat transfer tubes from a plurality of branch tubes arranged so as to be spaced apart from each other in the vertical direction. The axial fan includes a blade disposed around a boss that rotates. The blade has a rotational plane that faces the plurality of heat transfer tubes in the horizontal direction. The refrigerant circuit is a circuit to direct the refrigerant into the flow space such that the refrigerant flows upward in a two-phase gas-liquid state, and to cause the refrigerant to evaporate in the heat exchanger. The refrigerant flows in the header manifold in an annular or churn flow pattern in which gas-phase refrigerant collects at the center of the header manifold and liquid-phase refrigerant collects on the wall surface of the header manifold. When the distance from the center of the flow space in the horizontal plane is represented on a scale of 0 to 100%, where 0% represents the center of the flow space and 100% is the position of the wall surface of the header manifold, among the plurality of branch tubes located within a height range that allows the blade to rotate, the majority of the branch tubes located at or below the height of the boss are connected to the header manifold such that their distal ends are positioned at 0 to 50% of the distance from the center, and the majority of the branch tubes located above the height of the boss are connected to the header manifold such that their distal ends are positioned at more than 50% of the distance from the center.