Heat Exchanger Path Segmentation to Reduce Lowermost Frost Formation
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Solution Overview
Problem
Conventional heat exchangers in air conditioning systems experience increased frost formation in the lowermost heat exchange path during heating operations, leading to longer defrosting times and potential unmelted frost, as the refrigerant temperature is not sufficiently raised in these paths.
Innovation Solution
The heat exchanger design features a longer path effective length and increased flow resistance in the lowermost heat exchange path by extending the series connection of flat pipes and fins, allowing for better refrigerant temperature rise and reduced frost formation, with the path effective length of the first heat exchange path being twice that of other paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the path effective length of the lowermost heat exchange path is increased, then frost formation is reduced and defrosting efficiency is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The heat exchanger is divided into multiple heat exchange paths (first heat exchange path and second heat exchange path) with different path effective lengths. The first heat exchange path includes the lowermost flat pipe and has a longer path effective length, while the second heat exchange path includes upper flat pipes and has a shorter path effective length. This segmentation allows differential frost control across different zones of the heat exchanger.
Solution Approach 2:
The patent applies different path effective lengths to different heat exchange paths based on their specific needs. The lowermost heat exchange path (first heat exchange path) has a longer path effective length to reduce frost formation where it occurs most frequently, while upper heat exchange paths have shorter lengths. This local differentiation optimizes defrosting performance without unnecessarily complicating the entire system.
2Temperature
If the path effective length of the first heat exchange path is made longer than other paths, then refrigerant temperature rise is enhanced and frost formation is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The heat exchanger is divided into multiple heat exchange paths (first heat exchange path and second heat exchange path) with different path effective lengths. The first heat exchange path includes the lowermost flat pipe and has a longer path effective length, while the second heat exchange path includes upper flat pipes and has a shorter path effective length. This segmentation allows differential frost control across different zones of the heat exchanger.
Solution Approach 2:
The patent applies different path effective lengths to different heat exchange paths based on their specific needs. The lowermost heat exchange path (first heat exchange path) has a longer path effective length to reduce frost formation where it occurs most frequently, while upper heat exchange paths have shorter lengths. This local differentiation optimizes defrosting performance without unnecessarily complicating the entire system.
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 reduces frost formation and unmelted frost in the defrosting operation by enhancing refrigerant flow resistance and heat transfer in the lowermost path, ensuring efficient defrosting and improved system performance.
Implementation Method 1
the refrigerant in a gas-liquid two-phase state is divided and flows into each heat exchange path, is heated in each heat exchange path
Implementation Method 2
a heat exchanger including a plurality of flat pipes arranged in multiple stages in a stage direction corresponding to the up-down direction, each of the flat pipes including a passage for a refrigerant formed inside thereof, and a plurality of fins that partition a space between adjacent flat pipes into a plurality of air flow passages through which air flows
Implementation Method 3
When the air conditioning apparatus performs the defrosting operation, the above conventional heat exchanger is used as a radiator for the refrigerant. Specifically, when the above conventional heat exchanger is used as the evaporator for the refrigerant, the refrigerant in a gas-liquid two-phase state is divided and flows into each heat exchange path, is heated in each heat exchange path
Data Source
AI summary
A heat exchanger includes: flat pipes disposed in multiple stages in a stage direction corresponding to an up-down direction; and fins that partition a space between adjacent two of the flat pipes into air flow passages through which air flows. Each of the flat pipes includes a passage for a refrigerant inside thereof. The flat pipes are divided into heat exchange paths arrayed in multiple stages in the stage direction. One of the heat exchange paths that includes a lowermost one of the flat pipes is defined as a first heat exchange path. A length of the passage from a first end to a second end of a flow of the refrigerant in each of the heat exchange paths is defined as a path effective length.