Evaporator and refrigerant circuit
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Solution Overview
Problem
In refrigerant circuits with multi-stage heat transfer pipes, lubricating oil accumulates at the lower end of the header due to slow refrigerant flow, which cannot be effectively addressed by existing configurations that suppress liquid phase separation in the header.
Innovation Solution
The evaporator design includes a header with a smaller cross-sectional area at the lowermost stage connection, a bypass pipe to divert refrigerant flow, and a gradually increasing cross-sectional area as more heat transfer pipes connect, preventing lubricating oil accumulation by maintaining flow speed and facilitating easy manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the flow passage cross-sectional area of the header is gradually reduced to suppress liquid phase separation, then liquid refrigerant separation is improved, but lubricating oil accumulation occurs at the lower end of the header
Solution Approach 1:
The header flow passage is segmented into multiple sections with different cross-sectional area characteristics. The lower end portion has a smaller cross-sectional area to maintain flow speed and prevent oil accumulation, while the upper end has a larger cross-sectional area to accommodate multiple heat transfer pipe connections. This segmentation allows different functional requirements to be satisfied in different regions of the same component.
Solution Approach 2:
Different portions of the header are given different local qualities in terms of cross-sectional area. The lower end portion is designed with a smaller cross-sectional area to promote refrigerant flow velocity and prevent oil accumulation, while the upper end portion is designed with a larger cross-sectional area to facilitate connections with multiple heat transfer pipes. This local differentiation resolves the contradiction between preventing oil accumulation and accommodating pipe connections.
2Reliability
If the flow passage cross-sectional area at the lowermost stage connection is made smaller, then refrigerant flow speed is maintained and oil accumulation is suppressed, but manufacturing complexity increases
Solution Approach 1:
The header incorporates a dynamic variation in cross-sectional area along its length, transitioning from a smaller area at the lower end to a larger area at the upper end. This dynamic design allows the header to optimize refrigerant flow characteristics while remaining manufacturable through standard forming processes for tapered or variable-section pipes.
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 effectively suppresses lubricating oil accumulation within the header, ensuring smooth discharge and reducing manufacturing costs by maintaining consistent flow speed and preventing oil buildup.
Implementation Method 1
the lubricating oil that has flowed through the plurality of heat transfer pipes join together at a lower end of the header
Implementation Method 2
a flow passage cross-sectional area of a portion of the header to which the heat transfer pipe located at a lowermost stage among the plurality of heat transfer pipes is connected is smaller than a flow passage cross-sectional area at the upper end of the header
Data Source
Figure 1
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AI summary
The accumulation of lubricating oil within a header is suppressed in a configuration including a plurality of heat transfer pipes. A heat exchanger 10A includes a plurality of heat transfer pipes 11 that are provided at intervals in a vertical direction and allow a refrigerant to flow therethrough toward first ends; and a header 20A that extends in the vertical direction, has the first ends of the plurality of heat transfer pipes 11 connected thereto, and allows the refrigerant to flow from a lower end 20s toward an upper end 20t to which a refrigerant pipe 4 is connected. A flow passage cross-sectional area of a portion of the header 20A to which a heat transfer pipe 11A located at a lowermost stage among the plurality of heat transfer pipes 11 is connected is smaller than a flow passage cross-sectional area at the upper end 20t of the header 20A.